485BPOS

Registration Nos. 002-11101

811-00242

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☐
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 231	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☐
Amendment No. 159	☒

(Check appropriate box or boxes.)

NATIXIS FUNDS TRUST II

(Exact Name of Registrant as Specified in Charter)

888 Boylston Street, Boston, Massachusetts	02199
(Address of principal executive offices)	(Zip Code)

Registrant’s Telephone Number, including Area Code (617) 449-2822

Russell Kane, Esq.

Natixis Distribution, L.P.

888 Boylston Street

Boston, Massachusetts 02199

(Name and Address of Agent for Service)

Copy to:

John M. Loder, Esq.

Ropes & Gray

800 Boylston Street

Boston, Massachusetts 02199

Approximate Date of 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 II

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this registration statement under Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment No. 231 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 May, 2020.

NATIXIS FUNDS TRUST II
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, Chief Executive Officer and Trustee	May 21, 2020
/s/ Michael C. Kardok   Michael C. Kardok	Treasurer (Principal Financial Officer and Principal Accounting Officer)	May 21, 2020
Kevin P. Charleston*   Kevin P. Charleston	Trustee	May 21, 2020
Kenneth A. Drucker*   Kenneth A. Drucker	Trustee, Chairperson of the Board	May 21, 2020
Edmond J. English*   Edmond J. English	Trustee	May 21, 2020
Richard A. Goglia*   Richard A. Goglia	Trustee	May 21, 2020
Wendell J. Knox*   Wendell J. Knox	Trustee	May 21, 2020
Martin T. Meehan*   Martin T. Meehan	Trustee	May 21, 2020

Maureen B. Mitchell*   Maureen Mitchell	Trustee	May 21, 2020
James P. Palermo*   James P. Palermo	Trustee	May 21, 2020
Erik R. Sirri*   Erik R. Sirri	Trustee	May 21, 2020
Peter J. Smail*   Peter J. Smail	Trustee	May 21, 2020
Kirk A. Sykes*   Kirk A. Sykes	Trustee	May 21, 2020
Cynthia L. Walker*   Cynthia L. Walker	Trustee	May 21, 2020

*By:	/s/ Russell Kane
	Russell Kane
	Attorney-In-Fact 1, 2
	May 21, 2020

¹  Powers of Attorney for Kevin P. Charleston, Kenneth A. Drucker, Edmond J. English, David L. Giunta, Richard A. Goglia, Wendell J. Knox, Martin T. Meehan, Maureen B. Mitchell, James P. Palermo, Erik R. Sirri, Peter J. Smail and Cynthia L. Walker dated December 5, 2018, effective December 10, 2018, designating John M. Loder, Russell Kane, Kirk Johnson and Michael Kardok as attorneys to sign for each Trustee is incorporated by reference to exhibit (p)(1) to PEA No. 222 to the Registration Statement filed on February 28, 2019.

² Power of Attorney for Kirk A. Sykes dated August 24, 2019, effective September 1, 2019, designating John M. Loder, Russell Kane, Kirk Johnson and Michael Kardok as attorneys to sign for Mr. Sykes is incorporated by reference to exhibit (p)(2) to PEA No. 227 to the Registration Statement filed on March 2, 2020.

Natixis Funds Trust II

Exhibit Index

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	Dec. 31, 2019
Registrant Name	dei_EntityRegistrantName	Natixis Funds Trust II
Central Index Key	dei_EntityCentralIndexKey	0000052136
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Apr. 28, 2020
Document Effective Date	dei_DocumentEffectiveDate	May 01, 2020
Prospectus Date	rr_ProspectusDate	May 01, 2020

XML

Total

(Natixis Oakmark 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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 75 of the Prospectus, in Appendix A to the Prospectus and on page 135 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (Natixis Oakmark Fund) - USD ($)	Class A		Class C	Class N	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none	none
Redemption fees	none		none	none	none	none

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

Annual Fund Operating Expenses - (Natixis Oakmark Fund)		Class A	Class C	Class N	Class T		Class Y
Management fees		0.68%	0.68%	0.68%	0.68%		0.68%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none	0.25%		none
Other expenses		0.24%	0.24%	0.57%	0.24%	[1]	0.24%
Total annual fund operating expenses		1.17%	1.92%	1.25%	1.17%		0.92%
Fee waiver and/or expense reimbursement	[2],[3]	none	none	0.42%	none		none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.17%	1.92%	0.83%	1.17%		0.92%

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 for Class N 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (Natixis Oakmark Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	687	925	1,182	1,914
Class C	295	603	1,037	2,243
Class N	85	355	646	1,474
Class T	366	612	878	1,635
Class Y	94	293	509	1,131

If shares are not redeemed:

Expense Example, No Redemption - (Natixis Oakmark Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	195	603	1,037	2,243

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 15% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund primarily invests in common stocks of U.S. companies. The Fund generally invests in securities of larger capitalization companies in any industry. Harris Associates L.P. ("Harris Associates") uses a value investment philosophy in selecting equity securities, including common stocks. This value investment philosophy is based upon the belief that, over time, a company's stock price converges with the company's intrinsic value. By "intrinsic 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 what Harris Associates believes is a company's intrinsic value presents the best opportunity to achieve the Fund's investment objectives.

Harris Associates uses this value investment philosophy to identify companies that it believes have discounted stock prices compared to what Harris Associates believes are the companies' intrinsic 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 company management ownership.

Once Harris Associates identifies a stock that it believes is selling at a significant discount to Harris Associates' estimate of 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 value 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 60 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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.

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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, ten-year, and life-of-class periods (as applicable) 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
First Quarter 2012, 15.85%

Lowest Quarterly Return:
Fourth Quarter 2018, -17.07%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (Natixis Oakmark Fund)	Past 1 Year	Past 5 Years	Past 10 Years	Life of Fund/Life of Class N	Inception Date
Class Y	27.06%	8.82%	11.85%
Class Y | Return After Taxes on Distributions	24.40%	7.24%	10.52%
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	17.77%	6.73%	9.61%
Class A	19.45%	7.26%	10.90%
Class C	24.82%	7.75%	10.74%
Class N	27.16%			9.80%	May 01, 2017
Class T	23.59%	8.00%	11.29%
S&P 500® Index	31.49%	11.70%	13.56%	14.20%	May 01, 2017

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 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 Fund 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 Value Opportunity 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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 75 of the Prospectus, in Appendix A to the Prospectus and on page 135 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (Vaughan Nelson Value Opportunity Fund) - USD ($)	Class A		Class C	Class N	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none	none
Redemption fees	none		none	none	none	none

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

Annual Fund Operating Expenses - (Vaughan Nelson Value Opportunity Fund)		Class A	Class C	Class N	Class T		Class Y
Management fees		0.80%	0.80%	0.80%	0.80%		0.80%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none	0.25%		none
Other expenses		0.23%	0.22%	0.13%	0.23%	[1]	0.22%
Acquired fund fees and expenses	[2]	0.02%	0.02%	0.02%	0.02%		0.02%
Total annual fund operating expenses		1.30%	2.04%	0.95%	1.30%		1.04%
Fee waiver and/or expense reimbursement	[3]	0.06%	0.06%	0.02%	0.06%		0.05%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.24%	1.98%	0.93%	1.24%		0.99%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (Vaughan Nelson Value Opportunity Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	694	958	1,241	2,048
Class C	301	634	1,093	2,364
Class N	95	301	524	1,165
Class T	373	646	939	1,773
Class Y	101	326	569	1,266

If shares are not redeemed:

Expense Example, No Redemption - (Vaughan Nelson Value Opportunity Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	201	634	1,093	2,364

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 52% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

Under normal market conditions, the Fund will invest primarily in companies that, at the time of purchase, have market capitalizations either within the capitalization range of the Russell Midcap® Value Index, an unmanaged index that measures the performance of companies with lower price-to-book ratios and lower forecasted growth values within the broader Russell Midcap® Index, or of $15 billion or less. While the market capitalization range for the Russell Midcap® Value Index fluctuates, at December 31, 2019, it was $823.7 million to $43.8 billion. However, the Fund does not have any market capitalization limits and may invest in companies with smaller or larger capitalizations. 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 similar securities representing direct or indirect ownership interests in business organizations.

Vaughan Nelson Investment Management, L.P. ("Vaughan Nelson") invests in medium-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:

• Vaughan Nelson employs a value-driven investment philosophy that selects stocks selling at a relatively low value based on business fundamentals, economic margin analysis and discounted cash flow models. Vaughan Nelson selects companies that it believes are out of favor or misunderstood.
• Vaughan Nelson narrows the investment universe by using value-driven screens to create a research universe of companies with market capitalizations between $1 billion and $20 billion.
• Vaughan Nelson uses fundamental analysis to construct a portfolio 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 those expected at the time of investment.

The Fund may also:

• Invest in convertible preferred stock and convertible debt securities.
• Invest in foreign securities, including emerging markets securities.
• Invest in other investment companies, to the extent permitted by the Investment Company Act of 1940.
• Invest in REITs.
• 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").

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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. Equity securities may take the form of stock in corporations, limited partnership interests, interests in limited liability companies, REITs or other trusts and other similar securities representing direct or indirect ownership interests in business organizations.

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.

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.

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

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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 other countries (such as the United States) 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.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including exchange-traded funds, in which it invests in addition to its own expenses.

Large Investor Risk: Ownership of shares of the Fund that 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. Liquidity issues may also make it difficult to value the Fund's investments.

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, ten-year, and life-of-class periods (as applicable) 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
Fourth Quarter 2010, 16.12%

Lowest Quarterly Return:
Third Quarter 2011, -21.12%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (Vaughan Nelson Value Opportunity Fund)	Past 1 Year	Past 5 Years	Past 10 Years	Life of Fund/Life of Class N	Inception Date
Class Y	30.52%	4.96%	10.55%
Class Y | Return After Taxes on Distributions	30.19%	4.04%	9.54%
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	18.30%	3.72%	8.52%
Class A	22.72%	3.46%	9.62%
Class C	28.25%	3.92%	9.46%
Class N	30.67%	5.06%		8.99%	May 01, 2013
Class T	26.92%	4.17%	9.99%
Russell MidCap® Value Index	27.06%	7.62%	12.41%	10.40%	May 01, 2013

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 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 Fund 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] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] Natixis Advisors, L.P. ("Natixis Advisors") has given a binding contractual undertaking to the Fund to reimburse any and all transfer agency expenses for Class N shares. This undertaking is in effect through April 30, 2021 and may be terminated before then only with the consent of the Fund's Board of Trustees.

