485BPOS

Filed with the Securities and Exchange Commission on March 12, 2018

1933 Act Registration File No. 033-20827

1940 Act File No. 811- 05518

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933		[	X	]
Pre-Effective Amendment No.		[		]
Post-Effective Amendment No.	241	[	X	]

and/or

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940		[	X	]
Amendment No.	243	[	X	]

(Check Appropriate Box or Boxes)

THE RBB FUND, INC.

(Exact Name of Registrant as Specified in Charter)

615 East Michigan Street,

Milwaukee, Wisconsin  53202

(Address of Principal Executive Offices, including Zip Code)

Registrant’s Telephone Number, including Area Code:  (302) 791-1851

Copies to:

SALVATORE FAIA	MICHAEL P. MALLOY, ESQUIRE
The RBB Fund, Inc.	Drinker Biddle & Reath LLP
615 East Michigan Street,	One Logan Square, Suite 2000
Milwaukee, Wisconsin  53202	Philadelphia, Pennsylvania 19103-6996

Approximate Date of Proposed Public Offering: As soon as practicable after the Registration Statement becomes effective.

[	X	]	immediately upon filing pursuant to paragraph (b)
[		]	on (date) pursuant to paragraph (b)
[		]	60 days after filing pursuant to paragraph (a)(1)
[		]	on (date) pursuant to paragraph (a)(1)
[		]	75 days after filing pursuant to paragraph (a)(2)
[		]	on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

[ ] This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

This Post-Effective Amendment ("PEA") No. 241 to the Registration Statement for The RBB Fund, Inc. (the "Company") on Form N-1A hereby incorporates Parts A, B and C from the Company's PEA No. 239 on Form N-1A filed February 22, 2018. This PEA No. 241 is filed for the sole purpose of submitting the XBRL exhibit for the risk/return summary first provided in PEA No. 239 to the Company's Registration Statement.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended (the "1933 Act"), and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Amendment to the Registration Statement under Rule 485(b) under the 1933 Act and that it has duly caused this Amendment to the Registration Statement to be signed on its behalf by the undersigned, thereto duly authorized, in the City of Chadds Ford, and State of Pennsylvania on the 12th day of March, 2018.

THE RBB FUND, INC.
By:	/s/ Salvatore Faia
	Salvatore Faia
	President

Pursuant to the requirements of the 1933 Act, this Amendment to Registrant’s Registration Statement has been signed below by the following persons in the capacities and on the date indicated.

SIGNATURE	TITLE	DATE
/s/ Salvatore Faia	President (Principal Executive Officer)	March 12, 2018
Salvatore Faia	and Chief Compliance Officer
/s/ James G. Shaw	Treasurer (Chief Financial Officer) and Secretary	March 12, 2018
James G. Shaw
*J. Richard Carnall	Director	March 12, 2018
J. Richard Carnall
*Julian A. Brodsky	Director	March 12, 2018
Julian A. Brodsky
*Arnold M. Reichman	Director	March 12, 2018
Arnold M. Reichman
*Robert Sablowsky	Director	March 12, 2018
Robert Sablowsky
*Robert Straniere	Director	March 12, 2018
Robert Straniere
*Nicholas A. Giordano	Director	March 12, 2018
Nicholas A. Giordano
*Gregory P. Chandler	Director	March 12, 2018
Gregory P. Chandler

*By:	/s/ Salvatore Faia	March 12, 2018
	Salvatore Faia
	Attorney-in-Fact

2 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Julian A. Brodsky, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ Julian A. Brodsky
	Julian A. Brodsky

3 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, J. Richard Carnall, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ J. Richard Carnall
	J. Richard Carnall

4 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Nicholas A. Giordano, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ Nicholas A. Giordano
	Nicholas A. Giordano

5 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Arnold M. Reichman, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ Arnold M. Reichman
	Arnold M. Reichman

6 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Robert Sablowsky, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ Robert Sablowsky
	Robert Sablowsky

7 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Robert A. Straniere, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 16, 2017
	/s/ Robert Straniere
	Robert Straniere

8 

THE RBB FUND, INC.

(the “Company”)

POWER OF ATTORNEY

Know All Men by These Presents, that the undersigned, Gregory P. Chandler, hereby constitutes and appoints Salvatore Faia, Michael P. Malloy, James G. Shaw, Edward Paz, and Robert Amweg, his true and lawful attorneys, to execute in his name, place, and stead, in his capacity as Director or officer, or both, of the Company, the Registration Statement and any amendments thereto and all instruments necessary or incidental in connection therewith, and to file the same with the Securities and Exchange Commission; and said attorneys shall have full power and authority to do and perform in his name and on his behalf, in any and all capacities, every act whatsoever requisite or necessary to be done in the premises, as fully and to all intents and purposes as he might or could do in person, said acts of said attorneys being hereby ratified and approved.

DATED:	February 17, 2017
	/s/ Gregory P. Chandler
	Gregory P. Chandler

9 

INDEX TO EXHIBITS

Exhibit	Exhibit No.
Instance Document	EX-101.INS
Schema Document	EX-101.SCH
Calculation Linkbase Document	EX-101.CAL
Definition Linkbase Document	EX-101.DEF
Label Linkbase Document	EX-101.LAB
Presentation Linkbase Document	EX-101.PRE

10

XML

Label	Element	Value
Document And Entity Information [Abstract]	rbb_DocumentAndEntityInformationAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Aug. 31, 2017
Registrant Name	dei_EntityRegistrantName	RBB FUND, INC.
Central Index Key	dei_EntityCentralIndexKey	0000831114
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Feb. 23, 2018
Document Effective Date	dei_DocumentEffectiveDate	Feb. 23, 2018
Prospectus Date	rr_ProspectusDate	Feb. 22, 2018

XML

Institutional Class Prospectus | Boston Partners Small Cap Value Fund II

SUMMARY SECTION — BOSTON PARTNERS SMALL CAP VALUE FUND II

Investment Objective

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Current income is a secondary objective.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Small Cap Value Fund II Institutional Class
Management fees	1.00%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.18%
Acquired fund fees and expenses	0.01%	[1]
Total annual Fund operating expenses	1.19%
Fee waiver and/or expense reimbursement	(0.09%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.10%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Small Cap Value Fund II | Institutional Class | USD ($)	1,121	3,689	6,457	14,352

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 24% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers with small market capitalizations and identified by the Adviser as having value characteristics. A small market capitalization issuer generally is considered to be one whose market capitalization is, at the time the Fund makes the investment, similar to the market capitalization of companies in the Russell 2000^® Value Index. The Russell 2000^® Value Index is an unmanaged index that contains stocks from the Russell 2000^® Index with less than average growth orientation. As of November 30, 2017, the median market capitalization of this index was $1.77 billion and the largest stock was $7.25 billion. Please note that this range is as of a particular point in time and is subject to change.

The Fund generally invests in the equity securities of small companies. The Adviser will seek to invest in companies it considers to be well managed and to have attractive fundamental financial characteristics. The Adviser believes greater potential for price appreciation exists among small companies since they tend to be less widely followed by other securities analysts and thus may be more likely to be undervalued by the market. The Fund may invest from time to time a portion of its assets, not to exceed 20% (under normal conditions) at the time of purchase, in companies with larger market capitalizations.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may also invest up to 25% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small Cap Companies Risk. The Fund will invest in smaller issuers which are more volatile and less liquid than investments in issuers with a market capitalization greater than the market capitalization of companies in the Russell 2000^® Value Index. Small market capitalization issuers are not as diversified in their business activities as issuers with market capitalizations greater than the market capitalization of companies in the Russell 2000^® Value Index and are more susceptible to changes in the business cycle.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Small Cap Value Fund II's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	29.32% (quarter ended June 30, 2009)
Worst Quarter:	-26.32% (quarter ended December 31, 2008)

Average Annual Total Returns for the Periods Ended
December 31, 2017

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Small Cap Value Fund II		1 Year	5 Years	10 Years
Institutional Class		9.78%	13.19%	9.81%
Institutional Class | After Taxes on Distributions	[1]	8.56%	12.42%	9.35%
Institutional Class | After Taxes on Distributions and Sales		6.38%	10.46%	8.01%
Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)		7.84%	13.01%	8.17%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's investment adviser, Boston Partners Global Investors, Inc. (the "Adviser"), has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.10%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Institutional Class Prospectus | Boston Partners Small Cap Value Fund II

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS SMALL CAP VALUE FUND II

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Current income is a secondary objective.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 24% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

24.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers with small market capitalizations and identified by the Adviser as having value characteristics. A small market capitalization issuer generally is considered to be one whose market capitalization is, at the time the Fund makes the investment, similar to the market capitalization of companies in the Russell 2000^® Value Index. The Russell 2000^® Value Index is an unmanaged index that contains stocks from the Russell 2000^® Index with less than average growth orientation. As of November 30, 2017, the median market capitalization of this index was $1.77 billion and the largest stock was $7.25 billion. Please note that this range is as of a particular point in time and is subject to change.

The Fund generally invests in the equity securities of small companies. The Adviser will seek to invest in companies it considers to be well managed and to have attractive fundamental financial characteristics. The Adviser believes greater potential for price appreciation exists among small companies since they tend to be less widely followed by other securities analysts and thus may be more likely to be undervalued by the market. The Fund may invest from time to time a portion of its assets, not to exceed 20% (under normal conditions) at the time of purchase, in companies with larger market capitalizations.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may also invest up to 25% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small Cap Companies Risk. The Fund will invest in smaller issuers which are more volatile and less liquid than investments in issuers with a market capitalization greater than the market capitalization of companies in the Russell 2000^® Value Index. Small market capitalization issuers are not as diversified in their business activities as issuers with market capitalizations greater than the market capitalization of companies in the Russell 2000^® Value Index and are more susceptible to changes in the business cycle.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Small Cap Value Fund II's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for the Calendar Years Ended December 31 

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	29.32% (quarter ended June 30, 2009)
Worst Quarter:	-26.32% (quarter ended December 31, 2008)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

29.32%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.32%)

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns for the Periods Ended
December 31, 2017

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners Small Cap Value Fund II | Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

7.84%

5 Years

rr_AverageAnnualReturnYear05

13.01%

10 Years

rr_AverageAnnualReturnYear10

8.17%

Institutional Class | Institutional Class Prospectus | Boston Partners Small Cap Value Fund II

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BPSIX

Management fees

rr_ManagementFeesOverAssets

1.00%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.18%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.19%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.09%)

^[2]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.10%

One Year

rr_ExpenseExampleYear01

$ 1,121

Three Years

rr_ExpenseExampleYear03

3,689

Five Years

rr_ExpenseExampleYear05

6,457

Ten Years

rr_ExpenseExampleYear10

$ 14,352

Annual Return 2008

rr_AnnualReturn2008

(34.67%)

Annual Return 2009

rr_AnnualReturn2009

49.39%

Annual Return 2010

rr_AnnualReturn2010

18.50%

Annual Return 2011

rr_AnnualReturn2011

(3.43%)

Annual Return 2012

rr_AnnualReturn2012

22.87%

Annual Return 2013

rr_AnnualReturn2013

34.74%

Annual Return 2014

rr_AnnualReturn2014

4.21%

Annual Return 2015

rr_AnnualReturn2015

(4.33%)

Annual Return 2016

rr_AnnualReturn2016

25.97%

Annual Return 2017

rr_AnnualReturn2017

9.78%

1 Year

rr_AverageAnnualReturnYear01

9.78%

5 Years

rr_AverageAnnualReturnYear05

13.19%

10 Years

rr_AverageAnnualReturnYear10

9.81%

Institutional Class | Institutional Class Prospectus | Boston Partners Small Cap Value Fund II | After Taxes on Distributions

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

8.56%

^[3]

5 Years

rr_AverageAnnualReturnYear05

12.42%

^[3]

10 Years

rr_AverageAnnualReturnYear10

9.35%

^[3]

Institutional Class | Institutional Class Prospectus | Boston Partners Small Cap Value Fund II | After Taxes on Distributions and Sales

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

6.38%

5 Years

rr_AverageAnnualReturnYear05

10.46%

10 Years

rr_AverageAnnualReturnYear10

8.01%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's investment adviser, Boston Partners Global Investors, Inc. (the "Adviser"), has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.10%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Institutional Class Prospectus | Boston Partners All-Cap Value Fund

SUMMARY SECTION — BOSTON PARTNERS ALL-CAP VALUE FUND

Investment Objective

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Current income is a secondary objective.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners All-Cap Value Fund Institutional Class
Management fees	0.70%	[1]
Distribution and/or Service (12b-1) fees	none
Other expenses	0.18%
Acquired fund fees and expenses	0.01%	[2]
Total annual Fund operating expenses	0.89%
Fee waiver and/or expense reimbursement	(0.09%)	[3]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	0.80%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners All-Cap Value Fund | Institutional Class | USD ($)	817	2,749	4,842	10,878

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 27% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers across the capitalization spectrum and identified by the Adviser as having value characteristics.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return on equity and earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may also invest up to 20% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 10% of its net assets in securities that can be converted into common stock, such as certain debt securities and preferred stock.

The Fund may hedge overall portfolio exposure up to 40% of its net assets through the purchase and sale of index and individual put and call options.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners All-Cap Value Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	18.60% (quarter ended June 30, 2009)
Worst Quarter:	-17.49% (quarter ended September 30, 2011)

Average Annual Total Returns for the Periods Ended
December 31, 2017

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners All-Cap Value Fund		1 Year	5 Years	10 Years
Institutional Class		17.87%	16.36%	10.17%
Institutional Class | After Taxes on Distributions	[1]	16.69%	15.02%	9.27%
Institutional Class | After Taxes on Distributions and Sales		11.05%	12.95%	8.18%
Russell 3000® Value Index (reflects no deduction for fees, expenses or taxes)		13.19%	13.95%	7.19%

[1] Prior to February 28, 2017, the management fee was 0.80%.

[2] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[3] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 0.80% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 0.80%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Institutional Class Prospectus | Boston Partners All-Cap Value Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS ALL-CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Current income is a secondary objective.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 27% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

27.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers across the capitalization spectrum and identified by the Adviser as having value characteristics.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return on equity and earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may also invest up to 20% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 10% of its net assets in securities that can be converted into common stock, such as certain debt securities and preferred stock.

The Fund may hedge overall portfolio exposure up to 40% of its net assets through the purchase and sale of index and individual put and call options.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the Boston Partners All-Cap Value Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31 

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	18.60% (quarter ended June 30, 2009)
Worst Quarter:	-17.49% (quarter ended September 30, 2011)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Jun. 30, 2009

Highest Quarterly Return

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18.60%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Sep. 30, 2011

Lowest Quarterly Return

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(17.49%)

Performance Table Heading

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Average Annual Total Returns for the Periods Ended
December 31, 2017

Performance Table Not Relevant to Tax Deferred

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table One Class of after Tax Shown [Text]

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners All-Cap Value Fund | Russell 3000® Value Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

13.19%

5 Years

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13.95%

10 Years

rr_AverageAnnualReturnYear10

7.19%

Institutional Class | Institutional Class Prospectus | Boston Partners All-Cap Value Fund

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPAIX

Management fees

rr_ManagementFeesOverAssets

0.70%

^[1]

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.18%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.89%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.09%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.80%

One Year

rr_ExpenseExampleYear01

$ 817

Three Years

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2,749

Five Years

rr_ExpenseExampleYear05

4,842

Ten Years

rr_ExpenseExampleYear10

$ 10,878

Annual Return 2008

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(27.26%)

Annual Return 2009

rr_AnnualReturn2009

30.97%

Annual Return 2010

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13.42%

Annual Return 2011

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(1.38%)

Annual Return 2012

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15.83%

Annual Return 2013

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39.12%

Annual Return 2014

rr_AnnualReturn2014

12.23%

Annual Return 2015

rr_AnnualReturn2015

0.95%

Annual Return 2016

rr_AnnualReturn2016

14.82%

Annual Return 2017

rr_AnnualReturn2017

17.87%

1 Year

rr_AverageAnnualReturnYear01

17.87%

5 Years

rr_AverageAnnualReturnYear05

16.36%

10 Years

rr_AverageAnnualReturnYear10

10.17%

Institutional Class | Institutional Class Prospectus | Boston Partners All-Cap Value Fund | After Taxes on Distributions

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

16.69%

^[4]

5 Years

rr_AverageAnnualReturnYear05

15.02%

^[4]

10 Years

rr_AverageAnnualReturnYear10

9.27%

^[4]

Institutional Class | Institutional Class Prospectus | Boston Partners All-Cap Value Fund | After Taxes on Distributions and Sales

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

11.05%

5 Years

rr_AverageAnnualReturnYear05

12.95%

10 Years

rr_AverageAnnualReturnYear10

8.18%

[1] Prior to February 28, 2017, the management fee was 0.80%.

