485BPOS

Registration Nos. 2-98326

811-04323

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☐
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 133	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☐
Amendment No. 134	☒

(Check appropriate box or boxes.)

NATIXIS FUNDS TRUST I

(Exact Name of Registrant as Specified in Charter)

399 Boylston Street, Boston, Massachusetts (Address of principal executive offices)	02116 (Zip Code)
Registrant’s Telephone Number, including Area Code	(617) 449-2822

Russell Kane, Esq.

NGAM Distribution, L.P.

399 Boylston Street

Boston, Massachusetts 02116

(Name and Address of Agent for Service)

Copy to:

John M. Loder, Esq.

Ropes & Gray

800 Boylston Street

Boston, Massachusetts 02116

Approximate Date of Proposed Public Offering

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

☒ immediately upon filing pursuant to paragraph (b)

☐ on (date) pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ on (date) pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

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

NATIXIS FUNDS TRUST I

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 Post-Effective Amendment to its Registration Statement under Rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Post-Effective Amendment 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 21^st day of April, 2017.

NATIXIS FUNDS TRUST I
By:	/s/ David L. Giunta
	David L. Giunta President and Chief Executive Officer

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 Chief Executive Officer and Trustee	April 21, 2017
/s/ Michael C. Kardok     Michael C. Kardok	Treasurer	April 21, 2017
Kevin P. Charleston*     Kevin P. Charleston	Trustee	April 21, 2017
Kenneth A. Drucker*     Kenneth A. Drucker	Trustee, Chairperson of the Board	April 21, 2017
Edmond J. English*     Edmond J. English	Trustee	April 21, 2017
Richard A. Goglia*     Richard A. Goglia	Trustee	April 21, 2017
Wendell J. Knox*     Wendell J. Knox	Trustee	April 21, 2017
Martin T. Meehan*     Martin T. Meehan	Trustee	April 21, 2017
Sandra O. Moose*     Sandra O. Moose	Trustee	April 21, 2017
James P. Palermo*     James P. Palermo	Trustee	April 21, 2017
Erik Sirri*     Erik Sirri	Trustee	April 21, 2017

Peter Smail*     Peter Smail	Trustee	April 21, 2017
Cynthia L. Walker*     Cynthia L. Walker	Trustee	April 21, 2017

*By:	/s/ Russell Kane
	Russell Kane Attorney-In-Fact1 April 21, 2017

¹  Powers of Attorney for Kevin P. Charleston, Kenneth A. Drucker, Edmond J. English, Richard A. Goglia, Wendell J. Knox, Martin T. Meehan, Sandra O. Moose, James P. Palermo, Erik R. Sirri, Peter J. Smail and Cynthia L. Walker is incorporated by reference to exhibit (p)(1) to PEA No. 126 to the Registration Statement filed on December 9, 2016.

Natixis Funds Trust I

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
Prospectus:	rr_ProspectusTable
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Mar. 31, 2017
Registrant Name	dei_EntityRegistrantName	Natixis Funds Trust I
Central Index Key	dei_EntityCentralIndexKey	0000770540
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Mar. 30, 2017
Document Effective Date	dei_DocumentEffectiveDate	Mar. 31, 2017
Prospectus Date	rr_ProspectusDate	Mar. 31, 2017

XML

(Loomis Sayles Core Plus 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 74 of the Prospectus and on page 104 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 Core Plus Bond Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	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 Core Plus Bond Fund)	Class T
Management fees	0.33%
Distribution and/or service (12b-1) fees	0.25%
Other expenses	0.15%	[1]
Total annual fund operating expenses	0.73%
Fee waiver and/or expense reimbursement	none	[2]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	0.73%

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:

Expense Example - (Loomis Sayles Core Plus Bond Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	323	478	646	1,134

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 143% 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 bonds, which include debt securities of any maturity. In addition, the Fund will invest at least 65% of its net assets in investment grade securities. "Investment grade" securities are those securities that are rated in one of the top four ratings categories at the time of purchase by at least one of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or S&P Global Ratings ("S&P")), or, if unrated, are determined by the Adviser to be of comparable quality. For purposes of this restriction, investment grade securities also include cash and cash equivalent securities. The Fund will generally seek to maintain an effective duration of +/- 2 years relative to the Bloomberg Barclays U.S. Aggregate Bond Index. Duration is a measure of the expected life of a fixed-income security that is used to determine the sensitivity of a security's price to changes in interest rates. A fund with a longer average portfolio duration will be more sensitive to changes in interest rates than a fund with a shorter average portfolio duration. By way of example, the price of a bond fund with an average duration of five years would be expected to fall approximately 5% if interest rates rose by one percentage point. While the effective duration for the Bloomberg Barclays U.S. Aggregate Bond Index fluctuates, as of December 31, 2016, the effective duration was approximately 5.89 years. The Fund may also invest up to 20% of its assets, at the time of purchase, in bonds rated below investment grade (i.e., none of the three major ratings agencies (Moody's, Fitch or S&P) have rated the securities in one of their top four ratings categories) (commonly known as "junk bonds"), or, if unrated, securities determined by the Adviser to be of comparable quality, and up to 10% of its assets in non-U.S. dollar-denominated securities. There is no minimum rating for the securities in which the Fund may invest.

The Fund's investments may include securities issued by U.S. and non-U.S. corporations and governments, securities issued by supranational entities, U.S. government-sponsored agency debenture and pass-through securities, commercial mortgage-backed and other asset-backed securities and inflation-linked securities.

The portfolio management team seeks to build and manage a portfolio that will perform well on a benchmark-relative and, secondarily, on an absolute basis in the market environment it anticipates over the short to intermediate term. The primary factors for broad sector positioning are the Adviser's expected performance of sectors in the benchmark and the incremental performance or diversification benefits the Fund's portfolio managers anticipate from opportunistic allocations to securities that are not included in the Fund's benchmark. In addition, the Fund's portfolio managers will look at individual security selection, position size and overall duration contribution to the portfolio.

Purchase and sale considerations also include overall portfolio yield, interest rate sensitivity across different maturities held, fixed-income sector fundamentals and outlook, technical supply/demand factors, credit risk, cash flow variability, security optionality and structure, as well as potential currency and liquidity risk. The Adviser also considers economic factors. Individual securities are assessed on a risk/return basis, both on a benchmark-relative and on an absolute return basis, and on their fit within the overall portfolio strategy.

Specifically, the Adviser follows a total return-oriented investment approach and considers broad sector allocation, quality and liquidity bias, yield curve positioning and duration in selecting securities for the Fund. The Fund's portfolio managers consider economic and market conditions as well as issuer-specific data, such as fixed-charge coverage, the relationship between cash flows and debt service obligations, the experience and perceived strength of management or security structure, price responsiveness of the security to interest rate changes, earnings prospects, debt as a percentage of assets, borrowing requirements, debt maturity schedules and liquidation value.

In selecting investments for the Fund, the Adviser's research analysts and sector teams work closely with the Fund's portfolio managers to develop an outlook for the economy from research produced by various financial firms and specific forecasting services or from economic data released by U.S. and foreign governments, as well as the Federal Reserve Bank. The analysts conduct a thorough review of individual securities to identify what they consider attractive values in the high quality bond market through the use of quantitative tools such as internal and external computer systems and software. The Adviser continuously monitors an issuer's creditworthiness or cash flow stability to assess whether the obligation remains an appropriate investment for the Fund. It may relax its emphasis on quality with respect to a given security if it believes that the issuer's financial outlook is promising. This may create an opportunity for higher returns. The Adviser seeks to balance opportunities for yield and price performance by combining macro economic analysis with individual security selection. Fund holdings are generally diversified across sectors and industry groups such as utilities or telecommunications, which tend to move independently of the ebbs and flows in economic growth.

In connection with its principal investment strategies, the Fund may also invest in securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"), structured notes, foreign securities, including those in emerging markets, mortgage-related securities, including mortgage dollar rolls, futures and swaps (including credit default swaps). The Fund may use such derivatives for hedging or investment purposes. The Fund may also engage in currency transactions, including forward currency contracts. Except as provided above or as required by applicable law, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

The Fund may engage in active and frequent trading of securities and other instruments. Effects of frequent trading may include high transaction costs, which may lower the Fund's returns, and realization of short-term capital gains, distributions of which are taxable to shareholders who are individuals as ordinary income. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

Principal Investment 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: 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/counterparty 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/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivatives transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with over-the-counter ("OTC") derivatives transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivatives transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may be subject to currency risk because it may invest in currency-related instruments and may invest in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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: Derivative instruments (such as those in which the Fund may invest, including structured notes, futures, swaps, (including credit default swaps) and foreign currency transactions) are subject to changes in the value of the underlying assets or indices on which such instruments 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 that 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 OTC derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate as expected with changes in the value of 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. The Fund's derivative counterparties may experience financial difficulties or otherwise be unwilling or unable to honor their obligations, possibly resulting in losses to the Fund.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in developed markets.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Interest Rate Risk: Interest rate risk is the risk that the value of the Fund's investments will fall if interest rates rise. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. Interest rate risk generally is greater for funds that invest in fixed-income securities with relatively longer durations than for funds that invest in fixed-income securities with shorter durations. In addition, an economic downturn or period of rising interest rates could adversely affect the market for these securities and reduce the Fund's ability to sell them, negatively impacting the performance of the Fund.