[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 1.30%, 2.05%, 1.00%, 1.30% and 1.05% of the Fund's average daily net assets for Class A, C, N, T and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 A, C, N, T and Y 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] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[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 1.20%, 1.95%, 0.90%, 1.20% and 0.95% of the Fund's average daily net assets for Class A, C, N, T and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 A, C, N, T and Y 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

(AlphaSimplex Global Alternatives Fund)

Prospectus:

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Objective [Heading]

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Investment Goal

Objective, Primary [Text Block]

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The Fund pursues an absolute return strategy that seeks to provide capital appreciation consistent with the risk-return characteristics of a diversified portfolio of hedge funds. The secondary goal of the Fund is to achieve these returns with less volatility than major equity indices.

Expense [Heading]

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Fund Fees & Expenses

Expense Narrative [Text Block]

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The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

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You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

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$ 50,000

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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

Fee Waiver or Reimbursement over Assets, Date of Termination

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April 30, 2021

Expenses Deferred Charges [Text Block]

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A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

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If shares are redeemed:

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

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If shares are not redeemed:

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes 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 125% of the average value of its portfolio.

Portfolio Turnover, Rate

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125.00%

Strategy [Heading]

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Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund seeks to achieve long and short exposure to global equity, bond, currency and commodity markets through a wide range of derivative instruments and direct investments. Under normal market conditions, the Adviser typically will make extensive use of derivative instruments, in particular futures, forward contracts and swaps on global equity and fixed-income securities, securities indices (including both broad- and narrow-based securities indices), currencies, commodities and other instruments. These investments are intended to provide the Fund with risk and return characteristics similar to those of a diversified portfolio of hedge funds. The Fund may also make direct long and short investments in equity and fixed-income securities.

The Fund seeks to generate absolute returns over time rather than track the performance of any particular index of hedge fund returns. In selecting investments for the Fund, the Adviser uses quantitative models to estimate the market exposures that drive the aggregate returns of a diverse set of hedge funds. The Adviser seeks to capture these market exposures in the aggregate while adding value through dynamic allocation among market exposures and volatility management. These market exposures may include, for example, exposures to the returns of stocks, fixed-income securities (including U.S. and non-U.S. government securities, as well as corporate debt securities), currencies and commodities. In estimating these market exposures, the Adviser may use various approaches, including analyses of the returns of hedge funds included in one or more commercially available databases selected by the Adviser (for example, the Lipper TASS hedge fund database) and regulatory filings. The Fund may also directly employ various strategies commonly used by hedge funds that seek to profit from underlying risk factors, such as merger arbitrage and trend-following strategies. In a merger arbitrage strategy, the Adviser buys shares of target companies in corporate reorganizations and establishes short positions in shares of the acquiring companies. Trend-following strategies analyze markets over various time horizons to invest either long or short in assets whose values are rising or falling, respectively.

The Adviser will have great flexibility to allocate the Fund's exposure among various securities, indices, currencies, commodities and other instruments; the amount of the Fund's assets that may be allocated to various strategies and among investments is expected to vary over time. When buying and selling securities and other instruments for the Fund, the Adviser also may consider other factors, such as: (i) the Fund's obligations under its various derivative positions; (ii) portfolio rebalancing; (iii) redemption requests; (iv) yield management; (v) credit management; and (vi) volatility management. The Fund will not invest directly in hedge funds. The Fund may invest in non-U.S. securities and instruments and securities and instruments traded outside the United States, and expects to engage in non-U.S. currency transactions.

The Adviser currently targets an annualized volatility level of 9% or less (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

Under normal market conditions, it is expected that no more than 25% of the Fund's total assets will be dedicated to initial and variation margin payments relating to the Fund's derivative transactions. The gross notional value of the Fund's derivative investments, however, will generally exceed 25% of the Fund's assets, and may significantly exceed the total value of the Fund's assets. The Adviser will invest a portion of the Fund's assets, which may vary over time, in short-term, high-quality securities. Such investments will be used primarily to finance the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity, and may include: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions or agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks, and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements. The Adviser will select such investments based on various factors, including the security's maturity and credit rating.

Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives through a wholly-owned subsidiary organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). Under normal market conditions, no more than 10% of the Fund's total assets will be dedicated to initial and variation margin payments relating to these transactions.

The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit) of issuers in such industry. 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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to time.

Risk [Heading]

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Principal Investment Risks

Risk Narrative [Text Block]

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

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures, swaps, forward contracts, and other foreign currency transactions and commodity-linked derivatives) 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 commodities markets, 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 futures, swaps, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative or the underlying assets decrease in value over time.

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. 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.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary is not registered under the Investment Company Act of 1940 (the "1940 Act") and is not subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Commodity Subsidiary, respectively, are organized, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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.

Hedge Fund Risk: Hedge funds are typically unregulated private investment pools available only to sophisticated investors. They are often illiquid and highly leveraged. Although the Fund will not invest directly in hedge funds, because the Fund's investments are intended to provide exposure to the factors that drive hedge fund returns, an investment in the Fund will be subject to many of the same risks associated with an investment in a diversified portfolio of hedge funds. Therefore, the Fund's performance may be lower than the returns of the broader stock market and the Fund's net asset value may fluctuate substantially over time.

Index/Tracking Error Risk: Although the Fund does not seek to track any particular index, the Fund seeks to analyze the factors that drive hedge fund returns, as determined by reference to one or more indices. These indices may not provide an accurate representation of hedge fund returns generally, and the Adviser's strategy may not successfully identify or be able to replicate factors that drive returns. There is a risk that hedge fund return data provided by third party hedge fund index providers may be inaccurate or may not accurately reflect hedge fund returns due to survivorship bias, self-reporting bias or other biases.

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. Potential future changes in government monetary policy may affect the level of interest rates.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, ten-year and life-of-class periods (as applicable) compare to those of a broad measure of market performance. The Barclay Fund of Funds Index is a measure of the average return of all funds of funds in the Barclay database. 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 im.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]

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Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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

Bar Chart Closing [Text Block]

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Highest Quarterly Return:
Third Quarter 2010, 7.23%

Lowest Quarterly Return:
First Quarter 2016, -8.36%

Performance Table Heading

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Average Annual Total Returns (for the periods ended December 31, 2019)

Performance Table Closing [Text Block]

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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 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 the Fund's fees, expenses or taxes, but does reflect the management fees and other expenses of both the funds of funds in the index and the hedge funds in which those funds of funds invest.

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

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

Performance Table Uses Highest Federal Rate

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

Performance Table Not Relevant to Tax Deferred

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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]

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

Performance Information Illustrates Variability of Returns [Text]

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

Performance Table One Class of after Tax Shown [Text]

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

Performance Availability Website Address [Text]

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im.natixis.com

Performance Availability Phone [Text]

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800-225-5478

(AlphaSimplex Global Alternatives Fund) | Bloomberg Barclay Fund of Funds Index

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

5.86%

Past 5 Years

rr_AverageAnnualReturnYear05

1.20%

Past 10 Years

rr_AverageAnnualReturnYear10

2.04%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.99%

Inception Date

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May 01, 2013

(AlphaSimplex Global Alternatives Fund) | Class A

Prospectus:

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

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5.75%

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

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none

^[1]

Redemption fees

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none

Management fees

rr_ManagementFeesOverAssets

1.15%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.17%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.03%

^[3],[4]

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

rr_NetExpensesOverAssets

1.64%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 732

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,068

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,428

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,435

Past 1 Year

rr_AverageAnnualReturnYear01

3.96%

Past 5 Years

rr_AverageAnnualReturnYear05

0.04%

Past 10 Years

rr_AverageAnnualReturnYear10

2.54%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Global Alternatives Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.15%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.17%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

2.42%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.03%

^[3],[4]

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

rr_NetExpensesOverAssets

2.39%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 342

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

752

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,288

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,754

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

242

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

752

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,288

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,754

Past 1 Year

rr_AverageAnnualReturnYear01

8.48%

Past 5 Years

rr_AverageAnnualReturnYear05

0.48%

Past 10 Years

rr_AverageAnnualReturnYear10

2.38%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Global Alternatives Fund) | Class N

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.15%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.11%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.36%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.02%

^[3],[4]

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

rr_NetExpensesOverAssets

1.34%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 136

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

429

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

743

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,633

Past 1 Year

rr_AverageAnnualReturnYear01

10.48%

Past 5 Years

rr_AverageAnnualReturnYear05

1.50%

Past 10 Years

rr_AverageAnnualReturnYear10

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2013

(AlphaSimplex Global Alternatives 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

1.15%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.17%

^[5]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.03%

^[3],[4]

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

rr_NetExpensesOverAssets

1.64%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 413

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

760

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,132

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,174

Past 1 Year

rr_AverageAnnualReturnYear01

7.53%

Past 5 Years

rr_AverageAnnualReturnYear05

0.71%

Past 10 Years

rr_AverageAnnualReturnYear10

2.88%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Global Alternatives Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.15%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.17%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.42%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.03%

^[3],[4]

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

rr_NetExpensesOverAssets

1.39%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 142

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

446

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

773

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,699

Annual Return 2010

rr_AnnualReturn2010

7.22%

Annual Return 2011

rr_AnnualReturn2011

(3.00%)

Annual Return 2012

rr_AnnualReturn2012

3.68%

Annual Return 2013

rr_AnnualReturn2013

16.05%

Annual Return 2014

rr_AnnualReturn2014

3.77%

Annual Return 2015

rr_AnnualReturn2015

(2.38%)

Annual Return 2016

rr_AnnualReturn2016

(4.23%)

Annual Return 2017

rr_AnnualReturn2017

10.93%

Annual Return 2018

rr_AnnualReturn2018

(6.04%)

Annual Return 2019

rr_AnnualReturn2019

10.49%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Third Quarter 2010, 7.23%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.23%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: First Quarter 2016, -8.36%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(8.36%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2016

Past 1 Year

rr_AverageAnnualReturnYear01

10.49%

Past 5 Years

rr_AverageAnnualReturnYear05

1.49%

Past 10 Years

rr_AverageAnnualReturnYear10

3.41%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Global Alternatives Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

10.05%

Past 5 Years

rr_AverageAnnualReturnYear05

1.02%

Past 10 Years

rr_AverageAnnualReturnYear10

2.58%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Global Alternatives Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

6.28%

Past 5 Years

rr_AverageAnnualReturnYear05

0.98%

Past 10 Years

rr_AverageAnnualReturnYear10

2.40%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(AlphaSimplex Managed Futures Strategy Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund pursues an absolute return strategy that seeks to provide 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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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, 2021

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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 examples for Class A, Class C, Class T, and Class Y are 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed:

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

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed:

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. Due to the short-term nature of the Fund's investment portfolio, the Fund does not calculate a portfolio turnover rate.

