485BPOS

Registration Nos. 333-39133

811-06241

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	¨
Pre-Effective Amendment No.	¨
Post-Effective Amendment No. 62	x

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	¨
Amendment No. 65	x

(Check appropriate box or boxes.)

LOOMIS SAYLES FUNDS II

(Exact Name of Registrant as Specified in Charter)

399 Boylston Street, Boston, Massachusetts 02116

(Address of principal executive offices)                (Zip Code)

(617) 449-2810

Registrant’s Telephone Number, including Area Code

Copy to:

Coleen Downs Dinneen, Esq. Natixis Distribution, L.P. 399 Boylston Street Boston, Massachusetts 02116	John M. Loder, Esq. Ropes & Gray One International Place Boston, Massachusetts 02110
(Name and Address of Agent for Service)

Approximate Date of Public Offering

It is proposed that this filing will become effective (check appropriate box):

x Immediately upon filing pursuant to paragraph (b)

¨ On February 1, 2012 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.

LOOMIS SAYLES FUNDS II

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this registration statement under Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment No. 62 to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Boston, and the Commonwealth of Massachusetts on the 21st day of February, 2012.

LOOMIS SAYLES FUNDS II
By:	/s/ David L. Giunta
	David L. Giunta
	President

Pursuant to the requirements of the Securities Act of 1933, as amended, this amendment to the Registration Statement has been signed below by the following persons in the capacities and on the date indicated.

Signature	Title	Date
/s/ David L. Giunta
David L. Giunta	President and Trustee	February 21, 2012
/s/ Michael C. Kardok
Michael C. Kardok	Treasurer	February 21, 2012
Graham T. Allison, Jr.*
Graham T. Allison, Jr.	Trustee	February 21, 2012
Charles D. Baker*
Charles D. Baker	Trustee	February 21, 2012
Robert J. Blanding*
Robert J. Blanding	Trustee	February 21, 2012
Daniel M. Cain*
Daniel M. Cain	Trustee	February 21, 2012
Kenneth A. Drucker*
Kenneth A. Drucker	Trustee	February 21, 2012
John T. Hailer*
John T. Hailer	Trustee	February 21, 2012
Wendell J. Knox *
Wendell J. Knox	Trustee	February 21, 2012

Sandra O. Moose*
Sandra O. Moose	Trustee, Chairperson of the Board	February 21, 2012
Erik R. Sirri *
Erik R. Sirri	Trustee	February 21, 2012
Peter J. Smail *
Peter J. Smail	Trustee	February 21, 2012
Cynthia L. Walker*
Cynthia L. Walker	Trustee	February 21, 2012

*By:	/s/ Coleen Downs Dinneen
Coleen Downs Dinneen
Attorney-In-Fact(a),(b),(c),(d),(e),(f)
February 21, 2012

^(a)  Powers of Attorney for Graham T. Allison, Jr., Daniel M. Cain, John T. Hailer, Robert Blanding and Sandra O. Moose are incorporated by reference to exhibit (q) to PEA No. 37 to the Registration Statement filed on December 2, 2004.

^(b)  Power of Attorney for Cynthia L. Walker is incorporated by reference to exhibit (q)(2) to PEA No. 39 to the Registration Statement filed on December 2, 2005.

^(c)  Power of Attorney for Kenneth A. Drucker is incorporated by reference to exhibit (q)(4) to PEA No. 50 to the Registration Statement filed on July 17, 2008.

^(d)  Power of Attorney for Wendell J. Knox is incorporated by reference to exhibit (q)(4) to PEA No. 55 to the Registration Statement filed on November 23, 2009.

^(e)  Powers of Attorney for Erik R. Sirri and Peter J. Smail are incorporated by reference to exhibits (q)(5) and (q)(6), respectively, to PEA No. 56 to the Registration Statement filed on January 28, 2010.

^(f)  Power of Attorney for Charles D. Baker is incorporated by reference to exhibit (q)(7) to PEA No. 57 to the Registration Statement filed on January 28, 2011.

Loomis Sayles Funds II

Exhibit Index

Exhibits for Item 28 of Form N-1A

Exhibit	Exhibit Description
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Limited Term Government and Agency Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.00%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.46%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.21%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.92%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

0.85%

1 year

rr_ExpenseExampleYear01

384

3 years

rr_ExpenseExampleYear03

578

5 years

rr_ExpenseExampleYear05

787

10 years

rr_ExpenseExampleYear10

1,391

1 year

rr_ExpenseExampleNoRedemptionYear01

384

3 years

rr_ExpenseExampleNoRedemptionYear03

578

5 years

rr_ExpenseExampleNoRedemptionYear05

787

10 years

rr_ExpenseExampleNoRedemptionYear10

1,391

Annual Return 2002

rr_AnnualReturn2002

8.18%

Annual Return 2003

rr_AnnualReturn2003

1.50%

Annual Return 2004

rr_AnnualReturn2004

2.00%

Annual Return 2005

rr_AnnualReturn2005

1.18%

Annual Return 2006

rr_AnnualReturn2006

3.80%

Annual Return 2007

rr_AnnualReturn2007

5.23%

Annual Return 2008

rr_AnnualReturn2008

4.61%

Annual Return 2009

rr_AnnualReturn2009

7.73%

Annual Return 2010

rr_AnnualReturn2010

5.13%

Annual Return 2011

rr_AnnualReturn2011

2.59%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2002

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

3.55%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2004

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(1.76%)

Past 1 Year

rr_AverageAnnualReturnYear01

(0.51%)

Past 5 Years

rr_AverageAnnualReturnYear05

4.41%

Past 10 Years

rr_AverageAnnualReturnYear10

3.85%

Loomis Sayles Limited Term Government and Agency Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(1.33%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.20%

Past 10 Years

rr_AverageAnnualReturnYear10

2.53%

Loomis Sayles Limited Term Government and Agency Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(0.33%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.06%

Past 10 Years

rr_AverageAnnualReturnYear10

2.50%

Loomis Sayles Limited Term Government and Agency Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.46%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.22%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.68%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.08%

^[1]

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

rr_NetExpensesOverAssets

1.60%

1 year

rr_ExpenseExampleYear01

663

3 years

rr_ExpenseExampleYear03

822

5 years

rr_ExpenseExampleYear05

1,105

10 years

rr_ExpenseExampleYear10

1,778

1 year

rr_ExpenseExampleNoRedemptionYear01

163

3 years

rr_ExpenseExampleNoRedemptionYear03

522

5 years

rr_ExpenseExampleNoRedemptionYear05

905

10 years

rr_ExpenseExampleNoRedemptionYear10

1,778

Past 1 Year

rr_AverageAnnualReturnYear01

(3.17%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.93%

Past 10 Years

rr_AverageAnnualReturnYear10

3.42%

Loomis Sayles Limited Term Government and Agency Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.46%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.21%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

1.60%

1 year

rr_ExpenseExampleYear01

263

3 years

rr_ExpenseExampleYear03

520

5 years

rr_ExpenseExampleYear05

901

10 years

rr_ExpenseExampleYear10

1,970

1 year

rr_ExpenseExampleNoRedemptionYear01

163

3 years

rr_ExpenseExampleNoRedemptionYear03

520

5 years

rr_ExpenseExampleNoRedemptionYear05

901

10 years

rr_ExpenseExampleNoRedemptionYear10

1,970

Past 1 Year

rr_AverageAnnualReturnYear01

0.83%

Past 5 Years

rr_AverageAnnualReturnYear05

4.29%

Past 10 Years

rr_AverageAnnualReturnYear10

3.43%

Loomis Sayles Limited Term Government and Agency Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.46%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.21%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

0.60%

1 year

rr_ExpenseExampleYear01

61

3 years

rr_ExpenseExampleYear03

207

5 years

rr_ExpenseExampleYear05

366

10 years

rr_ExpenseExampleYear10

828

1 year

rr_ExpenseExampleNoRedemptionYear01

61

3 years

rr_ExpenseExampleNoRedemptionYear03

207

5 years

rr_ExpenseExampleNoRedemptionYear05

366

10 years

rr_ExpenseExampleNoRedemptionYear10

828

Past 1 Year

rr_AverageAnnualReturnYear01

2.85%

Past 5 Years

rr_AverageAnnualReturnYear05

5.33%

Past 10 Years

rr_AverageAnnualReturnYear10

4.45%

Loomis Sayles Limited Term Government and Agency Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Limited Term Government and Agency Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks high current return consistent with preservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 66% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

66.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investments issued or guaranteed by the U.S. government, its agencies or instrumentalities. The Adviser follows a total return-oriented investment approach in selecting securities for the Fund. It seeks securities that will provide the Fund with an average credit quality equal to the credit rating of the U.S. Government's long-term debt and an effective portfolio duration range of two to four years (although not all securities selected will have these characteristics and the Adviser may look for other characteristics if market conditions change). The Fund may invest in securities with credit quality above or below the credit rating of the U.S. Government's long-term debt. In determining credit quality, the Adviser will look to the highest credit rating assigned by Standard & Poor's Ratings Group ("S&P"), Fitch Investor Services, Inc. ("Fitch") or Moody's Investors Service, Inc. ("Moody's"). In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser's research analysts work closely with the Fund's portfolio managers to develop an outlook on the economy from research produced by various financial firms and specific forecasting services or from economic data released by the U.S. and foreign governments as well as the Federal Reserve Bank. The analysts also conduct a thorough review of individual securities to identify what they consider attractive values in the U.S. government security marketplace through the use of quantitative tools such as internal and external computer systems and software. The Adviser continuously monitors an issuer's creditworthiness to assess whether the obligation remains an appropriate investment for the Fund. The Adviser seeks to balance opportunities for yield and price performance by combining macroeconomic analysis with individual security selection. It emphasizes securities that tend to perform particularly well in response to interest rate changes, such as U.S. Treasury securities in a declining interest rate environment and mortgage-backed or U.S. government agency securities in a steady or rising interest rate environment. The Adviser seeks to increase the opportunity for higher yields while maintaining the greater price stability that intermediate-term bonds have compared to bonds with longer maturities. In connection with its principal investment strategies, the Fund may also invest in investment-grade corporate notes and bonds, zero-coupon bonds, Rule 144A securities, structured notes, foreign bonds denominated in U.S. dollars, asset-backed securities, mortgage-related securities including mortgage dollar rolls and futures. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Agency Securities Risk: Agency securities are subject to fixed-income securities risk. Certain debt securities issued or guaranteed by agencies of the U.S. government are guaranteed as to the payment of principal and interest by the relevant entity but have not been backed by the full faith and credit of the U.S. government. Instead, they have been supported only by the discretionary authority of the U.S. government to purchase the agency's obligations. An event affecting the guaranteeing entity could adversely affect the payment of principal or interest or both on the security and, therefore, these types of securities should be considered to be riskier than U.S. government securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The Fund's use of derivatives such as futures transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

       

Highest Quarterly Return:
Second Quarter 2002, 3.55%

Lowest Quarterly Return:
Second Quarter 2004, -1.76%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund's current adviser assumed that function on September 1, 2003. Prior to that, it served as subadviser to the Fund, a role it assumed in June 2001. The returns shown in the bar chart and table for periods prior to September 15, 2003 reflect the results of the CDC Nvest Limited Term U.S. Government Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Limited Term Government and Agency Fund | Barclays Capital U.S. 1-5 Year Government Bond Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

3.21%

Past 5 Years

rr_AverageAnnualReturnYear05

4.76%

Past 10 Years

rr_AverageAnnualReturnYear10

4.05%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.85%, 1.60%, 1.60% and 0.60% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 0.85%, 1.60%, 1.60% and 0.60% of the Fund's average daily net assets for Class A, B, C, and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Small Cap Growth Fund | Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.23%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.98%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

0.98%

1 year

rr_ExpenseExampleYear01

100

3 years

rr_ExpenseExampleYear03

312

5 years

rr_ExpenseExampleYear05

542

10 years

rr_ExpenseExampleYear10

1,201

Annual Return 2002

rr_AnnualReturn2002

(41.56%)

Annual Return 2003

rr_AnnualReturn2003

43.32%

Annual Return 2004

rr_AnnualReturn2004

9.43%

Annual Return 2005

rr_AnnualReturn2005

10.69%

Annual Return 2006

rr_AnnualReturn2006

14.31%

Annual Return 2007

rr_AnnualReturn2007

24.26%

Annual Return 2008

rr_AnnualReturn2008

(39.80%)

Annual Return 2009

rr_AnnualReturn2009

31.90%

Annual Return 2010

rr_AnnualReturn2010

31.40%

Annual Return 2011

rr_AnnualReturn2011

3.20%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

best quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

25.29%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

worst quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.86%)

One Year

rr_AverageAnnualReturnYear01

3.20%

Five Years

rr_AverageAnnualReturnYear05

6.00%

Ten Years

rr_AverageAnnualReturnYear10

4.49%

Life-of-Fund

rr_AverageAnnualReturnSinceInception

4.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

Loomis Sayles Small Cap Growth Fund | Institutional Class | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

3.20%

Five Years

rr_AverageAnnualReturnYear05

6.00%

Ten Years

rr_AverageAnnualReturnYear10

4.49%

Life-of-Fund

rr_AverageAnnualReturnSinceInception

4.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

Loomis Sayles Small Cap Growth Fund | Institutional Class | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

2.08%

Five Years

rr_AverageAnnualReturnYear05

5.18%

Ten Years

rr_AverageAnnualReturnYear10

3.92%

Life-of-Fund

rr_AverageAnnualReturnSinceInception

3.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

Loomis Sayles Small Cap Growth Fund | Retail Class

Risk/Return:

rr_RiskReturnAbstract

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.27%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.27%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.02%

^[1]

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

rr_NetExpensesOverAssets

1.25%

1 year

rr_ExpenseExampleYear01

127

3 years

rr_ExpenseExampleYear03

401

5 years

rr_ExpenseExampleYear05

695

10 years

rr_ExpenseExampleYear10

1,532

One Year

rr_AverageAnnualReturnYear01

2.88%

Five Years

rr_AverageAnnualReturnYear05

5.73%

Ten Years

rr_AverageAnnualReturnYear10

4.23%

Life-of-Fund

rr_AverageAnnualReturnSinceInception

4.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

Loomis Sayles Small Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Small Cap Growth Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund's investment objective is long-term capital growth from investments in common stocks or other equity securities.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

The Fund does not impose a sales charge, a redemption fee or an exchange fee.

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 76% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

76.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

The 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 then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and the Fund's operating expenses remain the same. The example for the Institutional Class shares is based on Total Annual Operating Expenses for all periods. The example for Retail Class shares is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in the equity securities of "small-cap companies," including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in an entity. Currently, the Fund defines a small-cap company to be one whose market capitalization either falls within the capitalization range of the Russell 2000 Index, an index that tracks stocks of 2,000 of the smallest U.S. companies, or is $3 billion or less at the time of investment. The Fund may invest the rest of its assets in companies of any size, including large-capitalization companies.

In deciding which securities to buy and sell, Loomis Sayles typically seeks to identify companies that it believes have distinctive products, technologies, or services; dynamic earnings growth; prospects for high levels of profitability; and solid management. Loomis Sayles typically does not consider current income when making buy/sell decisions.

The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. The Fund may also invest in Rule 144A securities.