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. 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.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to significant liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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 a 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, which is called extension risk. 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 following bar chart and table 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 T Shares

Highest Quarterly Return:
Second Quarter 2009, 7.84%

Lowest Quarterly Return:
Third Quarter 2008, -4.26%

Average Annual Total Returns

(for the periods ended December 31, 2016)

Average Annual Total Returns - (Loomis Sayles Core Plus Bond Fund)	Past 1 Year	Past 5 Years	Past 10 Years
Class T	4.53%	3.25%	5.67%
Class T | Return After Taxes on Distributions	3.11%	1.71%	3.90%
Class T | Return After Taxes on Distributions and Sale of Fund Shares	2.56%	1.84%	3.72%
Bloomberg Barclays U.S. Aggregate Bond Index	2.65%	2.23%	4.34%

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

[1] Other expenses are estimated for the current fiscal year.

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") and NGAM Advisors, L.P. ("NGAM Advisors"), the Fund's advisory administrator, have given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.80% of the Fund's average daily net assets for Class T shares, 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, 2019 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 the applicable expense limitation for Class T shares. 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 Multi-Asset Income Fund)

Investment Goal

The Fund seeks current income with a secondary objective of 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Shareholder Fees

(fees paid directly from your investment)

Shareholder Fees - (Loomis Sayles Multi-Asset Income Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	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 Multi-Asset Income Fund)	Class T
Management fees	0.55%
Distribution and/or service (12b-1) fees	0.25%
Other expenses	0.29%	[1]
Acquired fund fees and expenses	0.13%
Total annual fund operating expenses	1.22%
Fee waiver and/or expense reimbursement	0.14%	[2]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.08%

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 assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - (Loomis Sayles Multi-Asset Income Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	357	613	889	1,677

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 341% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

The Fund intends to pursue its investment goal by utilizing a flexible investment approach that allocates investments across a broad range of income-producing securities, while employing risk management strategies to mitigate downside risk. The Fund may invest in equity securities (including common stocks, preferred stocks, depositary receipts, warrants, securities convertible into common or preferred stocks and real estate investment trusts ("REITS")). The Fund may also invest up to 25% of its assets in publicly traded master limited partnerships ("MLPs"). The Fund may invest in fixed-income securities (including exchange-traded notes, structured notes, corporate debt, foreign and U.S. government and agency fixed-income securities, bank loans, adjustable floating rate loans and other floating rate debt instruments issued by U.S. and non-U.S. corporations and other business entities and convertible debt securities). The Fund may invest 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 unrated, are determined by Loomis Sayles & Company, L.P. ("Loomis Sayles" or the "Subadviser") to be of comparable quality. There is no minimum rating for the fixed-income securities in which the Fund may invest. The Fund may invest in securities of any maturity or market capitalization. The Fund may invest in foreign securities including those in emerging markets.

The Fund may shift its assets among various types of income-producing securities based upon the Subadviser's evaluation of changing market conditions, yield expectations and security-specific opportunities. Changes to the Fund's asset allocations are based on several criteria, including global market cycles, global economic regimes and the relative attractiveness of particular asset categories. Under normal market conditions, the Fund will typically invest between 20% and 80% of its assets in fixed-income securities and between 30% and 70% in equity securities. However, the Fund is not required to allocate its investments among asset classes in any fixed proportion and may invest up to 100% of its assets in either equity securities or fixed-income securities. A sudden change in market conditions could cause the Subadviser to substantially change the allocation of the Fund's assets over a relatively short period of time.

In selecting individual investments for the Fund, the Subadviser considers factors including, but not limited to, economic and business cycles as well as top-down sector valuations and fundamental, bottom-up security valuations. In deciding which equity securities to buy and sell, the Subadviser seeks to identify securities that it believes are, among other things, attractively valued based on the Subadviser's estimate of what a security is actually worth, with additional consideration given to income-producing securities. The Subadviser may utilize quantitative screening methods based on fundamental factors to identify issuers which may pay or grow dividends.

In deciding which fixed-income securities to buy and sell, the Subadviser may consider a number of factors including, but not limited to, diverging business cycles among countries and regions, the stability and volatility of a country's bond markets, the financial strength of the issuer, current interest rates, the Subadviser's expectations regarding general trends in interest rates and currency considerations. The Subadviser will also consider how purchasing or selling a security would impact the overall portfolio's risk profile (for example, its sensitivity to currency risk, interest rate risk and sector-specific risk) and potential return (income and capital gains).

When constructing the Fund's portfolio the Subadviser will use risk management tools in an effort to manage risk on an ongoing basis. These tools include the use of models that evaluate risk correlation to various market factors or asset classes, scenario analysis to measure the impact of certain market events and measuring the volatility of certain sectors and securities to understand the level of risk being contributed by these sectors and securities. The portfolio management team expects to actively evaluate each investment idea and to decide to buy or sell an investment based upon: (i) its return potential; (ii) its level of risk; and (iii) its fit within the team's overall macro strategy, with the goal of continually optimizing the Fund's portfolio.

The Fund may also:

• Invest in mortgage-related and asset-backed securities

• Invest in securities offered in initial public offerings ("IPOs") and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"). Rule 144A securities are privately offered securities and can be resold only to certain qualified institutional buyers.

• Engage in over-the-counter ("OTC") options, swap contracts (including credit default swaps) and currency transactions as well as futures transactions and other derivatives for hedging and investment purposes. The Fund may take both long and short positions in derivatives.

• Engage in active and frequent trading of securities and other instruments. Effects of frequent trading may include high transaction costs, which may lower the Fund's returns, and realization of short-term capital gains, distributions of which are taxable to shareholders who are individuals as ordinary income. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

Principal Investment 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 may not be optimal in every market condition. You could lose money on your investment in the Fund as a result of this allocation.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with OTC derivative transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivative transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including options, foreign currency transactions, futures transactions and swap transactions) are subject to changes in the value of the underlying assets or indices on which such instruments 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 that would have occurred had derivatives not been used. The Fund's use of derivatives 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 OTC traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate as expected with changes in the value of 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. The Fund's derivative counterparties may experience financial difficulties or otherwise be unwilling or unable to honor their obligations, possibly resulting in losses to the Fund.

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. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds generally take precedence over the claims of those who own preferred stock or 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.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Interest Rate Risk: Interest rate risk is the risk that the value of the Fund's investments will fall if interest rates rise. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. Interest rate risk generally is greater for funds that invest in fixed-income securities with relatively longer durations than for funds that invest in fixed-income securities with shorter durations. In addition, an economic downturn or period of rising interest rates could adversely affect the markets for these securities and reduce the Fund's ability to sell them, negatively impacting the performance of the Fund.

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. 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.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to greater liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Non-exchange traded derivatives are generally subject to greater liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

Master Limited Partnership Risk: Investments in MLPs involve risks in addition to the risks associated with investments in securities with similar characteristics, such as common stock of a corporation. Holders of common interests in MLPs typically have limited control and limited rights to vote on matters affecting the MLP. Conflicts of interest may also exist between an MLP's common interest holders and its general partner or managing member, including those arising from incentive distribution payments. Many interests in MLPs are subject to restrictions on resale and may therefore be less liquid than other investments, which may subject MLP interests to more abrupt or erratic price movements and may increase the difficulty of disposing of such interests at favorable times and prices. The Fund may gain exposure to MLPs through derivatives, including exchange-traded notes ("ETNs") and swaps, exposing the Fund to the risks of investing in derivatives generally. MLPs often own interests in energy infrastructure properties, including pipelines, or engage in activities related to the energy sector. Accordingly, to the extent the Fund invests in MLPs, it will likely be exposed to risks related to investments in the energy sector. In addition, if an MLP fails to meet the current legal requirements for treatment as a partnership, or if there are changes to the tax laws, an MLP could be treated as a corporation for U.S. federal income tax purposes, obligating the MLP to pay tax at the entity level and significantly reducing the income to the Fund from an investment in an MLP. The Fund's pursuit of its investment strategy will potentially be limited by the Fund's intention to qualify for the special tax treatment accorded a registered investment company and its shareholders and could adversely affect the Fund.

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 a 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, which is called extension risk. 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.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization companies.

Risk/Return Bar Chart and Table

The following bar chart and table 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 T Shares

Highest Quarterly Return:
Second Quarter 2009, 18.28%

Lowest Quarterly Return:
Fourth Quarter 2008, -18.23%

Average Annual Total Returns

(for the periods ended December 31, 2016)

Average Annual Total Returns - (Loomis Sayles Multi-Asset Income Fund)	Past 1 Year	Past 5 Years	Past 10 Years
Class T	7.38%	7.36%	5.63%
Class T | Return After Taxes on Distributions	5.44%	6.24%	4.35%
Class T | Return After Taxes on Distributions and Sale of Fund Shares	5.25%	5.45%	3.99%
Bloomberg Barclays U.S. Aggregate Bond Index	2.65%	2.23%	4.34%

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T shares. Prior to the stock market close August 31, 2015, the Fund had multiple subadvisers. The performance results shown above for the periods prior to the stock market close August 31, 2015 reflect results achieved by those subadvisers using different investment strategies.

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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

(Mirova Global Sustainable Equity Fund)

Investment Goal

The Fund seeks long-term 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Shareholder Fees

(fees paid directly from your investment)

Shareholder Fees - (Mirova Global Sustainable Equity Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - (Mirova Global Sustainable Equity Fund)	Class T
Management fees	0.80%
Distribution and/or service (12b-1) fees	0.25%
Other expenses	0.67%	[1]
Total annual fund operating expenses	1.72%
Fee waiver and/or expense reimbursement	0.42%	[2]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.30%

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 assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - (Mirova Global Sustainable Equity Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	379	735	1,118	2,193

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 the period March 31, 2016 through December 31, 2016, the Fund's portfolio turnover rate was 20% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its assets in equity securities, which may include common stocks, preferred stocks, depositary receipts and real estate investment trusts ("REITS"). The Fund invests in securities of companies located in no fewer than three countries, which may include the U.S. Under normal circumstances, the Fund will invest at least 40% of its assets in securities of companies located outside the U.S. and the Fund may invest up to 25% of its assets in securities of companies located in emerging markets. Emerging markets are economies that the Adviser believes are not generally recognized to be fully developed markets, as measured by gross national income, financial market infrastructure, market capitalization and/or other factors. The Fund may invest in growth and value companies of any size and may also invest in initial public offerings.