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to generate positive absolute returns over time. Under normal market conditions, the Adviser typically will make extensive use of a variety of derivative instruments, including futures and forward contracts, to capture the exposures suggested by its absolute return strategy while also seeking to add value through volatility management. These market exposures, which are expected to change over time, may include, for example, exposures to the returns of U.S. and non-U.S. equity and fixed-income securities indices (including both broad- and narrow-based securities indices), currencies and commodities. The Adviser will have great flexibility to allocate the Fund's derivatives exposure among various securities, indices, currencies, commodities and other instruments; the amount of the Fund's assets that may be allocated to derivative strategies and among these various instruments is expected to vary over time. The Adviser uses proprietary quantitative models to identify price trends in equity, fixed-income, currency and commodity instruments across time periods of various lengths. The Adviser believes that asset prices may show persistent trending behavior due to a number of behavioral biases among market participants as well as certain risk-management policies that will identify assets to purchase in upward-trending markets and identify assets to sell in downward-trending markets. The Adviser believes that following trends across a widely diversified set of assets, combined with active risk management, may allow it to earn a positive expected return over time. The Fund may have both "short" and "long" exposures within an asset class based upon the Adviser's analysis of multiple time horizons to identify trends in a particular asset class. A "short" exposure will benefit when the underlying asset class decreases in price. A "long" exposure will benefit when the underlying asset class increases in price. The Adviser will scale the notional exposure of the Fund's futures and currency forward positions with the objective of targeting a relatively stable level of annualized volatility for the Fund's overall portfolio. The Adviser currently targets an annualized volatility level of 17% or less (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

Under normal market conditions, it is expected that no more than 25% of the Fund's total assets will be dedicated to initial and variation margin payments relating to the Fund's derivative transactions. The gross notional value of the Fund's derivative investments, however, will generally exceed 25% of the Fund's total assets, and may significantly exceed the total value of the Fund's assets. The Fund expects that under normal market conditions it will invest at least 75% of its total assets in money market and other short-term, high-quality securities (such as bankers' acceptances, certificates of deposit, commercial paper, loan participations, repurchase agreements and time deposits) (the "Money Market Portion"), although the Fund may invest less than this percentage. The Adviser will determine the percentage of the Fund's assets that will be invested in the Money Market Portion at any time. The assets allocated to the Money Market Portion will be used primarily to support the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. Although the Fund will invest a significant portion of its assets in money market instruments, the Fund is not a "money market" fund and the value of the Money Market Portion as well as the value of the Fund's shares may decrease. The Fund is not subject to the portfolio quality, maturity and net asset value requirements applicable to money market funds, and the Fund will not seek to maintain a stable net asset value. The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit, repurchase agreements and time deposits) of issuers in such industry.

The Adviser will only invest the assets of the Money Market Portion in high-quality securities which are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities ("U.S. Government Obligations"); (ii) securities issued by foreign governments, their political subdivisions, agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives by investing in a wholly-owned subsidiary organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). Under normal market conditions, no more than 10% of the Fund's total assets will be dedicated to initial and variation margin payments relating to these transactions.

Although the Fund seeks positive absolute returns over time, it is likely that the Fund's investment returns may be volatile over short periods of time. The Fund may outperform the overall securities market during periods of flat or negative market performance and may underperform during periods of strong market performance. There can be no assurance that the Fund's returns over time or during any period will be positive or that the Fund will outperform the overall security markets over time or during any particular period.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. Due to the short-term nature of the Fund's investment portfolio, the Fund does not calculate a portfolio turnover rate. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures and forward contracts) 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 futures, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time.

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. 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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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 a significant portion of its assets 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.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary is not registered under the Investment Company Act of 1940 (the "1940 Act") and is not subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Commodity Subsidiary, respectively, are organized, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) compare to those of two broad measures of market performance. The SG Trend Index is equal-weighted, reconstituted and rebalanced annually. The index calculates the net daily rate of return for a pool of Commodity Trading Advisors selected from the larger managers that are open to new investment. AlphaSimplex Group, LLC is part of this Index. 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 im.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 Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

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

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
First Quarter 2015, 11.72%

Lowest Quarterly Return:
Second Quarter 2015, -10.57%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (for the periods ended December 31, 2019)

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 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 bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) 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

im.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(AlphaSimplex Managed Futures Strategy Fund) | Credit Suisse Managed Futures Liquid Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

(4.56%)

Past 5 Years

rr_AverageAnnualReturnYear05

(0.77%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.20%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Credit Suisse Managed Futures Liquid Index

Prospectus:

rr_ProspectusTable

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(2.17%)

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(AlphaSimplex Managed Futures Strategy Fund) | SG Trend Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

9.23%

Past 5 Years

rr_AverageAnnualReturnYear05

(0.75%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | SG Trend Index

Prospectus:

rr_ProspectusTable

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(AlphaSimplex Managed Futures Strategy Fund) | Class A

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[6]

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.25%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.29%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.79%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.09%

^[7]

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

rr_NetExpensesOverAssets

1.70%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 738

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,098

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,481

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,552

Past 1 Year

rr_AverageAnnualReturnYear01

1.84%

Past 5 Years

rr_AverageAnnualReturnYear05

(2.54%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.12%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.25%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.28%

Total annual fund operating expenses

rr_ExpensesOverAssets

2.53%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.08%

^[7]

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

rr_NetExpensesOverAssets

2.45%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 348

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

780

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,338

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,860

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

248

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

780

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,338

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,860

Past 1 Year

rr_AverageAnnualReturnYear01

6.30%

Past 5 Years

rr_AverageAnnualReturnYear05

(2.13%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.98%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Class N

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.25%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.36%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[7]

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

rr_NetExpensesOverAssets

1.36%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 138

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

431

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

745

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,635

Past 1 Year

rr_AverageAnnualReturnYear01

8.45%

Past 5 Years

rr_AverageAnnualReturnYear05

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

0.59%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(AlphaSimplex Managed Futures Strategy 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

1.25%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.29%

^[5]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.79%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.09%

^[7]

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

rr_NetExpensesOverAssets

1.70%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 418

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

791

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,187

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,295

Past 1 Year

rr_AverageAnnualReturnYear01

5.38%

Past 5 Years

rr_AverageAnnualReturnYear05

(1.87%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.48%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

1.25%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.28%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.53%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.08%

^[7]

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

rr_NetExpensesOverAssets

1.45%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 148

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

476

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

827

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,817

Annual Return 2011

rr_AnnualReturn2011

0.57%

Annual Return 2012

rr_AnnualReturn2012

(10.90%)

Annual Return 2013

rr_AnnualReturn2013

12.75%

Annual Return 2014

rr_AnnualReturn2014

22.21%

Annual Return 2015

rr_AnnualReturn2015

(1.22%)

Annual Return 2016

rr_AnnualReturn2016

(5.47%)

Annual Return 2017

rr_AnnualReturn2017

6.48%

Annual Return 2018

rr_AnnualReturn2018

(12.35%)

Annual Return 2019

rr_AnnualReturn2019

8.35%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: First Quarter 2015, 11.72%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.72%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2015

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Second Quarter 2015, -10.57%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(10.57%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2015

Past 1 Year

rr_AverageAnnualReturnYear01

8.35%

Past 5 Years

rr_AverageAnnualReturnYear05

(1.14%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

3.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

6.29%

Past 5 Years

rr_AverageAnnualReturnYear05

(1.93%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.69%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Managed Futures Strategy Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

4.95%

Past 5 Years

rr_AverageAnnualReturnYear05

(1.14%)

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.90%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 30, 2010

(AlphaSimplex Multi-Asset Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation. The secondary goal of the Fund is the protection of capital during unfavorable market conditions.

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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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, 2021

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed:

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

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed:

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 23% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

23.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund tactically allocates its investments across a range of asset classes and global markets. Under normal market conditions, the Adviser will typically use a variety of derivative instruments, including equity, fixed-income and currency futures contracts and currency forward contracts, as well as exchange-traded funds ("ETFs") and money market and other short-term, high-quality securities, to achieve exposures to the following asset classes: (i) U.S. equity securities; (ii) foreign developed market equity securities; (iii) emerging market equity and fixed-income securities; (iv) U.S. fixed-income securities; (v) foreign developed market fixed-income securities; and (vi) currencies. 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 will typically obtain its target allocations through the use of long and/or short positions in futures and/or forward contracts, as well as investments in ETFs, which can provide exposure to certain asset classes that may not be readily available via futures contracts (e.g., domestic and international corporate bonds). The Adviser utilizes various proprietary quantitative models to identify investment opportunities. The Fund may obtain exposure to below investment grade fixed-income securities, also known as "junk bonds," through its investments in ETFs. Below investment grade fixed-income securities are rated below investment grade quality (i.e., none of the three major rating agencies (Moody's Investors Service, Inc., Fitch Investor Services, Inc. or S&P Global Ratings) have rated the securities in one of their respective top four ratings categories).

The Adviser uses a quantitative systematic approach to identify investment opportunities. The approach consists of overweighting and/or underweighting allocations to asset classes based on a number of factors, including momentum signals (measurements of recent trends in asset prices), the relative portfolio risks of various asset classes, asset class correlations (measurements of relationships between asset class prices) and/or market volatility. For example, the Adviser may overweight an asset class that demonstrates increasing momentum relative to other asset classes.

The Adviser separately manages the Fund's investments in derivatives and ETFs (the "Multi-Asset Portion") and the Fund's investments in money market and other short-term, high-quality securities (the "Money Market Portion," described further below). The Multi-Asset Portion will obtain economic leverage through the use of derivative instruments. Leverage can vary over time based on market conditions and the net notional value of the Multi-Asset Portion's investments may significantly exceed the Fund's total assets. Because the Fund's investment exposure will often significantly exceed its total assets, it will be subject to increased risk compared to funds that do not leverage their investment exposure. While this increased investment exposure may magnify the Fund's potential for gains, it will also magnify the potential for losses. For these reasons, the Fund is intended for long-term investors.

The Adviser will seek to manage the annualized volatility (a statistical measure of the variation of returns) of the Fund's overall portfolio as part of the investment approach. The Adviser will monitor the portfolio daily and currently targets an annualized volatility level of 13% or less. The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This will increase the risk of investing in the Fund.

The Fund expects that, under normal market conditions, it will invest at least 40% of its total assets in the Money Market Portion. The Fund may invest less than this percentage in the Money Market Portion and the Adviser will determine the percentage of the Fund's assets that will be invested in the Money Market Portion at any time. The assets allocated to the Money Market Portion will be used primarily to provide collateral for the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. Although the Fund will invest a significant portion of its assets in money market instruments, the Fund is not a "money market" fund and the value of the Money Market Portion as well as the value of the Fund's shares may decrease. The Fund is not subject to the portfolio quality, maturity and net asset value requirements applicable to money market funds, and the Fund will not seek to maintain a stable net asset value. The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit, repurchase agreements and time deposits) of issuers in that industry.