The Fund may engage in foreign currency transactions, options (for hedging and investment purposes) and futures transactions.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund.

Credit Risk is the risk that the issuer or guarantor of a fixed-income security in which the Fund invests, or the counterparty to a derivatives or other transaction will fail financially or otherwise be unwilling or unable to meet their obligations to the Fund.

Currency Risk is the risk that the value of the Fund's investments will fall as a result of changes in exchange rates. Loomis Sayles may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged.

Derivatives Risk is the risk that the value of the Fund's derivative investments such as forward currency contracts and options and futures transactions will fall, for example, because of changes in the value of the underlying reference instruments, pricing difficulties or lack of correlation with the underlying investments. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. This risk is greater for forward currency contracts and other over-the-counter traded derivatives. Investing in derivatives gives rise to other risks, such as leverage risk, liquidity risk, credit risk, counterparty risk, interest rate risk and market risk. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used.

Emerging Markets Risk is the risk that the Fund's investments may face greater foreign securities risk. Investing in companies traded in emerging securities markets, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets.

Equity Securities Risk is the risk that the value of a stock may decline for a number of reasons which relate directly to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services, or the equity markets generally. Growth stocks are generally more sensitive to market movements than other types of stocks, primarily because their stock prices are based heavily on future expectations. If Loomis Sayles' assessment of the prospects for a company's growth is wrong, or if Loomis Sayles' judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that Loomis Sayles has placed on it.

Foreign Securities Risk is the risk that the value of the Fund's foreign investments will fall as a result of foreign political, social, economic or currency changes or other issues relating to foreign investing generally. The Fund's investments in foreign securities may be subject to foreign withholding taxes, which would decrease the yield on those securities.

Issuer Risk is the risk that the value of securities may decline due to a number of reasons relating to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services.

Leverage Risk is the risk associated with securities or practices (e.g., borrowing and the use of certain derivatives) and investment in certain types of derivatives that multiply small index or market movements into larger changes in value. Use of derivative instruments may involve leverage. When a derivative is used as a hedge against an offsetting position that the Fund also holds, any loss generated by the derivative should be substantially offset by gains on the hedged instrument, and vice versa. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. Futures and forward currency contracts are derivatives and may be subject to this type of risk.

Liquidity Risk is the risk that the Fund may be unable to find a buyer for its investments when it seeks to sell them or to receive the price it expects. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk is the risk that Loomis Sayles' investment techniques will be unsuccessful and cause the Fund to incur losses.

Market Risk is the risk that the market value of a security may move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions.

Small-Capitalization Companies Risk is the risk that the Fund's investments may be subject to more abrupt price movements, limited markets, increased volatility and less liquidity than investments in larger, more established companies, which could adversely affect the value of the portfolio.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following bar chart and table give an indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for the one-year, five-year, ten-year and life-of-fund periods compare to those of broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at www.loomissayles.com and/or by calling the Fund toll-free at 800-633-3330.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table give an indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for the one-year, five-year, ten-year and life-of-fund periods compare to those of broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-633-3330

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.loomissayles.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Institutional Class Shares

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

The Fund's best quarter was 25.29%, (second quarter of 2003), and the Fund's worst quarter was -26.86%, (fourth quarter of 2008).

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns for the periods ended December 31, 2011

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for the Institutional Class of the Fund. After-tax returns for other classes of the Fund will vary.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for the Institutional Class of the Fund. After-tax returns for other classes of the Fund will vary.

Loomis Sayles Small Cap Growth Fund | Russell 2000 Growth Index

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

(2.91%)

Five Years

rr_AverageAnnualReturnYear05

2.09%

Ten Years

rr_AverageAnnualReturnYear10

4.48%

Life-of-Fund

rr_AverageAnnualReturnSinceInception

3.94%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.00% and 1.25% of the Fund's average daily net assets for Institutional Class shares and Retail Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.00% and 1.25% of the Fund's average daily net assets for Institutional Class shares and Retail Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Value Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.23%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.98%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

0.98%

1 year

rr_ExpenseExampleYear01

669

3 years

rr_ExpenseExampleYear03

869

5 years

rr_ExpenseExampleYear05

1,086

10 years

rr_ExpenseExampleYear10

1,707

1 year

rr_ExpenseExampleNoRedemptionYear01

669

3 years

rr_ExpenseExampleNoRedemptionYear03

869

5 years

rr_ExpenseExampleNoRedemptionYear05

1,086

10 years

rr_ExpenseExampleNoRedemptionYear10

1,707

Past 1 Year

rr_AverageAnnualReturnYear01

(8.58%)

Past 5 Years

rr_AverageAnnualReturnYear05

(3.01%)

Past 10 Years

rr_AverageAnnualReturnYear10

3.74%

Loomis Sayles Value Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.23%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.73%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.73%

1 year

rr_ExpenseExampleYear01

676

3 years

rr_ExpenseExampleYear03

845

5 years

rr_ExpenseExampleYear05

1,139

10 years

rr_ExpenseExampleYear10

1,842

1 year

rr_ExpenseExampleNoRedemptionYear01

176

3 years

rr_ExpenseExampleNoRedemptionYear03

545

5 years

rr_ExpenseExampleNoRedemptionYear05

939

10 years

rr_ExpenseExampleNoRedemptionYear10

1,842

Past 1 Year

rr_AverageAnnualReturnYear01

(8.61%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.95%)

Past 10 Years

rr_AverageAnnualReturnYear10

3.48%

Loomis Sayles Value Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.23%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.73%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.73%

1 year

rr_ExpenseExampleYear01

276

3 years

rr_ExpenseExampleYear03

545

5 years

rr_ExpenseExampleYear05

939

10 years

rr_ExpenseExampleYear10

2,041

1 year

rr_ExpenseExampleNoRedemptionYear01

176

3 years

rr_ExpenseExampleNoRedemptionYear03

545

5 years

rr_ExpenseExampleNoRedemptionYear05

939

10 years

rr_ExpenseExampleNoRedemptionYear10

2,041

Past 1 Year

rr_AverageAnnualReturnYear01

(4.71%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.57%)

Past 10 Years

rr_AverageAnnualReturnYear10

3.49%

Loomis Sayles Value Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.74%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

0.74%

1 year

rr_ExpenseExampleYear01

76

3 years

rr_ExpenseExampleYear03

237

5 years

rr_ExpenseExampleYear05

411

10 years

rr_ExpenseExampleYear10

918

1 year

rr_ExpenseExampleNoRedemptionYear01

76

3 years

rr_ExpenseExampleNoRedemptionYear03

237

5 years

rr_ExpenseExampleNoRedemptionYear05

411

10 years

rr_ExpenseExampleNoRedemptionYear10

918

Annual Return 2002

rr_AnnualReturn2002

(16.69%)

Annual Return 2003

rr_AnnualReturn2003

26.24%

Annual Return 2004

rr_AnnualReturn2004

15.12%

Annual Return 2005

rr_AnnualReturn2005

12.80%

Annual Return 2006

rr_AnnualReturn2006

24.75%

Annual Return 2007

rr_AnnualReturn2007

6.17%

Annual Return 2008

rr_AnnualReturn2008

(33.32%)

Annual Return 2009

rr_AnnualReturn2009

20.16%

Annual Return 2010

rr_AnnualReturn2010

11.94%

Annual Return 2011

rr_AnnualReturn2011

(2.81%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.11%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.58%)

Past 1 Year

rr_AverageAnnualReturnYear01

(2.81%)

Past 5 Years

rr_AverageAnnualReturnYear05

(1.54%)

Past 10 Years

rr_AverageAnnualReturnYear10

4.66%

Loomis Sayles Value Fund | Class Y | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(3.04%)

Past 5 Years

rr_AverageAnnualReturnYear05

(1.95%)

Past 10 Years

rr_AverageAnnualReturnYear10

4.17%

Loomis Sayles Value Fund | Class Y | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(1.54%)

Past 5 Years

rr_AverageAnnualReturnYear05

(1.35%)

Past 10 Years

rr_AverageAnnualReturnYear10

3.97%

Loomis Sayles Value Fund | Admin Class

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.42%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.17%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.17%

1 year

rr_ExpenseExampleYear01

119

3 years

rr_ExpenseExampleYear03

372

5 years

rr_ExpenseExampleYear05

644

10 years

rr_ExpenseExampleYear10

1,420

1 year

rr_ExpenseExampleNoRedemptionYear01

119

3 years

rr_ExpenseExampleNoRedemptionYear03

372

5 years

rr_ExpenseExampleNoRedemptionYear05

644

10 years

rr_ExpenseExampleNoRedemptionYear10

1,420

Past 1 Year

rr_AverageAnnualReturnYear01

(3.21%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.10%)

Past 10 Years

rr_AverageAnnualReturnYear10

4.07%

Loomis Sayles Value Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Value Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund's investment objective is long-term growth of capital and income.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 29% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

29.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest primarily in equity securities, including common stocks, convertible securities and warrants. In deciding which securities to buy and sell, the Adviser generally looks for companies that it believes are undervalued by the market in relation to earnings, dividends, assets and/or growth prospects. The Fund's investments may include companies that have suffered significant business problems but that the Adviser believes have favorable prospects for recovery. The Adviser seeks to identify companies that it believes are, among other things, attractively valued based on the Adviser's estimate of intrinsic value. The Adviser generally seeks to find value by selecting individual stocks that it believes are attractive, rather than by attempting to achieve investment growth by rotating the Fund's holdings among various sectors of the economy. The Fund may also invest up to 20% of its assets in securities of foreign issuers including emerging market securities, invest in options for hedging and investment purposes, real estate investment trusts ("REITs") and Rule 144A securities. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as options transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties,there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Value stocks can perform differently from the market as a whole and from other types of stocks. Value stocks also present the risk that their lower valuations fairly reflect their business prospects and that investors will not agree that the stocks represent favorable investment opportunities, and they may fall out of favor with investors and underperform growth stocks during any given period. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2003, 18.11%

Lowest Quarterly Return:
Fourth Quarter 2008, -19.58%

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The returns shown in the table for Class A shares prior to June 1, 2007 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Retail Class shares (June 30, 2006), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class A shares. Prior to the inception of Class B and Class C shares (June 1, 2007), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B and Class C shares, respectively. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class A, B and C shares were offered in a separate prospectus and given that Class A, B and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y Shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Value Fund | Russell 1000 Value Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

0.39%

Past 5 Years

rr_AverageAnnualReturnYear05

(2.64%)

Past 10 Years

rr_AverageAnnualReturnYear10

3.89%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.10%, 1.85%, 1.85%, 0.85% and 1.35% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.10%, 1.85%, 1.85%, 0.85% and 1.35% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

[2] Other expenses include an administrative services fee of 0.25% for Admin Class shares.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Growth Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.39%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.14%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.14%

1 year

rr_ExpenseExampleYear01

685

3 years

rr_ExpenseExampleYear03

916

5 years

rr_ExpenseExampleYear05

1,167

10 years

rr_ExpenseExampleYear10

1,881

1 year

rr_ExpenseExampleNoRedemptionYear01

685

3 years

rr_ExpenseExampleNoRedemptionYear03

916

5 years

rr_ExpenseExampleNoRedemptionYear05

1,167

10 years

rr_ExpenseExampleNoRedemptionYear10

1,881

Annual Return 2002

rr_AnnualReturn2002

(23.09%)

Annual Return 2003

rr_AnnualReturn2003

32.17%

Annual Return 2004

rr_AnnualReturn2004

15.62%

Annual Return 2005

rr_AnnualReturn2005

10.53%

Annual Return 2006

rr_AnnualReturn2006

(3.49%)

Annual Return 2007

rr_AnnualReturn2007

21.88%

Annual Return 2008

rr_AnnualReturn2008

(50.07%)

Annual Return 2009

rr_AnnualReturn2009

32.16%

Annual Return 2010

rr_AnnualReturn2010

15.34%

Annual Return 2011

rr_AnnualReturn2011

0.32%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.73%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.00%)

Past 1 Year

rr_AverageAnnualReturnYear01

(5.38%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.59%)

Past 10 Years

rr_AverageAnnualReturnYear10

0.95%

Loomis Sayles Growth Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(5.40%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.59%)

Past 10 Years

rr_AverageAnnualReturnYear10

0.94%

Loomis Sayles Growth Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(3.47%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.18%)

Past 10 Years

rr_AverageAnnualReturnYear10

0.81%

Loomis Sayles Growth Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.39%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.89%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.89%

1 year

rr_ExpenseExampleYear01

692

3 years

rr_ExpenseExampleYear03

894

5 years

rr_ExpenseExampleYear05

1,221

10 years

rr_ExpenseExampleYear10

2,016

1 year

rr_ExpenseExampleNoRedemptionYear01

192

3 years

rr_ExpenseExampleNoRedemptionYear03

594

5 years

rr_ExpenseExampleNoRedemptionYear05

1,021

10 years

rr_ExpenseExampleNoRedemptionYear10

2,016

Past 1 Year

rr_AverageAnnualReturnYear01

(5.36%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.54%)

Past 10 Years

rr_AverageAnnualReturnYear10

0.81%

Loomis Sayles Growth Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.39%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.89%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.89%

1 year

rr_ExpenseExampleYear01

292

3 years

rr_ExpenseExampleYear03

594

5 years

rr_ExpenseExampleYear05

1,021

10 years

rr_ExpenseExampleYear10

2,212

1 year

rr_ExpenseExampleNoRedemptionYear01

192

3 years

rr_ExpenseExampleNoRedemptionYear03

594

5 years

rr_ExpenseExampleNoRedemptionYear05

1,021

10 years

rr_ExpenseExampleNoRedemptionYear10

2,212

Past 1 Year

rr_AverageAnnualReturnYear01

(1.37%)

Past 5 Years

rr_AverageAnnualReturnYear05

(2.15%)

Past 10 Years

rr_AverageAnnualReturnYear10

0.81%

Loomis Sayles Growth Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.50%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.39%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.89%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

0.89%

1 year

rr_ExpenseExampleYear01

91

3 years

rr_ExpenseExampleYear03

284

5 years

rr_ExpenseExampleYear05

493

10 years

rr_ExpenseExampleYear10

1,096

1 year

rr_ExpenseExampleNoRedemptionYear01

91

3 years

rr_ExpenseExampleNoRedemptionYear03

284

5 years

rr_ExpenseExampleNoRedemptionYear05

493

10 years

rr_ExpenseExampleNoRedemptionYear10

1,096

Past 1 Year

rr_AverageAnnualReturnYear01

0.72%

Past 5 Years

rr_AverageAnnualReturnYear05

(1.02%)

Past 10 Years

rr_AverageAnnualReturnYear10

1.88%

Loomis Sayles Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Growth Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund's investment goal is long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 16% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

16.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest primarily in equity securities, including common stocks, convertible securities and warrants. The Fund focuses on stocks of large capitalization companies, but the Fund may invest in companies of any size. The Fund normally invests across a wide range of sectors and industries. The Fund's portfolio manager employs a growth style of equity management that emphasizes companies with sustainable competitive advantages, secular long-term cash flow growth returns on invested capital above their cost of capital and the ability to manage for profitable growth that can create long-term value for shareholders. The Fund's portfolio manager aims to invest in companies when they trade at a significant discount to the estimate of intrinsic value. The Fund will consider selling a portfolio investment when the portfolio manager believes the issuer's investment fundamentals are beginning to deteriorate, when the investment no longer appears consistent with the portfolio manager's investment methodology, when the Fund must meet redemptions, in order to take advantage of more attractive investment opportunities, or for other investment reasons which the portfolio manager deems appropriate. The Fund may also invest any portion of its assets in equity securities of Canadian issuers, up to 20% of its assets in other foreign securities, including emerging market securities, engage in foreign currency transactions, invest in options for hedging and investment purposes and invest in Rule 144A securities. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts and options transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio manager may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Third Quarter 2010, 14.73%