The Adviser pursues the Fund's investment goal by investing in equity securities of companies that it expects will benefit from major long-term global trends. The Adviser believes that there are several long-term trends that can reshape the world now and in the future. These trends include those that are demographic in nature, such as population growth and an aging population, and others that are more socioeconomic, such as urbanization, evolving consumption in emerging markets and a changing global financial model. In addition, there are environmental trends such as climate change and natural resource depletion, as well as trends driven by technological innovation. In selecting companies to invest in, the Adviser focuses on providers of solutions to the issues arising from these trends, as well as companies that provide products and services that address or are otherwise aligned with these trends and the need to create a more sustainable world.

The Adviser selects securities based on an in-depth fundamental analysis of companies combining qualitative, financial and environmental, social and governance ("ESG") considerations. The Adviser emphasizes company-specific positive selection criteria over broad-based negative screens in assessing ESG practices. This means that the Adviser's research process is designed to prioritize investments in companies which it believes show good ESG practices and whose products and services help create a more sustainable world, rather than merely excluding companies which the Adviser believes show poor ESG practices. Nevertheless, as ESG criteria are integrated in the Fund's risk management process, the Adviser also seeks to avoid investing in companies which do not comply with the Adviser's minimum ESG standards. In deciding which securities to buy and sell, the Adviser generally seeks to invest in securities of companies that:

• relate to sustainable development themes derived from long-term global trends, providing solutions to address issues related to energy, mobility, building and cities, management of natural resources, consumption, healthcare, information technology or finance;

• demonstrate adherence to ESG practices, with respect to such issues as fair labor, anti-corruption, human rights, fair business practices and mitigation of environmental impact;

• have strong fundamentals, including sustainable business models, competitive positioning, effective management teams, acceptable risk profiles, and long-term growth potential; and

• offer attractive valuations.

In determining whether or not a company's risk profile is acceptable, the Adviser seeks to evaluate risks that may affect share price in the long-term, such as market, environmental, exchange rate, political, and reputation risks, among others. If the risk profile of a company is too high, the investment team may decide not to invest and/or sell a security and look for alternatives.

It is expected that the Adviser's views on long-term global trends and sustainable development themes will evolve over time.

Principal Investment 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 be subject to currency risk because it invests in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or common stock.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund's expenses.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization companies.

Sustainable Investment Style Risk: Because the Fund focuses on investments in companies that relate to certain sustainable development themes and demonstrate adherence to ESG practices, its universe of investments may be smaller than that of other funds and therefore the Fund may underperform the market as a whole if such investments underperform the market. The Fund may forgo opportunities to gain exposure to certain companies, industries, sectors or countries and it may choose to sell a security when it might otherwise be disadvantageous to do so.

Risk/Return Bar Chart and Table

Because the Fund has not yet completed a full calendar year, information related to Fund performance, including a bar chart showing annual returns, has not been included in this Prospectus. The performance information provided by the Fund in the future will give 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 compare against those of a broad measure of market performance.

(Natixis Oakmark International Fund)

Investment Goal

The Fund seeks long-term 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Shareholder Fees

(fees paid directly from your investment)

Shareholder Fees - (Natixis Oakmark International Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - (Natixis Oakmark International Fund)	Class T
Management fees	0.85%
Distribution and/or service (12b-1) fees	0.25%
Other expenses	0.24%	[1]
Total annual fund operating expenses	1.34%
Fee waiver and/or expense reimbursement	none	[2]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.34%

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:

Expense Example - (Natixis Oakmark International Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	383	664	966	1,822

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 41% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

The Fund invests primarily in a diversified portfolio of common stocks of non-U.S. companies. The Fund may invest in non-U.S. markets throughout the world, including emerging markets. Ordinarily, the Fund will invest in the securities of at least five countries outside the U.S. There are no geographic limits on the Fund's non-U.S. investments. Although the Fund invests primarily in common stocks of non-U.S. companies it may also invest in the securities of U.S. companies. The Fund may invest in the securities of small-, mid- and large-capitalization companies.

The Fund's subadviser, Harris Associates L.P. ("Harris Associates"), uses a value investment philosophy in selecting equity securities, such as common stocks, preferred stocks, warrants, and securities convertible into common stocks and preferred stocks. This investment philosophy is based upon the belief that, over time, a company's stock price converges with Harris Associates' estimate of its intrinsic or true business value. By "true business value," Harris Associates means its estimate of the price a knowledgeable buyer would pay to acquire the entire business. Harris Associates believes that investing in securities priced significantly below their true business value presents the best opportunity to achieve the Fund's investment objective.

Harris Associates uses this value philosophy to identify companies that it believes have discounted stock prices compared to the companies' true business values. In assessing such companies, Harris Associates looks for the following characteristics, although not all of the companies selected will have these attributes: (1) free cash flows and intelligent investment of excess cash; (2) earnings that are growing and are reasonably predictable; and (3) high level of manager ownership.

Once Harris Associates identifies a stock that it believes is selling at a significant discount to Harris Associates' estimated intrinsic value and that the issuer has one or more of the additional qualities mentioned above, Harris Associates generally will consider buying that security for the Fund. Harris Associates usually sells a security when the price approaches its estimated worth or the issuer's fundamentals change. Harris Associates monitors each holding and adjusts its price targets as warranted to reflect changes in the issuer's fundamentals. The Fund's portfolio typically holds 30 to 65 stocks.

Principal Investment 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 be subject to currency risk because it may invest in currency-related instruments and may invest in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or common stock. Small- and mid-capitalization and emerging growth companies may be subject to more abrupt price movements, limited markets and less liquidity than larger, more established companies, which could adversely affect the value of the Fund's equity portfolio.

Focused Investment Risk: Because the Fund may invest in a small number of industries or securities, it may have more risk because the impact of a single economic, political or regulatory occurrence may have a greater adverse impact on the Fund's net asset value.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

Risk/Return Bar Chart and Table

The following bar chart and table 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 life-of-fund 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 T Shares

Highest Quarterly Return:
First Quarter 2012, 17.17%

Lowest Quarterly Return:
Third Quarter 2011, -20.47%

Average Annual Total Returns

(for the periods ended December 31, 2016)

Average Annual Total Returns - (Natixis Oakmark International Fund)	Past 1 Year	Past 5 Years	Life of Fund (12/15/10)	Inception Date
Class T	5.52%	9.13%	5.01%	Dec. 15, 2010
Class T | Return After Taxes on Distributions	5.26%	8.69%	4.68%	Dec. 15, 2010
Class T | Return After Taxes on Distributions and Sale of Fund Shares	3.80%	7.41%	4.09%	Dec. 15, 2010
MSCI World ex USA Index (Net)	2.75%	6.07%	3.00%	Dec. 15, 2010

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which are offered in a separate prospectus and have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

(Natixis U.S. Equity Opportunities Fund)

Investment Goal

The Fund seeks 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Shareholder Fees

(fees paid directly from your investment)

Shareholder Fees - (Natixis U.S. Equity Opportunities Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - (Natixis U.S. Equity Opportunities Fund)	Class T
Management fees	0.80%
Distribution and/or service (12b-1) fees	0.25%
Fee/expense recovery	none	[1],[2]
Remainder of other expenses	0.18%	[2]
Other expenses	0.18%	[2]
Total annual fund operating expenses	1.23%
Fee waiver and/or expense reimbursement	none	[3]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.23%

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:

Expense Example - (Natixis U.S. Equity Opportunities Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	372	631	909	1,702

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 17% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

The Fund ordinarily invests at least 80% of its net assets (plus any borrowings made for investment purposes) in equity securities, including common stocks and preferred stocks. Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in securities of U.S. issuers. The Fund's approach to equity investing combines the styles of two subadvisers in selecting securities for each of the Fund's segments. The segments and their subadvisers are listed below.

• Harris Associates - Large Cap Value segment - Under normal circumstances, the Large Cap Value segment of the Fund managed by Harris Associates L.P. ("Harris Associates") will invest primarily in the common stocks of larger- capitalization companies that Harris Associates believes are trading at a substantial discount to the company's "true business value." By "true business value," Harris Associates means its estimate of the price a knowledgeable buyer would pay to acquire the entire business. Harris Associates believes that investing in securities priced significantly below their true business value presents the best opportunity to achieve the Fund's investment objectives. Harris Associates usually sells a security when the price approaches its estimated worth and monitors each holding and adjusts its price targets as warranted to reflect changes in the issuer's fundamentals. In determining whether an issuer is a U.S or foreign issuer for the Harris Associates – Large Cap Value segment, Harris Associates considers various factors, including its country of domicile, the primary stock exchange on which it trades, the location from which the majority of its revenue comes, and its reporting currency.

• Loomis Sayles - All Cap Growth segment - Under normal circumstances, the All Cap Growth segment of the Fund, managed by Loomis, Sayles & Company, L.P. ("Loomis Sayles"), will invest primarily in equity securities, including common stocks, preferred stocks, convertible securities and warrants. This segment may invest in companies of any size. The segment normally invests across a wide range of sectors and industries. The segment's portfolio manager employs a growth style of equity management that emphasizes companies with sustainable competitive advantages, long-term structural growth drivers, attractive cash flow returns on invested capital, and management teams focused on creating long-term value for shareholders. The segment's portfolio manager aims to invest in companies when they trade at a significant discount to the estimate of intrinsic value. The segment will consider selling a portfolio investment when the portfolio manager believes an unfavorable structural change occurs within a given business or the markets in which it operates, a critical underlying investment assumption is flawed, when a more attractive reward-to-risk opportunity becomes available, when the portfolio manager believes the current price fully reflects intrinsic value, or for other investment reasons which the portfolio manager deems appropriate. Although certain equity securities purchased by the Loomis Sayles – All Cap Growth segment of the Fund may be issued by domestic companies incorporated outside of the United States, Loomis Sayles does not consider these securities to be foreign if they are included in the U.S. equity indices published by S&P Global Ratings or Russell Investments or if the security's country of risk defined by Bloomberg is the United States.