[2] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[3] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 0.80% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 0.80%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[4] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Long/Short Equity Fund

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT EQUITY FUND

Investment Objective

The Fund seeks long-term capital appreciation while reducing exposure to general equity market risk. The Fund seeks a total return greater than that of the S&P 500^® Index over a full market cycle.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Long/Short Equity Fund Institutional Class
Management fees	2.25%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.14%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.16%
Interest expense on borrowings	0.25%
Total annual Fund operating expenses	2.81%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Long/Short Equity Fund | Institutional Class | USD ($)	2,841	8,710	14,840	31,377

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 63% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities principally traded in the United States markets. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the United States equity market generally. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in equity securities. Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 125% of the Fund's net assets.

The Fund's long and short positions may involve (without limit) equity securities of foreign issuers that are traded in the markets of the United States. The Fund may also invest up to 20% of its total assets directly in equity securities of foreign issuers.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations. High yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Equity Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	38.60% (quarter ended June 30, 2009)
Worst Quarter:	-19.45% (quarter ended December 31, 2008)

Average Annual Total Returns for the Periods Ended
December 31, 2017

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods. Although the Fund compares its average total return to a broad-based securities market index, the Fund seeks returns that are not correlated to securities market returns. The Fund seeks to achieve a 12-15% return over a full market cycle; however, there can be no guarantee that such returns will be achieved.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Long/Short Equity Fund		1 Year	5 Years	10 Years
Institutional Class		2.77%	7.06%	11.79%
Institutional Class | After Taxes on Distributions	[1]	2.58%	5.87%	9.63%
Institutional Class | After Taxes on Distributions and Sales		1.71%	5.35%	8.84%
S&P 500® Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	8.50%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class exceeds 2.50% of the average daily net assets attributable to the Fund's Institutional Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 2.50%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Label

Element

Value

Institutional Class Prospectus | Boston Partners Long/Short Equity Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation while reducing exposure to general equity market risk. The Fund seeks a total return greater than that of the S&P 500^® Index over a full market cycle.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 63% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

63.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities principally traded in the United States markets. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the United States equity market generally. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in equity securities. Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 125% of the Fund's net assets.

The Fund's long and short positions may involve (without limit) equity securities of foreign issuers that are traded in the markets of the United States. The Fund may also invest up to 20% of its total assets directly in equity securities of foreign issuers.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations. High yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Equity Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31 

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	38.60% (quarter ended June 30, 2009)
Worst Quarter:	-19.45% (quarter ended December 31, 2008)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

38.60%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.45%)

Performance Table Heading

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Average Annual Total Returns for the Periods Ended
December 31, 2017

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods. Although the Fund compares its average total return to a broad-based securities market index, the Fund seeks returns that are not correlated to securities market returns. The Fund seeks to achieve a 12-15% return over a full market cycle; however, there can be no guarantee that such returns will be achieved.

Institutional Class Prospectus | Boston Partners Long/Short Equity Fund | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BPLSX

Management fees

rr_ManagementFeesOverAssets

2.25%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.14%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.16%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.25%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.81%

^[2]

One Year

rr_ExpenseExampleYear01

$ 2,841

Three Years

rr_ExpenseExampleYear03

8,710

Five Years

rr_ExpenseExampleYear05

14,840

Ten Years

rr_ExpenseExampleYear10

$ 31,377

Annual Return 2008

rr_AnnualReturn2008

(21.15%)

Annual Return 2009

rr_AnnualReturn2009

82.37%

Annual Return 2010

rr_AnnualReturn2010

26.44%

Annual Return 2011

rr_AnnualReturn2011

5.92%

Annual Return 2012

rr_AnnualReturn2012

12.47%

Annual Return 2013

rr_AnnualReturn2013

7.90%

Annual Return 2014

rr_AnnualReturn2014

4.72%

Annual Return 2015

rr_AnnualReturn2015

(1.09%)

Annual Return 2016

rr_AnnualReturn2016

22.48%

Annual Return 2017

rr_AnnualReturn2017

2.77%

1 Year

rr_AverageAnnualReturnYear01

2.77%

5 Years

rr_AverageAnnualReturnYear05

7.06%

10 Years

rr_AverageAnnualReturnYear10

11.79%

Institutional Class Prospectus | Boston Partners Long/Short Equity Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

rr_AverageAnnualReturnYear05

15.79%

10 Years

rr_AverageAnnualReturnYear10

8.50%

Institutional Class Prospectus | Boston Partners Long/Short Equity Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

2.58%

^[3]

5 Years

rr_AverageAnnualReturnYear05

5.87%

^[3]

10 Years

rr_AverageAnnualReturnYear10

9.63%

^[3]

Institutional Class Prospectus | Boston Partners Long/Short Equity Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

1.71%

5 Years

rr_AverageAnnualReturnYear05

5.35%

10 Years

rr_AverageAnnualReturnYear10

8.84%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class exceeds 2.50% of the average daily net assets attributable to the Fund's Institutional Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 2.50%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Institutional Class Prospectus | Boston Partners Long/Short Research Fund

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT RESEARCH FUND

Investment Objective

The Fund seeks to provide long-term total return.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Long/Short Research Fund Institutional Class
Management fees	1.25%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.12%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.80%
Interest expense on borrowings	0.06%
Total annual Fund operating expenses	2.24%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Long/Short Research Fund | Institutional Class | USD ($)	2,271	7,002	11,999	25,748

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 54% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund uses a hedged strategy. The Fund actively invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales (i.e. sales of securities the Fund does not own) are invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage.

The Fund invests, both long and short, in equity securities issued by large-, mid- and small (or "micro") cap companies, as well as other instruments that are convertible into equity securities. Selling securities short is a form of leverage. Equity securities in which the Fund may invest include exchange-traded and over-the-counter common and preferred stocks, warrants, rights, convertible securities, depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Fund may also invest in depositary receipts and equity securities of foreign companies (denominated in either U.S. dollars or foreign currencies), put and call options, futures, indexed securities and fixed-income securities (including bonds, notes, asset-backed securities, convertible securities, Eurodollar and Yankee dollar instruments, preferred stocks and money market instruments) and high yield securities (commonly referred to as "junk bonds"). Fixed income securities in which the Fund invests include those rated between AAA and D by a nationally recognized statistical rating organization, or deemed of comparable quality by the Adviser. The Adviser may also temporarily invest uninvested cash in money market funds and similar collective investment vehicles. The Fund may also seek to increase its income by lending portfolio securities.

The Adviser determines the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the U.S. equity market by investing less than 100% of its assets in net long positions. Selection of individual securities to be held long or sold short will be based on a mix of quantitative techniques and fundamental security analysis. The Adviser selects stocks on the basis of three criteria: value, fundamental business strength and momentum. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

Although the Fund seeks to follow a hedged strategy, there can be no assurance that the Fund's portfolio or investments will be insulated from market moves or effectively hedged against risk.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The principal derivative instruments in which the Fund invests are futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations (of any rating, including defaulted securities and unrated securities), including bonds and debentures, issued by corporations and business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and financial practices.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may be incorrect in the stocks it buys and believes to be undervalued and in stocks it sells short and believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 300%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  Indexed Securities Risk. The Fund may invest in indexed securities whose value is linked to securities indices. Most such securities have values that rise and fall according to the change in one or more specified indices and may have characteristics similar to direct investments in the underlying securities. Depending on the index, such securities may have greater volatility than the market as a whole.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Research Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	8.37% (quarter ended December 31, 2011)
Worst Quarter:	-9.89% (quarter ended September 30, 2011)

Average Annual Total Returns for the Periods Ended
December 31, 2017

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Long/Short Research Fund		1 Year	5 Years	Since Inception	Inception Date
Institutional Class		10.10%	7.89%	8.70%	Sep. 30, 2010
Institutional Class | After Taxes on Distributions	[1]	10.10%	7.60%	8.46%	Sep. 30, 2010
Institutional Class | After Taxes on Distributions and Sales		5.71%	6.18%	6.98%	Sep. 30, 2010
S&P 500® Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	14.86%	Sep. 30, 2010

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to forgo all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) exceeds 1.50% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 1.50%. This contractual limitation is in effect until at least February 28, 2019 and may not be terminated without Board approval. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.50% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Institutional Class Prospectus | Boston Partners Long/Short Research Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT RESEARCH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term total return.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 54% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

54.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund uses a hedged strategy. The Fund actively invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales (i.e. sales of securities the Fund does not own) are invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage.

The Fund invests, both long and short, in equity securities issued by large-, mid- and small (or "micro") cap companies, as well as other instruments that are convertible into equity securities. Selling securities short is a form of leverage. Equity securities in which the Fund may invest include exchange-traded and over-the-counter common and preferred stocks, warrants, rights, convertible securities, depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Fund may also invest in depositary receipts and equity securities of foreign companies (denominated in either U.S. dollars or foreign currencies), put and call options, futures, indexed securities and fixed-income securities (including bonds, notes, asset-backed securities, convertible securities, Eurodollar and Yankee dollar instruments, preferred stocks and money market instruments) and high yield securities (commonly referred to as "junk bonds"). Fixed income securities in which the Fund invests include those rated between AAA and D by a nationally recognized statistical rating organization, or deemed of comparable quality by the Adviser. The Adviser may also temporarily invest uninvested cash in money market funds and similar collective investment vehicles. The Fund may also seek to increase its income by lending portfolio securities.

The Adviser determines the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the U.S. equity market by investing less than 100% of its assets in net long positions. Selection of individual securities to be held long or sold short will be based on a mix of quantitative techniques and fundamental security analysis. The Adviser selects stocks on the basis of three criteria: value, fundamental business strength and momentum. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

Although the Fund seeks to follow a hedged strategy, there can be no assurance that the Fund's portfolio or investments will be insulated from market moves or effectively hedged against risk.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The principal derivative instruments in which the Fund invests are futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations (of any rating, including defaulted securities and unrated securities), including bonds and debentures, issued by corporations and business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and financial practices.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may be incorrect in the stocks it buys and believes to be undervalued and in stocks it sells short and believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 300%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  Indexed Securities Risk. The Fund may invest in indexed securities whose value is linked to securities indices. Most such securities have values that rise and fall according to the change in one or more specified indices and may have characteristics similar to direct investments in the underlying securities. Depending on the index, such securities may have greater volatility than the market as a whole.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

Risk Lose Money [Text]

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Investors may lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Research Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-888-261-4073

Performance Availability Website Address [Text]

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www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	8.37% (quarter ended December 31, 2011)
Worst Quarter:	-9.89% (quarter ended September 30, 2011)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Dec. 31, 2011

Highest Quarterly Return

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8.37%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Sep. 30, 2011

Lowest Quarterly Return

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(9.89%)

Performance Table Heading

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Average Annual Total Returns for the Periods Ended
December 31, 2017

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners Long/Short Research Fund | Institutional Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPIRX

Management fees

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1.25%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

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0.12%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.80%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.06%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.24%

^[2]

One Year

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$ 2,271

Three Years

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7,002

Five Years

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11,999

Ten Years

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$ 25,748

Annual Return 2011

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3.40%

Annual Return 2012

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13.37%

Annual Return 2013

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17.77%

Annual Return 2014

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7.15%

Annual Return 2015

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1.52%

Annual Return 2016

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3.62%

Annual Return 2017

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10.10%

1 Year

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10.10%

5 Years

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7.89%

Since Inception

rr_AverageAnnualReturnSinceInception

8.70%

Inception Date

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Sep. 30, 2010

Institutional Class Prospectus | Boston Partners Long/Short Research Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

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15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

14.86%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2010

Institutional Class Prospectus | Boston Partners Long/Short Research Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

10.10%

^[3]

5 Years

rr_AverageAnnualReturnYear05

7.60%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

8.46%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2010

^[3]

Institutional Class Prospectus | Boston Partners Long/Short Research Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

5.71%

5 Years

rr_AverageAnnualReturnYear05

6.18%

Since Inception

rr_AverageAnnualReturnSinceInception

6.98%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2010

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to forgo all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) exceeds 1.50% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 1.50%. This contractual limitation is in effect until at least February 28, 2019 and may not be terminated without Board approval. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.50% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund

SUMMARY SECTION — WPG PARTNERS SMALL/MICRO CAP VALUE FUND

Investment Objective

The Fund seeks capital appreciation by investing primarily in common stocks, securities convertible into common stocks and in special situations.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Annual Fund Operating Expenses	Institutional Class Prospectus WPG Partners Small/Micro Cap Value Fund Institutional Class
Management fees	0.80%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.49%
Total annual Fund operating expenses	1.29%
Fee waiver and/or expense reimbursement	(0.19%)	[1]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.10%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund | Institutional Class | USD ($)	1,121	3,902	6,894	15,398

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 78% of the average value of its portfolio.

Summary of Principal Investment Strategies

Currently, the Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in equity securities of U.S. companies that, at the time of purchase, have a market capitalization that is within the range of the market capitalization of issuers in the Russell 2000^® Value Index. As of November 30, 2017, the median market capitalization of the companies in the Russell 2000^® Value Index is $726 million and the largest stock is $9.33 billion. The Fund may invest in depository receipts and equity securities of foreign companies. Although the Fund invests primarily in common stocks, the Fund may invest in all types of equity and equity-related securities, including (without limitation):

•  Securities convertible into common stocks.

•  Shares of real estate investment trusts ("REITs").

•  Warrants and rights to purchase common stocks.

•  Preferred stocks.

•  Exchange traded limited partnerships.

Special Situations: The Fund may invest in companies that may experience unusual and possibly unique developments which may create a special opportunity for significant returns. Special situations include: significant technological improvements or important discoveries; reorganizations, recapitalizations or mergers; favorable resolutions of litigation; new management or material changes in company policies; and actual or potential changes in control of a company.

Strategies: The Adviser uses a value approach to select the Fund's investments. Using this investment style, the Adviser seeks securities selling at substantial discounts to their underlying values and then holds these securities until the market values reflect what the Adviser believes to be their intrinsic values. The Adviser employs a bottom-up strategy, focusing on undervalued industries that the Adviser believes are experiencing positive change. The Adviser then uses both qualitative and quantitative methods to assess a security's potential value. The portfolio managers managing the Fund meet with a multitude of companies annually to identify companies with increasing returns on capital in their core businesses which are selling at attractive valuations.

Factors the Adviser looks for in selecting investments include (without limitation):

•  Increasing returns on invested capital.

•  Companies who have demonstrated an ability to generate high return on invested capital (ROIC).

•  Companies which provide solid cash flows with appropriate capital.

•  Potential catalysts such as new products, cyclical upturns and changes in management.

•  Low market valuations relative to earnings forecast, book value, cash flow and sales.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate. 

Summary of Principal Risks

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Small Cap Companies Risk. The small capitalization equity securities in which the Fund may invest will often be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Special Situations Risk. The Fund will seek to benefit from "special situations," such as mergers, reorganizations, or other unusual events expected to affect a particular issuer. There is a risk that the "special situation" might not occur or involve longer time frames than originally expected, which could have a negative impact on the price of the issuer's securities and fail to produce gains or produce a loss for the Fund.

•  Rights and Warrants Risk. The purchase of rights or warrants involves the risk that the Fund could lose the purchase value of a right or warrant if the right to subscribe to additional shares is not executed prior to the right's or warrant's expiration. Also, the purchase of rights and/or warrants involves the risk that the effective price paid for the right and/or warrant added to the subscription price of the related security may exceed the value of the subscribed security's market price such as when there is no movement in the level of the underlying security.