Lowest Quarterly Return:
Fourth Quarter 2008, -26.00%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The returns shown in the chart and table for Class A shares prior to September 15, 2003 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Class B and Class C shares (September 12, 2003), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B shares and Class C shares, respectively. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Growth Fund | Russell 1000 Growth Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

2.64%

Past 5 Years

rr_AverageAnnualReturnYear05

2.50%

Past 10 Years

rr_AverageAnnualReturnYear10

2.60%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Investment Grade Bond Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.50%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.16%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.81%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

0.81%

1 year

rr_ExpenseExampleYear01

529

3 years

rr_ExpenseExampleYear03

697

5 years

rr_ExpenseExampleYear05

879

10 years

rr_ExpenseExampleYear10

1,407

1 year

rr_ExpenseExampleNoRedemptionYear01

529

3 years

rr_ExpenseExampleNoRedemptionYear03

697

5 years

rr_ExpenseExampleNoRedemptionYear05

879

10 years

rr_ExpenseExampleNoRedemptionYear10

1,407

Past 1 Year

rr_AverageAnnualReturnYear01

0.12%

Past 5 Years

rr_AverageAnnualReturnYear05

6.50%

Past 10 Years

rr_AverageAnnualReturnYear10

8.08%

Loomis Sayles Investment Grade Bond Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.16%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.56%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.56%

1 year

rr_ExpenseExampleYear01

659

3 years

rr_ExpenseExampleYear03

793

5 years

rr_ExpenseExampleYear05

1,050

10 years

rr_ExpenseExampleYear10

1,655

1 year

rr_ExpenseExampleNoRedemptionYear01

159

3 years

rr_ExpenseExampleNoRedemptionYear03

493

5 years

rr_ExpenseExampleNoRedemptionYear05

850

10 years

rr_ExpenseExampleNoRedemptionYear10

1,655

Past 1 Year

rr_AverageAnnualReturnYear01

(0.79%)

Past 5 Years

rr_AverageAnnualReturnYear05

6.27%

Past 10 Years

rr_AverageAnnualReturnYear10

7.67%

Loomis Sayles Investment Grade Bond Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.16%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.56%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.56%

1 year

rr_ExpenseExampleYear01

259

3 years

rr_ExpenseExampleYear03

493

5 years

rr_ExpenseExampleYear05

850

10 years

rr_ExpenseExampleYear10

1,856

1 year

rr_ExpenseExampleNoRedemptionYear01

159

3 years

rr_ExpenseExampleNoRedemptionYear03

493

5 years

rr_ExpenseExampleNoRedemptionYear05

850

10 years

rr_ExpenseExampleNoRedemptionYear10

1,856

Past 1 Year

rr_AverageAnnualReturnYear01

3.09%

Past 5 Years

rr_AverageAnnualReturnYear05

6.67%

Past 10 Years

rr_AverageAnnualReturnYear10

7.71%

Loomis Sayles Investment Grade Bond Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.16%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.56%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

0.56%

1 year

rr_ExpenseExampleYear01

57

3 years

rr_ExpenseExampleYear03

179

5 years

rr_ExpenseExampleYear05

313

10 years

rr_ExpenseExampleYear10

701

1 year

rr_ExpenseExampleNoRedemptionYear01

57

3 years

rr_ExpenseExampleNoRedemptionYear03

179

5 years

rr_ExpenseExampleNoRedemptionYear05

313

10 years

rr_ExpenseExampleNoRedemptionYear10

701

Annual Return 2002

rr_AnnualReturn2002

10.84%

Annual Return 2003

rr_AnnualReturn2003

19.61%

Annual Return 2004

rr_AnnualReturn2004

9.91%

Annual Return 2005

rr_AnnualReturn2005

2.34%

Annual Return 2006

rr_AnnualReturn2006

8.07%

Annual Return 2007

rr_AnnualReturn2007

9.93%

Annual Return 2008

rr_AnnualReturn2008

(11.42%)

Annual Return 2009

rr_AnnualReturn2009

27.27%

Annual Return 2010

rr_AnnualReturn2010

11.52%

Annual Return 2011

rr_AnnualReturn2011

5.08%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

12.65%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(7.19%)

Past 1 Year

rr_AverageAnnualReturnYear01

5.08%

Past 5 Years

rr_AverageAnnualReturnYear05

7.75%

Past 10 Years

rr_AverageAnnualReturnYear10

8.88%

Loomis Sayles Investment Grade Bond Fund | Class Y | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

2.85%

Past 5 Years

rr_AverageAnnualReturnYear05

5.45%

Past 10 Years

rr_AverageAnnualReturnYear10

6.43%

Loomis Sayles Investment Grade Bond Fund | Class Y | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

3.43%

Past 5 Years

rr_AverageAnnualReturnYear05

5.30%

Past 10 Years

rr_AverageAnnualReturnYear10

6.25%

Loomis Sayles Investment Grade Bond Fund | Admin Class

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.42%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.07%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.07%

1 year

rr_ExpenseExampleYear01

109

3 years

rr_ExpenseExampleYear03

340

5 years

rr_ExpenseExampleYear05

590

10 years

rr_ExpenseExampleYear10

1,306

1 year

rr_ExpenseExampleNoRedemptionYear01

109

3 years

rr_ExpenseExampleNoRedemptionYear03

340

5 years

rr_ExpenseExampleNoRedemptionYear05

590

10 years

rr_ExpenseExampleNoRedemptionYear10

1,306

Past 1 Year

rr_AverageAnnualReturnYear01

4.52%

Past 5 Years

rr_AverageAnnualReturnYear05

7.05%

Past 10 Years

rr_AverageAnnualReturnYear10

8.05%

Loomis Sayles Investment Grade Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Investment Grade Bond Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks high total investment return through a combination of current income and capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 19% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

19.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investment-grade fixed-income securities (for example, bonds and other investments that Loomis Sayles believes have similar economic characteristics, such as notes, debentures and loans). "Investment-grade" securities are those securities that are rated as such at the time of purchase by at least one of the three major rating agencies —  Moody's Investors Service, Inc. ("Moody's"), Fitch Investor Services, Inc. ("Fitch") or Standard & Poor's Ratings Group ("S&P") or, if unrated, are determined by the Adviser to be of comparable quality. Although the Fund invests primarily in investment-grade fixed-income securities, it may invest up to 10% of its assets in below investment-grade fixed-income securities (also known as "junk bonds"). The Fund has the flexibility to invest up to 10% of its assets in equity securities (such as common stocks, preferred stocks and investment companies), but will limit its investments in common stocks to 5% of its assets. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major rating agencies (Moody's, Fitch or S&P) have rated the securities in one of their top four ratings categories) or, if unrated, are determined by the Adviser to be of comparable quality. There is no minimum rating for the securities in which the Fund may invest. The Fund may invest in fixed income-securities of any maturity. In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. Three themes typically drive the Fund's investment approach. First, the Adviser generally seeks fixed-income securities of issuers whose credit profiles it believes are improving. Second, the Fund makes significant use of non-market-related securities, which are securities that may not have a direct correlation with changes in interest rates. The Adviser believes that the Fund may generate positive returns by having a portion of the Fund's assets invested in non-market-related securities, rather than by relying primarily on changes in interest rates to produce returns for the Fund. Third, the Adviser analyzes different sectors of the economy and differences in the yields ("spreads") of various fixed-income securities in an effort to find securities that it believes may produce attractive returns for the Fund in comparison to their risk. The Adviser generally prefers securities that are protected against calls (early redemption by the issuer). In connection with its principal investment strategies, the Fund may also invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in securities of other foreign issuers, including emerging markets securities. The Fund may also invest in obligations of supranational entities without limit ( e.g. , the World Bank), corporate securities, U.S. government securities, commercial paper, zero-coupon securities, mortgage-backed securities, including mortgage dollar rolls, stripped mortgage-backed securities and collateralized mortgage obligations and other asset-backed securities, when-issued securities, convertible securities, Rule 144A securities and structured notes. The Fund may also engage in foreign currency hedging transactions and swap transactions (including credit default swaps) for hedging or investment purposes. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations.Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps, and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478. The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

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800-225-5478

Performance Availability Website Address [Text]

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ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

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The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

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Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

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Highest Quarterly Return:
Second Quarter 2009, 12.65%

Lowest Quarterly Return:
Third Quarter 2008, -7.19%

Performance Table Heading

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Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Narrative

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Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Closing [Text Block]

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The returns shown in the table for Class A shares prior to September 15, 2003 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. For the period from January 1, 2002 to January 31, 2002, during which time Retail Class shares were not outstanding, performance is that of Institutional Class shares, restated to reflect the higher net expenses and sales loads of Class A shares. Prior to the inception of Class B and Class C shares (September 12, 2003), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B and Class C shares, respectively. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class A, B and C shares were offered in a separate prospectus and given that Class A, B and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Loomis Sayles Investment Grade Bond Fund | Barclays Capital U.S. Government/Credit Bond Index

Risk/Return:

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Past 1 Year

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8.74%

Past 5 Years

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6.55%

Past 10 Years

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5.85%

[1] Other expenses include an administrative services fee of 0.25% for Admin Class shares.

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund's average daily net assets for Class A, B, C, and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Growth Fund

Loomis Sayles Growth Fund

Investment Goal

The Fund's investment goal is long-term growth of capital.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Growth Fund	Class A	Class B	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none
Redemption fees	none	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles Growth Fund		Class A	Class B	Class C	Class Y
Management fees		0.50%	0.50%	0.50%	0.50%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none
Other expenses		0.39%	0.39%	0.39%	0.39%
Total annual fund operating expenses		1.14%	1.89%	1.89%	0.89%
Fee waiver and/or expense reimbursement	[1]	none	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.14%	1.89%	1.89%	0.89%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Growth Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	685	692	292	91
3 years	916	894	594	284
5 years	1,167	1,221	1,021	493
10 years	1,881	2,016	2,212	1,096

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Growth Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	685	192	192	91
3 years	916	594	594	284
5 years	1,167	1,021	1,021	493
10 years	1,881	2,016	2,212	1,096

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 16% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest primarily in equity securities, including common stocks, convertible securities and warrants. The Fund focuses on stocks of large capitalization companies, but the Fund may invest in companies of any size. The Fund normally invests across a wide range of sectors and industries. The Fund's portfolio manager employs a growth style of equity management that emphasizes companies with sustainable competitive advantages, secular long-term cash flow growth returns on invested capital above their cost of capital and the ability to manage for profitable growth that can create long-term value for shareholders. The Fund's portfolio manager aims to invest in companies when they trade at a significant discount to the estimate of intrinsic value. The Fund will consider selling a portfolio investment when the portfolio manager believes the issuer's investment fundamentals are beginning to deteriorate, when the investment no longer appears consistent with the portfolio manager's investment methodology, when the Fund must meet redemptions, in order to take advantage of more attractive investment opportunities, or for other investment reasons which the portfolio manager deems appropriate. The Fund may also invest any portion of its assets in equity securities of Canadian issuers, up to 20% of its assets in other foreign securities, including emerging market securities, engage in foreign currency transactions, invest in options for hedging and investment purposes and invest in Rule 144A securities. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts and options transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio manager may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

Highest Quarterly Return:
Third Quarter 2010, 14.73%

Lowest Quarterly Return:
Fourth Quarter 2008, -26.00%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Growth Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class A	(5.38%)	(2.59%)	0.95%
Class A Return After Taxes on Distributions	(5.40%)	(2.59%)	0.94%
Class A Return After Taxes on Distributions & Sale of Fund Shares	(3.47%)	(2.18%)	0.81%
Class B	(5.36%)	(2.54%)	0.81%
Class C	(1.37%)	(2.15%)	0.81%
Class Y	0.72%	(1.02%)	1.88%
Russell 1000 Growth Index	2.64%	2.50%	2.60%

The returns shown in the chart and table for Class A shares prior to September 15, 2003 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Class B and Class C shares (September 12, 2003), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B shares and Class C shares, respectively. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Global Equity and Income Fund

Loomis Sayles Global Equity and Income Fund (formerly Loomis Sayles Global Markets Fund)

Investment Goal

The Fund's investment goal is high total investment return through a combination of capital appreciation and current income.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Global Equity and Income Fund	Class A	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	1.00%	none
Redemption fees	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles Global Equity and Income Fund		Class A	Class C	Class Y
Management fees		0.75%	0.75%	0.75%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none
Other expenses		0.24%	0.24%	0.24%
Total annual fund operating expenses		1.24%	1.99%	0.99%
Fee waiver and/or expense reimbursement	[1]	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.24%	1.99%	0.99%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Global Equity and Income Fund (USD $)	Class A	Class C	Class Y
1 year	694	302	101
3 years	946	624	315
5 years	1,217	1,073	547
10 years	1,989	2,317	1,213

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Global Equity and Income Fund (USD $)	Class A	Class C	Class Y
1 year	694	202	101
3 years	946	624	315
5 years	1,217	1,073	547
10 years	1,989	2,317	1,213

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 65% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in equity and fixed-income securities of U.S. and foreign issuers. Equity securities purchased by the Fund may include common stocks, preferred stocks, depositary receipts, warrants, securities convertible into common or preferred stocks, interests in real estate investment trusts ("REITs") and/or real estate-related securities and other equity-like interests in an issuer. The Fund will invest a significant portion of its assets outside the U.S., including securities of issuers located in emerging market countries. In deciding which domestic and international equity securities to buy and sell, the Adviser generally looks for companies that it believes have the potential for superior earnings growth relative to their current value. The Adviser also looks for companies that appear to be undervalued relative to the intrinsic value of the companies' assets or cash flows. In deciding which domestic and international fixed-income securities to buy and sell, the Adviser generally looks for securities that it believes are undervalued and have the potential for credit upgrades, which may include securities that are below investment-grade (also known as "junk bonds"). The Fund may also invest in foreign currencies, collateralized mortgage obligations, zero-coupon securities, when-issued securities, real estate investment trusts ("REITs"), Rule 144A securities and mortgage-related securities. The Fund may also engage in active and frequent trading of securities and engage in options or foreign currency transactions for hedging and investment purposes and futures transactions, foreign currency transactions and swap transactions (including credit default swaps). Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. The Adviser may hedge currency risk for the Fund (including "cross hedging" between two or more foreign currencies) if it believes the outlook for a particular foreign currency is unfavorable. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Allocation Risk: The Fund's investment performance depends on how its assets are allocated. The allocation, as set forth above, may not be optimal in every market condition. You could lose money on your investment in the Fund as a result of this allocation. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives, such as forward currency contracts, options and futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. Value stocks can perform differently from the market as a whole and from other types of stocks. Value stocks also present the risk that their lower valuations fairly reflect their business prospects and that investors will not agree that the stocks represent favorable investment opportunities, and they may fall out of favor with investors and underperform growth stocks during any given period. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce the Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related securities are subject to the risks of the mortgages underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium.REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478. The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class Y Shares