Subject to the allocation policy adopted by the Fund's Board of Trustees, NGAM Advisors, L.P. ("NGAM Advisors") generally allocates capital invested in the Fund equally (i.e., 50%) between its two segments. Under the allocation policy, NGAM Advisors may also allocate capital away from or towards each segment from time to time and may reallocate capital between the segments. Each subadviser manages its segment of the Fund's assets in accordance with its distinct investment style and strategy.

The Fund may also:

• Invest in securities offered in initial public offerings ("IPOs") and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities").

• Invest in convertible preferred stock and convertible debt securities.

• Invest in real estate investment trusts ("REITs").

• Invest in fixed-income securities, including U.S. government bonds and below-investment grade fixed-income securities (commonly known as "junk bonds").

• Hold securities of foreign issuers traded over-the-counter or on foreign exchanges, including securities in emerging markets and related currency hedging transactions.

• Invest in equity securities of Canadian issuers.

Principal Investment 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.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with over-the-counter ("OTC") derivative transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivative transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 subadviser's assessment of the prospects for a company's growth is wrong, or if the subadviser'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 subadviser 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 generally take precedence over the claims of those who own preferred stock or common stock.

Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. 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 (including the risk of default) to a greater extent 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 the Fund's ability to sell them.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund's expenses.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to greater liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Non-exchange traded derivatives are generally subject to greater liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization companies.

Risk/Return Bar Chart and Table

The following bar chart and table 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 T Shares

Highest Quarterly Return:
Third Quarter 2009, 17.80%

Lowest Quarterly Return:
Fourth Quarter 2008, -24.20%

Average Annual Total Returns

(for the periods ended December 31, 2016)

Average Annual Total Returns - (Natixis U.S. Equity Opportunities Fund)	Past 1 Year	Past 5 Years	Past 10 Years
Class T	9.05%	15.83%	8.67%
Class T | Return After Taxes on Distributions	8.54%	13.14%	7.29%
Class T | Return After Taxes on Distributions and Sale of Fund Shares	5.50%	12.28%	6.84%
S&P 500® Index	11.96%	14.66%	6.95%
Russell 1000® Index	12.05%	14.69%	7.08%

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T shares. The Fund uses multiple subadvisers. The performance results shown above reflect results achieved by previous subadvisers using different investment strategies.

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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

(Vaughan Nelson Small Cap Value Fund)

Investment Goal

The Fund seeks 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Shareholder Fees

(fees paid directly from your investment)

Shareholder Fees - (Vaughan Nelson Small Cap Value Fund)	Class T USD ($)
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Redemption fees	none

Annual Fund Operating Expenses

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

Annual Fund Operating Expenses - (Vaughan Nelson Small Cap Value Fund)	Class T
Management fees	0.90%
Distribution and/or service (12b-1) fees	0.25%
Other expenses	0.20%	[1]
Acquired fund fees and expenses	0.18%
Total annual fund operating expenses	1.53%
Fee waiver and/or expense reimbursement	none	[2]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	1.53%

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:

Expense Example - (Vaughan Nelson Small Cap Value Fund)	1 Year	3 Years	5 Years	10 Years
Class T | USD ($)	402	721	1,063	2,028

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 74% 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, including common stocks and preferred stocks, of "small-capitalization companies." Equity securities may take the form of stock in corporations, limited partnership interests, interests in limited liability companies, real estate investment trusts ("REITs") or other trusts and other similar securities. Currently, the Fund defines a small-capitalization company to be one whose market capitalization, at the time of purchase, either falls within the capitalization range of the Russell 2000® Value Index, an unmanaged index that measures the performance of those Russell 2000® companies with lower price-to-book ratios and lower forecasted growth values, or is $3.5 billion or less. While the market capitalization range for the Russell 2000® Value Index fluctuates, at December 31, 2016, it was $35.6 million to $10.3 billion. The Fund may, however, invest in companies with large- capitalizations.

Vaughan Nelson Investment Management, L.P. ("Vaughan Nelson") invests in small-capitalization companies with a focus on those companies meeting Vaughan Nelson's return expectations. Vaughan Nelson uses a bottom-up value oriented investment process in constructing the Fund's portfolio. Vaughan Nelson seeks companies with the following characteristics, although not all of the companies selected will have these attributes:

• Companies earning a positive return on capital with stable-to-improving returns.

• Companies valued at a discount to their asset value.

• Companies with an attractive and sustainable dividend level.

In selecting investments for the Fund, Vaughan Nelson generally employs the following strategies:

• Value-driven investment philosophy that selects stocks selling at a relatively low value based on discounted cash flow models. Vaughan Nelson selects companies that it believes are out of favor or misunderstood.

• Vaughan Nelson starts with an investment universe of 5,000 securities. Vaughan Nelson then uses value-driven screens to create a research universe of companies with market capitalizations of at least $100 million.

• Vaughan Nelson uses fundamental analysis to construct a portfolio of 60 to 80 securities that, in the opinion of Vaughan Nelson, is made up of quality companies with the potential to provide significant increases in share price over a three year period.

• Vaughan Nelson will generally sell a security when it reaches Vaughan Nelson's price target or when the issuer shows a change in financial condition, competitive pressures, poor management decisions or internal or external forces reducing future expected returns from the investment thesis.

The Fund may also:

• Invest in convertible preferred stock and convertible debt securities.

• Invest in foreign securities, including emerging market securities.

• Invest in REITs.

• Invest in securities offered in initial public offerings ("IPOs").

Principal Investment 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or 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. Zero-coupon securities may be subject to these risks to a greater extent than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market for 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/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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 Companies Risk: Small-capitalization companies are more likely than larger companies to have limited product lines, markets or financial resources, or to depend on a small, inexperienced management group. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of larger companies. Stocks of small-capitalization companies may therefore be more vulnerable to adverse developments than those of larger companies.

Risk/Return Bar Chart and Table

The following bar chart and table 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 T Shares

Highest Quarterly Return:
Third Quarter 2009, 18.56%

Lowest Quarterly Return:
Third Quarter 2011, -19.60%

Average Annual Total Returns

(for the periods ended December 31, 2016)

Average Annual Total Returns - (Vaughan Nelson Small Cap Value Fund)	Past 1 Year	Past 5 Years	Past 10 Years
Class T	17.27%	15.24%	9.98%
Class T | Return After Taxes on Distributions	15.23%	11.92%	7.59%
Class T | Return After Taxes on Distributions and Sale of Fund Shares	11.32%	11.66%	7.70%
Russell 2000® Value Index	31.74%	15.07%	6.26%

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which are offered in a separate prospectus and have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

[1] Other expenses are estimated for the current fiscal year.

[2] The Fund's investment 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% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[1] Other expenses are estimated for the current fiscal year.

[2] Natixis Asset Management U.S., LLC ("Natixis AM US" 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 1.30% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 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 the applicable expense limitation for Class T shares. 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.

[1] Other expenses are estimated for the current fiscal year.

[2] The Fund's investment adviser has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.45% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[1] Includes fee/expense recovery of less than 0.01%.

[2] Other expenses are estimated for the current fiscal year.

[3] The Fund's investment 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% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[1] Other expenses are estimated for the current fiscal year.

[2] The Fund's investment adviser has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.45% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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

(Loomis Sayles Core Plus Bond Fund)

Prospectus:

rr_ProspectusTable

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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 74 of the Prospectus and on page 104 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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, 2019

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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:

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 143% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

143.00%

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 bonds, which include debt securities of any maturity. In addition, the Fund will invest at least 65% of its net assets in investment grade securities. "Investment grade" securities are those securities that are rated in one of the top four ratings categories at the time of purchase by at least one of the three major ratings agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investors Services, Inc. ("Fitch") or S&P Global Ratings ("S&P")), or, if unrated, are determined by the Adviser to be of comparable quality. For purposes of this restriction, investment grade securities also include cash and cash equivalent securities. The Fund will generally seek to maintain an effective duration of +/- 2 years relative to the Bloomberg Barclays U.S. Aggregate Bond Index. Duration is a measure of the expected life of a fixed-income security that is used to determine the sensitivity of a security's price to changes in interest rates. A fund with a longer average portfolio duration will be more sensitive to changes in interest rates than a fund with a shorter average portfolio duration. By way of example, the price of a bond fund with an average duration of five years would be expected to fall approximately 5% if interest rates rose by one percentage point. While the effective duration for the Bloomberg Barclays U.S. Aggregate Bond Index fluctuates, as of December 31, 2016, the effective duration was approximately 5.89 years. The Fund may also invest up to 20% of its assets, at the time of purchase, in bonds rated below investment grade (i.e., none of the three major ratings agencies (Moody's, Fitch or S&P) have rated the securities in one of their top four ratings categories) (commonly known as "junk bonds"), or, if unrated, securities determined by the Adviser to be of comparable quality, and up to 10% of its assets in non-U.S. dollar-denominated securities. There is no minimum rating for the securities in which the Fund may invest.

The Fund's investments may include securities issued by U.S. and non-U.S. corporations and governments, securities issued by supranational entities, U.S. government-sponsored agency debenture and pass-through securities, commercial mortgage-backed and other asset-backed securities and inflation-linked securities.