Performance Information

The bar chart and table below illustrate the long-term performance of the WPG Partners Small/Micro Cap Value Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	28.51% (quarter ended June 30, 2009)
Worst Quarter:	-30.21% (quarter ended December 31, 2008)

Average Annual Total Returns
(for the Periods Ended December 31, 2017)  

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - WPG Partners Small/Micro Cap Value Fund		1 Year	5 Years	10 Years
Institutional Class		5.68%	8.35%	5.84%
Institutional Class | After Taxes on Distributions	[1]	3.43%	6.35%	4.83%
Institutional Class | After Taxes on Distributions and Sales		3.91%	6.07%	4.43%
Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)		7.84%	13.01%	8.17%

[1] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.10%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time, the Fund's total annual fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. In certain cases, the figure representing "Returns After Taxes on Distributions and Sale of Fund Shares" may be higher than the other return figures for the same period since a higher after-tax return results when a capital loss occurs upon redemption and provides an assumed tax deduction that benefits the investor.

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Value

Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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SUMMARY SECTION — WPG PARTNERS SMALL/MICRO CAP VALUE FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks capital appreciation by investing primarily in common stocks, securities convertible into common stocks and in special situations.

Expense [Heading]

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Expenses and Fees

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 78% of the average value of its portfolio.

Portfolio Turnover, Rate

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78.00%

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

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Currently, the Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in equity securities of U.S. companies that, at the time of purchase, have a market capitalization that is within the range of the market capitalization of issuers in the Russell 2000^® Value Index. As of November 30, 2017, the median market capitalization of the companies in the Russell 2000^® Value Index is $726 million and the largest stock is $9.33 billion. The Fund may invest in depository receipts and equity securities of foreign companies. Although the Fund invests primarily in common stocks, the Fund may invest in all types of equity and equity-related securities, including (without limitation):

•  Securities convertible into common stocks.

•  Shares of real estate investment trusts ("REITs").

•  Warrants and rights to purchase common stocks.

•  Preferred stocks.

•  Exchange traded limited partnerships.

Special Situations: The Fund may invest in companies that may experience unusual and possibly unique developments which may create a special opportunity for significant returns. Special situations include: significant technological improvements or important discoveries; reorganizations, recapitalizations or mergers; favorable resolutions of litigation; new management or material changes in company policies; and actual or potential changes in control of a company.

Strategies: The Adviser uses a value approach to select the Fund's investments. Using this investment style, the Adviser seeks securities selling at substantial discounts to their underlying values and then holds these securities until the market values reflect what the Adviser believes to be their intrinsic values. The Adviser employs a bottom-up strategy, focusing on undervalued industries that the Adviser believes are experiencing positive change. The Adviser then uses both qualitative and quantitative methods to assess a security's potential value. The portfolio managers managing the Fund meet with a multitude of companies annually to identify companies with increasing returns on capital in their core businesses which are selling at attractive valuations.

Factors the Adviser looks for in selecting investments include (without limitation):

•  Increasing returns on invested capital.

•  Companies who have demonstrated an ability to generate high return on invested capital (ROIC).

•  Companies which provide solid cash flows with appropriate capital.

•  Potential catalysts such as new products, cyclical upturns and changes in management.

•  Low market valuations relative to earnings forecast, book value, cash flow and sales.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate. 

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Small Cap Companies Risk. The small capitalization equity securities in which the Fund may invest will often be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Special Situations Risk. The Fund will seek to benefit from "special situations," such as mergers, reorganizations, or other unusual events expected to affect a particular issuer. There is a risk that the "special situation" might not occur or involve longer time frames than originally expected, which could have a negative impact on the price of the issuer's securities and fail to produce gains or produce a loss for the Fund.

•  Rights and Warrants Risk. The purchase of rights or warrants involves the risk that the Fund could lose the purchase value of a right or warrant if the right to subscribe to additional shares is not executed prior to the right's or warrant's expiration. Also, the purchase of rights and/or warrants involves the risk that the effective price paid for the right and/or warrant added to the subscription price of the related security may exceed the value of the subscribed security's market price such as when there is no movement in the level of the underlying security.

Risk Lose Money [Text]

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Investors may lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the WPG Partners Small/Micro Cap Value Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-888-261-4073

Performance Availability Website Address [Text]

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www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31 

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	28.51% (quarter ended June 30, 2009)
Worst Quarter:	-30.21% (quarter ended December 31, 2008)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Jun. 30, 2009

Highest Quarterly Return

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28.51%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Dec. 31, 2008

Lowest Quarterly Return

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(30.21%)

Performance Table Heading

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Average Annual Total Returns
(for the Periods Ended December 31, 2017)  

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In certain cases, the figure representing "Returns After Taxes on Distributions and Sale of Fund Shares" may be higher than the other return figures for the same period since a higher after-tax return results when a capital loss occurs upon redemption and provides an assumed tax deduction that benefits the investor.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund | Institutional Class

Prospectus [Line Items]

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Management fees

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0.80%

Distribution and/or Service (12b-1) fees

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none

Other expenses

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0.49%

Total annual Fund operating expenses

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1.29%

Fee waiver and/or expense reimbursement

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(0.19%)

^[1]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

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1.10%

One Year

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$ 1,121

Three Years

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3,902

Five Years

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6,894

Ten Years

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$ 15,398

Annual Return 2008

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(38.73%)

Annual Return 2009

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41.23%

Annual Return 2010

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26.10%

Annual Return 2011

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(11.95%)

Annual Return 2012

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22.88%

Annual Return 2013

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42.08%

Annual Return 2014

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(3.62%)

Annual Return 2015

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(13.74%)

Annual Return 2016

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19.63%

Annual Return 2017

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5.68%

1 Year

rr_AverageAnnualReturnYear01

5.68%

5 Years

rr_AverageAnnualReturnYear05

8.35%

10 Years

rr_AverageAnnualReturnYear10

5.84%

Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund | Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

WPGTX

1 Year

rr_AverageAnnualReturnYear01

7.84%

5 Years

rr_AverageAnnualReturnYear05

13.01%

10 Years

rr_AverageAnnualReturnYear10

8.17%

Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

3.43%

^[2]

5 Years

rr_AverageAnnualReturnYear05

6.35%

^[2]

10 Years

rr_AverageAnnualReturnYear10

4.83%

^[2]

Institutional Class Prospectus | WPG Partners Small/Micro Cap Value Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

3.91%

5 Years

rr_AverageAnnualReturnYear05

6.07%

10 Years

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4.43%

[1] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.10%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time, the Fund's total annual fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[2] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. In certain cases, the figure representing "Returns After Taxes on Distributions and Sale of Fund Shares" may be higher than the other return figures for the same period since a higher after-tax return results when a capital loss occurs upon redemption and provides an assumed tax deduction that benefits the investor.

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Institutional Class Prospectus | Boston Partners Global Equity Fund

SUMMARY SECTION — BOSTON PARTNERS GLOBAL EQUITY FUND

Investment Objective

The Fund seeks to provide long-term capital growth.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Global Equity Fund Institutional Class
Management fees	0.90%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.14%
Acquired fund fees and expenses	0.01%	[1]
Total annual Fund operating expenses	1.05%
Fee waiver and/or expense reimbursement	(0.10%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	0.95%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Global Equity Fund | Institutional Class | USD ($)	969	3,241	5,697	12,735

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 83% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a non-diversified portfolio of equity and equity-related securities issued by U.S. and non-U.S. companies of any capitalization size. The Fund may invest in all types of equity and equity- related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, participatory notes, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund generally invests in the equity securities of issuers believed by the Adviser to be undervalued in the marketplace, focusing on issuers that combine attractive valuations with catalysts for change. The Adviser applies a bottom-up stock selection process (i.e., one that focuses primarily on issuer-specific factors) in managing the Fund, using a combination of fundamental and quantitative analysis. In selecting investments for the Fund, the Adviser considers various factors such as price-to-book value, price-to-sales and earnings ratios, dividend yields, strength of management, and cash flow to identify securities that are trading at a price that appears to be lower than the issuer's inherent value.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. 

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public. The Fund may also seek to increase its income by lending portfolio securities.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

 Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Global Equity Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	11.70% (quarter ended March 31, 2012)
Worst Quarter:	-9.22% (quarter ended September 30, 2015)

Average Annual Total Returns
(for the Periods Ended December 31, 2017)  

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Global Equity Fund		1 Year	5 Years	Since Inception	Inception Date
Institutional Class		20.37%	12.75%	13.17%	Dec. 30, 2011
Institutional Class | After Taxes on Distributions	[1]	19.79%	12.02%	12.54%	Dec. 30, 2011
Institutional Class | After Taxes on Distributions and Sales		12.00%	9.99%	10.52%	Dec. 30, 2011
MSCI World Index (reflects no deduction for fees, expenses or taxes)		23.07%	12.26%	12.96%	Dec. 30, 2011

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 0.95% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 0.95%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 0.95% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Label

Element

Value

Institutional Class Prospectus | Boston Partners Global Equity Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

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SUMMARY SECTION — BOSTON PARTNERS GLOBAL EQUITY FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term capital growth.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 83% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

83.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a non-diversified portfolio of equity and equity-related securities issued by U.S. and non-U.S. companies of any capitalization size. The Fund may invest in all types of equity and equity- related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, participatory notes, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund generally invests in the equity securities of issuers believed by the Adviser to be undervalued in the marketplace, focusing on issuers that combine attractive valuations with catalysts for change. The Adviser applies a bottom-up stock selection process (i.e., one that focuses primarily on issuer-specific factors) in managing the Fund, using a combination of fundamental and quantitative analysis. In selecting investments for the Fund, the Adviser considers various factors such as price-to-book value, price-to-sales and earnings ratios, dividend yields, strength of management, and cash flow to identify securities that are trading at a price that appears to be lower than the issuer's inherent value.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. 

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public. The Fund may also seek to increase its income by lending portfolio securities.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Bar Chart and Performance Table [Heading]

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 Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Global Equity Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31 

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	11.70% (quarter ended March 31, 2012)
Worst Quarter:	-9.22% (quarter ended September 30, 2015)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.70%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.22%)

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the Periods Ended December 31, 2017)  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners Global Equity Fund | Institutional Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPGIX

Management fees

rr_ManagementFeesOverAssets

0.90%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.14%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.05%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

^[2]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.95%

One Year

rr_ExpenseExampleYear01

$ 969

Three Years

rr_ExpenseExampleYear03

3,241

Five Years

rr_ExpenseExampleYear05

5,697

Ten Years

rr_ExpenseExampleYear10

$ 12,735

Annual Return 2012

rr_AnnualReturn2012

15.34%

Annual Return 2013

rr_AnnualReturn2013

32.67%

Annual Return 2014

rr_AnnualReturn2014

4.34%

Annual Return 2015

rr_AnnualReturn2015

0.80%

Annual Return 2016

rr_AnnualReturn2016

8.50%

Annual Return 2017

rr_AnnualReturn2017

20.37%

1 Year

rr_AverageAnnualReturnYear01

20.37%

5 Years

rr_AverageAnnualReturnYear05

12.75%

Since Inception

rr_AverageAnnualReturnSinceInception

13.17%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

Institutional Class Prospectus | Boston Partners Global Equity Fund | MSCI World Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

23.07%

5 Years

rr_AverageAnnualReturnYear05

12.26%

Since Inception

rr_AverageAnnualReturnSinceInception

12.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

Institutional Class Prospectus | Boston Partners Global Equity Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

19.79%

^[3]

5 Years

rr_AverageAnnualReturnYear05

12.02%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

12.54%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

^[3]

Institutional Class Prospectus | Boston Partners Global Equity Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

12.00%

5 Years

rr_AverageAnnualReturnYear05

9.99%

Since Inception

rr_AverageAnnualReturnSinceInception

10.52%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Institutional Class shares exceeds 0.95% of the average daily net assets attributable to the Fund's Institutional Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 0.95%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 0.95% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Global Long/Short Fund

SUMMARY SECTION — BOSTON PARTNERS GLOBAL LONG/SHORT FUND

Investment Objective

The Fund seeks long-term growth of capital.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Global Long/Short Fund Institutional Class
Management fees	1.50%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.20%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.88%
Interest expense on borrowings	0.05%
Total annual Fund operating expenses	2.64%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and Fund operating expenses remain the same. Although your actual costs and returns might be different, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Global Long/Short Fund | Institutional Class | USD ($)	2,671	8,204	14,001	29,734

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 109% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities issued by U.S. and non-U.S. companies of any capitalization size.

With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, including return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund's portfolio is rebalanced regularly. The Adviser assesses each investment's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell an investment held long or close out a short position that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

Under normal circumstances, the Adviser expects to sell securities short so that the Fund's portfolio is approximately 50% net long with an average of between 30% and 70% net long.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by U.S. and foreign corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Global Long/Short Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Year Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	4.10% (quarter ended June 30, 2015)
Worst Quarter:	-2.06% (quarter ended September 30, 2015)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Global Long/Short Fund		1 Year	Since Inception	Inception Date
Institutional Class		7.55%	4.43%	Dec. 31, 2013
Institutional Class | After Taxes on Distributions	[1]	7.55%	4.39%	Dec. 31, 2013
Institutional Class | After Taxes on Distributions and Sales		4.27%	3.43%	Dec. 31, 2013
MSCI® World Index (reflects no deduction for fees, expenses or taxes)		23.07%	8.77%	Dec. 31, 2013

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 2.00% of the average daily net assets attributable to the Fund's Institutional Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.00%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.00% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Global Long/Short Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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SUMMARY SECTION — BOSTON PARTNERS GLOBAL LONG/SHORT FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The Fund seeks long-term growth of capital.

Expense [Heading]

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Expenses and Fees

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

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February 28, 2019

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 109% of the average value of its portfolio.

Portfolio Turnover, Rate

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109.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

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Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and Fund operating expenses remain the same. Although your actual costs and returns might be different, based on these assumptions your costs would be:

Strategy [Heading]

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Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities issued by U.S. and non-U.S. companies of any capitalization size.

With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, including return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund's portfolio is rebalanced regularly. The Adviser assesses each investment's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell an investment held long or close out a short position that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

Under normal circumstances, the Adviser expects to sell securities short so that the Fund's portfolio is approximately 50% net long with an average of between 30% and 70% net long.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by U.S. and foreign corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the Boston Partners Global Long/Short Fund's Institutional Class. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Year Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	4.10% (quarter ended June 30, 2015)
Worst Quarter:	-2.06% (quarter ended September 30, 2015)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2015

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

4.10%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.06%)

Performance Table Heading

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Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners Global Long/Short Fund | Institutional Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BGLSX

Management fees

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1.50%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.20%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.88%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.05%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.64%

^[2]

One Year

rr_ExpenseExampleYear01

$ 2,671

Three Years

rr_ExpenseExampleYear03

8,204

Five Years

rr_ExpenseExampleYear05

14,001

Ten Years

rr_ExpenseExampleYear10

$ 29,734

Annual Return 2014

rr_AnnualReturn2014

1.40%

Annual Return 2015

rr_AnnualReturn2015

6.55%

Annual Return 2016

rr_AnnualReturn2016

2.36%

Annual Return 2017

rr_AnnualReturn2017

7.55%

1 Year

rr_AverageAnnualReturnYear01

7.55%

Since Inception

rr_AverageAnnualReturnSinceInception

4.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2013

Institutional Class Prospectus | Boston Partners Global Long/Short Fund | MSCI® World Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

23.07%

Since Inception

rr_AverageAnnualReturnSinceInception

8.77%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2013

Institutional Class Prospectus | Boston Partners Global Long/Short Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

7.55%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

4.39%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2013

^[3]

Institutional Class Prospectus | Boston Partners Global Long/Short Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

4.27%

Since Inception

rr_AverageAnnualReturnSinceInception

3.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2013

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 2.00% of the average daily net assets attributable to the Fund's Institutional Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.00%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.00% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund

SUMMARY SECTION — BOSTON PARTNERS EMERGING MARKETS LONG/SHORT FUND

Investment Objective

The Fund seeks long-term growth of capital.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Emerging Markets Long/Short Fund Institutional Class
Management fees	1.85%
Distribution and/or Service (12b-1) fees	none
Other expenses	1.01%
Acquired fund fees and expenses	0.05%	[1]
Dividend expense on short sales	0.06%
Interest expense on borrowings	0.01%
Total annual Fund operating expenses	2.98%
Fee waiver and/or expense reimbursement	(0.91%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	2.07%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund | Institutional Class | USD ($)	2,100	8,359	14,874	32,348

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 184% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund will pursue its objective through a multi-strategy long-short portfolio of equity securities and financial investments with equity like characteristics designed to provide exposure to emerging markets. Securities are selected by the Adviser using its "three circles" approach which combines a quantitative screening with a fundamental bottom up selection process. This investment strategy is grounded in the following principles: (1) low valuation stocks outperform high valuation stocks; (2) companies with strong fundamentals, e.g. high and sustainable returns on invested capital, outperform companies with weak fundamentals; and (3) stocks with positive business momentum, e.g. rising earnings estimates, outperform stocks with negative business momentum. With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Adviser examines various factors in determining the value characteristics of issuers, including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return-on-equity and earnings growth and cash flow.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in the securities of emerging market issuers, related derivative instruments and other investments that are tied economically to emerging market countries. The Adviser considers an emerging market country to include any country that is: 1) generally recognized to be an emerging market country by the international financial community, including the World Bank; 2) classified by the United Nations as a developing country; or 3) included in the MSCI Emerging Markets Index. Due to the unique relationship between China and its separately administered regions, the Adviser includes Hong Kong and Macau as emerging markets, independent of above definitions 1 through 3. The Adviser determines that an investment is tied economically to an emerging market if such investment satisfies one or more of the following conditions: 1) the issuer's primary trading market is in an emerging market; 2) the issuer is organized under the laws of, derives at least 50% of its revenue from, or has at least 50% of its assets in emerging markets; 3) the investment is included in an index representative of emerging markets; and 4) the investment is exposed to the economic risks and returns of emerging markets.