Highest Quarterly Return:
Second Quarter 2009, 19.91%

Lowest Quarterly Return:
Third Quarter 2008, -19.64%

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Global Equity and Income Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class Y	(0.73%)	5.78%	9.45%
Class Y Return After Taxes on Distributions	(1.11%)	4.90%	8.54%
Class Y Return After Taxes on Distributions & Sale of Fund Shares	(0.25%)	4.53%	7.85%
Class A	(6.62%)	4.28%	8.54%
Class C	(2.65%)	4.73%	8.37%
MSCI World Index	(5.02%)	(1.82%)	4.15%
Citigroup World Government Bond Index	6.35%	7.13%	7.77%

The returns shown in the table prior to the inception of Class A and Class C shares (February 1, 2006) are those of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class A and Class C shares, respectively. Prior to February 1, 2012, Class A and C shares were offered in a separate prospectus and given that Class A and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles High Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.50%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.30%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.15%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.15%

1 year

rr_ExpenseExampleYear01

562

3 years

rr_ExpenseExampleYear03

799

5 years

rr_ExpenseExampleYear05

1,054

10 years

rr_ExpenseExampleYear10

1,785

1 year

rr_ExpenseExampleNoRedemptionYear01

562

3 years

rr_ExpenseExampleNoRedemptionYear03

799

5 years

rr_ExpenseExampleNoRedemptionYear05

1,054

10 years

rr_ExpenseExampleNoRedemptionYear10

1,785

Annual Return 2002

rr_AnnualReturn2002

(8.86%)

Annual Return 2003

rr_AnnualReturn2003

27.91%

Annual Return 2004

rr_AnnualReturn2004

10.35%

Annual Return 2005

rr_AnnualReturn2005

5.04%

Annual Return 2006

rr_AnnualReturn2006

13.86%

Annual Return 2007

rr_AnnualReturn2007

1.98%

Annual Return 2008

rr_AnnualReturn2008

(26.62%)

Annual Return 2009

rr_AnnualReturn2009

50.35%

Annual Return 2010

rr_AnnualReturn2010

13.69%

Annual Return 2011

rr_AnnualReturn2011

(2.98%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.38%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(18.10%)

Past 1 Year

rr_AverageAnnualReturnYear01

(7.29%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.45%

Past 10 Years

rr_AverageAnnualReturnYear10

6.20%

Loomis Sayles High Income Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(10.89%)

Past 5 Years

rr_AverageAnnualReturnYear05

0.50%

Past 10 Years

rr_AverageAnnualReturnYear10

3.30%

Loomis Sayles High Income Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(3.37%)

Past 5 Years

rr_AverageAnnualReturnYear05

1.32%

Past 10 Years

rr_AverageAnnualReturnYear10

3.61%

Loomis Sayles High Income Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.30%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.90%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.90%

1 year

rr_ExpenseExampleYear01

693

3 years

rr_ExpenseExampleYear03

897

5 years

rr_ExpenseExampleYear05

1,226

10 years

rr_ExpenseExampleYear10

2,027

1 year

rr_ExpenseExampleNoRedemptionYear01

193

3 years

rr_ExpenseExampleNoRedemptionYear03

597

5 years

rr_ExpenseExampleNoRedemptionYear05

1,026

10 years

rr_ExpenseExampleNoRedemptionYear10

2,027

Past 1 Year

rr_AverageAnnualReturnYear01

(7.62%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.39%

Past 10 Years

rr_AverageAnnualReturnYear10

5.90%

Loomis Sayles High Income Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.30%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.90%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

1.90%

1 year

rr_ExpenseExampleYear01

293

3 years

rr_ExpenseExampleYear03

597

5 years

rr_ExpenseExampleYear05

1,026

10 years

rr_ExpenseExampleYear10

2,222

1 year

rr_ExpenseExampleNoRedemptionYear01

193

3 years

rr_ExpenseExampleNoRedemptionYear03

597

5 years

rr_ExpenseExampleNoRedemptionYear05

1,026

10 years

rr_ExpenseExampleNoRedemptionYear10

2,222

Past 1 Year

rr_AverageAnnualReturnYear01

(4.33%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.68%

Past 10 Years

rr_AverageAnnualReturnYear10

5.90%

Loomis Sayles High Income Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.30%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.90%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

0.90%

1 year

rr_ExpenseExampleYear01

92

3 years

rr_ExpenseExampleYear03

287

5 years

rr_ExpenseExampleYear05

498

10 years

rr_ExpenseExampleYear10

1,108

1 year

rr_ExpenseExampleNoRedemptionYear01

92

3 years

rr_ExpenseExampleNoRedemptionYear03

287

5 years

rr_ExpenseExampleNoRedemptionYear05

498

10 years

rr_ExpenseExampleNoRedemptionYear10

1,108

Past 1 Year

rr_AverageAnnualReturnYear01

(2.53%)

Past 5 Years

rr_AverageAnnualReturnYear05

Past 10 Years

rr_AverageAnnualReturnYear10

Life of Class Y

rr_AverageAnnualReturnSinceInception

5.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 29, 2008

Loomis Sayles High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles High Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks high current income plus the opportunity for capital appreciation to produce a high total return.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 67% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

67.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

 If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

 If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest at least 65% of its assets in below investment-grade fixed-income securities (commonly known as "junk bonds"). Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")), have rated the securities in one of its top four rating categories) or, if the security is unrated, are determined by the Adviser to be of comparable quality. There is no minimum rating for the securities in which the Fund may invest. The Fund will normally invest at least 65% of its assets in U.S. corporate or U.S. dollar-denominated foreign fixed-income securities. The Fund may also invest up to 20% of its assets in foreign currency-denominated fixed-income securities, including those in emerging markets and related currency hedging transactions. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The Adviser performs its own extensive credit analysis to determine the creditworthiness and potential for capital appreciation of a security. The Fund's management minimizes both market timing and interest rate forecasting. Instead, it uses a strategy based on gaining a thorough understanding of industry and company dynamics as well as individual security characteristics such as issuer debt and debt maturity schedules, earnings prospects, responsiveness to changes in interest rates, experience and perceived strength of management, borrowing requirements and liquidation value, market price in relation to cash flow, interest and dividends. In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser utilizes the skills of its in-house team of more than 30 research analysts to cover a broad universe of industries, companies and markets. The Fund's portfolio managers take advantage of these extensive resources to identify securities that meet the Fund's investment criteria. The Adviser employs a selection strategy that focuses on a value-driven, bottom-up approach to identify securities that provide an opportunity for both generous yields and capital appreciation. The Adviser analyzes an individual company's potential for positive financial news to determine if it has growth potential. Examples of positive financial news include an upward turn in the business cycle, improvement in cash flows, rising profits or the awarding of new contracts. The Adviser emphasizes in-depth credit analysis, appreciation potential and diversification in its bond selection. Each bond is evaluated to assess the ability of its issuer to pay interest and, ultimately, principal (which helps the Fund generate an ongoing flow of income). The Adviser also assesses a bond's relation to market conditions within its industry and favors bonds whose prices may benefit from positive business developments. The Adviser seeks to diversify the Fund's holdings to reduce the inherent risk in below investment-grade fixed-income securities. In connection with its principal investment strategies, the Fund may also invest in structured notes, zero-coupon securities, pay-in-kind securities, Rule 144A securities, futures and swaps (including credit default swaps). Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged.Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce the Fund's ability to sell them. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions.

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

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The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

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Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

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Highest Quarterly Return:

Second Quarter 2009, 16.38%

Lowest Quarterly Return:
Fourth Quarter 2008, -18.10%

Performance Table Heading

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Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

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In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Narrative

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Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Closing [Text Block]

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The returns shown in the bar chart and table for the periods prior to September 15, 2003 reflect the results of the CDC Nvest High Income Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles High Income Fund | Barclays Capital U.S. Corporate High-Yield Bond Index

Risk/Return:

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Past 1 Year

rr_AverageAnnualReturnYear01

4.98%

Past 5 Years

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7.54%

Past 10 Years

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8.85%

Life of Class Y

rr_AverageAnnualReturnSinceInception

10.19%

[1] The expense information shown in the table above may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (expenses indirectly borne by the Fund through investments in certain pooled investment vehicles).

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.15%, 1.90%, 1.90% and 0.90% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.15%, 1.90%, 1.90% and 0.90% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Loomis Sayles High Income Fund

Loomis Sayles High Income Fund

Investment Goal

The Fund seeks high current income plus the opportunity for capital appreciation to produce a high total return.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles High Income Fund	Class A	Class B	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.50%	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none
Redemption fees	none	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles High Income Fund		Class A	Class B	Class C	Class Y
Management fees		0.60%	0.60%	0.60%	0.60%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none
Other expenses	[1]	0.30%	0.30%	0.30%	0.30%
Total annual fund operating expenses		1.15%	1.90%	1.90%	0.90%
Fee waiver and/or expense reimbursement	[2]	none	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.15%	1.90%	1.90%	0.90%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

 If shares are redeemed

Expense Example - Loomis Sayles High Income Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	562	693	293	92
3 years	799	897	597	287
5 years	1,054	1,226	1,026	498
10 years	1,785	2,027	2,222	1,108

 If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles High Income Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	562	193	193	92
3 years	799	597	597	287
5 years	1,054	1,026	1,026	498
10 years	1,785	2,027	2,222	1,108

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 67% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest at least 65% of its assets in below investment-grade fixed-income securities (commonly known as "junk bonds"). Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")), have rated the securities in one of its top four rating categories) or, if the security is unrated, are determined by the Adviser to be of comparable quality. There is no minimum rating for the securities in which the Fund may invest. The Fund will normally invest at least 65% of its assets in U.S. corporate or U.S. dollar-denominated foreign fixed-income securities. The Fund may also invest up to 20% of its assets in foreign currency-denominated fixed-income securities, including those in emerging markets and related currency hedging transactions. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The Adviser performs its own extensive credit analysis to determine the creditworthiness and potential for capital appreciation of a security. The Fund's management minimizes both market timing and interest rate forecasting. Instead, it uses a strategy based on gaining a thorough understanding of industry and company dynamics as well as individual security characteristics such as issuer debt and debt maturity schedules, earnings prospects, responsiveness to changes in interest rates, experience and perceived strength of management, borrowing requirements and liquidation value, market price in relation to cash flow, interest and dividends. In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser utilizes the skills of its in-house team of more than 30 research analysts to cover a broad universe of industries, companies and markets. The Fund's portfolio managers take advantage of these extensive resources to identify securities that meet the Fund's investment criteria. The Adviser employs a selection strategy that focuses on a value-driven, bottom-up approach to identify securities that provide an opportunity for both generous yields and capital appreciation. The Adviser analyzes an individual company's potential for positive financial news to determine if it has growth potential. Examples of positive financial news include an upward turn in the business cycle, improvement in cash flows, rising profits or the awarding of new contracts. The Adviser emphasizes in-depth credit analysis, appreciation potential and diversification in its bond selection. Each bond is evaluated to assess the ability of its issuer to pay interest and, ultimately, principal (which helps the Fund generate an ongoing flow of income). The Adviser also assesses a bond's relation to market conditions within its industry and favors bonds whose prices may benefit from positive business developments. The Adviser seeks to diversify the Fund's holdings to reduce the inherent risk in below investment-grade fixed-income securities. In connection with its principal investment strategies, the Fund may also invest in structured notes, zero-coupon securities, pay-in-kind securities, Rule 144A securities, futures and swaps (including credit default swaps). Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged.Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce the Fund's ability to sell them. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

 

Highest Quarterly Return:

Second Quarter 2009, 16.38%

Lowest Quarterly Return:
Fourth Quarter 2008, -18.10%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles High Income Fund	Past 1 Year	Past 5 Years	Past 10 Years	Life of Class Y	Inception Date
Class A	(7.29%)	3.45%	6.20%
Class A Return After Taxes on Distributions	(10.89%)	0.50%	3.30%
Class A Return After Taxes on Distributions & Sale of Fund Shares	(3.37%)	1.32%	3.61%
Class B	(7.62%)	3.39%	5.90%
Class C	(4.33%)	3.68%	5.90%
Class Y	(2.53%)			5.88%	Feb. 29, 2008
Barclays Capital U.S. Corporate High-Yield Bond Index	4.98%	7.54%	8.85%	10.19%

The returns shown in the bar chart and table for the periods prior to September 15, 2003 reflect the results of the CDC Nvest High Income Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] The expense information shown in the table above may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (expenses indirectly borne by the Fund through investments in certain pooled investment vehicles).

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.15%, 1.90%, 1.90% and 0.90% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.15%, 1.90%, 1.90% and 0.90% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Mid Cap Growth Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.32%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.32%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

1.25%

1 year

rr_ExpenseExampleYear01

695

3 years

rr_ExpenseExampleYear03

963

5 years

rr_ExpenseExampleYear05

1,251

10 years

rr_ExpenseExampleYear10

2,068

1 year

rr_ExpenseExampleNoRedemptionYear01

695

3 years

rr_ExpenseExampleNoRedemptionYear03

963

5 years

rr_ExpenseExampleNoRedemptionYear05

1,251

10 years

rr_ExpenseExampleNoRedemptionYear10

2,068

Annual Return 2002

rr_AnnualReturn2002

(36.62%)

Annual Return 2003

rr_AnnualReturn2003

39.71%

Annual Return 2004

rr_AnnualReturn2004

18.97%

Annual Return 2005

rr_AnnualReturn2005

15.16%

Annual Return 2006

rr_AnnualReturn2006

6.68%

Annual Return 2007

rr_AnnualReturn2007

39.39%

Annual Return 2008

rr_AnnualReturn2008

(45.66%)

Annual Return 2009

rr_AnnualReturn2009

26.44%

Annual Return 2010

rr_AnnualReturn2010

34.54%

Annual Return 2011

rr_AnnualReturn2011

(7.33%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.49%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.07%)

Past 1 Year

rr_AverageAnnualReturnYear01

(12.67%)

Past 5 Years

rr_AverageAnnualReturnYear05

2.39%

Past 10 Years

rr_AverageAnnualReturnYear10

3.83%

Loomis Sayles Mid Cap Growth Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(12.67%)

Past 5 Years

rr_AverageAnnualReturnYear05

2.39%

Past 10 Years

rr_AverageAnnualReturnYear10

3.81%

Loomis Sayles Mid Cap Growth Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(8.23%)

Past 5 Years

rr_AverageAnnualReturnYear05

2.04%

Past 10 Years

rr_AverageAnnualReturnYear10

3.32%

Loomis Sayles Mid Cap Growth Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.33%

Total annual fund operating expenses

rr_ExpensesOverAssets

2.08%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

2.01%

1 year

rr_ExpenseExampleYear01

304

3 years

rr_ExpenseExampleYear03

645

5 years

rr_ExpenseExampleYear05

1,112

10 years

rr_ExpenseExampleYear10

2,405

1 year

rr_ExpenseExampleNoRedemptionYear01

204

3 years

rr_ExpenseExampleNoRedemptionYear03

645

5 years

rr_ExpenseExampleNoRedemptionYear05

1,112

10 years

rr_ExpenseExampleNoRedemptionYear10

2,405

Past 1 Year

rr_AverageAnnualReturnYear01

(8.95%)