The Adviser will only invest the assets of the Money Market Portion in high-quality securities which are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions, agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

The Fund expects to add commodities as an available asset class for investment at a future date. Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives by investing in a wholly-owned subsidiary expected to be organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). The Fund anticipates registering the Commodity Subsidiary upon the attainment of approximately $100 million in assets under management. The maximum exposure to commodities will be 20% of total assets.

The Fund is non-diversified, which means that it may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers. Because the Fund may invest in the securities of a limited number of issuers, an investment in the Fund may involve a higher degree of risk than would be present in a diversified portfolio.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders.

Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures and forward contracts) 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 commodities markets, 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 futures, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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 (if any) required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivative 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative or the underlying assets decrease in value over time.

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. 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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

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.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary will not be registered under the Investment Company Act of 1940 (the "1940 Act") and will not be subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund is organized and the Commodity Subsidiary is expected to be organized, respectively, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivatives transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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 other countries (such as the United States) 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.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

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

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk Nondiversified Status [Text]

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

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year and life-of-fund periods compare to those of two broad measures of market performance. The Blended Index is an unmanaged, blended index composed of the following weights: 60% MSCI World Index (Net) and 40% Bloomberg Barclays U.S. Aggregate Bond Index. The two indices composing the Blended Index measure, respectively, the performance of global equity securities and global sovereign fixed-income securities. 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 im.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]

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Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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

Bar Chart Closing [Text Block]

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Highest Quarterly Return:
Fourth Quarter 2019, 7.43%

Lowest Quarterly Return:
Fourth Quarter 2018, -9.89%

Performance Table Heading

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Average Annual Total Returns (for the periods ended December 31, 2019)

Performance Table Closing [Text Block]

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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 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]

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

Performance Table Uses Highest Federal Rate

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

Performance Table Not Relevant to Tax Deferred

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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]

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

Performance Information Illustrates Variability of Returns [Text]

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

Performance Table One Class of after Tax Shown [Text]

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

Performance Availability Website Address [Text]

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im.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(AlphaSimplex Multi-Asset Fund) | Morningstar Global Allocation Index

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

18.53%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

8.35%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Blended Index

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

20.01%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

7.84%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class A

Prospectus:

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[8]

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.70%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.67%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[9]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.47%

^[10]

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

rr_NetExpensesOverAssets

1.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 690

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,028

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,389

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,401

Past 1 Year

rr_AverageAnnualReturnYear01

9.91%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

4.84%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class C

Prospectus:

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.70%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.68%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[9]

Total annual fund operating expenses

rr_ExpensesOverAssets

2.43%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.48%

^[10]

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

rr_NetExpensesOverAssets

1.95%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 298

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

712

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,252

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,730

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

198

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

712

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,252

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,730

Past 1 Year

rr_AverageAnnualReturnYear01

14.75%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

5.57%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class T

Prospectus:

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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

0.70%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.67%

^[5]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[9]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.47%

^[10]

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

rr_NetExpensesOverAssets

1.20%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 369

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

719

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,092

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,138

Past 1 Year

rr_AverageAnnualReturnYear01

13.66%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

5.70%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.70%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.67%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[9]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.42%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.47%

^[10]

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

rr_NetExpensesOverAssets

0.95%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 97

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

403

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

732

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,661

Annual Return 2016

rr_AnnualReturn2016

2.57%

Annual Return 2017

rr_AnnualReturn2017

21.19%

Annual Return 2018

rr_AnnualReturn2018

(9.39%)

Annual Return 2019

rr_AnnualReturn2019

16.82%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Fourth Quarter 2019, 7.43%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.43%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2019

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2018, -9.89%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.89%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2018

Past 1 Year

rr_AverageAnnualReturnYear01

16.82%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

6.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

15.70%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

5.15%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Multi-Asset Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

9.95%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

4.59%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2015

(AlphaSimplex Tactical U.S. Market Fund)

Prospectus:

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Objective [Heading]

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Investment Goal

Objective, Primary [Text Block]

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The Fund seeks long-term capital appreciation, with emphasis on the protection of capital during unfavorable market conditions.

Expense [Heading]

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Fund Fees & Expenses

Expense Narrative [Text Block]

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The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

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You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Shareholder Fees Caption [Text]

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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, 2021

Expenses Deferred Charges [Text Block]

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A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

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If shares are redeemed:

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

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If shares are not redeemed:

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes 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 37% of the average value of its portfolio.

Portfolio Turnover, Rate

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37.00%

Strategy [Heading]

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Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund pursues its investment goal primarily through investments in equity securities that broadly represent the U.S. equities market (including common stocks, preferred stocks and exchange-traded funds ("ETFs") related to equity investments); derivative instruments related to the U.S. equities market (primarily futures contracts on U.S. equity indices); and fixed-income securities (including money market and other short-term or variable-rate, high-quality securities and related ETFs). Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investments that are tied economically to the U.S. The Adviser considers an investment to be tied economically to the U.S. if the investment is included in an index representative of the U.S., the investment's returns are linked to the performance of such an index, or the investment is exposed to the economic risks and returns of the U.S. The Adviser may use quantitative models to determine when to magnify the Fund's exposure to the U.S. equity market, for example, through the purchase of futures contracts, or, alternatively, when to decrease such exposure, for example, through the sale of futures contracts or through the purchase of ETFs that it believes may effectively hedge equity investments. The Adviser may increase the Fund's exposure to the U.S. equity market to up to 130% of the Fund's total assets when it believes that the risk of loss is justified by potential returns. The Adviser may decrease such exposure to as little as 0% of the Fund's total assets, in an attempt to limit the effects of extreme market drawdowns, when it believes that the risk of loss is not offset by potential returns. Such increases and decreases may lag changes in the market, and there is no guarantee that the Adviser's models will accurately predict market movement. Because the Fund's equity market exposure will often exceed its total assets, it will be subject to increased risk compared to funds that do not leverage their equity market exposure. While this increased exposure to equity investments may magnify the Fund's potential for gains, it also may magnify the potential for loss. For these reasons, the Fund is intended for long-term investors.

Equity Securities Investments. The equity securities portion of the Fund is managed by Natixis Advisors, L.P. (through its division, Active Index Advisors®) ("Natixis Advisors"), with the exception of any investments in ETFs, which are selected by the Adviser. Natixis Advisors utilizes a proprietary sampling system when deciding which securities to purchase, with the goal of tracking the performance of the large-capitalization U.S. equity market. In an attempt to reduce adverse tax consequences, the portion of the Fund managed by Natixis Advisors may hold securities that are not considered to represent the large-capitalization U.S. equity market, or hold securities in amounts disproportionate to their weights within the large-capitalization U.S. equity market. The portfolio may experience tracking error and is not guaranteed to replicate exactly the large-capitalization U.S. equity market.

Derivative Investments. As discussed above, the Adviser seeks to complement the equity portion of the Fund with investments in derivative instruments intended to enhance return and, during times of significant market decline, mitigate losses. In addition, the Adviser uses futures contracts to manage volatility and adjusts the Fund's exposure to equity investments in times of significantly increased volatility (including, when volatility is more than double the long-term average volatility of the U.S. equity markets). As of March 31, 2020, the long-term average annualized volatility of the U.S. equity markets was 19.1%. The Fund's actual or realized volatility during certain periods or over time may materially exceed the long-term average annualized volatility of the U.S. equity markets, for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. The Fund may have both "short" and "long" exposures to equity investments simultaneously. The Fund will benefit from a "short" exposure when equity and equity-related investments decrease in price, and will benefit from a "long" exposure when equity and equity-related investments increase in price.

Fixed-Income Investments. The assets allocated to the fixed-income portion will be used primarily to support the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. The fixed-income portion of the Fund will only invest in high-quality securities that are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions or agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic and foreign banks, including domestic or foreign branches or subsidiaries of such banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

When buying and selling securities and other instruments for the Fund, and when allocating assets to Natixis Advisors, the Adviser may consider: (i) the Adviser's proprietary quantitative models, including the outlook on volatility and market decline; (ii) the Fund's obligations under its various derivative positions; (iii) redemption requests; (iv) yield management; (v) credit management; and (vi) volatility management.

The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit) of issuers in such industry.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs that reduce Fund returns.

With the exception of the Fund's 80% policy, the percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to time. In accordance with applicable requirements of the U.S. Securities and Exchange Commission (the "SEC"), the Fund will notify shareholders prior to any change to the 80% policy discussed above taking effect.

Risk [Heading]

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Principal Investment Risks

Risk Narrative [Text Block]

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

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures contracts) 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 futures contracts, involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time.

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

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Index/Tracking Error Risk: This is the risk that, to the extent the Fund's principal investment strategies utilize indices, the Fund's performance may not track the performance of such indices. For example, the equity securities in which the Fund invests may not provide investment performance matching the performance of broad-based large capitalization U.S. equity indices. Similarly, changes in the value of the derivatives in which the Fund invests may not correlate perfectly with the underlying assets or indices associated with such derivatives. Moreover, the ETFs in which the Fund invests may not replicate the performance of the indices they track and may, therefore, result in loss to the Fund.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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. Potential future changes in government monetary policy may affect the level of interest rates.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The 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 compare to those of two broad measures of market performance. The Barclay Equity Long/Short Index is comprised of equity-oriented hedge funds which hold both long and short stock positions and tend to tactically vary their net market exposure, i.e., market beta, based on their assessment of market risk and expected return. Index returns are recalculated by Barclay Hedge Ltd. throughout each month. The Fund does not expect to update the index returns provided if subsequent recalculations cause such returns to change. In addition, because of these recalculations, the Barclay Equity Long/Short Index returns reported by the Fund may differ from the index returns for the same period published by others. 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 im.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]

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Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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

Bar Chart Closing [Text Block]

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Highest Quarterly Return:
Fourth Quarter 2019, 10.28%

Lowest Quarterly Return:
Fourth Quarter 2018, -12.94%

Performance Table Heading

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Average Annual Total Returns (for the periods ended December 31, 2019)

Performance Table Closing [Text Block]

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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 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 Fund 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]

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

Performance Table Uses Highest Federal Rate

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

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-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]

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

Performance Information Illustrates Variability of Returns [Text]

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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 compare to those of two broad measures of market performance.