In managing the Fund's portfolio, the Adviser will seek to identify mispriced publicly traded equity securities of emerging market companies including shorting securities that the Adviser believes will underperform and purchasing securities that the Adviser believes will outperform.

The long portion of the portfolio will emphasize low valuation, positive business momentum and high quality securities. The short portfolio will emphasize securities with high valuation risk, high balance sheet risk and signs of slowing sales and earnings momentum.

The Fund's portfolio is rebalanced regularly to maintain the optimal risk/return trade-off. The Adviser assesses each stock's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell a stock held long or close out a short position in a stock that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

The equity securities in which the Fund will invest include equity securities issued by large-, mid- and small- or micro-cap companies, as well as exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers").

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded. The Fund will primarily invest in fixed income instruments, including high yield fixed income obligations, when the Fund believes that such instruments offer a better risk/reward profile than comparable equity opportunities.

Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 50% of the Fund's net assets with a typical range of 30% to 70% net long.

The Fund's long and short positions may involve (without limit) equity securities of non-U.S. issuers that are traded in the markets of the United States.

In addition to the short sales discussed above, the Fund may make short sales "against the box," a transaction in which the Fund enters into a short sale of a security which the Fund owns. The proceeds of the short sale will be held by a broker until the settlement date at which time the Fund delivers the security to close the short position. The Fund receives the net proceeds from the short sale. It is currently expected that the majority of the Fund's short sales will not be against the box.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments will be spread over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may participate as a purchaser in initial public offerings of securities ("IPOs"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may also seek to increase its income by lending portfolio securities.

The Fund will invest in derivatives, including put and call options, futures, contracts for differences, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. Contracts for differences offer exposure to price changes in an underlying security without ownership of such security, typically by providing investors the ability to trade on margin. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

• Limited Operating History Risk. The Fund has a limited operating history upon which prospective investors can evaluate its performance. Although the investment strategies described herein may have been utilized by investment accounts managed by the Adviser's investment team, past performance is not indicative of future results.

• New Fund Risk. As a new Fund, there can be no assurance that the Fund will grow to or maintain economically viable size.

• Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may not be successful in its strategy of taking long positions in securities the Adviser believes to be undervalued and short positions in securities the Adviser believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make. Investments the Fund makes may not perform as well as expected, and/or the Fund's portfolio management practices may not work to achieve their desired result.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling is speculative and also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in the value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, contracts for differences, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Exchange Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in the duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

• Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Performance Information

The bar chart and table below illustrate the long-term performance of the Fund. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

The Fund commenced operations as a series of The RBB Fund, Inc. on December 15, 2015, when substantially all of the assets of Boston Partners Emerging Markets Long/Short Equity (the "Prior Account") transferred to the Fund. The Fund is managed in all material respects in a manner equivalent to the management of the Prior Account. Accordingly, the performance information shown below for periods prior to December 15, 2015 is that of the Prior Account. The Fund's objectives, policies, guidelines and restrictions are in all material respects equivalent to the Prior Account. The Fund is managed by Joseph F. Feeney, Jr. and Paul Korngiebel, the same Prior Account portfolio managers that managed the Prior Account since its inception in 2015. The Prior Account was not registered under the Investment Company Act of 1940, as amended ("1940 Act"), and thus was not subject to certain investment and operational restrictions that are imposed by the 1940 Act. If the Prior Account had been registered under the 1940 Act, its performance may have been adversely affected. Accordingly, future Fund performance may be different than the Prior Account's restated past performance. The Prior Account's performance has been restated to reflect estimated expenses of the Fund. After-tax performance returns are not included for the Prior Account. The Prior Account was not a regulated investment company under Subchapter M of the Internal Revenue Code and therefore did not distribute current or accumulated earnings and profits and was not subject to the diversification and source of income requirements applicable to regulated investment companies.

Total Returns for the Calendar Year Ended December 31 

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	9.42% (quarter ended March 31, 2017)
Worst Quarter:	-6.25% (quarter ended September 30, 2015)

Average Annual Total Returns for the Periods Ended
December 31, 2017

The table below compares the average annual total returns for the Fund's Institutional Class, including the Prior Account, both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Institutional Class Prospectus - Boston Partners Emerging Markets Long/Short Fund		1 Year	Since Inception	Inception Date	[1]
Institutional Class		24.78%	8.93%	Mar. 01, 2015
Institutional Class | After Taxes on Distributions	[2]	21.91%	6.66%	Mar. 01, 2015
Institutional Class | After Taxes on Distributions and Sales		14.24%	5.83%	Mar. 01, 2015
MSCI® Emerging Markets Index (reflects no deduction for fees, expenses or taxes)		37.73%	8.66%	Mar. 01, 2015

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] Effective as of June 13, 2017, the Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 2.00% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.00%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.00% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] The "Since Inception" performance includes performance from the Prior Account beginning on March 1, 2015 until the Fund's commencement of operations on December 15, 2015.

[2] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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SUMMARY SECTION — BOSTON PARTNERS EMERGING MARKETS LONG/SHORT FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The Fund seeks long-term growth of capital.

Expense [Heading]

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Expenses and Fees

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)  

Fee Waiver or Reimbursement over Assets, Date of Termination

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February 28, 2019

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 184% of the average value of its portfolio.

Portfolio Turnover, Rate

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184.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

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Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund will pursue its objective through a multi-strategy long-short portfolio of equity securities and financial investments with equity like characteristics designed to provide exposure to emerging markets. Securities are selected by the Adviser using its "three circles" approach which combines a quantitative screening with a fundamental bottom up selection process. This investment strategy is grounded in the following principles: (1) low valuation stocks outperform high valuation stocks; (2) companies with strong fundamentals, e.g. high and sustainable returns on invested capital, outperform companies with weak fundamentals; and (3) stocks with positive business momentum, e.g. rising earnings estimates, outperform stocks with negative business momentum. With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Adviser examines various factors in determining the value characteristics of issuers, including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return-on-equity and earnings growth and cash flow.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in the securities of emerging market issuers, related derivative instruments and other investments that are tied economically to emerging market countries. The Adviser considers an emerging market country to include any country that is: 1) generally recognized to be an emerging market country by the international financial community, including the World Bank; 2) classified by the United Nations as a developing country; or 3) included in the MSCI Emerging Markets Index. Due to the unique relationship between China and its separately administered regions, the Adviser includes Hong Kong and Macau as emerging markets, independent of above definitions 1 through 3. The Adviser determines that an investment is tied economically to an emerging market if such investment satisfies one or more of the following conditions: 1) the issuer's primary trading market is in an emerging market; 2) the issuer is organized under the laws of, derives at least 50% of its revenue from, or has at least 50% of its assets in emerging markets; 3) the investment is included in an index representative of emerging markets; and 4) the investment is exposed to the economic risks and returns of emerging markets.

In managing the Fund's portfolio, the Adviser will seek to identify mispriced publicly traded equity securities of emerging market companies including shorting securities that the Adviser believes will underperform and purchasing securities that the Adviser believes will outperform.

The long portion of the portfolio will emphasize low valuation, positive business momentum and high quality securities. The short portfolio will emphasize securities with high valuation risk, high balance sheet risk and signs of slowing sales and earnings momentum.

The Fund's portfolio is rebalanced regularly to maintain the optimal risk/return trade-off. The Adviser assesses each stock's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell a stock held long or close out a short position in a stock that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

The equity securities in which the Fund will invest include equity securities issued by large-, mid- and small- or micro-cap companies, as well as exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers").

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded. The Fund will primarily invest in fixed income instruments, including high yield fixed income obligations, when the Fund believes that such instruments offer a better risk/reward profile than comparable equity opportunities.

Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 50% of the Fund's net assets with a typical range of 30% to 70% net long.

The Fund's long and short positions may involve (without limit) equity securities of non-U.S. issuers that are traded in the markets of the United States.

In addition to the short sales discussed above, the Fund may make short sales "against the box," a transaction in which the Fund enters into a short sale of a security which the Fund owns. The proceeds of the short sale will be held by a broker until the settlement date at which time the Fund delivers the security to close the short position. The Fund receives the net proceeds from the short sale. It is currently expected that the majority of the Fund's short sales will not be against the box.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments will be spread over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may participate as a purchaser in initial public offerings of securities ("IPOs"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may also seek to increase its income by lending portfolio securities.

The Fund will invest in derivatives, including put and call options, futures, contracts for differences, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. Contracts for differences offer exposure to price changes in an underlying security without ownership of such security, typically by providing investors the ability to trade on margin. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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• Limited Operating History Risk. The Fund has a limited operating history upon which prospective investors can evaluate its performance. Although the investment strategies described herein may have been utilized by investment accounts managed by the Adviser's investment team, past performance is not indicative of future results.

• New Fund Risk. As a new Fund, there can be no assurance that the Fund will grow to or maintain economically viable size.

• Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may not be successful in its strategy of taking long positions in securities the Adviser believes to be undervalued and short positions in securities the Adviser believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make. Investments the Fund makes may not perform as well as expected, and/or the Fund's portfolio management practices may not work to achieve their desired result.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling is speculative and also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in the value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, contracts for differences, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Exchange Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in the duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

• Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Risk Lose Money [Text]

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Investors may lose money.

Risk Nondiversified Status [Text]

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The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the Fund. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

The Fund commenced operations as a series of The RBB Fund, Inc. on December 15, 2015, when substantially all of the assets of Boston Partners Emerging Markets Long/Short Equity (the "Prior Account") transferred to the Fund. The Fund is managed in all material respects in a manner equivalent to the management of the Prior Account. Accordingly, the performance information shown below for periods prior to December 15, 2015 is that of the Prior Account. The Fund's objectives, policies, guidelines and restrictions are in all material respects equivalent to the Prior Account. The Fund is managed by Joseph F. Feeney, Jr. and Paul Korngiebel, the same Prior Account portfolio managers that managed the Prior Account since its inception in 2015. The Prior Account was not registered under the Investment Company Act of 1940, as amended ("1940 Act"), and thus was not subject to certain investment and operational restrictions that are imposed by the 1940 Act. If the Prior Account had been registered under the 1940 Act, its performance may have been adversely affected. Accordingly, future Fund performance may be different than the Prior Account's restated past performance. The Prior Account's performance has been restated to reflect estimated expenses of the Fund. After-tax performance returns are not included for the Prior Account. The Prior Account was not a regulated investment company under Subchapter M of the Internal Revenue Code and therefore did not distribute current or accumulated earnings and profits and was not subject to the diversification and source of income requirements applicable to regulated investment companies.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-888-261-4073

Performance Availability Website Address [Text]

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www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Year Ended December 31 

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	9.42% (quarter ended March 31, 2017)
Worst Quarter:	-6.25% (quarter ended September 30, 2015)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Mar. 31, 2017

Highest Quarterly Return

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9.42%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Sep. 30, 2015

Lowest Quarterly Return

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(6.25%)

Performance Table Heading

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Average Annual Total Returns for the Periods Ended
December 31, 2017

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Institutional Class, including the Prior Account, both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund | Institutional Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BELSX

Management fees

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1.85%

Distribution and/or Service (12b-1) fees

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none

Other expenses

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1.01%

Dividend expense on short sales

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0.06%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.01%

Acquired fund fees and expenses

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0.05%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.98%

Fee waiver and/or expense reimbursement

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(0.91%)

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Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

2.07%

One Year

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$ 2,100

Three Years

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8,359

Five Years

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14,874

Ten Years

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$ 32,348

Annual Return 2015

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(5.35%)

Annual Return 2016

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7.91%

Annual Return 2017

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24.78%

1 Year

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24.78%

Since Inception

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8.93%

Inception Date

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Mar. 01, 2015

^[3]

Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund | MSCI® Emerging Markets Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

37.73%

Since Inception

rr_AverageAnnualReturnSinceInception

8.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 01, 2015

^[3]

Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund | After Taxes on Distributions | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

21.91%

^[4]

Since Inception

rr_AverageAnnualReturnSinceInception

6.66%

^[4]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 01, 2015

^[3],[4]

Institutional Class Prospectus | Boston Partners Emerging Markets Long/Short Fund | After Taxes on Distributions and Sales | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

14.24%

Since Inception

rr_AverageAnnualReturnSinceInception

5.83%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 01, 2015

^[3]

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] Effective as of June 13, 2017, the Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 2.00% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.00%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.00% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] The "Since Inception" performance includes performance from the Prior Account beginning on March 1, 2015 until the Fund's commencement of operations on December 15, 2015.

[4] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Institutional Class Prospectus | Boston Partners Emerging Markets Fund

SUMMARY SECTION — BOSTON PARTNERS EMERGING MARKETS FUND

Investment Objective

The Fund seeks long-term growth of capital.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses	Institutional Class Prospectus Boston Partners Emerging Markets Fund Institutional Class
Management fees	0.85%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.49%	[1]
Total annual Fund operating expenses	1.34%
Fee waiver and/or expense reimbursement	(0.24%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.10%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years
Institutional Class Prospectus | Boston Partners Emerging Markets Fund | Institutional Class | USD ($)	1,121	4,009

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. No portfolio turnover rate is provided for the Fund because the Fund had not completed its first fiscal year as of the date of this Prospectus.

Summary of Principal Investment Strategies

The Fund will pursue its objective through a value oriented, research-driven strategy of investing in equity securities and financial instruments with equity like characteristics designed to provide exposure to emerging markets. Securities are selected by the Adviser using its "three circles" approach which combines a quantitative screening with a fundamental bottom up selection process. This investment strategy is grounded in the following principles: (1) low valuation stocks outperform high valuation stocks; (2) companies with strong fundamentals, e.g. high and sustainable returns on invested capital, outperform companies with weak fundamentals; and (3) stocks with positive business momentum, e.g. rising earnings estimates, outperform stocks with negative business momentum. The Adviser examines various factors in determining the value characteristics of issuers, including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return-on-equity and earnings growth and cash flow.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in the securities of emerging market issuers, related derivative instruments and other investments that are tied economically to emerging market countries. The Adviser considers an emerging market country to include any country that is: 1) generally recognized to be an emerging market country by the international financial community, including the World Bank; 2) classified by the United Nations as a developing country; or 3) included in the MSCI Emerging Markets Index. Due to the unique relationship between China and its separately administered regions, the Adviser includes Hong Kong and Macau as emerging markets, independent of above definitions 1 through 3. The Adviser determines that an investment is tied economically to an emerging market if such investment satisfies one or more of the following conditions: 1) the issuer's primary trading market is in an emerging market; 2) the issuer is organized under the laws of, derives at least 50% of its revenue from, or has at least 50% of its assets in emerging markets; 3) the investment is included in an index representative of emerging markets; and 4) the investment is exposed to the economic risks and returns of emerging markets.