Past 5 Years

rr_AverageAnnualReturnYear05

2.82%

Past 10 Years

rr_AverageAnnualReturnYear10

3.64%

Loomis Sayles Mid Cap Growth Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.32%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.07%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.07%

^[1]

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

rr_NetExpensesOverAssets

1.00%

1 year

rr_ExpenseExampleYear01

102

3 years

rr_ExpenseExampleYear03

333

5 years

rr_ExpenseExampleYear05

583

10 years

rr_ExpenseExampleYear10

1,299

1 year

rr_ExpenseExampleNoRedemptionYear01

102

3 years

rr_ExpenseExampleNoRedemptionYear03

333

5 years

rr_ExpenseExampleNoRedemptionYear05

583

10 years

rr_ExpenseExampleNoRedemptionYear10

1,299

Past 1 Year

rr_AverageAnnualReturnYear01

(7.13%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.86%

Past 10 Years

rr_AverageAnnualReturnYear10

4.71%

Loomis Sayles Mid Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Mid Cap Growth Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund's investment objective is long-term capital growth from investments in common stocks or similar securities.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

 Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 204% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

204.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in common stocks or other equity securities, including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in companies whose market capitalization falls within the Russell Midcap Growth Index. While the market capitalization range for this index fluctuates, at December 31, 2011, it was $54.7 million to $19.2 billion. The Fund may invest the rest of its assets in companies of any size. In deciding which securities to buy and sell, the Adviser seeks to identify companies that it believes have distinctive products, technologies or services, dynamic earnings growth, prospects for high levels of profitability and/or solid management. The Adviser typically does not consider current income when making buy/sell decisions. The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. The Fund may engage in foreign currency transactions, options for hedging and investment purposes and futures transactions, and may also engage in securities lending. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The Fund also may invest in securities offered in the secondary markets or in initial public offerings, real estate investment trusts ("REITs") and Rule 144A securities. The Fund may engage in active and frequent trading of securities. Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts and options and futures transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Securities issued in IPOs tend to involve greater market risk than other equity securities due, in part, to public perception and the lack of publicly available information and trading history. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio manager may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2003, 19.49%

Lowest Quarterly Return:
Third Quarter 2008, -26.07%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The returns shown in the chart and table for Class A shares prior to February 1, 2009 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Class C shares (February 2, 2009), performance is that of Retail Class shares, which were redesignated as Class A shares, restated to reflect the higher net expenses and sales loads of Class C shares. The Fund (formerly, Loomis Sayles Aggressive Growth Fund) changed its name and revised its investment strategies on February 1, 2007. The Fund's performance may have been different had the current investment strategies been in place for all of the periods shown. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Mid Cap Growth Fund | Russell Midcap Growth Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(1.65%)

Past 5 Years

rr_AverageAnnualReturnYear05

2.44%

Past 10 Years

rr_AverageAnnualReturnYear10

5.29%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles International Bond Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.50%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.79%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.64%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.54%

^[1]

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

rr_NetExpensesOverAssets

1.10%

1 year

rr_ExpenseExampleYear01

557

3 years

rr_ExpenseExampleYear03

894

5 years

rr_ExpenseExampleYear05

1,253

10 years

rr_ExpenseExampleYear10

2,263

1 year

rr_ExpenseExampleNoRedemptionYear01

557

3 years

rr_ExpenseExampleNoRedemptionYear03

894

5 years

rr_ExpenseExampleNoRedemptionYear05

1,253

10 years

rr_ExpenseExampleNoRedemptionYear10

2,263

Annual Return 2009

rr_AnnualReturn2009

17.28%

Annual Return 2010

rr_AnnualReturn2010

6.84%

Annual Return 2011

rr_AnnualReturn2011

4.41%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.59%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2009

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(3.76%)

Past 1 Year

rr_AverageAnnualReturnYear01

(0.30%)

Life of Fund

rr_AverageAnnualReturnSinceInception

4.56%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Loomis Sayles International Bond Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(4.42%)

Life of Fund

rr_AverageAnnualReturnSinceInception

2.55%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Loomis Sayles International Bond Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

0.11%

Life of Fund

rr_AverageAnnualReturnSinceInception

2.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Loomis Sayles International Bond Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.80%

Total annual fund operating expenses

rr_ExpensesOverAssets

2.40%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.55%

^[1]

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

rr_NetExpensesOverAssets

1.85%

1 year

rr_ExpenseExampleYear01

288

3 years

rr_ExpenseExampleYear03

696

5 years

rr_ExpenseExampleYear05

1,231

10 years

rr_ExpenseExampleYear10

2,694

1 year

rr_ExpenseExampleNoRedemptionYear01

188

3 years

rr_ExpenseExampleNoRedemptionYear03

696

5 years

rr_ExpenseExampleNoRedemptionYear05

1,231

10 years

rr_ExpenseExampleNoRedemptionYear10

2,694

Past 1 Year

rr_AverageAnnualReturnYear01

2.77%

Life of Fund

rr_AverageAnnualReturnSinceInception

5.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Loomis Sayles International Bond Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.60%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.76%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.36%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.51%

^[1]

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

rr_NetExpensesOverAssets

0.85%

1 year

rr_ExpenseExampleYear01

87

3 years

rr_ExpenseExampleYear03

380

5 years

rr_ExpenseExampleYear05

696

10 years

rr_ExpenseExampleYear10

1,591

1 year

rr_ExpenseExampleNoRedemptionYear01

87

3 years

rr_ExpenseExampleNoRedemptionYear03

380

5 years

rr_ExpenseExampleNoRedemptionYear05

696

10 years

rr_ExpenseExampleNoRedemptionYear10

1,591

Past 1 Year

rr_AverageAnnualReturnYear01

4.69%

Life of Fund

rr_AverageAnnualReturnSinceInception

6.04%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Loomis Sayles International Bond Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles International Bond Fund

Objective [Heading]

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Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks high total investment return through a combination of high current income and capital appreciation.

Expense [Heading]

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Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 136% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

136.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund expects to invest at least 80% of its net assets (plus any borrowings made for investment purposes) in fixed-income securities. The Fund is non-diversified, which means that it may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers than a diversified fund. The Fund invests primarily (at least 65% of its net assets) in fixed-income securities of issuers located outside the United States. Securities held by the Fund may be denominated in any currency and may be of issuers located in emerging market countries. The Fund invests primarily in investment-grade fixed-income securities. "Investment-grade" securities are those securities that are rated as such at the time of purchase by at least one of the three major rating agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")) or, if unrated, are determined by the Adviser to be of comparable quality, although the Fund may invest up to 35% of its assets in below investment-grade fixed-income securities (commonly known as "junk bonds"). There is no minimum rating for securities in which the Fund will invest. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's, Fitch or S&P) have rated the securities in one of its top four ratings categories) or, if unrated, are determined by the Adviser to be of comparable quality. The Fund may invest in fixed-income securities of any maturity. The Fund may also invest in foreign currencies and may engage in other foreign currency transactions for investment or for hedging purposes. In deciding which securities to buy and sell, the Adviser may consider, among other things, the stability and volatility of a country's bond markets, the financial strength of the issuer, current interest rates, current valuations, currency considerations, the Adviser's expectations regarding general trends in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. Three themes typically drive the Fund's investment approach. First, the Adviser generally seeks fixed-income securities of issuers whose credit profiles it believes are improving. The Adviser's credit research team provides deep fundamental and quantitative analysis as well as ratings on over 1,000 credits worldwide. The broad coverage combined with the objective to identify attractive investment opportunities makes this an important component of the investment approach. Second, the Adviser analyzes political, economic, and other fundamental factors and combines this analysis with a comparison of the yield spreads of various fixed-income securities in an effort to find securities that it believes may produce attractive returns for the Fund in comparison to their risk. Third, if a security that is believed to be attractive is denominated in a foreign currency, the Adviser analyzes whether to accept or to hedge the currency risk. In certain instances, the Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The fixed-income securities in which the Fund may invest include public or private debt obligations issued or guaranteed by U.S. or non-U.S. issuers, including, but not limited to, corporations, governments (including their agencies, instrumentalities and sponsored entities), supranational entities, partnerships and trusts. The Fund may also invest in preferred stocks, convertible securities, when-issued securities, Rule 144A securities, mortgage- or asset-backed securities and zero-coupon securities issued by any of the above-named entities. In connection with its principal investment strategies, the Fund may also invest in inflation- and index-linked securities, senior loans, structured notes, common stocks (limited to shares acquired as a result of a financial restructuring, bankruptcy or similar transaction or from an exchange or conversion of a permissible security held in the portfolio), and derivatives, including options, futures, options on futures, forward contracts and swap contracts (including credit default swaps). The Fund may also engage in active and frequent trading of securities. Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities.
Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, options and futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Senior loans typically have adjustable interest rates. As a result, it is expected that the values of senior loans held by the Fund will fluctuate less in response to interest rate changes than will fixed-rate debt securities; however, the interest rates paid by these loans will generally decrease if interest rates fall. Senior loans and other fixed-income securities are subject to the risk that borrowers pay off the debts sooner than expected. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts.
Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets. Non-Diversification Risk: Compared with other mutual funds, the Fund may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers. Therefore, the Fund may have more risk because changes in the value of a single security or the impact of a single economic, political or regulatory occurrence may have a greater adverse impact on the Fund's net asset value ("NAV").

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Non-Diversification Risk: Compared with other mutual funds, the Fund may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers. Therefore, the Fund may have more risk because changes in the value of a single security or the impact of a single economic, political or regulatory occurrence may have a greater adverse impact on the Fund's net asset value ("NAV").

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year and life-of-fund compare with those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year and life-of-fund compare with those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Third Quarter 2010, 11.59%

 Lowest Quarterly Return:
First Quarter 2009, -3.76%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles International Bond Fund | Barclays Capital Global Aggregate ex-USD Bond Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

4.36%

Life of Fund

rr_AverageAnnualReturnSinceInception

4.52%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.10%, 1.85% and 0.85% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.10%, 1.85% and 0.85% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Sep. 30, 2011
Registrant Name	dei_EntityRegistrantName	LOOMIS SAYLES FUNDS II
Central Index Key	dei_EntityCentralIndexKey	0000872649
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Jan. 30, 2012
Document Effective Date	dei_DocumentEffectiveDate	Feb. 01, 2012
Prospectus Date	rr_ProspectusDate	Feb. 01, 2012

XML

Loomis Sayles Investment Grade Bond Fund

Loomis Sayles Investment Grade Bond Fund

Investment Goal

The Fund seeks high total investment return through a combination of current income and capital appreciation.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Investment Grade Bond Fund	Class A	Class B	Class C	Class Y	Admin Class
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.50%	none	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none	none
Redemption fees	none	none	none	none	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - Loomis Sayles Investment Grade Bond Fund		Class A	Class B	Class C	Class Y	Admin Class
Management fees		0.40%	0.40%	0.40%	0.40%	0.40%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none	0.25%
Other expenses	[1]	0.16%	0.16%	0.16%	0.16%	0.42%
Total annual fund operating expenses		0.81%	1.56%	1.56%	0.56%	1.07%
Fee waiver and/or expense reimbursement	[2]	none	none	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.81%	1.56%	1.56%	0.56%	1.07%

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 $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Investment Grade Bond Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	529	659	259	57	109
3 years	697	793	493	179	340
5 years	879	1,050	850	313	590
10 years	1,407	1,655	1,856	701	1,306

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Investment Grade Bond Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	529	159	159	57	109
3 years	697	493	493	179	340
5 years	879	850	850	313	590
10 years	1,407	1,655	1,856	701	1,306

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 19% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investment-grade fixed-income securities (for example, bonds and other investments that Loomis Sayles believes have similar economic characteristics, such as notes, debentures and loans). "Investment-grade" securities are those securities that are rated as such at the time of purchase by at least one of the three major rating agencies —  Moody's Investors Service, Inc. ("Moody's"), Fitch Investor Services, Inc. ("Fitch") or Standard & Poor's Ratings Group ("S&P") or, if unrated, are determined by the Adviser to be of comparable quality. Although the Fund invests primarily in investment-grade fixed-income securities, it may invest up to 10% of its assets in below investment-grade fixed-income securities (also known as "junk bonds"). The Fund has the flexibility to invest up to 10% of its assets in equity securities (such as common stocks, preferred stocks and investment companies), but will limit its investments in common stocks to 5% of its assets. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major rating agencies (Moody's, Fitch or S&P) have rated the securities in one of their top four ratings categories) or, if unrated, are determined by the Adviser to be of comparable quality. There is no minimum rating for the securities in which the Fund may invest. The Fund may invest in fixed income-securities of any maturity. In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. Three themes typically drive the Fund's investment approach. First, the Adviser generally seeks fixed-income securities of issuers whose credit profiles it believes are improving. Second, the Fund makes significant use of non-market-related securities, which are securities that may not have a direct correlation with changes in interest rates. The Adviser believes that the Fund may generate positive returns by having a portion of the Fund's assets invested in non-market-related securities, rather than by relying primarily on changes in interest rates to produce returns for the Fund. Third, the Adviser analyzes different sectors of the economy and differences in the yields ("spreads") of various fixed-income securities in an effort to find securities that it believes may produce attractive returns for the Fund in comparison to their risk. The Adviser generally prefers securities that are protected against calls (early redemption by the issuer). In connection with its principal investment strategies, the Fund may also invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in securities of other foreign issuers, including emerging markets securities. The Fund may also invest in obligations of supranational entities without limit ( e.g. , the World Bank), corporate securities, U.S. government securities, commercial paper, zero-coupon securities, mortgage-backed securities, including mortgage dollar rolls, stripped mortgage-backed securities and collateralized mortgage obligations and other asset-backed securities, when-issued securities, convertible securities, Rule 144A securities and structured notes. The Fund may also engage in foreign currency hedging transactions and swap transactions (including credit default swaps) for hedging or investment purposes. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations.Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps, and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478. The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class Y Shares

Highest Quarterly Return:
Second Quarter 2009, 12.65%

Lowest Quarterly Return:
Third Quarter 2008, -7.19%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Investment Grade Bond Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class Y	5.08%	7.75%	8.88%
Class Y Return After Taxes on Distributions	2.85%	5.45%	6.43%
Class Y Return After Taxes on Distributions & Sale of Fund Shares	3.43%	5.30%	6.25%
Class A	0.12%	6.50%	8.08%
Class B	(0.79%)	6.27%	7.67%
Class C	3.09%	6.67%	7.71%
Admin Class	4.52%	7.05%	8.05%
Barclays Capital U.S. Government/Credit Bond Index	8.74%	6.55%	5.85%

The returns shown in the table for Class A shares prior to September 15, 2003 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. For the period from January 1, 2002 to January 31, 2002, during which time Retail Class shares were not outstanding, performance is that of Institutional Class shares, restated to reflect the higher net expenses and sales loads of Class A shares. Prior to the inception of Class B and Class C shares (September 12, 2003), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B and Class C shares, respectively. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class A, B and C shares were offered in a separate prospectus and given that Class A, B and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

[1] Other expenses include an administrative services fee of 0.25% for Admin Class shares.