The portfolio management team seeks to build and manage a portfolio that will perform well on a benchmark-relative and, secondarily, on an absolute basis in the market environment it anticipates over the short to intermediate term. The primary factors for broad sector positioning are the Adviser's expected performance of sectors in the benchmark and the incremental performance or diversification benefits the Fund's portfolio managers anticipate from opportunistic allocations to securities that are not included in the Fund's benchmark. In addition, the Fund's portfolio managers will look at individual security selection, position size and overall duration contribution to the portfolio.

Purchase and sale considerations also include overall portfolio yield, interest rate sensitivity across different maturities held, fixed-income sector fundamentals and outlook, technical supply/demand factors, credit risk, cash flow variability, security optionality and structure, as well as potential currency and liquidity risk. The Adviser also considers economic factors. Individual securities are assessed on a risk/return basis, both on a benchmark-relative and on an absolute return basis, and on their fit within the overall portfolio strategy.

Specifically, the Adviser follows a total return-oriented investment approach and considers broad sector allocation, quality and liquidity bias, yield curve positioning and duration in selecting securities for the Fund. The Fund's portfolio managers consider economic and market conditions as well as issuer-specific data, such as fixed-charge coverage, the relationship between cash flows and debt service obligations, the experience and perceived strength of management or security structure, price responsiveness of the security to interest rate changes, earnings prospects, debt as a percentage of assets, borrowing requirements, debt maturity schedules and liquidation value.

In selecting investments for the Fund, the Adviser's research analysts and sector teams work closely with the Fund's portfolio managers to develop an outlook for the economy from research produced by various financial firms and specific forecasting services or from economic data released by U.S. and foreign governments, as well as the Federal Reserve Bank. The analysts conduct a thorough review of individual securities to identify what they consider attractive values in the high quality bond market through the use of quantitative tools such as internal and external computer systems and software. The Adviser continuously monitors an issuer's creditworthiness or cash flow stability to assess whether the obligation remains an appropriate investment for the Fund. It may relax its emphasis on quality with respect to a given security if it believes that the issuer's financial outlook is promising. This may create an opportunity for higher returns. The Adviser seeks to balance opportunities for yield and price performance by combining macro economic analysis with individual security selection. Fund holdings are generally diversified across sectors and industry groups such as utilities or telecommunications, which tend to move independently of the ebbs and flows in economic growth.

In connection with its principal investment strategies, the Fund may also invest in securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"), structured notes, foreign securities, including those in emerging markets, mortgage-related securities, including mortgage dollar rolls, futures and swaps (including credit default swaps). The Fund may use such derivatives for hedging or investment purposes. The Fund may also engage in currency transactions, including forward currency contracts. Except as provided above or as required by applicable law, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

The Fund may engage in active and frequent trading of securities and other instruments. Effects of frequent trading may include high transaction costs, which may lower the Fund's returns, and realization of short-term capital gains, distributions of which are taxable to shareholders who are individuals as ordinary income. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

Risk [Heading]

rr_RiskHeading

Principal Investment 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: 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/counterparty 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/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivatives transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with over-the-counter ("OTC") derivatives transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivatives transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may be subject to currency risk because it may invest in currency-related instruments and may invest in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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: Derivative instruments (such as those in which the Fund may invest, including structured notes, futures, swaps, (including credit default swaps) and foreign currency transactions) are subject to changes in the value of the underlying assets or indices on which such instruments 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 that 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 OTC derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate as expected with changes in the value of 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. The Fund's derivative counterparties may experience financial difficulties or otherwise be unwilling or unable to honor their obligations, possibly resulting in losses to the Fund.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in developed markets.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Interest Rate Risk: Interest rate risk is the risk that the value of the Fund's investments will fall if interest rates rise. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. Interest rate risk generally is greater for funds that invest in fixed-income securities with relatively longer durations than for funds that invest in fixed-income securities with shorter durations. In addition, an economic downturn or period of rising interest rates could adversely affect the market for these securities and reduce the Fund's ability to sell them, negatively impacting the performance of the Fund.

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. 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.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to significant liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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 a 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, which is called extension risk. 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 following bar chart and table 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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class T 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. A sales charge will reduce your return.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2009, 7.84%

Lowest Quarterly Return:
Third Quarter 2008, -4.26%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns

(for the periods ended December 31, 2016)

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Index performance reflects no deduction for fees, expenses or taxes.

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

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-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

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.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table 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 Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Loomis Sayles Core Plus Bond Fund) | Bloomberg Barclays U.S. Aggregate Bond Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.65%

Past 5 Years

rr_AverageAnnualReturnYear05

2.23%

Past 10 Years

rr_AverageAnnualReturnYear10

4.34%

(Loomis Sayles Core Plus Bond Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.33%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.73%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[2]

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

rr_NetExpensesOverAssets

0.73%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 323

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

478

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

646

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,134

Annual Return 2007

rr_AnnualReturn2007

6.06%

Annual Return 2008

rr_AnnualReturn2008

0.61%

Annual Return 2009

rr_AnnualReturn2009

16.62%

Annual Return 2010

rr_AnnualReturn2010

10.35%

Annual Return 2011

rr_AnnualReturn2011

7.68%

Annual Return 2012

rr_AnnualReturn2012

11.31%

Annual Return 2013

rr_AnnualReturn2013

(0.82%)

Annual Return 2014

rr_AnnualReturn2014

6.18%

Annual Return 2015

rr_AnnualReturn2015

(4.20%)

Annual Return 2016

rr_AnnualReturn2016

7.19%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Second Quarter 2009, 7.84%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.84%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Third Quarter 2008, -4.26%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.26%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Past 1 Year

rr_AverageAnnualReturnYear01

4.53%

Past 5 Years

rr_AverageAnnualReturnYear05

3.25%

Past 10 Years

rr_AverageAnnualReturnYear10

5.67%

(Loomis Sayles Core Plus Bond Fund) | Class T | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

3.11%

Past 5 Years

rr_AverageAnnualReturnYear05

1.71%

Past 10 Years

rr_AverageAnnualReturnYear10

3.90%

(Loomis Sayles Core Plus Bond Fund) | Class T | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.56%

Past 5 Years

rr_AverageAnnualReturnYear05

1.84%

Past 10 Years

rr_AverageAnnualReturnYear10

3.72%

(Loomis Sayles Multi-Asset Income Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks current income with a secondary objective of 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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

April 30, 2018

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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 assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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 341% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

341.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund intends to pursue its investment goal by utilizing a flexible investment approach that allocates investments across a broad range of income-producing securities, while employing risk management strategies to mitigate downside risk. The Fund may invest in equity securities (including common stocks, preferred stocks, depositary receipts, warrants, securities convertible into common or preferred stocks and real estate investment trusts ("REITS")). The Fund may also invest up to 25% of its assets in publicly traded master limited partnerships ("MLPs"). The Fund may invest in fixed-income securities (including exchange-traded notes, structured notes, corporate debt, foreign and U.S. government and agency fixed-income securities, bank loans, adjustable floating rate loans and other floating rate debt instruments issued by U.S. and non-U.S. corporations and other business entities and convertible debt securities). The Fund may invest 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 unrated, are determined by Loomis Sayles & Company, L.P. ("Loomis Sayles" or the "Subadviser") to be of comparable quality. There is no minimum rating for the fixed-income securities in which the Fund may invest. The Fund may invest in securities of any maturity or market capitalization. The Fund may invest in foreign securities including those in emerging markets.

The Fund may shift its assets among various types of income-producing securities based upon the Subadviser's evaluation of changing market conditions, yield expectations and security-specific opportunities. Changes to the Fund's asset allocations are based on several criteria, including global market cycles, global economic regimes and the relative attractiveness of particular asset categories. Under normal market conditions, the Fund will typically invest between 20% and 80% of its assets in fixed-income securities and between 30% and 70% in equity securities. However, the Fund is not required to allocate its investments among asset classes in any fixed proportion and may invest up to 100% of its assets in either equity securities or fixed-income securities. A sudden change in market conditions could cause the Subadviser to substantially change the allocation of the Fund's assets over a relatively short period of time.

In selecting individual investments for the Fund, the Subadviser considers factors including, but not limited to, economic and business cycles as well as top-down sector valuations and fundamental, bottom-up security valuations. In deciding which equity securities to buy and sell, the Subadviser seeks to identify securities that it believes are, among other things, attractively valued based on the Subadviser's estimate of what a security is actually worth, with additional consideration given to income-producing securities. The Subadviser may utilize quantitative screening methods based on fundamental factors to identify issuers which may pay or grow dividends.

In deciding which fixed-income securities to buy and sell, the Subadviser may consider a number of factors including, but not limited to, diverging business cycles among countries and regions, the stability and volatility of a country's bond markets, the financial strength of the issuer, current interest rates, the Subadviser's expectations regarding general trends in interest rates and currency considerations. The Subadviser will also consider how purchasing or selling a security would impact the overall portfolio's risk profile (for example, its sensitivity to currency risk, interest rate risk and sector-specific risk) and potential return (income and capital gains).

When constructing the Fund's portfolio the Subadviser will use risk management tools in an effort to manage risk on an ongoing basis. These tools include the use of models that evaluate risk correlation to various market factors or asset classes, scenario analysis to measure the impact of certain market events and measuring the volatility of certain sectors and securities to understand the level of risk being contributed by these sectors and securities. The portfolio management team expects to actively evaluate each investment idea and to decide to buy or sell an investment based upon: (i) its return potential; (ii) its level of risk; and (iii) its fit within the team's overall macro strategy, with the goal of continually optimizing the Fund's portfolio.

The Fund may also:

• Invest in mortgage-related and asset-backed securities

• Invest in securities offered in initial public offerings ("IPOs") and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"). Rule 144A securities are privately offered securities and can be resold only to certain qualified institutional buyers.