In managing the Fund's portfolio, the Adviser will seek to identify mispriced publicly traded equity securities of emerging market companies and purchase securities that the Adviser believes will outperform, emphasizing low valuation, positive business momentum and high quality.

The Fund's portfolio is rebalanced regularly to maintain the optimal risk/return trade-off. The Adviser assesses each stock's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell a stock that the Adviser believes no longer offers an appropriate return-to-risk tradeoff. The Fund's investment adviser may engage in active trading, and will not consider portfolio turnover a limiting factor in making decisions for the Fund.

The equity securities in which the Fund will invest, which may include equity securities of non-U.S. issuers that are traded in the markets of the United States, include equity securities issued by large-, mid- and small- or micro-cap companies, as well as exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers").

The Fund may invest up to 20% of its net assets in high yield debt obligations (commonly known as "junk bonds"), such as bonds and debentures, used by corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Junk bonds are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded. The Fund will primarily invest in fixed income instruments, including high yield debt obligations, when the Fund believes that such instruments offer a better risk/reward profile than comparable equity opportunities.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments will be spread over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may participate as a purchaser in initial public offerings of securities ("IPOs"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may also seek to increase its income by lending portfolio securities.

The Fund will invest in derivatives, including put and call options, futures, contracts for differences, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. Contracts for differences offer exposure to price changes in an underlying security without ownership of such security, typically by providing investors the ability to trade on margin. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

• Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund makes may not perform as well as expected, and/or the Fund's portfolio management practices may not work to achieve their desired result.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

• Large-Cap Companies Risk. The stocks of large capitalization companies as a group could fall out of favor with the market, causing the Fund to underperform investments that focus solely on small- or medium-capitalization stocks.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Portfolio Turnover Risk. The Fund may frequently trade its portfolio securities, resulting in higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. The Fund's transactions in derivative instruments may require the Fund to establish a segregated account consisting of cash or liquid securities in an amount sufficient to cover the transactions. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, contracts for differences, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Exchange Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in the duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in Junk Bonds, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such Junk Bonds are not considered to be investment grade.

• Equity Securities Risk. The Fund may invest in, or have exposure to, equity securities. Equity securities tend to be more volatile than other investment choices, such as debt and money market instruments. The value of your investment may decrease in response to overall stock market movements or the value of individual securities.

Performance Information

Performance information for the Fund is not included because the Fund did not have one full calendar year of performance prior to the date of this Prospectus. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

[1] "Other Expenses" are estimated for the current fiscal year.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 1.10%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

XML

Label

Element

Value

Institutional Class Prospectus | Boston Partners Emerging Markets Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS EMERGING MARKETS FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Institutional Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. No portfolio turnover rate is provided for the Fund because the Fund had not completed its first fiscal year as of the date of this Prospectus.

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

"Other Expenses" are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $100,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund will pursue its objective through a value oriented, research-driven strategy of investing in equity securities and financial instruments with equity like characteristics designed to provide exposure to emerging markets. Securities are selected by the Adviser using its "three circles" approach which combines a quantitative screening with a fundamental bottom up selection process. This investment strategy is grounded in the following principles: (1) low valuation stocks outperform high valuation stocks; (2) companies with strong fundamentals, e.g. high and sustainable returns on invested capital, outperform companies with weak fundamentals; and (3) stocks with positive business momentum, e.g. rising earnings estimates, outperform stocks with negative business momentum. The Adviser examines various factors in determining the value characteristics of issuers, including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return-on-equity and earnings growth and cash flow.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in the securities of emerging market issuers, related derivative instruments and other investments that are tied economically to emerging market countries. The Adviser considers an emerging market country to include any country that is: 1) generally recognized to be an emerging market country by the international financial community, including the World Bank; 2) classified by the United Nations as a developing country; or 3) included in the MSCI Emerging Markets Index. Due to the unique relationship between China and its separately administered regions, the Adviser includes Hong Kong and Macau as emerging markets, independent of above definitions 1 through 3. The Adviser determines that an investment is tied economically to an emerging market if such investment satisfies one or more of the following conditions: 1) the issuer's primary trading market is in an emerging market; 2) the issuer is organized under the laws of, derives at least 50% of its revenue from, or has at least 50% of its assets in emerging markets; 3) the investment is included in an index representative of emerging markets; and 4) the investment is exposed to the economic risks and returns of emerging markets.

In managing the Fund's portfolio, the Adviser will seek to identify mispriced publicly traded equity securities of emerging market companies and purchase securities that the Adviser believes will outperform, emphasizing low valuation, positive business momentum and high quality.

The Fund's portfolio is rebalanced regularly to maintain the optimal risk/return trade-off. The Adviser assesses each stock's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell a stock that the Adviser believes no longer offers an appropriate return-to-risk tradeoff. The Fund's investment adviser may engage in active trading, and will not consider portfolio turnover a limiting factor in making decisions for the Fund.

The equity securities in which the Fund will invest, which may include equity securities of non-U.S. issuers that are traded in the markets of the United States, include equity securities issued by large-, mid- and small- or micro-cap companies, as well as exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers").

The Fund may invest up to 20% of its net assets in high yield debt obligations (commonly known as "junk bonds"), such as bonds and debentures, used by corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Junk bonds are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded. The Fund will primarily invest in fixed income instruments, including high yield debt obligations, when the Fund believes that such instruments offer a better risk/reward profile than comparable equity opportunities.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments will be spread over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may participate as a purchaser in initial public offerings of securities ("IPOs"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may also seek to increase its income by lending portfolio securities.

The Fund will invest in derivatives, including put and call options, futures, contracts for differences, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes. Contracts for differences offer exposure to price changes in an underlying security without ownership of such security, typically by providing investors the ability to trade on margin. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund makes may not perform as well as expected, and/or the Fund's portfolio management practices may not work to achieve their desired result.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Micro-Cap Companies Risk. Micro-cap stocks may be very sensitive to changing economic conditions and market downturns because the issuers often have narrow markets for their products or services, fewer product lines, and more limited managerial and financial resources than larger issuers. The stocks of micro-cap companies may therefore be more volatile and the ability to sell them at a desirable time or price may be more limited.

• Small-Cap Companies Risk. The stocks of smaller companies may be subject to more abrupt, erratic market movements than stocks of larger, more established companies. Small companies may have limited product lines or financial resources, or may be dependent on a small or inexperienced management group, and their securities may trade less frequently and in lower volume than securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

• Mid-Cap Companies Risk. The stocks of mid-sized companies may be subject to more abrupt or erratic market movements than stocks of larger, more established companies.

• Large-Cap Companies Risk. The stocks of large capitalization companies as a group could fall out of favor with the market, causing the Fund to underperform investments that focus solely on small- or medium-capitalization stocks.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Portfolio Turnover Risk. The Fund may frequently trade its portfolio securities, resulting in higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. The Fund's transactions in derivative instruments may require the Fund to establish a segregated account consisting of cash or liquid securities in an amount sufficient to cover the transactions. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, contracts for differences, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Exchange Traded Fund Risk. Exchange traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in the duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in Junk Bonds, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such Junk Bonds are not considered to be investment grade.

• Equity Securities Risk. The Fund may invest in, or have exposure to, equity securities. Equity securities tend to be more volatile than other investment choices, such as debt and money market instruments. The value of your investment may decrease in response to overall stock market movements or the value of individual securities.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Performance information for the Fund is not included because the Fund did not have one full calendar year of performance prior to the date of this Prospectus. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Performance information for the Fund is not included because the Fund did not have one full calendar year of performance prior to the date of this Prospectus.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Institutional Class Prospectus | Boston Partners Emerging Markets Fund | Institutional Class

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BPEMX

Management fees

rr_ManagementFeesOverAssets

0.85%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.49%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.34%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.24%)

^[2]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.10%

One Year

rr_ExpenseExampleYear01

$ 1,121

Three Years

rr_ExpenseExampleYear03

$ 4,009

[1] "Other Expenses" are estimated for the current fiscal year.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Institutional Class shares exceeds 1.10% of the average daily net assets attributable to the Fund's Institutional Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 1.10%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.10% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

XML

Investor Class Prospectus | Boston Partners Small Cap Value Fund II

SUMMARY SECTION — BOSTON PARTNERS SMALL CAP VALUE FUND II

Investment Objective

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Current income is a secondary objective.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners Small Cap Value Fund II Investor Class
Management fees	1.00%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.18%
Acquired fund fees and expenses	0.01%	[1]
Total annual Fund operating expenses	1.44%
Fee waiver and/or expense reimbursement	(0.09%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.35%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners Small Cap Value Fund II | Investor Class | USD ($)	137	447	778	1,716

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 24% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers with small market capitalizations and identified by the Adviser as having value characteristics. A small market capitalization issuer generally is considered to be one whose market capitalization is, at the time the Fund makes the investment, similar to the market capitalization of companies in the Russell 2000^® Value Index. The Russell 2000^® Value Index is an unmanaged index that contains stocks from the Russell 2000^® Index with less than average growth orientation. As of November 30, 2017, the median market capitalization of this index was $1.77 billion and the largest stock was $7.25 billion. Please note that this range is as of a particular point in time and is subject to change.

The Fund generally invests in the equity securities of small companies. The Adviser will seek to invest in companies it considers to be well managed and to have attractive fundamental financial characteristics. The Adviser believes greater potential for price appreciation exists among small companies since they tend to be less widely followed by other securities analysts and thus may be more likely to be undervalued by the market. The Fund may invest from time to time a portion of its assets, not to exceed 20% (under normal conditions) at the time of purchase, in companies with larger market capitalizations.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may also invest up to 25% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small Cap Companies Risk. The Fund will invest in smaller issuers which are more volatile and less liquid than investments in issuers with a market capitalization greater than the market capitalization of companies in the Russell 2000^® Value Index. Small market capitalization issuers are not as diversified in their business activities as issuers with market capitalizations greater than the market capitalization of companies in the Russell 2000^® Value Index and are more susceptible to changes in the business cycle.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Small Cap Value Fund II's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	29.32% (quarter ended June 30, 2009)
Worst Quarter:	-26.42% (quarter ended December 31, 2008)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners Small Cap Value Fund II		1 Year	5 Years	10 Years
Investor Class		9.50%	12.90%	9.53%
Investor Class | After Taxes on Distributions	[1]	8.31%	12.16%	9.12%
Investor Class | After Taxes on Distributions and Sales		6.22%	10.23%	7.78%
Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)		7.84%	13.01%	8.17%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's investment adviser, Boston Partners Global Investors, Inc. (the "Adviser"), has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.35% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.35%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time, the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.35% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Investor Class Prospectus | Boston Partners Small Cap Value Fund II

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS SMALL CAP VALUE FUND II

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Current income is a secondary objective.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 24% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

24.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers with small market capitalizations and identified by the Adviser as having value characteristics. A small market capitalization issuer generally is considered to be one whose market capitalization is, at the time the Fund makes the investment, similar to the market capitalization of companies in the Russell 2000^® Value Index. The Russell 2000^® Value Index is an unmanaged index that contains stocks from the Russell 2000^® Index with less than average growth orientation. As of November 30, 2017, the median market capitalization of this index was $1.77 billion and the largest stock was $7.25 billion. Please note that this range is as of a particular point in time and is subject to change.

The Fund generally invests in the equity securities of small companies. The Adviser will seek to invest in companies it considers to be well managed and to have attractive fundamental financial characteristics. The Adviser believes greater potential for price appreciation exists among small companies since they tend to be less widely followed by other securities analysts and thus may be more likely to be undervalued by the market. The Fund may invest from time to time a portion of its assets, not to exceed 20% (under normal conditions) at the time of purchase, in companies with larger market capitalizations.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may also invest up to 25% of its total assets in non U.S. dollar-denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small Cap Companies Risk. The Fund will invest in smaller issuers which are more volatile and less liquid than investments in issuers with a market capitalization greater than the market capitalization of companies in the Russell 2000^® Value Index. Small market capitalization issuers are not as diversified in their business activities as issuers with market capitalizations greater than the market capitalization of companies in the Russell 2000^® Value Index and are more susceptible to changes in the business cycle.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Small Cap Value Fund II's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	29.32% (quarter ended June 30, 2009)
Worst Quarter:	-26.42% (quarter ended December 31, 2008)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

29.32%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.42%)

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Investor Class Prospectus | Boston Partners Small Cap Value Fund II | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BPSCX

Management fees

rr_ManagementFeesOverAssets

1.00%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.18%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.44%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.09%)

^[2]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.35%

One Year

rr_ExpenseExampleYear01

$ 137

Three Years

rr_ExpenseExampleYear03

447

Five Years

rr_ExpenseExampleYear05

778

Ten Years

rr_ExpenseExampleYear10

$ 1,716

Annual Return 2008

rr_AnnualReturn2008

(34.82%)

Annual Return 2009

rr_AnnualReturn2009

48.99%

Annual Return 2010

rr_AnnualReturn2010

18.24%

Annual Return 2011

rr_AnnualReturn2011

(3.67%)

Annual Return 2012

rr_AnnualReturn2012

22.54%

Annual Return 2013

rr_AnnualReturn2013

34.40%

Annual Return 2014

rr_AnnualReturn2014

3.90%

Annual Return 2015

rr_AnnualReturn2015

(4.57%)

Annual Return 2016

rr_AnnualReturn2016

25.68%

Annual Return 2017

rr_AnnualReturn2017

9.50%

1 Year

rr_AverageAnnualReturnYear01

9.50%

5 Years

rr_AverageAnnualReturnYear05

12.90%

10 Years

rr_AverageAnnualReturnYear10

9.53%

Investor Class Prospectus | Boston Partners Small Cap Value Fund II | Russell 2000® Value Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

7.84%

5 Years

rr_AverageAnnualReturnYear05

13.01%

10 Years

rr_AverageAnnualReturnYear10

8.17%

Investor Class Prospectus | Boston Partners Small Cap Value Fund II | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

8.31%

^[3]

5 Years

rr_AverageAnnualReturnYear05

12.16%

^[3]

10 Years

rr_AverageAnnualReturnYear10

9.12%

^[3]

Investor Class Prospectus | Boston Partners Small Cap Value Fund II | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

6.22%

5 Years

rr_AverageAnnualReturnYear05

10.23%

10 Years

rr_AverageAnnualReturnYear10

7.78%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's investment adviser, Boston Partners Global Investors, Inc. (the "Adviser"), has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.35% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.35%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time, the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.35% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Investor Class Prospectus | Boston Partners All-Cap Value Fund

SUMMARY SECTION — BOSTON PARTNERS ALL-CAP VALUE FUND

Investment Objective

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Current income is a secondary objective.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners All-Cap Value Fund Investor Class
Management fees	0.70%	[1]
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.18%
Acquired fund fees and expenses	0.01%	[2]
Total annual Fund operating expenses	1.14%
Fee waiver and/or expense reimbursement	(0.09%)	[3]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.05%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners All-Cap Value Fund | Investor Class | USD ($)	107	353	619	1,378

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 27% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers across the capitalization spectrum and identified by the Adviser as having value characteristics.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return on equity and earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may also invest up to 20% of its total assets in non U.S. dollar denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 10% of its net assets in securities that can be converted into common stock, such as certain debt securities and preferred stock.