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund's average daily net assets for Class A, B, C, and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Prospectus Date	rr_ProspectusDate	Feb. 01, 2012

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Loomis Sayles Value Fund

Loomis Sayles Value Fund

Investment Goal

The Fund's investment objective is long-term growth of capital and income.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Value Fund	Class A	Class B	Class C	Class Y	Admin Class
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%	none	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none	none
Redemption fees	none	none	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles Value Fund		Class A	Class B	Class C	Class Y	Admin Class
Management fees		0.50%	0.50%	0.50%	0.50%	0.50%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none	0.25%
Other expenses		0.23%	0.23%	0.23%	0.24%	0.42%	[1]
Total annual fund operating expenses		0.98%	1.73%	1.73%	0.74%	1.17%
Fee waiver and/or expense reimbursement	[2]	none	none	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.98%	1.73%	1.73%	0.74%	1.17%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Value Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	669	676	276	76	119
3 years	869	845	545	237	372
5 years	1,086	1,139	939	411	644
10 years	1,707	1,842	2,041	918	1,420

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Value Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	669	176	176	76	119
3 years	869	545	545	237	372
5 years	1,086	939	939	411	644
10 years	1,707	1,842	2,041	918	1,420

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 29% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest primarily in equity securities, including common stocks, convertible securities and warrants. In deciding which securities to buy and sell, the Adviser generally looks for companies that it believes are undervalued by the market in relation to earnings, dividends, assets and/or growth prospects. The Fund's investments may include companies that have suffered significant business problems but that the Adviser believes have favorable prospects for recovery. The Adviser seeks to identify companies that it believes are, among other things, attractively valued based on the Adviser's estimate of intrinsic value. The Adviser generally seeks to find value by selecting individual stocks that it believes are attractive, rather than by attempting to achieve investment growth by rotating the Fund's holdings among various sectors of the economy. The Fund may also invest up to 20% of its assets in securities of foreign issuers including emerging market securities, invest in options for hedging and investment purposes, real estate investment trusts ("REITs") and Rule 144A securities. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as options transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties,there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Value stocks can perform differently from the market as a whole and from other types of stocks. Value stocks also present the risk that their lower valuations fairly reflect their business prospects and that investors will not agree that the stocks represent favorable investment opportunities, and they may fall out of favor with investors and underperform growth stocks during any given period. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class Y Shares

Highest Quarterly Return:
Second Quarter 2003, 18.11%

Lowest Quarterly Return:
Fourth Quarter 2008, -19.58%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Value Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class Y	(2.81%)	(1.54%)	4.66%
Class Y Return After Taxes on Distributions	(3.04%)	(1.95%)	4.17%
Class Y Return After Taxes on Distributions & Sale of Fund Shares	(1.54%)	(1.35%)	3.97%
Class A	(8.58%)	(3.01%)	3.74%
Class B	(8.61%)	(2.95%)	3.48%
Class C	(4.71%)	(2.57%)	3.49%
Admin Class	(3.21%)	(2.10%)	4.07%
Russell 1000 Value Index	0.39%	(2.64%)	3.89%

The returns shown in the table for Class A shares prior to June 1, 2007 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Retail Class shares (June 30, 2006), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class A shares. Prior to the inception of Class B and Class C shares (June 1, 2007), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B and Class C shares, respectively. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class A, B and C shares were offered in a separate prospectus and given that Class A, B and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y Shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Other expenses include an administrative services fee of 0.25% for Admin Class shares.

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.10%, 1.85%, 1.85%, 0.85% and 1.35% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.10%, 1.85%, 1.85%, 0.85% and 1.35% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Strategic Income Fund

Loomis Sayles Strategic Income Fund

Investment Goal

The Fund seeks high current income

with a secondary objective of capital growth.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Strategic Income Fund	Class A	Class B	Class C	Class Y	Admin Class
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.50%	none	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none	none
Redemption fees	none	none	none	none	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - Loomis Sayles Strategic Income Fund		Class A	Class B	Class C	Class Y	Admin Class
Management fees		0.56%	0.56%	0.56%	0.56%	0.56%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none	0.25%
Other expenses	[1][2]	0.14%	0.14%	0.14%	0.14%	0.40%
Total annual fund operating expenses		0.95%	1.70%	1.70%	0.70%	1.21%
Fee waiver and/or expense reimbursement	[3]	none	none	none	none	none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.95%	1.70%	1.70%	0.70%	1.21%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

 If shares are redeemed

Expense Example - Loomis Sayles Strategic Income Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	543	673	273	72	123
3 years	739	836	536	224	384
5 years	952	1,123	923	390	665
10 years	1,564	1,810	2,009	871	1,466

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Strategic Income Fund (USD $)	Class A	Class B	Class C	Class Y	Admin Class
1 year	543	173	173	72	123
3 years	739	536	536	224	384
5 years	952	923	923	390	665
10 years	1,564	1,810	2,009	871	1,466

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 25% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest substantially all of its assets in income producing securities (including below investment-grade securities, or "junk bonds") with a focus on U.S. corporate bonds, convertible securities, foreign debt instruments, including those in emerging markets and related foreign currency transactions, and U.S. government securities. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")), have rated the securities in one of its top four rating categories) or, if the security is unrated, are determined by the Adviser to be of comparable quality. The Fund may invest up to 35% of its assets in preferred stocks and dividend-paying common stocks. The portfolio managers may shift the Fund's assets among various types of income-producing securities based upon changing market conditions. The Adviser performs its own extensive credit analyses to determine the creditworthiness and potential for capital appreciation of a security. The Fund's portfolio managers use a flexible approach to identify securities in the global marketplace with characteristics including discounted price compared to economic value, undervalued credit ratings with strong or improving credit profiles and yield premium relative to its benchmark (although not all of the securities selected will have these attributes). In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser utilizes the skills of its in-house team of more than 30 research analysts to cover a broad universe of industries, companies and markets. The Fund's portfolio managers take advantage of these extensive resources to identify securities that meet the Fund's investment criteria. The Adviser seeks to buy bonds that offer a positive yield advantage over the market and, in its view, have room to increase in price. It may also invest to take advantage of what the portfolio managers believe are temporary disparities in the yield of different segments of the market for U.S. government securities. The Adviser provides the portfolio managers with maximum flexibility to find investment opportunities in a wide range of markets, both domestic and foreign. This flexible approach provides the Fund with access to a wide array of investment opportunities. The three key sectors that the portfolio managers focus upon are U.S. corporate issues (including convertible securities), foreign debt securities and U.S. government securities. The Fund's portfolio managers maintain a core of the Fund's investments in corporate bond issues and shift its assets among other income-producing securities as opportunities develop. The Fund generally seeks to maintain a high level of diversification as a form of risk management. In connection with its principal investment strategies, the Fund may also invest in Rule 144A securities, structured notes, zero-coupon bonds, pay-in-kind bonds, mortgage-related securities, stripped securities and futures, swaps (including credit default swaps) and foreign currency transactions for hedging and investment purposes. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

Highest Quarterly Return:
Second Quarter 2009, 18.02%

Lowest Quarterly Return:
Third Quarter 2008, -13.38%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Strategic Income Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class A	(0.29%)	5.39%	10.25%
Class A Return After Taxes on Distributions	(2.33%)	3.05%	7.85%
Class A Return After Taxes on Distributions & Sale of Fund Shares	(0.09%)	3.20%	7.50%
Class B	(2.31%)	5.03%	9.81%
Class C	1.59%	5.35%	9.81%
Class Y	3.54%	6.40%	10.93%
Admin Class	3.05%	5.82%	10.28%
Barclays Capital U.S. Aggregate Bond Index	7.84%	6.50%	5.78%
Barclays Capital U.S. Universal Bond Index	7.40%	6.39%	6.01%

The returns shown in the bar chart and table for the periods prior to September 15, 2003 reflect the results of the CDC Nvest Strategic Income Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class Y and Admin Class shares were offered in a separate prospectus and given that Class Y and Admin Class shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] The expense information shown in the table above may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (expenses indirectly borne by the Fund through investments in certain pooled investment vehicles).

[2] Other Expenses include an administrative service fee of 0.25% for Admin Class shares.

[3] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00%, 2.00%, 1.00% and 1.50% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00%, 2.00%, 1.00% and 1.50% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Limited Term Government and Agency Fund

Loomis Sayles Limited Term Government and Agency Fund

Investment Goal

The Fund seeks high current return consistent with preservation of capital.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Limited Term Government and Agency Fund	Class A	Class B	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	3.00%	none	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.00%	1.00%	none
Redemption fees	none	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles Limited Term Government and Agency Fund		Class A	Class B	Class C	Class Y
Management fees		0.46%	0.46%	0.46%	0.46%
Distribution and/or service (12b-1) fees		0.25%	1.00%	1.00%	none
Other expenses		0.21%	0.22%	0.21%	0.21%
Total annual fund operating expenses		0.92%	1.68%	1.67%	0.67%
Fee waiver and/or expense reimbursement	[1]	0.07%	0.08%	0.07%	0.07%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.85%	1.60%	1.60%	0.60%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Limited Term Government and Agency Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	384	663	263	61
3 years	578	822	520	207
5 years	787	1,105	901	366
10 years	1,391	1,778	1,970	828

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Limited Term Government and Agency Fund (USD $)	Class A	Class B	Class C	Class Y
1 year	384	163	163	61
3 years	578	522	520	207
5 years	787	905	901	366
10 years	1,391	1,778	1,970	828

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 66% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investments issued or guaranteed by the U.S. government, its agencies or instrumentalities. The Adviser follows a total return-oriented investment approach in selecting securities for the Fund. It seeks securities that will provide the Fund with an average credit quality equal to the credit rating of the U.S. Government's long-term debt and an effective portfolio duration range of two to four years (although not all securities selected will have these characteristics and the Adviser may look for other characteristics if market conditions change). The Fund may invest in securities with credit quality above or below the credit rating of the U.S. Government's long-term debt. In determining credit quality, the Adviser will look to the highest credit rating assigned by Standard & Poor's Ratings Group ("S&P"), Fitch Investor Services, Inc. ("Fitch") or Moody's Investors Service, Inc. ("Moody's"). In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser's research analysts work closely with the Fund's portfolio managers to develop an outlook on the economy from research produced by various financial firms and specific forecasting services or from economic data released by the U.S. and foreign governments as well as the Federal Reserve Bank. The analysts also conduct a thorough review of individual securities to identify what they consider attractive values in the U.S. government security marketplace through the use of quantitative tools such as internal and external computer systems and software. The Adviser continuously monitors an issuer's creditworthiness to assess whether the obligation remains an appropriate investment for the Fund. The Adviser seeks to balance opportunities for yield and price performance by combining macroeconomic analysis with individual security selection. It emphasizes securities that tend to perform particularly well in response to interest rate changes, such as U.S. Treasury securities in a declining interest rate environment and mortgage-backed or U.S. government agency securities in a steady or rising interest rate environment. The Adviser seeks to increase the opportunity for higher yields while maintaining the greater price stability that intermediate-term bonds have compared to bonds with longer maturities. In connection with its principal investment strategies, the Fund may also invest in investment-grade corporate notes and bonds, zero-coupon bonds, Rule 144A securities, structured notes, foreign bonds denominated in U.S. dollars, asset-backed securities, mortgage-related securities including mortgage dollar rolls and futures. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Agency Securities Risk: Agency securities are subject to fixed-income securities risk. Certain debt securities issued or guaranteed by agencies of the U.S. government are guaranteed as to the payment of principal and interest by the relevant entity but have not been backed by the full faith and credit of the U.S. government. Instead, they have been supported only by the discretionary authority of the U.S. government to purchase the agency's obligations. An event affecting the guaranteeing entity could adversely affect the payment of principal or interest or both on the security and, therefore, these types of securities should be considered to be riskier than U.S. government securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The Fund's use of derivatives such as futures transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

       

Highest Quarterly Return:
Second Quarter 2002, 3.55%

Lowest Quarterly Return:
Second Quarter 2004, -1.76%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Limited Term Government and Agency Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class A	(0.51%)	4.41%	3.85%
Class A Return After Taxes on Distributions	(1.33%)	3.20%	2.53%
Class A Return After Taxes on Distributions & Sale of Fund Shares	(0.33%)	3.06%	2.50%
Class B	(3.17%)	3.93%	3.42%
Class C	0.83%	4.29%	3.43%
Class Y	2.85%	5.33%	4.45%
Barclays Capital U.S. 1-5 Year Government Bond Index	3.21%	4.76%	4.05%

The Fund's current adviser assumed that function on September 1, 2003. Prior to that, it served as subadviser to the Fund, a role it assumed in June 2001. The returns shown in the bar chart and table for periods prior to September 15, 2003 reflect the results of the CDC Nvest Limited Term U.S. Government Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.85%, 1.60%, 1.60% and 0.60% of the Fund's average daily net assets for Class A, B, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 0.85%, 1.60%, 1.60% and 0.60% of the Fund's average daily net assets for Class A, B, C, and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Global Equity and Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.24%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.24%

1 year

rr_ExpenseExampleYear01

694

3 years

rr_ExpenseExampleYear03

946

5 years

rr_ExpenseExampleYear05

1,217

10 years

rr_ExpenseExampleYear10

1,989

1 year

rr_ExpenseExampleNoRedemptionYear01

694

3 years

rr_ExpenseExampleNoRedemptionYear03

946

5 years

rr_ExpenseExampleNoRedemptionYear05

1,217

10 years

rr_ExpenseExampleNoRedemptionYear10

1,989

Past 1 Year

rr_AverageAnnualReturnYear01

(6.62%)

Past 5 Years

rr_AverageAnnualReturnYear05

4.28%

Past 10 Years

rr_AverageAnnualReturnYear10

8.54%

Loomis Sayles Global Equity and Income Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.99%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

1.99%

1 year

rr_ExpenseExampleYear01

302

3 years

rr_ExpenseExampleYear03

624

5 years

rr_ExpenseExampleYear05

1,073

10 years

rr_ExpenseExampleYear10

2,317

1 year

rr_ExpenseExampleNoRedemptionYear01

202

3 years

rr_ExpenseExampleNoRedemptionYear03

624

5 years

rr_ExpenseExampleNoRedemptionYear05

1,073

10 years

rr_ExpenseExampleNoRedemptionYear10

2,317

Past 1 Year

rr_AverageAnnualReturnYear01

(2.65%)

Past 5 Years

rr_AverageAnnualReturnYear05

4.73%

Past 10 Years

rr_AverageAnnualReturnYear10

8.37%

Loomis Sayles Global Equity and Income Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.75%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.99%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

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

rr_NetExpensesOverAssets

0.99%

1 year

rr_ExpenseExampleYear01

101

3 years

rr_ExpenseExampleYear03

315

5 years

rr_ExpenseExampleYear05

547

10 years

rr_ExpenseExampleYear10

1,213

1 year

rr_ExpenseExampleNoRedemptionYear01

101

3 years

rr_ExpenseExampleNoRedemptionYear03

315

5 years

rr_ExpenseExampleNoRedemptionYear05

547

10 years

rr_ExpenseExampleNoRedemptionYear10

1,213

Annual Return 2002

rr_AnnualReturn2002

(0.27%)

Annual Return 2003

rr_AnnualReturn2003

31.16%

Annual Return 2004

rr_AnnualReturn2004

14.12%

Annual Return 2005

rr_AnnualReturn2005

12.38%

Annual Return 2006

rr_AnnualReturn2006

11.06%

Annual Return 2007

rr_AnnualReturn2007

26.49%

Annual Return 2008

rr_AnnualReturn2008

(39.19%)