• Engage in over-the-counter ("OTC") options, swap contracts (including credit default swaps) and currency transactions as well as futures transactions and other derivatives for hedging and investment purposes. The Fund may take both long and short positions in derivatives.

• Engage in active and frequent trading of securities and other instruments. Effects of frequent trading may include high transaction costs, which may lower the Fund's returns, and realization of short-term capital gains, distributions of which are taxable to shareholders who are individuals as ordinary income. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

Risk [Heading]

rr_RiskHeading

Principal Investment 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 may not be optimal in every market condition. You could lose money on your investment in the Fund as a result of this allocation.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with OTC derivative transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivative transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including options, foreign currency transactions, futures transactions and swap transactions) are subject to changes in the value of the underlying assets or indices on which such instruments 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 that would have occurred had derivatives not been used. The Fund's use of derivatives 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 OTC traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate as expected with changes in the value of 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. The Fund's derivative counterparties may experience financial difficulties or otherwise be unwilling or unable to honor their obligations, possibly resulting in losses to the Fund.

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. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer's bonds generally take precedence over the claims of those who own preferred stock or 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.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Interest Rate Risk: Interest rate risk is the risk that the value of the Fund's investments will fall if interest rates rise. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. Interest rate risk generally is greater for funds that invest in fixed-income securities with relatively longer durations than for funds that invest in fixed-income securities with shorter durations. In addition, an economic downturn or period of rising interest rates could adversely affect the markets for these securities and reduce the Fund's ability to sell them, negatively impacting the performance of the Fund.

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. 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.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to greater liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Non-exchange traded derivatives are generally subject to greater liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

Master Limited Partnership Risk: Investments in MLPs involve risks in addition to the risks associated with investments in securities with similar characteristics, such as common stock of a corporation. Holders of common interests in MLPs typically have limited control and limited rights to vote on matters affecting the MLP. Conflicts of interest may also exist between an MLP's common interest holders and its general partner or managing member, including those arising from incentive distribution payments. Many interests in MLPs are subject to restrictions on resale and may therefore be less liquid than other investments, which may subject MLP interests to more abrupt or erratic price movements and may increase the difficulty of disposing of such interests at favorable times and prices. The Fund may gain exposure to MLPs through derivatives, including exchange-traded notes ("ETNs") and swaps, exposing the Fund to the risks of investing in derivatives generally. MLPs often own interests in energy infrastructure properties, including pipelines, or engage in activities related to the energy sector. Accordingly, to the extent the Fund invests in MLPs, it will likely be exposed to risks related to investments in the energy sector. In addition, if an MLP fails to meet the current legal requirements for treatment as a partnership, or if there are changes to the tax laws, an MLP could be treated as a corporation for U.S. federal income tax purposes, obligating the MLP to pay tax at the entity level and significantly reducing the income to the Fund from an investment in an MLP. The Fund's pursuit of its investment strategy will potentially be limited by the Fund's intention to qualify for the special tax treatment accorded a registered investment company and its shareholders and could adversely affect the Fund.

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 a 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, which is called extension risk. 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.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization 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 following bar chart and table 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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class T 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. A sales charge will reduce your return.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Second Quarter 2009, 18.28%

Lowest Quarterly Return:
Fourth Quarter 2008, -18.23%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns

(for the periods ended December 31, 2016)

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T shares. Prior to the stock market close August 31, 2015, the Fund had multiple subadvisers. The performance results shown above for the periods prior to the stock market close August 31, 2015 reflect results achieved by those subadvisers using different investment strategies.

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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Index performance reflects no deduction for fees, expenses or taxes.

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

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-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

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.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table 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 Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Loomis Sayles Multi-Asset Income Fund) | Bloomberg Barclays U.S. Aggregate Bond Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.65%

Past 5 Years

rr_AverageAnnualReturnYear05

2.23%

Past 10 Years

rr_AverageAnnualReturnYear10

4.34%

(Loomis Sayles Multi-Asset Income Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.55%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.29%

^[3]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.13%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.22%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.14%

^[4]

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

rr_NetExpensesOverAssets

1.08%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 357

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

613

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

889

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,677

Annual Return 2007

rr_AnnualReturn2007

(2.80%)

Annual Return 2008

rr_AnnualReturn2008

(25.26%)

Annual Return 2009

rr_AnnualReturn2009

33.32%

Annual Return 2010

rr_AnnualReturn2010

16.73%

Annual Return 2011

rr_AnnualReturn2011

7.21%

Annual Return 2012

rr_AnnualReturn2012

13.22%

Annual Return 2013

rr_AnnualReturn2013

5.84%

Annual Return 2014

rr_AnnualReturn2014

13.08%

Annual Return 2015

rr_AnnualReturn2015

(1.96%)

Annual Return 2016

rr_AnnualReturn2016

10.14%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Second Quarter 2009, 18.28%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.28%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2008, -18.23%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(18.23%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Past 1 Year

rr_AverageAnnualReturnYear01

7.38%

Past 5 Years

rr_AverageAnnualReturnYear05

7.36%

Past 10 Years

rr_AverageAnnualReturnYear10

5.63%

(Loomis Sayles Multi-Asset Income Fund) | Class T | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.44%

Past 5 Years

rr_AverageAnnualReturnYear05

6.24%

Past 10 Years

rr_AverageAnnualReturnYear10

4.35%

(Loomis Sayles Multi-Asset Income Fund) | Class T | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.25%

Past 5 Years

rr_AverageAnnualReturnYear05

5.45%

Past 10 Years

rr_AverageAnnualReturnYear10

3.99%

(Mirova Global Sustainable Equity Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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

April 30, 2018

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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 assuming that such waiver and/or reimbursement will only be in place through the date noted above and on the Total Annual Fund Operating Expenses for the remaining periods. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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 the period March 31, 2016 through December 31, 2016, the Fund's portfolio turnover rate was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its assets in equity securities, which may include common stocks, preferred stocks, depositary receipts and real estate investment trusts ("REITS"). The Fund invests in securities of companies located in no fewer than three countries, which may include the U.S. Under normal circumstances, the Fund will invest at least 40% of its assets in securities of companies located outside the U.S. and the Fund may invest up to 25% of its assets in securities of companies located in emerging markets. Emerging markets are economies that the Adviser believes are not generally recognized to be fully developed markets, as measured by gross national income, financial market infrastructure, market capitalization and/or other factors. The Fund may invest in growth and value companies of any size and may also invest in initial public offerings.

The Adviser pursues the Fund's investment goal by investing in equity securities of companies that it expects will benefit from major long-term global trends. The Adviser believes that there are several long-term trends that can reshape the world now and in the future. These trends include those that are demographic in nature, such as population growth and an aging population, and others that are more socioeconomic, such as urbanization, evolving consumption in emerging markets and a changing global financial model. In addition, there are environmental trends such as climate change and natural resource depletion, as well as trends driven by technological innovation. In selecting companies to invest in, the Adviser focuses on providers of solutions to the issues arising from these trends, as well as companies that provide products and services that address or are otherwise aligned with these trends and the need to create a more sustainable world.

The Adviser selects securities based on an in-depth fundamental analysis of companies combining qualitative, financial and environmental, social and governance ("ESG") considerations. The Adviser emphasizes company-specific positive selection criteria over broad-based negative screens in assessing ESG practices. This means that the Adviser's research process is designed to prioritize investments in companies which it believes show good ESG practices and whose products and services help create a more sustainable world, rather than merely excluding companies which the Adviser believes show poor ESG practices. Nevertheless, as ESG criteria are integrated in the Fund's risk management process, the Adviser also seeks to avoid investing in companies which do not comply with the Adviser's minimum ESG standards. In deciding which securities to buy and sell, the Adviser generally seeks to invest in securities of companies that:

• relate to sustainable development themes derived from long-term global trends, providing solutions to address issues related to energy, mobility, building and cities, management of natural resources, consumption, healthcare, information technology or finance;

• demonstrate adherence to ESG practices, with respect to such issues as fair labor, anti-corruption, human rights, fair business practices and mitigation of environmental impact;

• have strong fundamentals, including sustainable business models, competitive positioning, effective management teams, acceptable risk profiles, and long-term growth potential; and

• offer attractive valuations.

In determining whether or not a company's risk profile is acceptable, the Adviser seeks to evaluate risks that may affect share price in the long-term, such as market, environmental, exchange rate, political, and reputation risks, among others. If the risk profile of a company is too high, the investment team may decide not to invest and/or sell a security and look for alternatives.

It is expected that the Adviser's views on long-term global trends and sustainable development themes will evolve over time.

Risk [Heading]

rr_RiskHeading

Principal Investment 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 be subject to currency risk because it invests in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or common stock.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund's expenses.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization companies.

Sustainable Investment Style Risk: Because the Fund focuses on investments in companies that relate to certain sustainable development themes and demonstrate adherence to ESG practices, its universe of investments may be smaller than that of other funds and therefore the Fund may underperform the market as a whole if such investments underperform the market. The Fund may forgo opportunities to gain exposure to certain companies, industries, sectors or countries and it may choose to sell a security when it might otherwise be disadvantageous to do so.

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

Because the Fund has not yet completed a full calendar year, information related to Fund performance, including a bar chart showing annual returns, has not been included in this Prospectus. The performance information provided by the Fund in the future will give 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 compare against those of a broad measure of market performance.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The performance information provided by the Fund in the future will give 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 compare against those of a broad measure of market performance.

(Mirova Global Sustainable Equity Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.67%

^[3]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.72%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.42%

^[5]

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

rr_NetExpensesOverAssets

1.30%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 379

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

735

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,118

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,193

(Natixis Oakmark International Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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

April 30, 2018

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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:

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 41% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

41.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in a diversified portfolio of common stocks of non-U.S. companies. The Fund may invest in non-U.S. markets throughout the world, including emerging markets. Ordinarily, the Fund will invest in the securities of at least five countries outside the U.S. There are no geographic limits on the Fund's non-U.S. investments. Although the Fund invests primarily in common stocks of non-U.S. companies it may also invest in the securities of U.S. companies. The Fund may invest in the securities of small-, mid- and large-capitalization companies.