Performance Table One Class of after Tax Shown [Text]

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

Performance Availability Website Address [Text]

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im.natixis.com

Performance Availability Phone [Text]

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800-225-5478

(AlphaSimplex Tactical U.S. Market Fund) | S&P 500® Index

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

31.49%

Past 5 Years

rr_AverageAnnualReturnYear05

11.70%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

13.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Barclay Equity Long/Short Index

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

7.08%

Past 5 Years

rr_AverageAnnualReturnYear05

3.25%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

3.83%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Class A

Prospectus:

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[11]

Redemption fees

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none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.26%

^[12]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.31%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[13]

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

rr_NetExpensesOverAssets

1.25%

Expense Example, with Redemption, 1 Year

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$ 695

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

961

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,246

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,058

Past 1 Year

rr_AverageAnnualReturnYear01

15.84%

Past 5 Years

rr_AverageAnnualReturnYear05

7.12%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

10.11%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.26%

^[12]

Total annual fund operating expenses

rr_ExpensesOverAssets

2.06%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[13]

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

rr_NetExpensesOverAssets

2.00%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 303

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

640

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,103

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,385

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

203

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

640

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,103

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,385

Past 1 Year

rr_AverageAnnualReturnYear01

21.04%

Past 5 Years

rr_AverageAnnualReturnYear05

7.58%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

10.34%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market 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

0.26%

^[12],[14]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.31%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[13]

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

rr_NetExpensesOverAssets

1.25%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 374

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

649

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

945

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,784

Past 1 Year

rr_AverageAnnualReturnYear01

19.86%

Past 5 Years

rr_AverageAnnualReturnYear05

7.85%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

10.71%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.26%

^[12]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.06%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[13]

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

rr_NetExpensesOverAssets

1.00%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 102

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

331

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

579

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,289

Annual Return 2014

rr_AnnualReturn2014

14.92%

Annual Return 2015

rr_AnnualReturn2015

(2.74%)

Annual Return 2016

rr_AnnualReturn2016

4.41%

Annual Return 2017

rr_AnnualReturn2017

25.67%

Annual Return 2018

rr_AnnualReturn2018

(3.67%)

Annual Return 2019

rr_AnnualReturn2019

23.34%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Fourth Quarter 2019, 10.28%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.28%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2019

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2018, -12.94%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(12.94%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2018

Past 1 Year

rr_AverageAnnualReturnYear01

23.34%

Past 5 Years

rr_AverageAnnualReturnYear05

8.68%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

11.46%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

23.05%

Past 5 Years

rr_AverageAnnualReturnYear05

8.12%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

10.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(AlphaSimplex Tactical U.S. Market Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

13.97%

Past 5 Years

rr_AverageAnnualReturnYear05

6.76%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

8.97%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 2013

(Loomis Sayles Intermediate Municipal Bond Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks a high level of federal tax-exempt current income, consistent with the preservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fund Fees & Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 100,000

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, 2021

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A 0.75% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $500,000 or more that are redeemed within eighteen months of the date of purchase.

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed:

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

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed:

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 11% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

11.00%

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 borrowings made for investment purposes) in municipal securities that pay interest exempt from federal income taxes. Municipal securities are debt instruments typically issued by or on behalf of state and local governments, territories or possessions of the United States, including the District of Columbia, and their political subdivisions, agencies and instrumentalities and may include general obligation, revenue and private activity bonds and notes. In addition, the Fund may invest up to 20% of its assets in securities that pay interest subject to federal income taxation. The Fund may invest up to 20% of its assets in debt securities subject to the federal alternative minimum tax. The Fund's investments may include securities issued by the U.S. government, its agencies and instrumentalities and corporate debt securities. The Fund will invest primarily in investment grade fixed-income 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., Fitch Investors Services, Inc. or S&P Global Ratings), or, if unrated, are determined by Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Subadviser") to be of comparable quality. The Subadviser considers pre-refunded bonds and municipal securities escrowed to maturity using U.S. Treasury securities or U.S. government agency securities to be investment grade securities, regardless of rating. The Fund may also invest up to 10% of its assets in securities that are not investment grade (commonly known as "junk bonds"). Under normal circumstances, the dollar-weighted average maturity of the Fund's portfolio is expected to be between 3 and 10 years although the Fund may invest in securities of any maturity.

The portfolio management team seeks to build a portfolio based on a number of factors including sector, duration and maturity distribution, yield, expected return, credit momentum outlook (sector and security level), credit quality, security structure, issue size and liquidity. Through the use of quantitative and fundamental analysis, the pool of possible portfolio investments is screened using these factors to arrive at a narrower universe of securities that the Subadviser believes are suitable for the Fund's portfolio. Potential investments are also subject to a portfolio risk assessment that may include the following:

• Determining the ability of creditors to fully repay debt obligations in a timely manner.
• Use of a wide variety of internal and external quantitative and analytical and informational sources to assess likelihood of repayment.
• Monitoring rating agency and third party surveillance sources with an emphasis on core holdings.

The Subadviser may sell a security for a variety of reasons, including duration management, yield curve positioning, sector rotation, a change in credit momentum outlook or if more attractive investment opportunities are identified.

The Fund may also:

• Invest in when-issued securities and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities").
• Enter into futures transactions for hedging and investment purposes.
• Invest in other investment companies to the extent permitted by the Investment Company Act of 1940.

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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

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. Derivatives, and particularly OTC derivatives, are generally subject to liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies in which it invests in addition to its own expenses.

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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, such as options, foreign currency transactions, 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 over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate 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.

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.

Municipal Securities Risk: Municipal bonds are investments issued by states, cities, public authorities or political subdivisions to raise money for public purposes, including general obligation bonds and revenue obligations. Municipal securities are subject to information risk, liquidity risk, credit risk and the risks that economic, political, fiscal or regulatory events, legislative changes and the enforceability of rights of municipal bond holders could adversely affect the values of municipal bonds. Municipal obligations may be susceptible to downgrades or defaults during recessions or similar periods of economic stress and insolvent municipalities may file for bankruptcy, which could significantly affect the rights of creditors and the value of the municipal securities. In addition, if the municipal securities held by the Fund fail to meet certain legal requirements allowing interest distributed from such securities to be tax-exempt, the interest received and distributed to shareholders by the Fund may be taxable.

Risk Lose Money [Text]

rr_RiskLoseMoney

You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and life-of-fund periods (as applicable) 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 im.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 Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

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

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
First Quarter 2019, 2.66%

Lowest Quarterly Return:
Fourth Quarter 2016, -3.76%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (for the periods ended December 31, 2019)

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 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 bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and life-of-fund periods (as applicable) 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

im.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Loomis Sayles Intermediate Municipal Bond Fund) | Bloomberg Barclays Municipal Bond Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

7.54%

Past 5 Years

rr_AverageAnnualReturnYear05

3.53%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

3.39%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal Bond Fund) | Class A

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.00%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[15]

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

1.19%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.85%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.14%

^[16]

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

rr_NetExpensesOverAssets

0.71%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 370

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

757

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,167

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,313

Past 1 Year

rr_AverageAnnualReturnYear01

3.33%

Past 5 Years

rr_AverageAnnualReturnYear05

1.96%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.86%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal Bond Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

1.20%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

2.61%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.15%

^[16]

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

rr_NetExpensesOverAssets

1.46%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 249

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

702

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,282

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,859

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

149

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

702

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,282

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,859

Past 1 Year

rr_AverageAnnualReturnYear01

4.64%

Past 5 Years

rr_AverageAnnualReturnYear05

1.85%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.55%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal 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

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

1.19%

^[5]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.85%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.14%

^[16]

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

rr_NetExpensesOverAssets

0.71%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 321

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

709

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,122

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,274

Past 1 Year

rr_AverageAnnualReturnYear01

3.83%

Past 5 Years

rr_AverageAnnualReturnYear05

2.06%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.95%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal Bond Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

1.20%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.61%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.15%

^[16]

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

rr_NetExpensesOverAssets

0.46%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 47

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

395

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

767

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,814

Annual Return 2013

rr_AnnualReturn2013

(2.31%)

Annual Return 2014

rr_AnnualReturn2014

6.36%

Annual Return 2015

rr_AnnualReturn2015

2.63%

Annual Return 2016

rr_AnnualReturn2016

(0.55%)

Annual Return 2017

rr_AnnualReturn2017

5.13%

Annual Return 2018

rr_AnnualReturn2018

0.58%

Annual Return 2019

rr_AnnualReturn2019

6.80%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: First Quarter 2019, 2.66%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

2.66%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2019

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2016, -3.76%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(3.76%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2016

Past 1 Year

rr_AverageAnnualReturnYear01

6.80%

Past 5 Years

rr_AverageAnnualReturnYear05

2.88%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal Bond Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

6.79%

Past 5 Years

rr_AverageAnnualReturnYear05

2.88%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Intermediate Municipal Bond Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.11%

Past 5 Years

rr_AverageAnnualReturnYear05

2.69%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.44%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 2012

(Loomis Sayles Strategic Alpha Fund)

Prospectus:

rr_ProspectusTable

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide an attractive absolute total return, complemented by prudent investment management designed to manage risks and protect investor capital. The secondary goal of the Fund is to achieve these returns with relatively low volatility.

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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

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You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

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$ 100,000

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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

Fee Waiver or Reimbursement over Assets, Date of Termination

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April 30, 2021

Expenses Deferred Charges [Text Block]

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A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

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If shares are redeemed:

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

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If shares are not redeemed:

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes 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 414% of the average value of its portfolio.

Portfolio Turnover, Rate

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414.00%

Strategy [Heading]

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Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund has an absolute total return investment objective, which means that it is not managed relative to an index and that it attempts to achieve positive total returns over a full market cycle. The Fund intends to pursue its objective by utilizing a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies to mitigate downside risk. The Fund may invest up to 100% of its total assets in below investment grade fixed-income securities (also known as "junk bonds") and derivatives that have returns related to the returns on below investment grade fixed-income securities, although it is expected that, under normal market conditions, the Fund's net exposure (i.e., long exposures obtained through direct investments in securities and in derivatives minus short exposures obtained through derivatives) to below investment grade fixed-income assets generally will not exceed 50% of the Fund's total assets. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major rating agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investor Services, Inc. or S&P Global Ratings ("S&P")) have rated the securities in one of their respective top four ratings categories). Under normal market conditions, the Fund also may invest up to 50% of its total assets in investments denominated in non-U.S. currencies and related derivatives, including up to 20% in investments denominated in emerging market currencies and related derivatives. The Fund expects that its exposure to these asset classes will often be obtained substantially through the use of derivative instruments. The Fund defines an "emerging market currency" as a currency of a country that carries a sovereign debt quality rating that is rated below investment grade by either S&P or Moody's, or is unrated by both S&P and Moody's. Currency positions that are intended to hedge the Fund's non-U.S. currency exposure (i.e., currency positions that are not made for investment purposes) will offset positions in the same currency that are made for investment purposes when calculating the limitation on investments in non-U.S. and emerging market currency investments because the Fund believes that hedging a currency position is likely to negate some or all of the currency risk associated with the original currency position. The Fund does not have limits on the duration of its portfolio, and the Fund's duration will change over time. The Fund also may invest in equity securities (including preferred stocks) as well as derivatives whose returns are linked to the returns of equity securities.