Annual Return 2009

rr_AnnualReturn2009

42.52%

Annual Return 2010

rr_AnnualReturn2010

21.69%

Annual Return 2011

rr_AnnualReturn2011

(0.73%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.91%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.64%)

Past 1 Year

rr_AverageAnnualReturnYear01

(0.73%)

Past 5 Years

rr_AverageAnnualReturnYear05

5.78%

Past 10 Years

rr_AverageAnnualReturnYear10

9.45%

Loomis Sayles Global Equity and Income Fund | Class Y | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(1.11%)

Past 5 Years

rr_AverageAnnualReturnYear05

4.90%

Past 10 Years

rr_AverageAnnualReturnYear10

8.54%

Loomis Sayles Global Equity and Income Fund | Class Y | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(0.25%)

Past 5 Years

rr_AverageAnnualReturnYear05

4.53%

Past 10 Years

rr_AverageAnnualReturnYear10

7.85%

Loomis Sayles Global Equity and Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Global Equity and Income Fund (formerly Loomis Sayles Global Markets Fund)

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund's investment goal is high total investment return through a combination of capital appreciation and current income.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 65% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

65.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in equity and fixed-income securities of U.S. and foreign issuers. Equity securities purchased by the Fund may include common stocks, preferred stocks, depositary receipts, warrants, securities convertible into common or preferred stocks, interests in real estate investment trusts ("REITs") and/or real estate-related securities and other equity-like interests in an issuer. The Fund will invest a significant portion of its assets outside the U.S., including securities of issuers located in emerging market countries. In deciding which domestic and international equity securities to buy and sell, the Adviser generally looks for companies that it believes have the potential for superior earnings growth relative to their current value. The Adviser also looks for companies that appear to be undervalued relative to the intrinsic value of the companies' assets or cash flows. In deciding which domestic and international fixed-income securities to buy and sell, the Adviser generally looks for securities that it believes are undervalued and have the potential for credit upgrades, which may include securities that are below investment-grade (also known as "junk bonds"). The Fund may also invest in foreign currencies, collateralized mortgage obligations, zero-coupon securities, when-issued securities, real estate investment trusts ("REITs"), Rule 144A securities and mortgage-related securities. The Fund may also engage in active and frequent trading of securities and engage in options or foreign currency transactions for hedging and investment purposes and futures transactions, foreign currency transactions and swap transactions (including credit default swaps). Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. The Adviser may hedge currency risk for the Fund (including "cross hedging" between two or more foreign currencies) if it believes the outlook for a particular foreign currency is unfavorable. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Allocation Risk: The Fund's investment performance depends on how its assets are allocated. The allocation, as set forth above, may not be optimal in every market condition. You could lose money on your investment in the Fund as a result of this allocation. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives, such as forward currency contracts, options and futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. Value stocks can perform differently from the market as a whole and from other types of stocks. Value stocks also present the risk that their lower valuations fairly reflect their business prospects and that investors will not agree that the stocks represent favorable investment opportunities, and they may fall out of favor with investors and underperform growth stocks during any given period. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce the Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related securities are subject to the risks of the mortgages underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium.REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478. The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2009, 19.91%

Lowest Quarterly Return:
Third Quarter 2008, -19.64%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The returns shown in the table prior to the inception of Class A and Class C shares (February 1, 2006) are those of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class A and Class C shares, respectively. Prior to February 1, 2012, Class A and C shares were offered in a separate prospectus and given that Class A and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Global Equity and Income Fund | MSCI World Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(5.02%)

Past 5 Years

rr_AverageAnnualReturnYear05

(1.82%)

Past 10 Years

rr_AverageAnnualReturnYear10

4.15%

Loomis Sayles Global Equity and Income Fund | Citigroup World Government Bond Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

6.35%

Past 5 Years

rr_AverageAnnualReturnYear05

7.13%

Past 10 Years

rr_AverageAnnualReturnYear10

7.77%

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

LOOMIS SAYLES FUNDS II

Prospectus Date

rr_ProspectusDate

Feb. 01, 2012

Loomis Sayles Strategic Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.50%

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.56%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.14%

^[1],[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.95%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[3]

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

rr_NetExpensesOverAssets

0.95%

1 year

rr_ExpenseExampleYear01

543

3 years

rr_ExpenseExampleYear03

739

5 years

rr_ExpenseExampleYear05

952

10 years

rr_ExpenseExampleYear10

1,564

1 year

rr_ExpenseExampleNoRedemptionYear01

543

3 years

rr_ExpenseExampleNoRedemptionYear03

739

5 years

rr_ExpenseExampleNoRedemptionYear05

952

10 years

rr_ExpenseExampleNoRedemptionYear10

1,564

Annual Return 2002

rr_AnnualReturn2002

15.47%

Annual Return 2003

rr_AnnualReturn2003

34.84%

Annual Return 2004

rr_AnnualReturn2004

12.93%

Annual Return 2005

rr_AnnualReturn2005

3.74%

Annual Return 2006

rr_AnnualReturn2006

11.85%

Annual Return 2007

rr_AnnualReturn2007

7.26%

Annual Return 2008

rr_AnnualReturn2008

(23.15%)

Annual Return 2009

rr_AnnualReturn2009

39.30%

Annual Return 2010

rr_AnnualReturn2010

13.53%

Annual Return 2011

rr_AnnualReturn2011

3.35%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.02%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(13.38%)

Past 1 Year

rr_AverageAnnualReturnYear01

(0.29%)

Past 5 Years

rr_AverageAnnualReturnYear05

5.39%

Past 10 Years

rr_AverageAnnualReturnYear10

10.25%

Loomis Sayles Strategic Income Fund | Class A | Return After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(2.33%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.05%

Past 10 Years

rr_AverageAnnualReturnYear10

7.85%

Loomis Sayles Strategic Income Fund | Class A | Return After Taxes on Distributions & Sale of Fund Shares

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

(0.09%)

Past 5 Years

rr_AverageAnnualReturnYear05

3.20%

Past 10 Years

rr_AverageAnnualReturnYear10

7.50%

Loomis Sayles Strategic Income Fund | Class B

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

5.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.56%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.14%

^[1],[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.70%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[3]

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

rr_NetExpensesOverAssets

1.70%

1 year

rr_ExpenseExampleYear01

673

3 years

rr_ExpenseExampleYear03

836

5 years

rr_ExpenseExampleYear05

1,123

10 years

rr_ExpenseExampleYear10

1,810

1 year

rr_ExpenseExampleNoRedemptionYear01

173

3 years

rr_ExpenseExampleNoRedemptionYear03

536

5 years

rr_ExpenseExampleNoRedemptionYear05

923

10 years

rr_ExpenseExampleNoRedemptionYear10

1,810

Past 1 Year

rr_AverageAnnualReturnYear01

(2.31%)

Past 5 Years

rr_AverageAnnualReturnYear05

5.03%

Past 10 Years

rr_AverageAnnualReturnYear10

9.81%

Loomis Sayles Strategic Income Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.56%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.14%

^[1],[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.70%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[3]

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

rr_NetExpensesOverAssets

1.70%

1 year

rr_ExpenseExampleYear01

273

3 years

rr_ExpenseExampleYear03

536

5 years

rr_ExpenseExampleYear05

923

10 years

rr_ExpenseExampleYear10

2,009

1 year

rr_ExpenseExampleNoRedemptionYear01

173

3 years

rr_ExpenseExampleNoRedemptionYear03

536

5 years

rr_ExpenseExampleNoRedemptionYear05

923

10 years

rr_ExpenseExampleNoRedemptionYear10

2,009

Past 1 Year

rr_AverageAnnualReturnYear01

1.59%

Past 5 Years

rr_AverageAnnualReturnYear05

5.35%

Past 10 Years

rr_AverageAnnualReturnYear10

9.81%

Loomis Sayles Strategic Income Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.56%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.14%

^[1],[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.70%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[3]

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

rr_NetExpensesOverAssets

0.70%

1 year

rr_ExpenseExampleYear01

72

3 years

rr_ExpenseExampleYear03

224

5 years

rr_ExpenseExampleYear05

390

10 years

rr_ExpenseExampleYear10

871

1 year

rr_ExpenseExampleNoRedemptionYear01

72

3 years

rr_ExpenseExampleNoRedemptionYear03

224

5 years

rr_ExpenseExampleNoRedemptionYear05

390

10 years

rr_ExpenseExampleNoRedemptionYear10

871

Past 1 Year

rr_AverageAnnualReturnYear01

3.54%

Past 5 Years

rr_AverageAnnualReturnYear05

6.40%

Past 10 Years

rr_AverageAnnualReturnYear10

10.93%

Loomis Sayles Strategic Income Fund | Admin Class

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fees

rr_RedemptionFeeOverRedemption

none

Management fees

rr_ManagementFeesOverAssets

0.56%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.40%

^[1],[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.21%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[3]

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

rr_NetExpensesOverAssets

1.21%

1 year

rr_ExpenseExampleYear01

123

3 years

rr_ExpenseExampleYear03

384

5 years

rr_ExpenseExampleYear05

665

10 years

rr_ExpenseExampleYear10

1,466

1 year

rr_ExpenseExampleNoRedemptionYear01

123

3 years

rr_ExpenseExampleNoRedemptionYear03

384

5 years

rr_ExpenseExampleNoRedemptionYear05

665

10 years

rr_ExpenseExampleNoRedemptionYear10

1,466

Past 1 Year

rr_AverageAnnualReturnYear01

3.05%

Past 5 Years

rr_AverageAnnualReturnYear05

5.82%

Past 10 Years

rr_AverageAnnualReturnYear10

10.28%

Loomis Sayles Strategic Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Loomis Sayles Strategic Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks high current income

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

with a secondary objective of capital growth.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees(fees paid directly from your investment)

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

January 31, 2013

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 25% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

25.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

 If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund will invest substantially all of its assets in income producing securities (including below investment-grade securities, or "junk bonds") with a focus on U.S. corporate bonds, convertible securities, foreign debt instruments, including those in emerging markets and related foreign currency transactions, and U.S. government securities. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")), have rated the securities in one of its top four rating categories) or, if the security is unrated, are determined by the Adviser to be of comparable quality. The Fund may invest up to 35% of its assets in preferred stocks and dividend-paying common stocks. The portfolio managers may shift the Fund's assets among various types of income-producing securities based upon changing market conditions. The Adviser performs its own extensive credit analyses to determine the creditworthiness and potential for capital appreciation of a security. The Fund's portfolio managers use a flexible approach to identify securities in the global marketplace with characteristics including discounted price compared to economic value, undervalued credit ratings with strong or improving credit profiles and yield premium relative to its benchmark (although not all of the securities selected will have these attributes). In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. In selecting investments for the Fund, the Adviser utilizes the skills of its in-house team of more than 30 research analysts to cover a broad universe of industries, companies and markets. The Fund's portfolio managers take advantage of these extensive resources to identify securities that meet the Fund's investment criteria. The Adviser seeks to buy bonds that offer a positive yield advantage over the market and, in its view, have room to increase in price. It may also invest to take advantage of what the portfolio managers believe are temporary disparities in the yield of different segments of the market for U.S. government securities. The Adviser provides the portfolio managers with maximum flexibility to find investment opportunities in a wide range of markets, both domestic and foreign. This flexible approach provides the Fund with access to a wide array of investment opportunities. The three key sectors that the portfolio managers focus upon are U.S. corporate issues (including convertible securities), foreign debt securities and U.S. government securities. The Fund's portfolio managers maintain a core of the Fund's investments in corporate bond issues and shift its assets among other income-producing securities as opportunities develop. The Fund generally seeks to maintain a high level of diversification as a form of risk management. In connection with its principal investment strategies, the Fund may also invest in Rule 144A securities, structured notes, zero-coupon bonds, pay-in-kind bonds, mortgage-related securities, stripped securities and futures, swaps (including credit default swaps) and foreign currency transactions for hedging and investment purposes. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of two broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class A Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2009, 18.02%

Lowest Quarterly Return:
Third Quarter 2008, -13.38%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary.

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The returns shown in the bar chart and table for the periods prior to September 15, 2003 reflect the results of the CDC Nvest Strategic Income Fund, whose assets and liabilities were reorganized into the Fund on September 12, 2003. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class Y and Admin Class shares were offered in a separate prospectus and given that Class Y and Admin Class shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

Loomis Sayles Strategic Income Fund | Barclays Capital U.S. Aggregate Bond Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

7.84%

Past 5 Years

rr_AverageAnnualReturnYear05

6.50%

Past 10 Years

rr_AverageAnnualReturnYear10

5.78%

Loomis Sayles Strategic Income Fund | Barclays Capital U.S. Universal Bond Index

Risk/Return:

rr_RiskReturnAbstract

Past 1 Year

rr_AverageAnnualReturnYear01

7.40%

Past 5 Years

rr_AverageAnnualReturnYear05

6.39%

Past 10 Years

rr_AverageAnnualReturnYear10

6.01%

[1] The expense information shown in the table above may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (expenses indirectly borne by the Fund through investments in certain pooled investment vehicles).

[2] Other Expenses include an administrative service fee of 0.25% for Admin Class shares.