The Fund's subadviser, Harris Associates L.P. ("Harris Associates"), uses a value investment philosophy in selecting equity securities, such as common stocks, preferred stocks, warrants, and securities convertible into common stocks and preferred stocks. This investment philosophy is based upon the belief that, over time, a company's stock price converges with Harris Associates' estimate of its intrinsic or true business value. By "true business value," Harris Associates means its estimate of the price a knowledgeable buyer would pay to acquire the entire business. Harris Associates believes that investing in securities priced significantly below their true business value presents the best opportunity to achieve the Fund's investment objective.

Harris Associates uses this value philosophy to identify companies that it believes have discounted stock prices compared to the companies' true business values. In assessing such companies, Harris Associates looks for the following characteristics, although not all of the companies selected will have these attributes: (1) free cash flows and intelligent investment of excess cash; (2) earnings that are growing and are reasonably predictable; and (3) high level of manager ownership.

Once Harris Associates identifies a stock that it believes is selling at a significant discount to Harris Associates' estimated intrinsic value and that the issuer has one or more of the additional qualities mentioned above, Harris Associates generally will consider buying that security for the Fund. Harris Associates usually sells a security when the price approaches its estimated worth or the issuer's fundamentals change. Harris Associates monitors each holding and adjusts its price targets as warranted to reflect changes in the issuer's fundamentals. The Fund's portfolio typically holds 30 to 65 stocks.

Risk [Heading]

rr_RiskHeading

Principal Investment 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 be subject to currency risk because it may invest in currency-related instruments and may invest in securities or other instruments denominated in, or that generate income denominated in, foreign currencies. 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or common stock. Small- and mid-capitalization and emerging growth companies may be subject to more abrupt price movements, limited markets and less liquidity than larger, more established companies, which could adversely affect the value of the Fund's equity portfolio.

Focused Investment Risk: Because the Fund may invest in a small number of industries or securities, it may have more risk because the impact of a single economic, political or regulatory occurrence may have a greater adverse impact on the Fund's net asset value.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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 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 life-of-fund 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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class T 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. A sales charge will reduce your return.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
First Quarter 2012, 17.17%

Lowest Quarterly Return:
Third Quarter 2011, -20.47%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns

(for the periods ended December 31, 2016)

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which are offered in a separate prospectus and have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Index performance reflects no deduction for fees, expenses or taxes.

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

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-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

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.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table 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 life-of-fund periods compare to those of a broad measure of market performance.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Natixis Oakmark International Fund) | MSCI World ex USA Index (Net)

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.75%

Past 5 Years

rr_AverageAnnualReturnYear05

6.07%

Life of Fund (12/15/10)

rr_AverageAnnualReturnSinceInception

3.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Natixis Oakmark International Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.85%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.24%

^[3]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.34%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[6]

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

rr_NetExpensesOverAssets

1.34%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 383

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

664

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

966

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,822

Annual Return 2011

rr_AnnualReturn2011

(14.55%)

Annual Return 2012

rr_AnnualReturn2012

28.78%

Annual Return 2013

rr_AnnualReturn2013

28.13%

Annual Return 2014

rr_AnnualReturn2014

(6.05%)

Annual Return 2015

rr_AnnualReturn2015

(5.35%)

Annual Return 2016

rr_AnnualReturn2016

8.19%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: First Quarter 2012, 17.17%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.17%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Third Quarter 2011, -20.47%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(20.47%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Past 1 Year

rr_AverageAnnualReturnYear01

5.52%

Past 5 Years

rr_AverageAnnualReturnYear05

9.13%

Life of Fund (12/15/10)

rr_AverageAnnualReturnSinceInception

5.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Natixis Oakmark International Fund) | Class T | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.26%

Past 5 Years

rr_AverageAnnualReturnYear05

8.69%

Life of Fund (12/15/10)

rr_AverageAnnualReturnSinceInception

4.68%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Natixis Oakmark International Fund) | Class T | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

3.80%

Past 5 Years

rr_AverageAnnualReturnYear05

7.41%

Life of Fund (12/15/10)

rr_AverageAnnualReturnSinceInception

4.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Natixis U.S. Equity Opportunities Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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

April 30, 2018

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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:

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 17% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

17.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund ordinarily invests at least 80% of its net assets (plus any borrowings made for investment purposes) in equity securities, including common stocks and preferred stocks. Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in securities of U.S. issuers. The Fund's approach to equity investing combines the styles of two subadvisers in selecting securities for each of the Fund's segments. The segments and their subadvisers are listed below.

• Harris Associates - Large Cap Value segment - Under normal circumstances, the Large Cap Value segment of the Fund managed by Harris Associates L.P. ("Harris Associates") will invest primarily in the common stocks of larger- capitalization companies that Harris Associates believes are trading at a substantial discount to the company's "true business value." By "true business value," Harris Associates means its estimate of the price a knowledgeable buyer would pay to acquire the entire business. Harris Associates believes that investing in securities priced significantly below their true business value presents the best opportunity to achieve the Fund's investment objectives. Harris Associates usually sells a security when the price approaches its estimated worth and monitors each holding and adjusts its price targets as warranted to reflect changes in the issuer's fundamentals. In determining whether an issuer is a U.S or foreign issuer for the Harris Associates – Large Cap Value segment, Harris Associates considers various factors, including its country of domicile, the primary stock exchange on which it trades, the location from which the majority of its revenue comes, and its reporting currency.

• Loomis Sayles - All Cap Growth segment - Under normal circumstances, the All Cap Growth segment of the Fund, managed by Loomis, Sayles & Company, L.P. ("Loomis Sayles"), will invest primarily in equity securities, including common stocks, preferred stocks, convertible securities and warrants. This segment may invest in companies of any size. The segment normally invests across a wide range of sectors and industries. The segment's portfolio manager employs a growth style of equity management that emphasizes companies with sustainable competitive advantages, long-term structural growth drivers, attractive cash flow returns on invested capital, and management teams focused on creating long-term value for shareholders. The segment's portfolio manager aims to invest in companies when they trade at a significant discount to the estimate of intrinsic value. The segment will consider selling a portfolio investment when the portfolio manager believes an unfavorable structural change occurs within a given business or the markets in which it operates, a critical underlying investment assumption is flawed, when a more attractive reward-to-risk opportunity becomes available, when the portfolio manager believes the current price fully reflects intrinsic value, or for other investment reasons which the portfolio manager deems appropriate. Although certain equity securities purchased by the Loomis Sayles – All Cap Growth segment of the Fund may be issued by domestic companies incorporated outside of the United States, Loomis Sayles does not consider these securities to be foreign if they are included in the U.S. equity indices published by S&P Global Ratings or Russell Investments or if the security's country of risk defined by Bloomberg is the United States.

Subject to the allocation policy adopted by the Fund's Board of Trustees, NGAM Advisors, L.P. ("NGAM Advisors") generally allocates capital invested in the Fund equally (i.e., 50%) between its two segments. Under the allocation policy, NGAM Advisors may also allocate capital away from or towards each segment from time to time and may reallocate capital between the segments. Each subadviser manages its segment of the Fund's assets in accordance with its distinct investment style and strategy.

The Fund may also:

• Invest in securities offered in initial public offerings ("IPOs") and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities").

• Invest in convertible preferred stock and convertible debt securities.

• Invest in real estate investment trusts ("REITs").

• Invest in fixed-income securities, including U.S. government bonds and below-investment grade fixed-income securities (commonly known as "junk bonds").

• Hold securities of foreign issuers traded over-the-counter or on foreign exchanges, including securities in emerging markets and related currency hedging transactions.

• Invest in equity securities of Canadian issuers.

Risk [Heading]

rr_RiskHeading

Principal Investment 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.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or 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. The Fund will be subject to credit risks with respect to the counterparties of its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee of an exchange clearing house, are not available in connection with over-the-counter ("OTC") derivative transactions, such as foreign currency transactions. As a result, in instances when the Fund enters into OTC derivative transactions, the Fund will be subject to the risk that its counterparties will not perform their obligations under the transactions and that the Fund will sustain losses or be unable to realize gains.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 subadviser's assessment of the prospects for a company's growth is wrong, or if the subadviser'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 subadviser 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 generally take precedence over the claims of those who own preferred stock or common stock.

Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. 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 (including the risk of default) to a greater extent 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 the Fund's ability to sell them.

Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Large Investor Risk: Ownership of shares of the Fund may be concentrated in one or a few large investors. Such investors may redeem shares in large quantities or on a frequent basis. Redemptions by a large investor can affect the performance of the Fund, may increase realized capital gains, including short-term capital gains taxable as ordinary income, may accelerate the realization of taxable income to shareholders and may increase transaction costs. These transactions potentially limit the use of any capital loss carryforwards and certain other losses to offset future realized capital gains (if any). Such transactions may also increase the Fund's expenses.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to greater liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities. Non-exchange traded derivatives are generally subject to greater liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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- and Mid-Capitalization Companies Risk: Compared to large-capitalization companies, small- and mid-capitalization companies are more likely to have limited product lines, markets or financial resources. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of large-capitalization companies. As a result, it may be relatively more difficult for the Fund to buy and sell securities of small- and mid-capitalization 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 following bar chart and table 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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class T 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. A sales charge will reduce your return.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Third Quarter 2009, 17.80%

Lowest Quarterly Return:
Fourth Quarter 2008, -24.20%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns

(for the periods ended December 31, 2016)

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T shares. The Fund uses multiple subadvisers. The performance results shown above reflect results achieved by previous subadvisers using different investment strategies.