In selecting investments for the Fund, the Adviser develops long-term portfolio themes driven by macro-economic indicators. These include global economic trends, demographic trends and labor supply, analysis of global capital flows and assessments of geopolitical factors. The Adviser then develops shorter-term portfolio strategies based on factors including, but not limited to, economic, credit and Federal Reserve cycles, and top-down sector valuations and bottom-up security valuations. The Adviser seeks to actively manage risk, with a focus on managing the Fund's exposure to credit, interest rate and currency risks in relation to the market. Additionally, the portfolio managers will use risk management tools, such as models that evaluate risk correlation to various market factors or asset classes, to seek to manage risk on an ongoing basis. 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 Adviser incorporates systematic and quantitative models with respect to selection of certain investments.

The Adviser currently targets an annualized volatility range of 4% to 6% (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed or be lower than its target volatility range for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

The Fund will pursue its investment goal by obtaining long investment exposures through investments in securities and derivatives and short investment exposures substantially through derivatives. A "long" investment exposure is an investment that rises in value with a rise in the value of an asset, asset class or index and declines in value with a decline in the value of that asset, asset class or index. A "short" investment exposure is an investment that rises in value with a decline in the value of an asset, asset class or index and declines in value with a rise in the value of that asset, asset class or index. The value of the Fund's long and short investment exposures may, at times, each reach 100% of the assets invested in the Fund (excluding instruments primarily used for duration management or yield curve management and short-term investments (such as cash and money market instruments)), although these exposures may be higher or lower at any given time.

Fixed-Income Investments. In connection with its principal investment strategies, the Fund may invest in a broad range of U.S. and non-U.S. fixed-income securities, including, but not limited to, corporate bonds, municipal securities, U.S. and non-U.S. government securities (including their agencies, instrumentalities and sponsored entities), securities of supranational entities, emerging market securities, commercial and residential mortgage-backed securities, collateralized mortgage obligations, other mortgage-related securities (such as adjustable rate mortgage securities), asset-backed securities, collateralized loan obligations, bank loans, convertible bonds, securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"), real estate investment trusts ("REITs"), zero-coupon securities, step coupon securities, pay-in-kind ("PIK") securities, inflation-linked bonds, variable and floating rate securities, private placements and commercial paper.

Non-U.S. Currency Investments. Under normal market conditions, the Fund may engage in a broad range of transactions involving non-U.S. and emerging market currencies, including, but not limited to, purchasing and selling forward currency exchange contracts in non-U.S. or emerging market currencies, investing in non-U.S. currency futures contracts, investing in options on non-U.S. currencies and non-U.S. currency futures, investing in cross-currency instruments (such as swaps), investing directly in non-U.S. currencies and investing in securities denominated in non-U.S. currencies. The Fund may engage in non-U.S. currency transactions for investment or for hedging purposes.

Derivative Investments. For investment and hedging purposes, the Fund may invest substantially in a broad range of derivatives instruments and sometimes the majority of its investment returns will derive from its derivative investments. These derivative instruments include, but are not limited to, futures contracts (such as treasury futures and index futures), forward contracts, options (such as options on futures contracts, options on securities, interest rate/bond options, currency options, options on swaps and over-the-counter ("OTC") options), warrants (such as non-U.S. currency warrants), swap transactions (such as interest rate swaps, total return swaps and index swaps) and structured notes (such as equity-linked notes). In addition, the Fund may invest in credit derivative products that may be used to manage default risk and credit exposure. Examples of such products include, but are not limited to, credit default swap index products (such as LCDX, CMBX and ABX index products), single name credit default swaps, loan credit default swaps and asset-backed credit default swaps. The Fund may, at times, invest substantially all of its assets in derivatives and securities used to support its obligations under those derivatives. The Fund's strategy may be highly dependent on the use of derivatives, and to the extent that they become unavailable or unattractive the Fund may be unable to fully implement its investment strategy.

Equity Investments. In connection with its principal investment strategies, the Fund may invest in common stocks, preferred stocks and convertible preferred stocks.

The Fund is non-diversified, which means it may invest a greater portion of its assets in a particular issuer and may invest in fewer issuers. Because the Fund may invest in the securities of fewer issuers, an investment in the Fund may involve a higher degree of risk than would be present in a diversified portfolio.

The Fund expects to 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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to time. In addition, when calculating these exposures, the Fund may use the market value, the notional value, an adjusted notional value or some other measure of the value of a derivative in order to reflect what the Adviser believes to be the most accurate assessment of the Fund's real economic exposure. The total notional value of the Fund's derivative instruments may significantly exceed the total value of the Fund's assets.

Although the Fund seeks positive total returns over time, the Fund's investment returns may be volatile over short periods of time. The Fund may outperform the overall securities market during periods of flat or negative performance and may underperform during periods of strong market performance. There can be no assurance that the Fund's returns over time or during any period will be positive.

Risk [Heading]

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Principal Investment Risks

Risk Narrative [Text Block]

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

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to 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.

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.

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. The value of zero-coupon and PIK bonds may be more sensitive to fluctuations in interest rates 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, negatively impacting the performance of the Fund. Potential future changes in government monetary policy may affect the level of interest rates.

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.

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 other countries (such as the United States) 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.

Agency Securities Risk: Certain debt securities issued or guaranteed by agencies of the U.S. government are guaranteed as to the payment of principal and interest by the relevant entity but have not been backed by the full faith and credit of the U.S. government. Instead, they have been supported only by the discretionary authority of the U.S. government to purchase the agency's obligations. An event affecting the guaranteeing entity could adversely affect the payment of principal or interest or both on the security and, therefore, these types of securities should be considered to be riskier than U.S. government securities.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures contracts, forward contracts, options, warrants 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, such as futures, forward contracts, options, warrants, foreign currency transactions, swaps, credit default swaps and equity-linked and other structured notes, involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time. When used, derivatives may affect the amount, timing or character of distributions payable to, and thus taxes payable by, shareholders. Similarly, for accounting and performance reporting purposes, income and gain characteristics may be different than if the Fund held the underlying securities or assets directly.

Equity Securities Risk: The value of the Fund's investments in preferred stocks 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. 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.

Inflation/Deflation Risk: Inflation risk is the risk that the value of assets or income from investments will be worth less in the future as inflation decreases the present value of future payments. Deflation risk is the risk that prices throughout the economy decline over time (the opposite of inflation). Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of the Fund's portfolio. Because the Fund seeks positive returns that exceed the rate of inflation over time, if the portfolio managers' inflation forecasts are incorrect, the Fund may be more severely impacted than other funds.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities also results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Fund's Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

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

Short Exposure Risk: A short exposure through a derivative may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

Risk Nondiversified Status [Text]

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

Risk Lose Money [Text]

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You may lose money by investing in the Fund.

Bar Chart and Performance Table [Heading]

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Risk/Return Bar Chart and Table

Performance Narrative [Text Block]

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The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) compare to those of two broad measures of market performance. The 3-Month LIBOR +300 basis points represents the average rate at which a leading bank, for a given currency (in this case, U.S. dollars), can obtain unsecured funding, and is representative of short-term interest rates. 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 im.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]

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Total Returns for Class Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

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

Bar Chart Closing [Text Block]

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Highest Quarterly Return:
First Quarter 2012, 5.54%

Lowest Quarterly Return:
Third Quarter 2011, -4.71%

Performance Table Heading

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Average Annual Total Returns (for the periods ended December 31, 2019)

Performance Table Closing [Text Block]

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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 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 Fund 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]

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

Performance Table Uses Highest Federal Rate

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

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-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]

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

Performance Information Illustrates Variability of Returns [Text]

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

Performance Table One Class of after Tax Shown [Text]

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

Performance Availability Website Address [Text]

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im.natixis.com

Performance Availability Phone [Text]

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800-225-5478

(Loomis Sayles Strategic Alpha Fund) | 3-Month LIBOR

Prospectus:

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Past 1 Year

rr_AverageAnnualReturnYear01

2.33%

Past 5 Years

rr_AverageAnnualReturnYear05

1.39%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

0.91%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | 3-Month LIBOR

Prospectus:

rr_ProspectusTable

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(Loomis Sayles Strategic Alpha Fund) | 3-month LIBOR +300 basis points

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

5.33%

Past 5 Years

rr_AverageAnnualReturnYear05

4.39%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

3.89%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | 3-month LIBOR +300 basis points

Prospectus:

rr_ProspectusTable

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

5.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(Loomis Sayles Strategic Alpha Fund) | Class A

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.25%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[17]

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.59%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[18]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.99%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[19]

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

rr_NetExpensesOverAssets

0.99%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 522

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

727

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

949

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,586

Past 1 Year

rr_AverageAnnualReturnYear01

(0.85%)

Past 5 Years

rr_AverageAnnualReturnYear05

1.47%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.59%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[18]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.74%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[19]

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

rr_NetExpensesOverAssets

1.74%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 277

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

548

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

944

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,052

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

177

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

548

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

944

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,052

Past 1 Year

rr_AverageAnnualReturnYear01

1.87%

Past 5 Years

rr_AverageAnnualReturnYear05

1.59%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.77%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | Class N

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.59%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.08%

^[18]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.67%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[19]

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

rr_NetExpensesOverAssets

0.67%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 68

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

214

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

373

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 835

Past 1 Year

rr_AverageAnnualReturnYear01

3.92%

Past 5 Years

rr_AverageAnnualReturnYear05

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(Loomis Sayles Strategic Alpha 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

0.59%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[14],[18]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.99%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[19]

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

rr_NetExpensesOverAssets

0.99%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 348

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

557

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

783

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,433

Past 1 Year

rr_AverageAnnualReturnYear01

0.96%

Past 5 Years

rr_AverageAnnualReturnYear05

1.83%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.59%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[18]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.74%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[19]

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

rr_NetExpensesOverAssets

0.74%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 76

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

237

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

411

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 918

Annual Return 2011

rr_AnnualReturn2011

(3.78%)

Annual Return 2012

rr_AnnualReturn2012

12.57%

Annual Return 2013

rr_AnnualReturn2013

1.19%

Annual Return 2014

rr_AnnualReturn2014

2.52%

Annual Return 2015

rr_AnnualReturn2015

(1.43%)

Annual Return 2016

rr_AnnualReturn2016

6.86%

Annual Return 2017

rr_AnnualReturn2017

3.38%

Annual Return 2018

rr_AnnualReturn2018

0.53%

Annual Return 2019

rr_AnnualReturn2019

3.96%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: First Quarter 2012, 5.54%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.54%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Third Quarter 2011, -4.71%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.71%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Past 1 Year

rr_AverageAnnualReturnYear01

3.96%

Past 5 Years

rr_AverageAnnualReturnYear05

2.62%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

2.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.69%

Past 5 Years

rr_AverageAnnualReturnYear05

1.28%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Loomis Sayles Strategic Alpha Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

2.35%

Past 5 Years

rr_AverageAnnualReturnYear05

1.41%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

1.62%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 15, 2010

(Natixis Oakmark 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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 75 of the Prospectus, in Appendix A to the Prospectus and on page 135 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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, 2021

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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 for Class N 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed:

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

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed:

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 15% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

15.00%

Strategy [Heading]

rr_StrategyHeading

Investments, Risks and Performance Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund primarily invests in common stocks of U.S. companies. The Fund generally invests in securities of larger capitalization companies in any industry. Harris Associates L.P. ("Harris Associates") uses a value investment philosophy in selecting equity securities, including common stocks. This value investment philosophy is based upon the belief that, over time, a company's stock price converges with the company's intrinsic value. By "intrinsic 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 what Harris Associates believes is a company's intrinsic value presents the best opportunity to achieve the Fund's investment objectives.