[3] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00%, 2.00%, 1.00% and 1.50% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00%, 2.00%, 1.00% and 1.50% of the Fund's average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles International Bond Fund

Loomis Sayles International Bond Fund

Investment Goal

The Fund seeks high total investment return through a combination of high current income and capital appreciation.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles International Bond Fund	Class A	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.50%	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	1.00%	none
Redemption fees	none	none	none

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

Annual Fund Operating Expenses - Loomis Sayles International Bond Fund		Class A	Class C	Class Y
Management fees		0.60%	0.60%	0.60%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none
Other expenses		0.79%	0.80%	0.76%
Total annual fund operating expenses		1.64%	2.40%	1.36%
Fee waiver and/or expense reimbursement	[1]	0.54%	0.55%	0.51%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.10%	1.85%	0.85%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles International Bond Fund (USD $)	Class A	Class C	Class Y
1 year	557	288	87
3 years	894	696	380
5 years	1,253	1,231	696
10 years	2,263	2,694	1,591

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles International Bond Fund (USD $)	Class A	Class C	Class Y
1 year	557	188	87
3 years	894	696	380
5 years	1,253	1,231	696
10 years	2,263	2,694	1,591

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 136% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund expects to invest at least 80% of its net assets (plus any borrowings made for investment purposes) in fixed-income securities. The Fund is non-diversified, which means that it may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers than a diversified fund. The Fund invests primarily (at least 65% of its net assets) in fixed-income securities of issuers located outside the United States. Securities held by the Fund may be denominated in any currency and may be of issuers located in emerging market countries. The Fund invests primarily in investment-grade fixed-income securities. "Investment-grade" securities are those securities that are rated as such at the time of purchase by at least one of the three major rating agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or Standard and Poor's Ratings Group ("S&P")) or, if unrated, are determined by the Adviser to be of comparable quality, although the Fund may invest up to 35% of its assets in below investment-grade fixed-income securities (commonly known as "junk bonds"). There is no minimum rating for securities in which the Fund will invest. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major ratings agencies (Moody's, Fitch or S&P) have rated the securities in one of its top four ratings categories) or, if unrated, are determined by the Adviser to be of comparable quality. The Fund may invest in fixed-income securities of any maturity. The Fund may also invest in foreign currencies and may engage in other foreign currency transactions for investment or for hedging purposes. In deciding which securities to buy and sell, the Adviser may consider, among other things, the stability and volatility of a country's bond markets, the financial strength of the issuer, current interest rates, current valuations, currency considerations, the Adviser's expectations regarding general trends in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments. Three themes typically drive the Fund's investment approach. First, the Adviser generally seeks fixed-income securities of issuers whose credit profiles it believes are improving. The Adviser's credit research team provides deep fundamental and quantitative analysis as well as ratings on over 1,000 credits worldwide. The broad coverage combined with the objective to identify attractive investment opportunities makes this an important component of the investment approach. Second, the Adviser analyzes political, economic, and other fundamental factors and combines this analysis with a comparison of the yield spreads of various fixed-income securities in an effort to find securities that it believes may produce attractive returns for the Fund in comparison to their risk. Third, if a security that is believed to be attractive is denominated in a foreign currency, the Adviser analyzes whether to accept or to hedge the currency risk. In certain instances, the Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The fixed-income securities in which the Fund may invest include public or private debt obligations issued or guaranteed by U.S. or non-U.S. issuers, including, but not limited to, corporations, governments (including their agencies, instrumentalities and sponsored entities), supranational entities, partnerships and trusts. The Fund may also invest in preferred stocks, convertible securities, when-issued securities, Rule 144A securities, mortgage- or asset-backed securities and zero-coupon securities issued by any of the above-named entities. In connection with its principal investment strategies, the Fund may also invest in inflation- and index-linked securities, senior loans, structured notes, common stocks (limited to shares acquired as a result of a financial restructuring, bankruptcy or similar transaction or from an exchange or conversion of a permissible security held in the portfolio), and derivatives, including options, futures, options on futures, forward contracts and swap contracts (including credit default swaps). The Fund may also engage in active and frequent trading of securities. Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund's investments in below investment-grade fixed-income securities, also known as "junk bonds," may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities.
Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts, structured notes, options and futures transactions and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security's value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer's continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund's ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund's investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Senior loans typically have adjustable interest rates. As a result, it is expected that the values of senior loans held by the Fund will fluctuate less in response to interest rate changes than will fixed-rate debt securities; however, the interest rates paid by these loans will generally decrease if interest rates fall. Senior loans and other fixed-income securities are subject to the risk that borrowers pay off the debts sooner than expected. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts.
Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets. Non-Diversification Risk: Compared with other mutual funds, the Fund may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers. Therefore, the Fund may have more risk because changes in the value of a single security or the impact of a single economic, political or regulatory occurrence may have a greater adverse impact on the Fund's net asset value ("NAV").

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year and life-of-fund compare with those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

Highest Quarterly Return:
Third Quarter 2010, 11.59%

 Lowest Quarterly Return:
First Quarter 2009, -3.76%

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles International Bond Fund	Past 1 Year	Life of Fund	Inception Date
Class A	(0.30%)	4.56%	Feb. 01, 2008
Class A Return After Taxes on Distributions	(4.42%)	2.55%	Feb. 01, 2008
Class A Return After Taxes on Distributions & Sale of Fund Shares	0.11%	2.78%	Feb. 01, 2008
Class C	2.77%	5.00%	Feb. 01, 2008
Class Y	4.69%	6.04%	Feb. 01, 2008
Barclays Capital Global Aggregate ex-USD Bond Index	4.36%	4.52%

Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.10%, 1.85% and 0.85% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.10%, 1.85% and 0.85% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Mid Cap Growth Fund

Loomis Sayles Mid Cap Growth Fund

Investment Goal

The Fund's investment objective is long-term capital growth from investments in common stocks or similar securities.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 36 of the Prospectus and on page 106 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

 Shareholder Fees(fees paid directly from your investment)

Shareholder Fees - Loomis Sayles Mid Cap Growth Fund	Class A	Class C	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%	none	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	1.00%	none
Redemption fees	none	none	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - Loomis Sayles Mid Cap Growth Fund		Class A	Class C	Class Y
Management fees		0.75%	0.75%	0.75%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none
Other expenses		0.32%	0.33%	0.32%
Total annual fund operating expenses		1.32%	2.08%	1.07%
Fee waiver and/or expense reimbursement	[1]	0.07%	0.07%	0.07%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.25%	2.01%	1.00%

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 then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed

Expense Example - Loomis Sayles Mid Cap Growth Fund (USD $)	Class A	Class C	Class Y
1 year	695	304	102
3 years	963	645	333
5 years	1,251	1,112	583
10 years	2,068	2,405	1,299

If shares are not redeemed

Expense Example, No Redemption - Loomis Sayles Mid Cap Growth Fund (USD $)	Class A	Class C	Class Y
1 year	695	204	102
3 years	963	645	333
5 years	1,251	1,112	583
10 years	2,068	2,405	1,299

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 204% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in common stocks or other equity securities, including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in companies whose market capitalization falls within the Russell Midcap Growth Index. While the market capitalization range for this index fluctuates, at December 31, 2011, it was $54.7 million to $19.2 billion. The Fund may invest the rest of its assets in companies of any size. In deciding which securities to buy and sell, the Adviser seeks to identify companies that it believes have distinctive products, technologies or services, dynamic earnings growth, prospects for high levels of profitability and/or solid management. The Adviser typically does not consider current income when making buy/sell decisions. The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. The Fund may engage in foreign currency transactions, options for hedging and investment purposes and futures transactions, and may also engage in securities lending. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. The Fund also may invest in securities offered in the secondary markets or in initial public offerings, real estate investment trusts ("REITs") and Rule 144A securities. The Fund may engage in active and frequent trading of securities. Frequent trading may produce high transaction costs and a high level of taxable capital gains, which may lower the Fund's return. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund's exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund's liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund's use of derivatives such as forward currency contracts and options and futures transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund's investments in equity securities could be subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. Securities issued in IPOs tend to involve greater market risk than other equity securities due, in part, to public perception and the lack of publicly available information and trading history. Rule 144A securities may be less liquid than other equity securities. Growth stocks are generally more sensitive to market movements than other types of stocks primarily because their stock prices are based heavily on future expectations. If the Adviser's assessment of the prospects for a company's growth is wrong, or if the Adviser's judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that the Adviser has placed on it. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds and preferred stock generally take precedence over the claims of those who own common stock.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund's investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Issuer Risk: The value of the Fund's investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund's returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund's portfolio manager may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions. REITs Risk: Investments in the real estate industry, including REITs, are particularly sensitive to economic downturns and are sensitive to factors such as changes in real estate values, property taxes and tax laws, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents and the management skill and creditworthiness of the issuer. Companies in the real estate industry also may be subject to liabilities under environmental and hazardous waste laws. In addition, the value of a REIT is affected by changes in the value of the properties owned by the REIT or mortgage loans held by the REIT. REITs are also subject to default and prepayment risk. Many REITs are highly leveraged, increasing their risk. The Fund will indirectly bear its proportionate share of expenses, including management fees, paid by each REIT in which it invests in addition to the expenses of the Fund. Small Capitalization Risk: The general risks associated with corporate income-producing securities are particularly pronounced for securities issued by companies with smaller market capitalizations. These companies may have limited product lines, markets or financial resources or they may depend on a few key employees. As a result, they may be subject to greater levels of credit, market and issuer risk. Securities of smaller companies may trade less frequently and in lesser volume than more widely-held securities and their values may fluctuate more sharply than other securities. Further, securities of smaller companies may perform differently in different cycles than securities of larger companies. Companies with medium-sized market capitalizations may have risks similar to those of smaller companies.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

Total Returns for Class A Shares

Highest Quarterly Return:
Second Quarter 2003, 19.49%

Lowest Quarterly Return:
Third Quarter 2008, -26.07%

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns - Loomis Sayles Mid Cap Growth Fund	Past 1 Year	Past 5 Years	Past 10 Years
Class A	(12.67%)	2.39%	3.83%
Class A Return After Taxes on Distributions	(12.67%)	2.39%	3.81%
Class A Return After Taxes on Distributions & Sale of Fund Shares	(8.23%)	2.04%	3.32%
Class C	(8.95%)	2.82%	3.64%
Class Y	(7.13%)	3.86%	4.71%
Russell Midcap Growth Index	(1.65%)	2.44%	5.29%

The returns shown in the chart and table for Class A shares prior to February 1, 2009 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. Prior to the inception of Class C shares (February 2, 2009), performance is that of Retail Class shares, which were redesignated as Class A shares, restated to reflect the higher net expenses and sales loads of Class C shares. The Fund (formerly, Loomis Sayles Aggressive Growth Fund) changed its name and revised its investment strategies on February 1, 2007. The Fund's performance may have been different had the current investment strategies been in place for all of the periods shown. Prior to February 1, 2012, Class Y shares were offered in a separate prospectus and given that Class Y shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class A Shares.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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. In some cases the after-tax returns may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.25%, 2.00% and 1.00% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Loomis Sayles Small Cap Growth Fund

Loomis Sayles Small Cap Growth Fund

Investment Objective

The Fund's investment objective is long-term capital growth from investments in common stocks or other equity securities.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

The Fund does not impose a sales charge, a redemption fee or an exchange fee.

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Loomis Sayles Small Cap Growth Fund		Institutional Class	Retail Class
Management fees		0.75%	0.75%
Distribution and/or service (12b-1) fees		none	0.25%
Other expenses		0.23%	0.27%
Total annual fund operating expenses		0.98%	1.27%
Fee waiver and/or expense reimbursement	[1]	none	0.02%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.98%	1.25%

Example

The 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 then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and the Fund's operating expenses remain the same. The example for the Institutional Class shares is based on Total Annual Operating Expenses for all periods. The example for Retail Class shares is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - Loomis Sayles Small Cap Growth Fund (USD $)	1 year	3 years	5 years	10 years
Institutional Class	100	312	542	1,201
Retail Class	127	401	695	1,532

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 for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During its most recently ended fiscal year, the Fund's portfolio turnover rate was 76% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

The Fund normally will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in the equity securities of "small-cap companies," including preferred stocks, warrants, securities convertible into common or preferred stocks and other equity-like interests in an entity. Currently, the Fund defines a small-cap company to be one whose market capitalization either falls within the capitalization range of the Russell 2000 Index, an index that tracks stocks of 2,000 of the smallest U.S. companies, or is $3 billion or less at the time of investment. The Fund may invest the rest of its assets in companies of any size, including large-capitalization companies.

In deciding which securities to buy and sell, Loomis Sayles typically seeks to identify companies that it believes have distinctive products, technologies, or services; dynamic earnings growth; prospects for high levels of profitability; and solid management. Loomis Sayles typically does not consider current income when making buy/sell decisions.

The Fund may invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in other foreign securities, including emerging markets securities. The Fund may also invest in Rule 144A securities.

The Fund may engage in foreign currency transactions, options (for hedging and investment purposes) and futures transactions.

Principal Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund.

Credit Risk is the risk that the issuer or guarantor of a fixed-income security in which the Fund invests, or the counterparty to a derivatives or other transaction will fail financially or otherwise be unwilling or unable to meet their obligations to the Fund.

Currency Risk is the risk that the value of the Fund's investments will fall as a result of changes in exchange rates. Loomis Sayles may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged.

Derivatives Risk is the risk that the value of the Fund's derivative investments such as forward currency contracts and options and futures transactions will fall, for example, because of changes in the value of the underlying reference instruments, pricing difficulties or lack of correlation with the underlying investments. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund's derivative counterparties, there can be no assurance that the Fund's derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. This risk is greater for forward currency contracts and other over-the-counter traded derivatives. Investing in derivatives gives rise to other risks, such as leverage risk, liquidity risk, credit risk, counterparty risk, interest rate risk and market risk. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used.

Emerging Markets Risk is the risk that the Fund's investments may face greater foreign securities risk. Investing in companies traded in emerging securities markets, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets.

Equity Securities Risk is the risk that the value of a stock may decline for a number of reasons which relate directly to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services, or the equity markets generally. Growth stocks are generally more sensitive to market movements than other types of stocks, primarily because their stock prices are based heavily on future expectations. If Loomis Sayles' assessment of the prospects for a company's growth is wrong, or if Loomis Sayles' judgment of how other investors will value the company's growth is wrong, then the price of the company's stock may fall or not approach the value that Loomis Sayles has placed on it.

Foreign Securities Risk is the risk that the value of the Fund's foreign investments will fall as a result of foreign political, social, economic or currency changes or other issues relating to foreign investing generally. The Fund's investments in foreign securities may be subject to foreign withholding taxes, which would decrease the yield on those securities.

Issuer Risk is the risk that the value of securities may decline due to a number of reasons relating to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services.

Leverage Risk is the risk associated with securities or practices (e.g., borrowing and the use of certain derivatives) and investment in certain types of derivatives that multiply small index or market movements into larger changes in value. Use of derivative instruments may involve leverage. When a derivative is used as a hedge against an offsetting position that the Fund also holds, any loss generated by the derivative should be substantially offset by gains on the hedged instrument, and vice versa. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. Futures and forward currency contracts are derivatives and may be subject to this type of risk.

Liquidity Risk is the risk that the Fund may be unable to find a buyer for its investments when it seeks to sell them or to receive the price it expects. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk is the risk that Loomis Sayles' investment techniques will be unsuccessful and cause the Fund to incur losses.

Market Risk is the risk that the market value of a security may move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer's financial condition, as well as overall market and economic conditions.

Small-Capitalization Companies Risk is the risk that the Fund's investments may be subject to more abrupt price movements, limited markets, increased volatility and less liquidity than investments in larger, more established companies, which could adversely affect the value of the portfolio.

Risk/Return Bar Chart and Table

The following bar chart and table give an indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for the one-year, five-year, ten-year and life-of-fund periods compare to those of broad measure of market performance. The Fund's past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at www.loomissayles.com and/or by calling the Fund toll-free at 800-633-3330.

Total Returns for Institutional Class Shares

The Fund's best quarter was 25.29%, (second quarter of 2003), and the Fund's worst quarter was -26.86%, (fourth quarter of 2008).

Average Annual Total Returns for the periods ended December 31, 2011

Average Annual Total Returns - Loomis Sayles Small Cap Growth Fund	One Year	Five Years	Ten Years	Life-of-Fund	Inception Date
Institutional Class	3.20%	6.00%	4.49%	4.45%	Dec. 31, 1996
Institutional Class Return After Taxes on Distributions	3.20%	6.00%	4.49%	4.21%	Dec. 31, 1996
Institutional Class Return After Taxes on Distributions & Sale of Fund Shares	2.08%	5.18%	3.92%	3.79%	Dec. 31, 1996
Retail Class	2.88%	5.73%	4.23%	4.18%	Dec. 31, 1996
Russell 2000 Growth Index	(2.91%)	2.09%	4.48%	3.94%

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 shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for the Institutional Class of the Fund. After-tax returns for other classes of the Fund will vary.

[1] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.00% and 1.25% of the Fund's average daily net assets for Institutional Class shares and Retail Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 1.00% and 1.25% of the Fund's average daily net assets for Institutional Class shares and Retail Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.