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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Index performance reflects no deduction for fees, expenses or taxes.

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

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-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

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.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table 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 Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Natixis U.S. Equity Opportunities Fund) | S&P 500® Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

11.96%

Past 5 Years

rr_AverageAnnualReturnYear05

14.66%

Past 10 Years

rr_AverageAnnualReturnYear10

6.95%

(Natixis U.S. Equity Opportunities Fund) | Russell 1000® Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

12.05%

Past 5 Years

rr_AverageAnnualReturnYear05

14.69%

Past 10 Years

rr_AverageAnnualReturnYear10

7.08%

(Natixis U.S. Equity Opportunities Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Fee/expense recovery

rr_Component1OtherExpensesOverAssets

none

^[7],[8]

Remainder of other expenses

rr_Component2OtherExpensesOverAssets

0.18%

^[8]

Other expenses

rr_OtherExpensesOverAssets

0.18%

^[8]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.23%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

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

rr_NetExpensesOverAssets

1.23%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 372

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

631

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

909

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,702

Annual Return 2007

rr_AnnualReturn2007

13.69%

Annual Return 2008

rr_AnnualReturn2008

(40.05%)

Annual Return 2009

rr_AnnualReturn2009

36.41%

Annual Return 2010

rr_AnnualReturn2010

21.90%

Annual Return 2011

rr_AnnualReturn2011

(2.79%)

Annual Return 2012

rr_AnnualReturn2012

17.79%

Annual Return 2013

rr_AnnualReturn2013

35.75%

Annual Return 2014

rr_AnnualReturn2014

12.94%

Annual Return 2015

rr_AnnualReturn2015

5.86%

Annual Return 2016

rr_AnnualReturn2016

11.86%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Third Quarter 2009, 17.80%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.80%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2008, -24.20%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(24.20%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Past 1 Year

rr_AverageAnnualReturnYear01

9.05%

Past 5 Years

rr_AverageAnnualReturnYear05

15.83%

Past 10 Years

rr_AverageAnnualReturnYear10

8.67%

(Natixis U.S. Equity Opportunities Fund) | Class T | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

8.54%

Past 5 Years

rr_AverageAnnualReturnYear05

13.14%

Past 10 Years

rr_AverageAnnualReturnYear10

7.29%

(Natixis U.S. Equity Opportunities Fund) | Class T | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.50%

Past 5 Years

rr_AverageAnnualReturnYear05

12.28%

Past 10 Years

rr_AverageAnnualReturnYear10

6.84%

(Vaughan Nelson Small Cap Value Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks 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 a sales charge discount if you invest at least $250,000 in the Fund. More information about this and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 59 of the Prospectus.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for a sales charge discount if you invest at least $250,000 in the Fund.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 250,000

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

April 30, 2018

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are estimated for the current fiscal year.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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:

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 74% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

74.00%

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, including common stocks and preferred stocks, of "small-capitalization companies." Equity securities may take the form of stock in corporations, limited partnership interests, interests in limited liability companies, real estate investment trusts ("REITs") or other trusts and other similar securities. Currently, the Fund defines a small-capitalization company to be one whose market capitalization, at the time of purchase, either falls within the capitalization range of the Russell 2000® Value Index, an unmanaged index that measures the performance of those Russell 2000® companies with lower price-to-book ratios and lower forecasted growth values, or is $3.5 billion or less. While the market capitalization range for the Russell 2000® Value Index fluctuates, at December 31, 2016, it was $35.6 million to $10.3 billion. The Fund may, however, invest in companies with large- capitalizations.

Vaughan Nelson Investment Management, L.P. ("Vaughan Nelson") invests in small-capitalization companies with a focus on those companies meeting Vaughan Nelson's return expectations. Vaughan Nelson uses a bottom-up value oriented investment process in constructing the Fund's portfolio. Vaughan Nelson seeks companies with the following characteristics, although not all of the companies selected will have these attributes:

• Companies earning a positive return on capital with stable-to-improving returns.

• Companies valued at a discount to their asset value.

• Companies with an attractive and sustainable dividend level.

In selecting investments for the Fund, Vaughan Nelson generally employs the following strategies:

• Value-driven investment philosophy that selects stocks selling at a relatively low value based on discounted cash flow models. Vaughan Nelson selects companies that it believes are out of favor or misunderstood.

• Vaughan Nelson starts with an investment universe of 5,000 securities. Vaughan Nelson then uses value-driven screens to create a research universe of companies with market capitalizations of at least $100 million.

• Vaughan Nelson uses fundamental analysis to construct a portfolio of 60 to 80 securities that, in the opinion of Vaughan Nelson, is made up of quality companies with the potential to provide significant increases in share price over a three year period.

• Vaughan Nelson will generally sell a security when it reaches Vaughan Nelson's price target or when the issuer shows a change in financial condition, competitive pressures, poor management decisions or internal or external forces reducing future expected returns from the investment thesis.

The Fund may also:

• Invest in convertible preferred stock and convertible debt securities.

• Invest in foreign securities, including emerging market securities.

• Invest in REITs.

• Invest in securities offered in initial public offerings ("IPOs").

Risk [Heading]

rr_RiskHeading

Principal Investment 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.

Emerging Markets Risk: In addition to the risks of investing in foreign investments generally, emerging markets investments are subject to greater risks arising from political or economic instability, nationalization or confiscatory taxation, currency exchange restrictions, sanctions by the U.S. government and an issuer's unwillingness or inability to make principal or interest payments on its obligations. Emerging markets companies may be smaller and have shorter operating histories than companies in 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. 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 generally take precedence over the claims of those who own preferred stock or 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. Zero-coupon securities may be subject to these risks to a greater extent than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market for 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/counterparty and information risks. The Fund's investments in foreign securities also are subject to foreign currency fluctuations and other foreign currency-related risks. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity.

Liquidity 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. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services.

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 Companies Risk: Small-capitalization companies are more likely than larger companies to have limited product lines, markets or financial resources, or to depend on a small, inexperienced management group. Stocks of these companies often trade less frequently and in limited volume and their prices may fluctuate more than stocks of larger companies. Stocks of small-capitalization companies may therefore be more vulnerable to adverse developments than those of larger 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 following bar chart and table 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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns for Class T 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. A sales charge will reduce your return.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Third Quarter 2009, 18.56%

Lowest Quarterly Return:
Third Quarter 2011, -19.60%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns

(for the periods ended December 31, 2016)

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

The Fund did not have Class T shares outstanding during the periods shown above. The returns of Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which are offered in a separate prospectus and have the same expenses as Class T shares, restated in the table to reflect the different sales load applicable to Class T 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-advantaged 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. Index performance reflects no deduction for fees, expenses or taxes.

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

Index performance reflects no deduction for fees, expenses or taxes.

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

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-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts.

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.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table 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 Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

The after-tax returns are shown for only one class of the Fund.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

ngam.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Vaughan Nelson Small Cap Value Fund) | Russell 2000® Value Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

31.74%

Past 5 Years

rr_AverageAnnualReturnYear05

15.07%

Past 10 Years

rr_AverageAnnualReturnYear10

6.26%

(Vaughan Nelson Small Cap Value Fund) | Class T

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.90%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.20%

^[3]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.18%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.53%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[10]

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

rr_NetExpensesOverAssets

1.53%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 402

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

721

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,063

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,028

Annual Return 2007

rr_AnnualReturn2007

5.84%

Annual Return 2008

rr_AnnualReturn2008

(21.11%)

Annual Return 2009

rr_AnnualReturn2009

28.30%

Annual Return 2010

rr_AnnualReturn2010

23.67%

Annual Return 2011

rr_AnnualReturn2011

(3.77%)

Annual Return 2012

rr_AnnualReturn2012

14.93%

Annual Return 2013

rr_AnnualReturn2013

39.01%

Annual Return 2014

rr_AnnualReturn2014

8.79%

Annual Return 2015

rr_AnnualReturn2015

(0.29%)

Annual Return 2016

rr_AnnualReturn2016

20.24%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Third Quarter 2009, 18.56%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.56%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Third Quarter 2011, -19.60%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.60%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Past 1 Year

rr_AverageAnnualReturnYear01

17.27%

Past 5 Years

rr_AverageAnnualReturnYear05

15.24%

Past 10 Years

rr_AverageAnnualReturnYear10

9.98%

(Vaughan Nelson Small Cap Value Fund) | Class T | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

15.23%

Past 5 Years

rr_AverageAnnualReturnYear05

11.92%

Past 10 Years

rr_AverageAnnualReturnYear10

7.59%

(Vaughan Nelson Small Cap Value Fund) | Class T | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

11.32%

Past 5 Years

rr_AverageAnnualReturnYear05

11.66%

Past 10 Years

rr_AverageAnnualReturnYear10

7.70%

[1] Other expenses are estimated for the current fiscal year.

[2] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") and NGAM Advisors, L.P. ("NGAM Advisors"), the Fund's advisory administrator, have given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.80% of the Fund's average daily net assets for Class T shares, 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, 2019 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 the applicable expense limitation for Class T shares. 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.

[3] Other expenses are estimated for the current fiscal year.

[4] The Fund's investment 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% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[5] Natixis Asset Management U.S., LLC ("Natixis AM US" 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 1.30% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 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 the applicable expense limitation for Class T shares. 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.

[6] The Fund's investment adviser has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.45% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[7] Includes fee/expense recovery of less than 0.01%.

[8] Other expenses are estimated for the current fiscal year.

[9] The Fund's investment 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% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.

[10] The Fund's investment adviser has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.45% of the Fund's average daily net assets for Class T shares, 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 April 30, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Fund's investment 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 the applicable expense limitations for Class T shares. 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.