Harris Associates uses this value investment philosophy to identify companies that it believes have discounted stock prices compared to what Harris Associates believes are the companies' intrinsic 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 company management ownership.

Once Harris Associates identifies a stock that it believes is selling at a significant discount to Harris Associates' estimate of 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 value 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 60 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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.

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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, ten-year, and life-of-class periods (as applicable) 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 im.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 Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

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

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
First Quarter 2012, 15.85%

Lowest Quarterly Return:
Fourth Quarter 2018, -17.07%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (for the periods ended December 31, 2019)

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 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 Fund 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.

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 Fund 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, ten-year, and life-of-class periods (as applicable) 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

im.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Natixis Oakmark Fund) | S&P 500® Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

31.49%

Past 5 Years

rr_AverageAnnualReturnYear05

11.70%

Past 10 Years

rr_AverageAnnualReturnYear10

13.56%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

14.20%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(Natixis Oakmark Fund) | Class A

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[20]

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.68%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.17%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[21],[22]

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

rr_NetExpensesOverAssets

1.17%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 687

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

925

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,182

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,914

Past 1 Year

rr_AverageAnnualReturnYear01

19.45%

Past 5 Years

rr_AverageAnnualReturnYear05

7.26%

Past 10 Years

rr_AverageAnnualReturnYear10

10.90%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Natixis Oakmark Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.68%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.92%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[21],[22]

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

rr_NetExpensesOverAssets

1.92%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 295

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

603

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,037

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,243

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

195

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

603

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,037

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,243

Past 1 Year

rr_AverageAnnualReturnYear01

24.82%

Past 5 Years

rr_AverageAnnualReturnYear05

7.75%

Past 10 Years

rr_AverageAnnualReturnYear10

10.74%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Natixis Oakmark Fund) | Class N

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.68%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.57%

Total annual fund operating expenses

rr_ExpensesOverAssets

1.25%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.42%

^[21],[22]

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

rr_NetExpensesOverAssets

0.83%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 85

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

355

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

646

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,474

Past 1 Year

rr_AverageAnnualReturnYear01

27.16%

Past 5 Years

rr_AverageAnnualReturnYear05

Past 10 Years

rr_AverageAnnualReturnYear10

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

9.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2017

(Natixis Oakmark 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

0.68%

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

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.24%

^[23]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.17%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[21],[22]

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

rr_NetExpensesOverAssets

1.17%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 366

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

612

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

878

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,635

Past 1 Year

rr_AverageAnnualReturnYear01

23.59%

Past 5 Years

rr_AverageAnnualReturnYear05

8.00%

Past 10 Years

rr_AverageAnnualReturnYear10

11.29%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Natixis Oakmark Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.68%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.92%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[21],[22]

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

rr_NetExpensesOverAssets

0.92%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 94

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

293

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

509

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,131

Annual Return 2010

rr_AnnualReturn2010

13.47%

Annual Return 2011

rr_AnnualReturn2011

(1.40%)

Annual Return 2012

rr_AnnualReturn2012

17.33%

Annual Return 2013

rr_AnnualReturn2013

38.21%

Annual Return 2014

rr_AnnualReturn2014

10.70%

Annual Return 2015

rr_AnnualReturn2015

(4.18%)

Annual Return 2016

rr_AnnualReturn2016

18.69%

Annual Return 2017

rr_AnnualReturn2017

21.05%

Annual Return 2018

rr_AnnualReturn2018

(12.76%)

Annual Return 2019

rr_AnnualReturn2019

27.06%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: First Quarter 2012, 15.85%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.85%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Fourth Quarter 2018, -17.07%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(17.07%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2018

Past 1 Year

rr_AverageAnnualReturnYear01

27.06%

Past 5 Years

rr_AverageAnnualReturnYear05

8.82%

Past 10 Years

rr_AverageAnnualReturnYear10

11.85%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

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

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

24.40%

Past 5 Years

rr_AverageAnnualReturnYear05

7.24%

Past 10 Years

rr_AverageAnnualReturnYear10

10.52%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

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

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

17.77%

Past 5 Years

rr_AverageAnnualReturnYear05

6.73%

Past 10 Years

rr_AverageAnnualReturnYear10

9.61%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity 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, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 75 of the Prospectus, in Appendix A to the Prospectus and on page 135 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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, 2021

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If shares are redeemed:

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

rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed:

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 52% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

52.00%

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 primarily in companies that, at the time of purchase, have market capitalizations either within the capitalization range of the Russell Midcap® Value Index, an unmanaged index that measures the performance of companies with lower price-to-book ratios and lower forecasted growth values within the broader Russell Midcap® Index, or of $15 billion or less. While the market capitalization range for the Russell Midcap® Value Index fluctuates, at December 31, 2019, it was $823.7 million to $43.8 billion. However, the Fund does not have any market capitalization limits and may invest in companies with smaller or larger capitalizations. 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 similar securities representing direct or indirect ownership interests in business organizations.

Vaughan Nelson Investment Management, L.P. ("Vaughan Nelson") invests in medium-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:

• Vaughan Nelson employs a value-driven investment philosophy that selects stocks selling at a relatively low value based on business fundamentals, economic margin analysis and discounted cash flow models. Vaughan Nelson selects companies that it believes are out of favor or misunderstood.
• Vaughan Nelson narrows the investment universe by using value-driven screens to create a research universe of companies with market capitalizations between $1 billion and $20 billion.
• Vaughan Nelson uses fundamental analysis to construct a portfolio 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 those expected at the time of investment.

The Fund may also:

• Invest in convertible preferred stock and convertible debt securities.
• Invest in foreign securities, including emerging markets securities.
• Invest in other investment companies, to the extent permitted by the Investment Company Act of 1940.
• Invest in REITs.
• 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").

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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. Equity securities may take the form of stock in corporations, limited partnership interests, interests in limited liability companies, REITs or other trusts and other similar securities representing direct or indirect ownership interests in business organizations.

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.

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.

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

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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 other countries (such as the United States) 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.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including exchange-traded funds, in which it invests in addition to its own expenses.

Large Investor Risk: Ownership of shares of the Fund that 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. Liquidity issues may also make it difficult to value the Fund's investments.

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, ten-year, and life-of-class periods (as applicable) 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 im.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 Y Shares

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

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

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarterly Return:
Fourth Quarter 2010, 16.12%

Lowest Quarterly Return:
Third Quarter 2011, -21.12%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (for the periods ended December 31, 2019)

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 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 Fund 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 Fund 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, ten-year, and life-of-class periods (as applicable) 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

im.natixis.com

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-225-5478

(Vaughan Nelson Value Opportunity Fund) | Russell MidCap® Value Index

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

27.06%

Past 5 Years

rr_AverageAnnualReturnYear05

7.62%

Past 10 Years

rr_AverageAnnualReturnYear10

12.41%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

10.40%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2013

(Vaughan Nelson Value Opportunity Fund) | Class A

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

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

rr_MaximumDeferredSalesChargeOverOther

none

^[24]

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

0.23%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[25]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.30%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[26]

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

rr_NetExpensesOverAssets

1.24%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 694

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

958

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,241

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,048

Past 1 Year

rr_AverageAnnualReturnYear01

22.72%

Past 5 Years

rr_AverageAnnualReturnYear05

3.46%

Past 10 Years

rr_AverageAnnualReturnYear10

9.62%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity Fund) | Class C

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

1.00%

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.22%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[25]

Total annual fund operating expenses

rr_ExpensesOverAssets

2.04%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[26]

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

rr_NetExpensesOverAssets

1.98%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 301

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

634

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,093

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,364

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

201

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

634

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,093

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,364

Past 1 Year

rr_AverageAnnualReturnYear01

28.25%

Past 5 Years

rr_AverageAnnualReturnYear05

3.92%

Past 10 Years

rr_AverageAnnualReturnYear10

9.46%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity Fund) | Class N

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[25]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.95%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.02%

^[26]

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

rr_NetExpensesOverAssets

0.93%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 95

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

301

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

524

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,165

Past 1 Year

rr_AverageAnnualReturnYear01

30.67%

Past 5 Years

rr_AverageAnnualReturnYear05

5.06%

Past 10 Years

rr_AverageAnnualReturnYear10

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

8.99%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2013

(Vaughan Nelson Value Opportunity 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

0.23%

^[23]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[25]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.30%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.06%

^[26]

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

rr_NetExpensesOverAssets

1.24%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 373

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

646

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

939

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,773

Past 1 Year

rr_AverageAnnualReturnYear01

26.92%

Past 5 Years

rr_AverageAnnualReturnYear05

4.17%

Past 10 Years

rr_AverageAnnualReturnYear10

9.99%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity Fund) | Class Y

Prospectus:

rr_ProspectusTable

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

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

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

rr_MaximumDeferredSalesChargeOverOther

none

Redemption fees

rr_RedemptionFee

none

Management fees

rr_ManagementFeesOverAssets

0.80%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.22%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[25]

Total annual fund operating expenses

rr_ExpensesOverAssets

1.04%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.05%

^[26]

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

rr_NetExpensesOverAssets

0.99%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 101

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

326

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

569

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,266

Annual Return 2010

rr_AnnualReturn2010

19.96%

Annual Return 2011

rr_AnnualReturn2011

(2.53%)

Annual Return 2012

rr_AnnualReturn2012

16.28%

Annual Return 2013

rr_AnnualReturn2013

41.52%

Annual Return 2014

rr_AnnualReturn2014

11.23%

Annual Return 2015

rr_AnnualReturn2015

(3.47%)

Annual Return 2016

rr_AnnualReturn2016

6.14%

Annual Return 2017

rr_AnnualReturn2017

13.19%

Annual Return 2018

rr_AnnualReturn2018

(15.85%)

Annual Return 2019

rr_AnnualReturn2019

30.52%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarterly Return: Fourth Quarter 2010, 16.12%

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.12%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarterly Return: Third Quarter 2011, -21.12%

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(21.12%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Past 1 Year

rr_AverageAnnualReturnYear01

30.52%

Past 5 Years

rr_AverageAnnualReturnYear05

4.96%

Past 10 Years

rr_AverageAnnualReturnYear10

10.55%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity Fund) | Class Y | Return After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

30.19%

Past 5 Years

rr_AverageAnnualReturnYear05

4.04%

Past 10 Years

rr_AverageAnnualReturnYear10

9.54%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

(Vaughan Nelson Value Opportunity Fund) | Class Y | Return After Taxes on Distributions and Sale of Fund Shares

Prospectus:

rr_ProspectusTable

Past 1 Year

rr_AverageAnnualReturnYear01

18.30%

Past 5 Years

rr_AverageAnnualReturnYear05

3.72%

Past 10 Years

rr_AverageAnnualReturnYear10

8.52%

Life of Fund/Life of Class N

rr_AverageAnnualReturnSinceInception

[1] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[2] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[3] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.54%, 2.29%, 1.24%, 1.54% and 1.29% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, substitute dividend expenses on securities sold short, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y 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 fee/expense was waived/reimbursed.