The Fund may hedge overall portfolio exposure up to 40% of its net assets through the purchase and sale of index and individual put and call options.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small/Mid-Cap Companies Risk. Investing in securities of companies with micro, small or mid-sized capitalizations tends to be riskier than investing in securities of companies with large capitalizations. Securities of companies with micro, small and mid-sized capitalizations tend to be more volatile than those of large cap companies and, on occasion, may fluctuate in the opposite direction of large cap company securities or the broader stock market averages.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners All-Cap Value Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	18.56% (quarter ended June 30, 2009)
Worst Quarter:	-17.62% (quarter ended September 30, 2011)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners All-Cap Value Fund		1 Year	5 Years	10 Years
Investor Class		17.59%	16.10%	9.91%
Investor Class | After Taxes on Distributions	[1]	16.48%	14.82%	9.07%
Investor Class | After Taxes on Distributions and Sales		10.85%	12.74%	7.97%
Russell 3000® Value Index (reflects no deduction for fees, expenses or taxes)		13.19%	13.95%	7.19%

[1] Prior to February 28, 2017, the management fee was 0.80%.

[2] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[3] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.05% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.05%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Investor Class Prospectus | Boston Partners All-Cap Value Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS ALL-CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term growth of capital primarily through investment in equity securities.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Current income is a secondary objective.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 27% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

27.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a diversified portfolio consisting primarily of equity securities, such as common stocks of issuers across the capitalization spectrum and identified by the Adviser as having value characteristics.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Adviser examines various factors in determining the value characteristics of such issuers including price to book value ratios and price to earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, such as return on equity and earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may also invest up to 20% of its total assets in non U.S. dollar denominated securities.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest up to 10% of its net assets in securities that can be converted into common stock, such as certain debt securities and preferred stock.

The Fund may hedge overall portfolio exposure up to 40% of its net assets through the purchase and sale of index and individual put and call options.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Small/Mid-Cap Companies Risk. Investing in securities of companies with micro, small or mid-sized capitalizations tends to be riskier than investing in securities of companies with large capitalizations. Securities of companies with micro, small and mid-sized capitalizations tend to be more volatile than those of large cap companies and, on occasion, may fluctuate in the opposite direction of large cap company securities or the broader stock market averages.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners All-Cap Value Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	18.56% (quarter ended June 30, 2009)
Worst Quarter:	-17.62% (quarter ended September 30, 2011)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.56%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(17.62%)

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods.

Investor Class Prospectus | Boston Partners All-Cap Value Fund | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BPAVX

Management fees

rr_ManagementFeesOverAssets

0.70%

^[1]

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.18%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.14%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.09%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.05%

One Year

rr_ExpenseExampleYear01

$ 107

Three Years

rr_ExpenseExampleYear03

353

Five Years

rr_ExpenseExampleYear05

619

Ten Years

rr_ExpenseExampleYear10

$ 1,378

Annual Return 2008

rr_AnnualReturn2008

(27.56%)

Annual Return 2009

rr_AnnualReturn2009

30.77%

Annual Return 2010

rr_AnnualReturn2010

13.19%

Annual Return 2011

rr_AnnualReturn2011

(1.62%)

Annual Return 2012

rr_AnnualReturn2012

15.61%

Annual Return 2013

rr_AnnualReturn2013

38.92%

Annual Return 2014

rr_AnnualReturn2014

11.98%

Annual Return 2015

rr_AnnualReturn2015

0.69%

Annual Return 2016

rr_AnnualReturn2016

14.52%

Annual Return 2017

rr_AnnualReturn2017

17.59%

1 Year

rr_AverageAnnualReturnYear01

17.59%

5 Years

rr_AverageAnnualReturnYear05

16.10%

10 Years

rr_AverageAnnualReturnYear10

9.91%

Investor Class Prospectus | Boston Partners All-Cap Value Fund | Russell 3000® Value Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

13.19%

5 Years

rr_AverageAnnualReturnYear05

13.95%

10 Years

rr_AverageAnnualReturnYear10

7.19%

Investor Class Prospectus | Boston Partners All-Cap Value Fund | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

16.48%

^[4]

5 Years

rr_AverageAnnualReturnYear05

14.82%

^[4]

10 Years

rr_AverageAnnualReturnYear10

9.07%

^[4]

Investor Class Prospectus | Boston Partners All-Cap Value Fund | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

10.85%

5 Years

rr_AverageAnnualReturnYear05

12.74%

10 Years

rr_AverageAnnualReturnYear10

7.97%

[1] Prior to February 28, 2017, the management fee was 0.80%.

[2] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[3] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.05% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.05%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[4] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Investor Class Prospectus | Boston Partners Long/Short Equity Fund

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT EQUITY FUND

Investment Objective

The Fund seeks long-term capital appreciation while reducing exposure to general equity market risk. The Fund seeks a total return greater than that of the S&P 500^® Index over a full market cycle.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners Long/Short Equity Fund Investor Class
Management fees	2.25%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.14%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.16%
Interest expense on borrowings	0.25%
Total annual Fund operating expenses	3.06%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners Long/Short Equity Fund | Investor Class | USD ($)	309	945	1,606	3,374

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 63% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities principally traded in the United States markets. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the United States equity market generally. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in equity securities.

Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 125% of the Fund's net assets.

The Fund's long and short positions may involve (without limit) equity securities of foreign issuers that are traded in the markets of the United States. The Fund may also invest up to 20% of its total assets directly in equity securities of foreign issuers.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations. High yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Equity Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	38.45% (quarter ended June 30, 2009)
Worst Quarter:	-19.44% (quarter ended December 31, 2008)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods. Although the Fund compares its average total return to a broad-based securities market index, the Fund seeks returns that are not correlated to securities market returns. The Fund seeks to achieve a 12-15% return over a full market cycle; however, there can be no guarantee that such returns will be achieved.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners Long/Short Equity Fund		1 Year	5 Years	10 Years
Investor Class		2.55%	6.79%	11.45%
Investor Class | After Taxes on Distributions	[1]	2.34%	5.53%	9.22%
Investor Class | After Taxes on Distributions and Sales		1.60%	5.13%	8.53%
S&P 500® Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	8.50%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Investor Class shares exceeds 2.75% of the average daily net assets attributable to the Fund's Investor Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 2.75%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label

Element

Value

Investor Class Prospectus | Boston Partners Long/Short Equity Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation while reducing exposure to general equity market risk. The Fund seeks a total return greater than that of the S&P 500^® Index over a full market cycle.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 63% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

63.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage. The Fund invests, both long and short, in securities principally traded in the United States markets. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the United States equity market generally. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund intends, under normal circumstances, to invest at least 80% of its net assets (including borrowings for investment purposes) in equity securities.

Under normal circumstances, the Adviser expects that the Fund's long positions will not exceed approximately 125% of the Fund's net assets.

The Fund's long and short positions may involve (without limit) equity securities of foreign issuers that are traded in the markets of the United States. The Fund may also invest up to 20% of its total assets directly in equity securities of foreign issuers.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by corporations and other business organizations. High yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices.

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Equity Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Investor Class has varied year by year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	38.45% (quarter ended June 30, 2009)
Worst Quarter:	-19.44% (quarter ended December 31, 2008)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

38.45%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.44%)

Performance Table Heading

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Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and past ten calendar years to the average annual total returns of a broad-based securities market index for the same periods. Although the Fund compares its average total return to a broad-based securities market index, the Fund seeks returns that are not correlated to securities market returns. The Fund seeks to achieve a 12-15% return over a full market cycle; however, there can be no guarantee that such returns will be achieved.

Investor Class Prospectus | Boston Partners Long/Short Equity Fund | Investor Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPLEX

Management fees

rr_ManagementFeesOverAssets

2.25%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.14%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.16%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.25%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

3.06%

^[2]

One Year

rr_ExpenseExampleYear01

$ 309

Three Years

rr_ExpenseExampleYear03

945

Five Years

rr_ExpenseExampleYear05

1,606

Ten Years

rr_ExpenseExampleYear10

$ 3,374

Annual Return 2008

rr_AnnualReturn2008

(21.33%)

Annual Return 2009

rr_AnnualReturn2009

80.92%

Annual Return 2010

rr_AnnualReturn2010

26.14%

Annual Return 2011

rr_AnnualReturn2011

5.63%

Annual Return 2012

rr_AnnualReturn2012

12.25%

Annual Return 2013

rr_AnnualReturn2013

7.59%

Annual Return 2014

rr_AnnualReturn2014

4.49%

Annual Return 2015

rr_AnnualReturn2015

(1.39%)

Annual Return 2016

rr_AnnualReturn2016

22.19%

Annual Return 2017

rr_AnnualReturn2017

2.55%

1 Year

rr_AverageAnnualReturnYear01

2.55%

5 Years

rr_AverageAnnualReturnYear05

6.79%

10 Years

rr_AverageAnnualReturnYear10

11.45%

Investor Class Prospectus | Boston Partners Long/Short Equity Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

rr_AverageAnnualReturnYear05

15.79%

10 Years

rr_AverageAnnualReturnYear10

8.50%

Investor Class Prospectus | Boston Partners Long/Short Equity Fund | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

2.34%

^[3]

5 Years

rr_AverageAnnualReturnYear05

5.53%

^[3]

10 Years

rr_AverageAnnualReturnYear10

9.22%

^[3]

Investor Class Prospectus | Boston Partners Long/Short Equity Fund | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

1.60%

5 Years

rr_AverageAnnualReturnYear05

5.13%

10 Years

rr_AverageAnnualReturnYear10

8.53%

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Investor Class shares exceeds 2.75% of the average daily net assets attributable to the Fund's Investor Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and expense reimbursements) are expected to exceed 2.75%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. The Adviser may not recoup any of its waived investment advisory fees.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Investor Class Prospectus | Boston Partners Long/Short Research Fund

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT RESEARCH FUND

Investment Objective

The Fund seeks to provide long-term total return.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners Long/Short Research Fund Investor Class
Management fees	1.25%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.12%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.80%
Interest expense on borrowings	0.06%
Total annual Fund operating expenses	2.49%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners Long/Short Research Fund | Investor Class | USD ($)	252	776	1,326	2,826

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 54% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund uses a hedged strategy. The Fund actively invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales (i.e. sales of securities the Fund does not own) are invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage.

The Fund invests, both long and short, in equity securities issued by large-, mid- and small (or "micro")-cap companies, as well as other instruments that are convertible into equity securities. Equity securities in which the Fund may invest include exchange-traded and over-the-counter common and preferred stocks, warrants, rights, convertible securities, depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Fund may also invest in depository receipts and equity securities of foreign companies (denominated in either U.S. dollars or foreign currencies), put and call options, futures, indexed securities and fixed-income securities (including bonds, notes, asset-backed securities, convertible securities, Eurodollar and Yankee dollar instruments, preferred stocks and money market instruments) and high yield securities (commonly referred to as "junk bonds"). Fixed income securities in which the Fund invests include those rated between AAA and D by a nationally recognized statistical rating organization ("NRSRO"), or deemed of comparable quality by the Adviser. The Adviser may also temporarily invest uninvested cash in money market funds and similar collective investment vehicles. The Fund may also seek to increase its income by lending portfolio securities.

The Adviser determines the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the U.S. equity market by investing less than 100% of its assets in net long positions. Selection of individual securities to be held long or sold short will be based on a mix of quantitative techniques and fundamental security analysis. The Adviser selects stocks on the basis of three criteria: value, fundamental business strength and momentum. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

Although the Fund seeks to follow a hedged strategy, there can be no assurance that the Fund's portfolio or investments will be insulated from market moves or effectively hedged against risk.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The principal derivative instruments in which the Fund invests are futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations (of any rating, including defaulted securities and unrated securities), including bonds and debentures, issued by corporations and business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and financial practices.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may be incorrect in the stocks it buys and believes to be undervalued and in stocks it sells short and believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITS that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 300%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  Indexed Securities Risk. The Fund may invest in indexed securities whose value is linked to securities indices. Most such securities have values that rise and fall according to the change in one or more specified indices and may have characteristics similar to direct investments in the underlying securities. Depending on the index, such securities may have greater volatility than the market as a whole.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an Adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Research Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	8.29% (quarter ended December 31, 2011)
Worst Quarter:	-9.91% (quarter ended September 30, 2011)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners Long/Short Research Fund		1 Year	5 Years	Since Inception	Inception Date
Investor Class		9.80%	7.61%	8.04%	Nov. 29, 2010
Investor Class | After Taxes on Distributions	[1]	9.80%	7.33%	7.80%	Nov. 29, 2010
Investor Class | After Taxes on Distributions and Sales		5.54%	5.96%	6.42%	Nov. 29, 2010
S&P 500® Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	14.50%	Nov. 29, 2010

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to forgo all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total Annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) exceeds 1.75% of the average daily net assets attributable to the Fund's Investor Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total Annual Fund Operating Expenses (after fee waivers and expense reimbursements) are expected to exceed 1.75%.This contractual limitation is in effect until at least February 28, 2019 and may not be terminated without Board approval. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.75% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Label

Element

Value

Investor Class Prospectus | Boston Partners Long/Short Research Fund

Prospectus [Line Items]

rr_ProspectusLineItems

Risk/Return [Heading]

rr_RiskReturnHeading

SUMMARY SECTION — BOSTON PARTNERS LONG/SHORT RESEARCH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide long-term total return.

Expense [Heading]

rr_ExpenseHeading

Expenses and Fees

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 54% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

54.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund uses a hedged strategy. The Fund actively invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales (i.e. sales of securities the Fund does not own) are invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage.

The Fund invests, both long and short, in equity securities issued by large-, mid- and small (or "micro")-cap companies, as well as other instruments that are convertible into equity securities. Equity securities in which the Fund may invest include exchange-traded and over-the-counter common and preferred stocks, warrants, rights, convertible securities, depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Fund may also invest in depository receipts and equity securities of foreign companies (denominated in either U.S. dollars or foreign currencies), put and call options, futures, indexed securities and fixed-income securities (including bonds, notes, asset-backed securities, convertible securities, Eurodollar and Yankee dollar instruments, preferred stocks and money market instruments) and high yield securities (commonly referred to as "junk bonds"). Fixed income securities in which the Fund invests include those rated between AAA and D by a nationally recognized statistical rating organization ("NRSRO"), or deemed of comparable quality by the Adviser. The Adviser may also temporarily invest uninvested cash in money market funds and similar collective investment vehicles. The Fund may also seek to increase its income by lending portfolio securities.

The Adviser determines the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Fund seeks to construct a portfolio that has less volatility than the U.S. equity market by investing less than 100% of its assets in net long positions. Selection of individual securities to be held long or sold short will be based on a mix of quantitative techniques and fundamental security analysis. The Adviser selects stocks on the basis of three criteria: value, fundamental business strength and momentum. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals such as return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

Although the Fund seeks to follow a hedged strategy, there can be no assurance that the Fund's portfolio or investments will be insulated from market moves or effectively hedged against risk.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing less than 25% of its total assets in any one industry, except that the Fund may invest in exchange traded funds to the extent permitted by the Investment Company Act of 1940, as amended ("1940 Act"), and applicable SEC orders.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The principal derivative instruments in which the Fund invests are futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps. The Fund's investments in derivative instruments may be leveraged and result in losses exceeding the amounts invested.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the price of these stocks will not move even lower.

•  High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations (of any rating, including defaulted securities and unrated securities), including bonds and debentures, issued by corporations and business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

•  Foreign Securities Risk. International investing is subject to special risks, including currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and financial practices.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Management Risk. The Fund is subject to the risk of poor stock selection. The Adviser may be incorrect in the stocks it buys and believes to be undervalued and in stocks it sells short and believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio.

•  Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited.

