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Risk Return [Abstract] rr_RiskReturnAbstract  
ProspectusDate rr_ProspectusDate Jan. 13, 2012
Robeco Boston Partners Long/Short Research Fund (First Prospectus Summary) | Robeco Boston Partners Long/Short Research Fund
  
Risk Return [Abstract] rr_RiskReturnAbstract  
Risk/Return, Heading rr_RiskReturnHeading SUMMARY SECTION
Investment Objective, Heading rr_ObjectiveHeading Investment Objective
investment Objective, Primary rr_ObjectivePrimaryTextBlock 
The Fund seeks to provide long-term total return.
Expense, Heading rr_ExpenseHeading Expenses and Fees
Expense, Narrative rr_ExpenseNarrativeTextBlock 
This table describes the fees and expenses that you may pay if you buy and hold
Institutional Class shares of the Fund.
Shareholder Fees, Caption rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses, Caption rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that that you pay each year as a percentage of the value of your investment)
Portfolio Turnover, Heading rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover 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, 2011, the portfolio
turnover rate for the Fund was 61%.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 61.00%
Expense Example, Heading rr_ExpenseExampleHeading Example
Expense Example, Narrative 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:
Investment Strategy, Heading rr_StrategyHeading Summary of Principal Investment Strategies
Investment Strategy, Narrative rr_StrategyNarrativeTextBlock 
The Fund will use a hedged strategy. The Fund actively invests in long positions
in stocks identified by Robeco as undervalued and takes short positions in
stocks that Robeco has identified as overvalued. The cash proceeds from short
sales (i.e. sales of securities the Fund does not own) will be invested in
short-term cash instruments to produce a return on such proceeds just below the
federal funds rate.

The Fund will invest, 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 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, mortgage-backed securities, 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 will
invest include those rated between AAA and D by a nationally recognized
statistical rating organization ("NRSRO"), or deemed of comparable quality by
Robeco. Robeco 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.

Robeco 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 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. Robeco selects stocks on the basis of three criteria: value,
fundamental business strength and momentum. Robeco 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. Robeco 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 will seek 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 up to 30% in exchange-traded funds to the extent permitted by the
Investment Company Act of 1940 ("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 Robeco 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. Robeco will determine
when market conditions warrant temporary defensive measures.
Risk, Heading rr_RiskHeading Summary of Principal Risks
Risk, Narrative rr_RiskNarrativeTextBlock 
o 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 Robeco believes to
be undervalued, there is no guarantee that the price of these stocks will not
move even lower.

o 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.

o 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.

o 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.

o Management Risk. The Fund is subject to the risk of poor stock selection.
Robeco 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 Robeco
will manage both a long and a short portfolio, there is the risk that Robeco may
make more poor investment decisions than an adviser of a typical stock mutual
fund with only a long portfolio.

o 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.

o 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.

o 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 Robeco's judgment, such sale is not
desirable. Moreover, the lack of an efficient market for these securities may
make them difficult to value.

o REITs Risk. REITs may be affected by economic forces and other factors related
to the real estate industry. 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.

o 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. The
annual portfolio turnover rate for the Fund is not expected to exceed 300%;
however, it may be higher if Robeco believes it will improve the Fund's
performance.

o 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.

o 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.

o 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.

o 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.

o Exchange Traded Fund Risk. Exchange traded funds ("ETFs") are a type of
investment company bought and sold on a securities exchange. An ETF 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. The Fund may incur brokerage fees in
connection with its purchase of ETF shares.
Risk, Lose Money rr_RiskLoseMoney Investors may lose money.
Bar Chart and Performance Table, Heading rr_BarChartAndPerformanceTableHeading Performance Information
Performance, Narrative rr_PerformanceNarrativeTextBlock 
No performance information is available for the Fund because it has not been in
operation for a full calendar year. The performance information, when available,
will provide some indication of the risks of investing in the Fund. The Fund
intends to evaluate its performance as compared to that of the Standard & Poor's
500 Index. Updated performance information is available at www.robecoinvest.com
or 1-888-261-4073.
Performance, One Year or Less rr_PerformanceOneYearOrLess No performance information is available for the Fund because it has not been in operation for a full calendar year.
Performance, Availability Phone Number rr_PerformanceAvailabilityPhone 1-888-261-4073
Performance, Availability Website Address rr_PerformanceAvailabilityWebSiteAddress www.robecoinvest.com
Robeco Boston Partners Long/Short Research Fund (First Prospectus Summary) | Robeco Boston Partners Long/Short Research Fund | Institutional Class
  
Risk Return [Abstract] rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption fee (as a percentage of amount redeemed on shares held for less than 60 days, if applicable) rr_RedemptionFeeOverRedemption (1.00%)
Exchange fee (as a percentage of amount exchanged on shares held for less than 60 days, if applicable) rr_ExchangeFeeOverRedemption 1.00%
Management fees rr_ManagementFeesOverAssets 1.25%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Dividend expense on short sales rr_Component1OtherExpensesOverAssets 0.45%
Interest expense on borrowings rr_Component2OtherExpensesOverAssets 0.51%
Other operating expenses rr_Component3OtherExpensesOverAssets 1.99%
Total other expenses rr_OtherExpensesOverAssets 2.95%
Total annual Fund operating expenses rr_ExpensesOverAssets 4.20%
Fees forgone and expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (1.74%) [1]
Net expenses (includes dividend expenses on short sales and interest expense on borrowings) rr_NetExpensesOverAssets 2.46%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 2012-12-31
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 249
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 1,117
Expense Example, With Redemption, 5 Years rr_ExpenseExampleYear05 2,000
Expense Example, With Redemption, 10 Years rr_ExpenseExampleYear10 4,268
[1] The Fund's investment adviser, Robeco Investment Management, Inc. ("Robeco"), 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 acquired fund fees and expenses, 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 acquired fund fees and expenses, 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 December 31, 2012 and may not be terminated without Board approval. If at any time during the first three years the Fund's Advisory Agreement with Robeco is in effect, the Fund's Total annual Fund operating expenses for that year are less than 1.50%, Robeco is entitled to reimbursement by the Fund of the advisory fees forgone and other payments remitted by Robeco to the Fund during such three-year period.