•  Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

•  Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITS that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 300%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  Indexed Securities Risk. The Fund may invest in indexed securities whose value is linked to securities indices. Most such securities have values that rise and fall according to the change in one or more specified indices and may have characteristics similar to direct investments in the underlying securities. Depending on the index, such securities may have greater volatility than the market as a whole.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an Adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

Risk Lose Money [Text]

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Investors may lose money.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below illustrate the long-term performance of the Boston Partners Long/Short Research Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-888-261-4073

Performance Availability Website Address [Text]

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www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	8.29% (quarter ended December 31, 2011)
Worst Quarter:	-9.91% (quarter ended September 30, 2011)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Dec. 31, 2011

Highest Quarterly Return

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8.29%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Sep. 30, 2011

Lowest Quarterly Return

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(9.91%)

Performance Table Heading

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Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Investor Class Prospectus | Boston Partners Long/Short Research Fund | Investor Class

Prospectus [Line Items]

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Management fees

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1.25%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.12%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.80%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.06%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.49%

^[2]

One Year

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$ 252

Three Years

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776

Five Years

rr_ExpenseExampleYear05

1,326

Ten Years

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$ 2,826

Annual Return 2011

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3.12%

Annual Return 2012

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13.13%

Annual Return 2013

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17.45%

Annual Return 2014

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6.86%

Annual Return 2015

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1.27%

Annual Return 2016

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3.40%

Annual Return 2017

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9.80%

1 Year

rr_AverageAnnualReturnYear01

9.80%

5 Years

rr_AverageAnnualReturnYear05

7.61%

Since Inception

rr_AverageAnnualReturnSinceInception

8.04%

Inception Date

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Nov. 29, 2010

Investor Class Prospectus | Boston Partners Long/Short Research Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPRRX

1 Year

rr_AverageAnnualReturnYear01

21.83%

5 Years

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15.79%

Since Inception

rr_AverageAnnualReturnSinceInception

14.50%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 29, 2010

Investor Class Prospectus | Boston Partners Long/Short Research Fund | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

9.80%

^[3]

5 Years

rr_AverageAnnualReturnYear05

7.33%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

7.80%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 29, 2010

^[3]

Investor Class Prospectus | Boston Partners Long/Short Research Fund | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

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1 Year

rr_AverageAnnualReturnYear01

5.54%

5 Years

rr_AverageAnnualReturnYear05

5.96%

Since Inception

rr_AverageAnnualReturnSinceInception

6.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 29, 2010

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to forgo all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total Annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) exceeds 1.75% of the average daily net assets attributable to the Fund's Investor Class shares. Because short sale dividend expenses, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total Annual Fund Operating Expenses (after fee waivers and expense reimbursements) are expected to exceed 1.75%.This contractual limitation is in effect until at least February 28, 2019 and may not be terminated without Board approval. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.75% or the expense cap then in effect, whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Investor Class Prospectus | Boston Partners Global Equity Fund

SUMMARY SECTION — BOSTON PARTNERS GLOBAL EQUITY FUND

Investment Objective

The Fund seeks to provide long-term capital growth.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners Global Equity Fund Investor Class
Management fees	0.90%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.14%
Acquired fund fees and expenses	0.01%	[1]
Total annual Fund operating expenses	1.30%
Fee waiver and/or expense reimbursement	(0.10%)	[2]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	1.20%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners Global Equity Fund | Investor Class | USD ($)	122	402	703	1,559

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund's Institutional Class was 83% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a non-diversified portfolio of equity and equity-related securities issued by U.S. and non-U.S. companies of any capitalization size. The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, participatory notes, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")) and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund generally invests in the equity securities of issuers believed by the Adviser to be undervalued in the marketplace, focusing on issuers that combine attractive valuations with catalysts for change. The Adviser applies a bottom-up stock selection process (i.e., one that focuses primarily on issuer-specific factors) in managing the Fund, using a combination of fundamental and quantitative analysis. In selecting investments for the Fund, the Adviser considers various factors such as price-to-book value, price-to-sales and earnings ratios, dividend yields, strength of management, and cash flow to identify securities that are trading at a price that appears to be lower than the issuer's inherent value.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO").An IPO is a company's first offering of stock to the public. The Fund may also seek to increase its income by lending portfolio securities.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage fund and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Small/Mid-Cap Companies Risk. Investing in securities of companies with micro, small or mid-sized capitalizations tends to be riskier than investing in securities of companies with large capitalizations. Securities of companies with micro, small and mid-sized capitalizations tend to be more volatile than those of large cap companies and, on occasion, may fluctuate in the opposite direction of large cap company securities or the broader stock market averages.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. Redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees in addition to the Fund's own expenses.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Performance Information

As of the date of this Prospectus, the Boston Partners Global Equity Fund's Investor Class has not yet commenced operations. The bar chart and table below illustrate the performance of the Fund's Institutional Class, which is offered in a separate Prospectus. Had the Investor Class been operational during the periods in the chart and table below, it would have had substantially similar annual returns as the Institutional Class because the Investor Class is invested in the same portfolio of securities. Annual returns would differ only to the extent that the Investor Class and Institutional Class do not have the same expenses. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risk of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Years Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	11.70% (quarter ended March 31, 2012)
Worst Quarter:	-9.22% (quarter ended September 30, 2015)

Average Annual Total Returns
for the Period Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners Global Equity Fund		1 Year	5 Years	Since Inception	Inception Date
Investor Class		20.37%	12.75%	13.17%	Dec. 30, 2011
Investor Class | After Taxes on Distributions	[1]	19.79%	12.02%	12.54%	Dec. 30, 2011
Investor Class | After Taxes on Distributions and Sales		12.00%	9.99%	10.52%	Dec. 30, 2011
MSCI World Index (reflects no deduction for fees, expenses or taxes)		23.07%	12.26%	12.96%	Dec. 30, 2011

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.20% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.20%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.20% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Investor Class Prospectus | Boston Partners Global Equity Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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SUMMARY SECTION — BOSTON PARTNERS GLOBAL EQUITY FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The Fund seeks to provide long-term capital growth.

Expense [Heading]

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Expenses and Fees

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

February 28, 2019

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund's Institutional Class was 83% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

83.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the operating expenses of the Fund remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund pursues its objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a non-diversified portfolio of equity and equity-related securities issued by U.S. and non-U.S. companies of any capitalization size. The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, participatory notes, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")) and real estate investment trusts ("REITs"), and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund generally invests in the equity securities of issuers believed by the Adviser to be undervalued in the marketplace, focusing on issuers that combine attractive valuations with catalysts for change. The Adviser applies a bottom-up stock selection process (i.e., one that focuses primarily on issuer-specific factors) in managing the Fund, using a combination of fundamental and quantitative analysis. In selecting investments for the Fund, the Adviser considers various factors such as price-to-book value, price-to-sales and earnings ratios, dividend yields, strength of management, and cash flow to identify securities that are trading at a price that appears to be lower than the issuer's inherent value.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO").An IPO is a company's first offering of stock to the public. The Fund may also seek to increase its income by lending portfolio securities.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objective. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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•  Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the individual stocks in the Fund may not perform as well as expected, and/or the Fund's portfolio management practices do not work to achieve their desired result.

•  Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

•  Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

•  Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

•  Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

•  Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

•  Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations.

•  Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

•  REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage fund and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index.

•  Small/Mid-Cap Companies Risk. Investing in securities of companies with micro, small or mid-sized capitalizations tends to be riskier than investing in securities of companies with large capitalizations. Securities of companies with micro, small and mid-sized capitalizations tend to be more volatile than those of large cap companies and, on occasion, may fluctuate in the opposite direction of large cap company securities or the broader stock market averages.

The small capitalization equity securities in which the Fund invests may be traded only in the over-the- counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. Redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

•  Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker- dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

•  Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees in addition to the Fund's own expenses.

•  Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

•  IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

•  Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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As of the date of this Prospectus, the Boston Partners Global Equity Fund's Investor Class has not yet commenced operations. The bar chart and table below illustrate the performance of the Fund's Institutional Class, which is offered in a separate Prospectus. Had the Investor Class been operational during the periods in the chart and table below, it would have had substantially similar annual returns as the Institutional Class because the Investor Class is invested in the same portfolio of securities. Annual returns would differ only to the extent that the Investor Class and Institutional Class do not have the same expenses. The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risk of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart below shows you how the performance of the Fund's Institutional Class has varied year by year and provides some indication of the risk of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

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Total Returns for the Calendar Years Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	11.70% (quarter ended March 31, 2012)
Worst Quarter:	-9.22% (quarter ended September 30, 2015)

Bar Chart, Returns for Class Not Offered in Prospectus [Text]

rr_BarChartReturnsForClassNotOfferedInProspectus

The bar chart and table below illustrate the performance of the Fund's Institutional Class, which is offered in a separate Prospectus.

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.70%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.22%)

Performance Table Heading

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Average Annual Total Returns
for the Period Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Institutional Class both before and after taxes for the past calendar year, past five calendar years and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Investor Class Prospectus | Boston Partners Global Equity Fund | Investor Class

Prospectus [Line Items]

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Trading Symbol

dei_TradingSymbol

BPGRX

Management fees

rr_ManagementFeesOverAssets

0.90%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.14%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.30%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

^[2]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.20%

One Year

rr_ExpenseExampleYear01

$ 122

Three Years

rr_ExpenseExampleYear03

402

Five Years

rr_ExpenseExampleYear05

703

Ten Years

rr_ExpenseExampleYear10

$ 1,559

Annual Return 2012

rr_AnnualReturn2012

15.34%

Annual Return 2013

rr_AnnualReturn2013

32.67%

Annual Return 2014

rr_AnnualReturn2014

4.34%

Annual Return 2015

rr_AnnualReturn2015

0.80%

Annual Return 2016

rr_AnnualReturn2016

8.50%

Annual Return 2017

rr_AnnualReturn2017

20.37%

1 Year

rr_AverageAnnualReturnYear01

20.37%

5 Years

rr_AverageAnnualReturnYear05

12.75%

Since Inception

rr_AverageAnnualReturnSinceInception

13.17%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

Investor Class Prospectus | Boston Partners Global Equity Fund | MSCI World Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

23.07%

5 Years

rr_AverageAnnualReturnYear05

12.26%

Since Inception

rr_AverageAnnualReturnSinceInception

12.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

Investor Class Prospectus | Boston Partners Global Equity Fund | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

19.79%

^[3]

5 Years

rr_AverageAnnualReturnYear05

12.02%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

12.54%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

^[3]

Investor Class Prospectus | Boston Partners Global Equity Fund | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

12.00%

5 Years

rr_AverageAnnualReturnYear05

9.99%

Since Inception

rr_AverageAnnualReturnSinceInception

10.52%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2011

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses and Total annual Fund operating expenses after fee waiver and/or expense reimbursement shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (excluding certain items discussed below) for the Fund's Investor Class shares exceeds 1.20% of the average daily net assets attributable to the Fund's Investor Class shares. In determining the Adviser's obligation to waive advisory fees and/or reimburse expenses, the following expenses are not taken into account and could cause net Total annual Fund operating expenses to exceed 1.20%: short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expense, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 1.20% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Investor Class Prospectus | Boston Partners Global Long/Short Fund

SUMMARY SECTION — BOSTON PARTNERS GLOBAL LONG/SHORT FUND

Investment Objective

The Fund seeks long-term growth of capital.

Expenses and Fees

This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Annual Fund Operating Expenses	Investor Class Prospectus Boston Partners Global Long/Short Fund Investor Class
Management fees	1.50%
Distribution and/or Service (12b-1) fees	0.25%
Other expenses	0.20%
Acquired fund fees and expenses	0.01%	[1]
Dividend expense on short sales	0.88%
Interest expense on borrowings	0.05%
Total annual Fund operating expenses	2.89%	[2]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and Fund operating expenses remain the same. Although your actual costs and returns might be different, based on these assumptions your costs would be:

Expense Example	One Year	Three Years	Five Years	Ten Years
Investor Class Prospectus | Boston Partners Global Long/Short Fund | Investor Class | USD ($)	292	895	1,523	3,214

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 109% of the average value of its portfolio.

Summary of Principal Investment Strategies

The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage The Fund invests, both long and short, in securities issued by U.S. and non-U.S. companies of any capitalization size.

With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, including return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund's portfolio is rebalanced regularly. The Adviser assesses each investment's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell an investment held long or close out a short position that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

Under normal circumstances, the Adviser expects to sell securities short so that the Fund's portfolio is approximately 50% net long with an average of between 30% and 70% net long.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by U.S. and foreign corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objectives. The Adviser will determine when market conditions warrant temporary defensive measures.

Summary of Principal Risks

• Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

• Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Performance Information

The bar chart and table below illustrate the long-term performance of the Boston Partners Global Long/Short Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Total Returns for the Calendar Year Ended December 31

Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	4.01% (quarter ended June 30, 2015)
Worst Quarter:	-2.26% (quarter ended September 30, 2015)

Average Annual Total Returns
for the Periods Ended December 31, 2017  

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Average Annual Total Returns - Investor Class Prospectus - Boston Partners Global Long/Short Fund		1 Year	Since Inception	Inception Date
Investor Class		7.23%	4.90%	Apr. 11, 2014
Investor Class | After Taxes on Distributions	[1]	7.23%	4.87%	Apr. 11, 2014
Investor Class | After Taxes on Distributions and Sales		4.09%	3.79%	Apr. 11, 2014
MSCI® World Index (reflects no deduction for fees, expenses or taxes)		23.07%	9.33%	Apr. 11, 2014

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Investor Class shares exceeds 2.25% of the average daily net assets attributable to the Fund's Investor Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.25%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.25% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[1] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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Investor Class Prospectus | Boston Partners Global Long/Short Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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SUMMARY SECTION — BOSTON PARTNERS GLOBAL LONG/SHORT FUND

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The Fund seeks long-term growth of capital.

Expense [Heading]

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Expenses and Fees

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Investor Class shares of the Fund.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)    

Fee Waiver or Reimbursement over Assets, Date of Termination

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February 28, 2019

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total annual Fund operating expenses or in the Example, affect the Fund's performance. During the fiscal year ended August 31, 2017, the portfolio turnover rate for the Fund was 109% of the average value of its portfolio.

Portfolio Turnover, Rate

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109.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

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Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and that you sell your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and Fund operating expenses remain the same. Although your actual costs and returns might be different, based on these assumptions your costs would be:

Strategy [Heading]

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Summary of Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund invests in long positions in stocks identified by the Adviser as undervalued and takes short positions in stocks that the Adviser has identified as overvalued. The cash proceeds from short sales will be invested in short-term cash instruments to produce a return on such proceeds just below the federal funds rate. Short sales are considered speculative transactions and a form of leverage The Fund invests, both long and short, in securities issued by U.S. and non-U.S. companies of any capitalization size.

With a long position, the Fund purchases a stock outright; with a short position, the Fund sells a security that it does not own and must borrow to meet its settlement obligations. The Fund may invest in securities of companies operating for three years or less ("unseasoned issuers"). The Adviser will determine the size of each long or short position by analyzing the tradeoff between the attractiveness of each position and its impact on the risk of the overall portfolio. The Adviser examines various factors in determining the value characteristics of such issuers including price-to-book value ratios and price-to-earnings ratios. These value characteristics are examined in the context of the issuer's operating and financial fundamentals, including return on equity, earnings growth and cash flow. The Adviser selects securities for the Fund based on a continuous study of trends in industries and companies, earnings power and growth and other investment criteria.

The Fund may invest in all types of equity and equity-related securities, including without limitation exchange-traded and over-the-counter common and preferred stocks, warrants, options, rights, convertible securities, sponsored and unsponsored depositary receipts and shares, trust certificates, limited partnership interests, shares of other investment companies (including exchanged-traded funds ("ETFs")), real estate investment trusts ("REITs") and equity participations. An equity participation is a type of loan that gives the lender a portion of equity ownership in a property, in addition to principal and interest payments. A convertible security is a bond, debenture, note, preferred stock or other security that may be converted into or exchanged for a prescribed amount of common stock of the same or a different issuer within a particular period of time at a specified price or formula.

The Fund defines non-U.S. companies as companies (i) that are organized under the laws of a foreign country; (ii) whose principal trading market is in a foreign country; or (iii) that have a majority of their assets, or that derive a significant portion of their revenue or profits from businesses, investments or sales, outside of the United States. Under normal market conditions, the Fund invests significantly (ordinarily at least 40% — unless market conditions are not deemed favorable by the Adviser, in which case the Fund would invest at least 30%) in non-U.S. companies. The Fund principally will be invested in issuers located in countries with developed securities markets, but may also invest in issuers located in emerging markets. The Fund will allocate its assets among various regions and countries, including the United States (but in no less than three different countries).

The Fund's portfolio is rebalanced regularly. The Adviser assesses each investment's changing characteristics relative to its contribution to portfolio risk. The Adviser will sell an investment held long or close out a short position that the Adviser believes no longer offers an appropriate return-to-risk tradeoff.

Under normal circumstances, the Adviser expects to sell securities short so that the Fund's portfolio is approximately 50% net long with an average of between 30% and 70% net long.

To meet margin requirements, redemptions or pending investments, the Fund may also temporarily hold a portion of its assets in full faith and credit obligations of the United States government and in short-term notes, commercial paper or other money market instruments.

The Adviser will sell a stock when it no longer meets one or more investment criteria, either through obtaining target value or due to an adverse change in fundamentals or business momentum. Each holding has a target valuation established at purchase, which the Adviser constantly monitors and adjusts as appropriate.

The Fund may participate as a purchaser in initial public offerings of securities ("IPO"). An IPO is a company's first offering of stock to the public.

The Fund may invest from time to time a significant portion of its assets in smaller issuers which are more volatile and less liquid than investments in issuers with larger market capitalizations.

The Fund may invest up to 15% of its net assets in illiquid securities, including securities that are illiquid by virtue of the absence of a readily available market or legal or contractual restrictions on resale.

In general, the Fund's investments are broadly diversified over a number of industries and, as a matter of policy, the Fund is limited to investing a maximum of 25% of its total assets in any one industry.

The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, used by U.S. and foreign corporations and other business organizations (e.g. trusts or limited liability companies). Such high yield debt obligations are not considered to be investment grade. Non-investment grade fixed income securities (commonly known as "junk bonds") are rated BB or lower by Standard & Poor's Rating Group, or have a comparable rating by another nationally recognized statistical rating organization (or, if unrated are determined by the Adviser to be of comparable quality at the time of investment). The Fund may invest in securities of the lowest rating category, including securities in default. The Adviser may, but is not required to, sell a bond or note held by the Fund in the event that its credit rating is downgraded.

The Fund may (but is not required to) invest in derivatives, including put and call options, futures, forward contracts and swaps, in lieu of investing directly in a security, currency or instrument, for hedging and non-hedging purposes.

While the Adviser intends to fully invest the Fund's assets at all times in accordance with the above-mentioned policies, the Fund reserves the right to hold up to 100% of its assets, as a temporary defensive measure, in cash and eligible U.S. dollar-denominated money market instruments and make investments inconsistent with its investment objectives. The Adviser will determine when market conditions warrant temporary defensive measures.

Risk [Heading]

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Summary of Principal Risks

Risk Narrative [Text Block]

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• Management Risk. The Fund is subject to the risk of poor stock selection. In other words, the Adviser may not be successful in its strategy of taking long positions in stocks the manager believes to be undervalued and short positions in stocks the manager believes to be overvalued. Further, since the Adviser will manage both a long and a short portfolio, there is the risk that the Adviser may make more poor investment decisions than an adviser of a typical stock mutual fund with only a long portfolio may make.

• Market Risk. The net asset value ("NAV") of the Fund will change with changes in the market value of its portfolio positions. Investors may lose money. Although the long portfolio of the Fund will invest in stocks the Adviser believes to be undervalued, there is no guarantee that the prices of these stocks will not move even lower.

• High Yield Debt Obligations Risk. The Fund may invest up to 20% of its net assets in high yield debt obligations, such as bonds and debentures, issued by corporations and other business organizations. An issuer of debt obligations may default on its obligation to pay interest and repay principal. Also, changes in the financial strength of an issuer or changes in the credit rating of a security may affect its value. Such high yield debt obligations are referred to as "junk bonds" and are not considered to be investment grade.

• Foreign Securities Risk. International investing is subject to special risks, including, but not limited to, currency exchange rate volatility, political, social or economic instability, and differences in taxation, auditing and other financial practices. The Fund may invest in securities of foreign issuers either directly or through depositary receipts. Depositary receipts may be available through "sponsored" or "unsponsored" facilities. Holders of unsponsored depositary receipts generally bear all of the costs of the unsponsored facility. The depository of an unsponsored facility is frequently under no obligation to distribute shareholder communications received from the issuer of the deposited security or to pass through, to the holders of the receipts, voting rights with respect to the deposited securities. The depository of unsponsored depositary receipts may provide less information to receipt holders. Participatory notes ("P-notes") are derivative instruments used by investors to take positions in certain foreign securities. P-notes present similar risks to investing directly in such securities and also expose investors to counterparty risk.

• Emerging Markets Risk. Investment in emerging market securities involves greater risk than that associated with investment in securities of issuers in developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

• Currency Risk. Investment in foreign securities also involves currency risk associated with securities that trade or are denominated in currencies other than the U.S. dollar and which may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. dollar relative to a foreign currency may cause the U.S. dollar value of an investment in that country to decline. Foreign currencies also are subject to risks caused by inflation, interest rates, budget deficits and low savings rates, political factors and government controls.

• Short Sales Risk. Short sales of securities may result in gains if a security's price declines, but may result in losses if a security's price rises. In a rising market, short positions may be more likely to result in losses because securities sold short may be more likely to increase in value. Short selling also involves the risks of: increased leverage, and its accompanying potential for losses; the potential inability to reacquire a security in a timely manner, or at an acceptable price; the possibility of the lender terminating the loan at any time, forcing the Fund to close the transaction under unfavorable circumstances; the additional costs that may be incurred; and the potential loss of investment flexibility caused by the Fund's obligations to provide collateral to the lender and set aside assets to cover the open position. Short sales "against the box" may protect the Fund against the risk of losses in the value of a portfolio security because any decline in value of the security should be wholly or partially offset by a corresponding gain in the short position. Any potential gains in the security, however, would be wholly or partially offset by a corresponding loss in the short position. Short sales that are not "against the box" involve a form of investment leverage, and the amount of the Fund's loss on a short sale is potentially unlimited. The use of short sales may cause the Fund to have higher expenses than those of other equity mutual funds because of higher transaction costs, premiums, interest or dividends payable to the lender.

• Convertible Securities Risk. Securities that can be converted into common stock, such as certain securities and preferred stock, are subject to the usual risks associated with fixed income investments, such as interest rate risk and credit risk. In addition, because they react to changes in the value of the equity securities into which they will convert, convertible securities are also subject to the risks associated with equity securities.

• Options Risk. An option is a type of derivative instrument that gives the holder the right (but not the obligation) to buy (a "call") or sell (a "put") an asset in the near future at an agreed upon price prior to the expiration date of the option. The Fund may "cover" a call option by owning the security underlying the option or through other means. The value of options can be highly volatile, and their use can result in loss if the Adviser is incorrect in its expectation of price fluctuations. Losses incurred by the Fund in writing options can be potentially unlimited.

• Derivatives Risk. The Fund's investments in derivative instruments, which include futures and options on securities, securities indices or currencies, options on these futures, forward foreign currency contracts and interest rate or currency swaps, may be leveraged and result in losses exceeding the amounts invested.

• REITs Risk. REITs may be affected by economic forces and other factors related to the real estate industry. These risks include possible declines in the value of real estate, possible lack of availability of mortgage funds and unexpected vacancies of properties. REITs that invest in real estate mortgages are also subject to prepayment risk. Investing in REITs may involve risks similar to those associated with investing in small capitalization companies. REITs may have limited financial resources, may trade less frequently and in a limited volume and may be subject to more abrupt or erratic price movements than larger company securities. Historically, small capitalization stocks, such as REITs, have been more volatile in price than the larger capitalization stocks included in the S&P 500^® Index. The Fund will indirectly bear its proportionate share of any expenses, including management fees, paid by an externally managed REIT in which it invests.

• Unseasoned Issuers Risk. Unseasoned issuers may not have an established financial history and may have limited product lines, markets or financial resources. Unseasoned issuers may depend on a few key personnel for management and may be susceptible to losses and risks of bankruptcy. As a result, such securities may be more volatile and difficult to sell.

• Small-Cap Companies Risk. The small capitalization equity securities in which the Fund may invest may be traded only in the over-the-counter market or on a regional securities exchange, may be listed only in the quotation service commonly known as the "pink sheets," and may not be traded every day or in the volume typical of trading on a national securities exchange. These securities may also be subject to wide fluctuations in market value. The trading market for any given small capitalization equity security may be sufficiently small as to make it difficult for the Fund to dispose of a substantial block of such securities. The sale by the Fund of portfolio securities to meet redemptions may require the Fund to sell its small capitalization securities at a discount from market prices or during periods when, in the Adviser's judgment, such sale is not desirable. Moreover, the lack of an efficient market for these securities may make them difficult to value.

• Portfolio Turnover Risk. If the Fund frequently trades its portfolio securities, the Fund will incur higher brokerage commissions and transaction costs, which could lower the Fund's performance. In addition to lower performance, high portfolio turnover could result in taxable capital gains. A portfolio turnover rate of 100% is considered to be high. The annual portfolio turnover rate for the Fund is not expected to exceed 400%; however, it may be higher if the Adviser believes it will improve the Fund's performance.

• Segregated Account Risk. A security held in a segregated account cannot be sold while the position it is covering is outstanding, unless it is replaced with a similar security. As a result, there is a possibility that segregation of a large percentage of the Fund's assets could impede portfolio management or the Fund's ability to meet redemption requests or other current obligations.

• Illiquid Securities Risk. Investing in illiquid securities is subject to certain risks, such as limitations on resale and uncertainty in determining valuation. Limitations on resale may adversely affect the marketability of portfolio securities and the Fund might be unable to dispose of restricted or other illiquid securities promptly or at reasonable prices and might thereby experience difficulty satisfying redemptions within seven days. The Fund might, in order to dispose of restricted securities, have to register securities resulting in additional expense and delay. Adverse market conditions could impede such a public offering of such securities.

• IPO Risk. IPO risk is the risk that the market value of IPO shares will fluctuate considerably due to certain factors, such as the absence of a prior public market, unseasoned trading, the small number of shares available for trading and limited information about the issuer. The purchase of IPO shares may involve high transaction costs. IPO shares are subject to market risk and liquidity risk. When the Fund's asset base is small, a significant portion of the Fund's performance could be attributable to investments in IPOs, because such investments would have a magnified impact on the Fund. As the Fund's assets grow, the effect of the Fund's investments in IPOs on the Fund's performance probably will decline, which could reduce the Fund's performance. Because of the price volatility of IPO shares, the Fund may choose to hold IPO shares for a very short period of time. This may increase the turnover of the Fund's portfolio and may lead to increased expenses to the Fund, such as commissions and transaction costs. In addition, the Adviser cannot guarantee continued access to IPOs.

• Securities Lending Risk. The Fund may lend portfolio securities to institutions, such as certain broker-dealers. The Fund may experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

• Exchange-Traded Fund Risk. Exchange-traded funds ("ETFs") are a type of investment company bought and sold on a securities exchange. An ETF typically represents a fixed portfolio of securities designed to track a particular market index. The risks of owning an ETF generally reflect the risks of owning the underlying securities that they are designed to track, although lack of liquidity in an ETF could result in its being more volatile. Some ETFs are actively-managed by an investment adviser and/or sub-advisers. Actively-managed ETFs are subject to the risk of poor investment selection. The Fund may incur brokerage fees in connection with its purchase of ETF shares. The purchase of shares of ETFs may result in duplication of expenses, including advisory fees, in addition to the Fund's own expenses.

• Non-Diversification Risk. The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

Investors may lose money.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is non-diversified. Compared to other funds, the Fund may invest more of its assets in a smaller number of companies. Gains or losses on a single stock may have greater impact on the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the long-term performance of the Boston Partners Global Long/Short Fund's Investor Class. The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund. The bar chart assumes reinvestment of dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Performance reflects fee waivers in effect. If fee waivers were not in place, the Fund's performance would be reduced. Updated performance information is available at www.boston-partners.com or 1-888-261-4073.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart below shows you how the performance of the Fund's Investor Class has varied year to year and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-888-261-4073

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.boston-partners.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

As with all such investments, past performance (before and after taxes) is not an indication of future results.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for the Calendar Year Ended December 31

Bar Chart Closing [Text Block]

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Best and Worst Quarterly Performance (for the periods reflected in the chart above):

Best Quarter:	4.01% (quarter ended June 30, 2015)
Worst Quarter:	-2.26% (quarter ended September 30, 2015)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2015

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

4.01%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2015

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.26%)

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
for the Periods Ended December 31, 2017  

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

The table below compares the average annual total returns for the Fund's Investor Class both before and after taxes for the past calendar year and since inception to the average annual total returns of a broad-based securities market index for the same periods.

Investor Class Prospectus | Boston Partners Global Long/Short Fund | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

Trading Symbol

dei_TradingSymbol

BGRSX

Management fees

rr_ManagementFeesOverAssets

1.50%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.20%

Dividend expense on short sales

rbb_DividendExpenseOnShortSales

0.88%

Interest expense on borrowings

rbb_InterestExpenseOnBorrowings

0.05%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.89%

^[2]

One Year

rr_ExpenseExampleYear01

$ 292

Three Years

rr_ExpenseExampleYear03

895

Five Years

rr_ExpenseExampleYear05

1,523

Ten Years

rr_ExpenseExampleYear10

$ 3,214

Annual Return 2015

rr_AnnualReturn2015

6.26%

Annual Return 2016

rr_AnnualReturn2016

2.09%

Annual Return 2017

rr_AnnualReturn2017

7.23%

1 Year

rr_AverageAnnualReturnYear01

7.23%

Since Inception

rr_AverageAnnualReturnSinceInception

4.90%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 11, 2014

Investor Class Prospectus | Boston Partners Global Long/Short Fund | MSCI® World Index (reflects no deduction for fees, expenses or taxes)

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

23.07%

Since Inception

rr_AverageAnnualReturnSinceInception

9.33%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 11, 2014

Investor Class Prospectus | Boston Partners Global Long/Short Fund | After Taxes on Distributions | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

7.23%

^[3]

Since Inception

rr_AverageAnnualReturnSinceInception

4.87%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 11, 2014

^[3]

Investor Class Prospectus | Boston Partners Global Long/Short Fund | After Taxes on Distributions and Sales | Investor Class

Prospectus [Line Items]

rr_ProspectusLineItems

1 Year

rr_AverageAnnualReturnYear01

4.09%

Since Inception

rr_AverageAnnualReturnSinceInception

3.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 11, 2014

[1] Acquired fund fees and expenses are indirect fees and expenses that the Fund incurs from investing in the shares of other mutual funds, including money market funds and exchange traded funds. Please note that the amount of Total annual Fund operating expenses shown in the above table will differ from the "Financial Highlights" section of the prospectus, which reflects the operating expenses of the Fund and does not include indirect expenses such as acquired fund fees and expenses.

[2] The Fund's Adviser has contractually agreed to waive all or a portion of its advisory fee and/or reimburse expenses in an aggregate amount equal to the amount by which the Total annual Fund operating expenses (other than short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for the Fund's Investor Class shares exceeds 2.25% of the average daily net assets attributable to the Fund's Investor Class shares. Because dividend expenses on short sales, brokerage commissions, extraordinary items, interest and taxes are excluded from the expense limitation, Total annual Fund operating expenses (after fee waivers and/or expense reimbursements) are expected to exceed 2.25%. This contractual limitation is in effect until February 28, 2019 and may not be terminated without the approval of the Board of Directors of The RBB Fund, Inc. If at any time the Fund's Total annual Fund operating expenses (not including short sale dividend expenses, brokerage commissions, extraordinary items, interest or taxes) for a year are less than 2.25% or the expense cap then in effect, or whichever is less, the Adviser is entitled to reimbursement by the Fund of the advisory fees waived and other payments remitted by the Adviser to the Fund within three years from the date on which such waiver or reimbursement was made, provided such reimbursement does not cause the Fund to exceed expense limitations that were in effect at the time of the waiver or reimbursement.

[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

XML

Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Aug. 31, 2017
Registrant Name	dei_EntityRegistrantName	RBB FUND, INC.
Central Index Key	dei_EntityCentralIndexKey	0000831114
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Feb. 23, 2018
Document Effective Date	dei_DocumentEffectiveDate	Feb. 23, 2018
Prospectus Date	rr_ProspectusDate	Feb. 22, 2018