[4] Natixis Advisors, L.P. ("Natixis Advisors") has given a binding contractual undertaking to the Fund to reimburse any and all transfer agency expenses for Class N shares. This undertaking is in effect through April 30, 2021 and may be terminated before then only with the consent of the Fund's Board of Trustees.

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

[6] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[7] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.70%, 2.45%, 1.40%, 1.70% and 1.45% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fee/expense was waived/reimbursed.

[8] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[9] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[10] AlphaSimplex Group, LLC ("AlphaSimplex" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.15%, 1.90%, 1.15% and 0.90% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

[11] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[12] The expense information shown in the table above includes acquired fund fees and expenses of less than 0.01%; the ratios may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[13] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.24%, 1.99%, 1.24% and 0.99% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

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

[15] A 0.75% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $500,000 or more that are redeemed within eighteen months of the date of purchase.

[16] 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 0.70%, 1.45%, 0.70% and 0.45% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

[17] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[18] The expense information shown in the table above includes acquired fund fees and expenses of less than 0.01%.

[19] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.00%, 1.75%, 0.70%, 1.00% and 0.75% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y 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 fee/expense was waived/reimbursed.

[20] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[21] Natixis Advisors, L.P. ("Natixis Advisors") has given a binding contractual undertaking to the Fund to reimburse any and all transfer agency expenses for Class N shares. This undertaking is in effect through April 30, 2021 and may be terminated before then only with the consent of the Fund's Board of Trustees.

[22] 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 1.30%, 2.05%, 1.00%, 1.30% and 1.05% of the Fund's average daily net assets for Class A, C, N, T and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 A, C, N, T and Y 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.

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

[24] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[25] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[26] 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 1.20%, 1.95%, 0.90%, 1.20% and 0.95% of the Fund's average daily net assets for Class A, C, N, T and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 A, C, N, T and Y 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.

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Total

(AlphaSimplex Global Alternatives Fund)

Investment Goal

The Fund pursues an absolute return strategy that seeks to provide capital appreciation consistent with the risk-return characteristics of a diversified portfolio of hedge funds. The secondary goal of the Fund is to achieve these returns with less volatility than major equity indices.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (AlphaSimplex Global Alternatives Fund) - USD ($)	Class A		Class C	Class N	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none	none
Redemption fees	none		none	none	none	none

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

Annual Fund Operating Expenses - (AlphaSimplex Global Alternatives Fund)		Class A	Class C	Class N	Class T		Class Y
Management fees		1.15%	1.15%	1.15%	1.15%		1.15%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none	0.25%		none
Other expenses		0.17%	0.17%	0.11%	0.17%	[1]	0.17%
Acquired fund fees and expenses	[2]	0.10%	0.10%	0.10%	0.10%		0.10%
Total annual fund operating expenses		1.67%	2.42%	1.36%	1.67%		1.42%
Fee waiver and/or expense reimbursement	[3],[4]	0.03%	0.03%	0.02%	0.03%		0.03%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.64%	2.39%	1.34%	1.64%		1.39%

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (AlphaSimplex Global Alternatives Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	732	1,068	1,428	2,435
Class C	342	752	1,288	2,754
Class N	136	429	743	1,633
Class T	413	760	1,132	2,174
Class Y	142	446	773	1,699

If shares are not redeemed:

Expense Example, No Redemption - (AlphaSimplex Global Alternatives Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	242	752	1,288	2,754

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 125% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

The Fund seeks to achieve long and short exposure to global equity, bond, currency and commodity markets through a wide range of derivative instruments and direct investments. Under normal market conditions, the Adviser typically will make extensive use of derivative instruments, in particular futures, forward contracts and swaps on global equity and fixed-income securities, securities indices (including both broad- and narrow-based securities indices), currencies, commodities and other instruments. These investments are intended to provide the Fund with risk and return characteristics similar to those of a diversified portfolio of hedge funds. The Fund may also make direct long and short investments in equity and fixed-income securities.

The Fund seeks to generate absolute returns over time rather than track the performance of any particular index of hedge fund returns. In selecting investments for the Fund, the Adviser uses quantitative models to estimate the market exposures that drive the aggregate returns of a diverse set of hedge funds. The Adviser seeks to capture these market exposures in the aggregate while adding value through dynamic allocation among market exposures and volatility management. These market exposures may include, for example, exposures to the returns of stocks, fixed-income securities (including U.S. and non-U.S. government securities, as well as corporate debt securities), currencies and commodities. In estimating these market exposures, the Adviser may use various approaches, including analyses of the returns of hedge funds included in one or more commercially available databases selected by the Adviser (for example, the Lipper TASS hedge fund database) and regulatory filings. The Fund may also directly employ various strategies commonly used by hedge funds that seek to profit from underlying risk factors, such as merger arbitrage and trend-following strategies. In a merger arbitrage strategy, the Adviser buys shares of target companies in corporate reorganizations and establishes short positions in shares of the acquiring companies. Trend-following strategies analyze markets over various time horizons to invest either long or short in assets whose values are rising or falling, respectively.

The Adviser will have great flexibility to allocate the Fund's exposure among various securities, indices, currencies, commodities and other instruments; the amount of the Fund's assets that may be allocated to various strategies and among investments is expected to vary over time. When buying and selling securities and other instruments for the Fund, the Adviser also may consider other factors, such as: (i) the Fund's obligations under its various derivative positions; (ii) portfolio rebalancing; (iii) redemption requests; (iv) yield management; (v) credit management; and (vi) volatility management. The Fund will not invest directly in hedge funds. The Fund may invest in non-U.S. securities and instruments and securities and instruments traded outside the United States, and expects to engage in non-U.S. currency transactions.

The Adviser currently targets an annualized volatility level of 9% or less (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

Under normal market conditions, it is expected that no more than 25% of the Fund's total assets will be dedicated to initial and variation margin payments relating to the Fund's derivative transactions. The gross notional value of the Fund's derivative investments, however, will generally exceed 25% of the Fund's assets, and may significantly exceed the total value of the Fund's assets. The Adviser will invest a portion of the Fund's assets, which may vary over time, in short-term, high-quality securities. Such investments will be used primarily to finance the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity, and may include: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions or agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks, and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements. The Adviser will select such investments based on various factors, including the security's maturity and credit rating.

Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives through a wholly-owned subsidiary organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). Under normal market conditions, no more than 10% of the Fund's total assets will be dedicated to initial and variation margin payments relating to these transactions.

The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit) of issuers in such industry. 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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures, swaps, forward contracts, and other foreign currency transactions and commodity-linked derivatives) 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 commodities markets, 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 futures, swaps, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative or the underlying assets decrease in value over time.

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. 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.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary is not registered under the Investment Company Act of 1940 (the "1940 Act") and is not subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Commodity Subsidiary, respectively, are organized, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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.

Hedge Fund Risk: Hedge funds are typically unregulated private investment pools available only to sophisticated investors. They are often illiquid and highly leveraged. Although the Fund will not invest directly in hedge funds, because the Fund's investments are intended to provide exposure to the factors that drive hedge fund returns, an investment in the Fund will be subject to many of the same risks associated with an investment in a diversified portfolio of hedge funds. Therefore, the Fund's performance may be lower than the returns of the broader stock market and the Fund's net asset value may fluctuate substantially over time.

Index/Tracking Error Risk: Although the Fund does not seek to track any particular index, the Fund seeks to analyze the factors that drive hedge fund returns, as determined by reference to one or more indices. These indices may not provide an accurate representation of hedge fund returns generally, and the Adviser's strategy may not successfully identify or be able to replicate factors that drive returns. There is a risk that hedge fund return data provided by third party hedge fund index providers may be inaccurate or may not accurately reflect hedge fund returns due to survivorship bias, self-reporting bias or other biases.

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. Potential future changes in government monetary policy may affect the level of interest rates.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, ten-year and life-of-class periods (as applicable) compare to those of a broad measure of market performance. The Barclay Fund of Funds Index is a measure of the average return of all funds of funds in the Barclay database. 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
Third Quarter 2010, 7.23%

Lowest Quarterly Return:
First Quarter 2016, -8.36%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (AlphaSimplex Global Alternatives Fund)	Past 1 Year	Past 5 Years	Past 10 Years	Life of Fund/Life of Class N	Inception Date
Class Y	10.49%	1.49%	3.41%
Class Y | Return After Taxes on Distributions	10.05%	1.02%	2.58%
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	6.28%	0.98%	2.40%
Class A	3.96%	0.04%	2.54%
Class C	8.48%	0.48%	2.38%
Class N	10.48%	1.50%		2.88%	May 01, 2013
Class T	7.53%	0.71%	2.88%
Bloomberg Barclay Fund of Funds Index	5.86%	1.20%	2.04%	1.99%	May 01, 2013

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 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 the Fund's fees, expenses or taxes, but does reflect the management fees and other expenses of both the funds of funds in the index and the hedge funds in which those funds of funds invest.

(AlphaSimplex Managed Futures Strategy Fund)

Investment Goal

The Fund pursues an absolute return strategy that seeks to provide capital appreciation.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (AlphaSimplex Managed Futures Strategy Fund) - USD ($)	Class A		Class C	Class N	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none	none
Redemption fees	none		none	none	none	none

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

Annual Fund Operating Expenses - (AlphaSimplex Managed Futures Strategy Fund)		Class A	Class C	Class N	Class T		Class Y
Management fees		1.25%	1.25%	1.25%	1.25%		1.25%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none	0.25%		none
Other expenses		0.29%	0.28%	0.11%	0.29%	[1]	0.28%
Total annual fund operating expenses		1.79%	2.53%	1.36%	1.79%		1.53%
Fee waiver and/or expense reimbursement	[2]	0.09%	0.08%	none	0.09%		0.08%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.70%	2.45%	1.36%	1.70%		1.45%

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 examples for Class A, Class C, Class T, and Class Y are 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (AlphaSimplex Managed Futures Strategy Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	738	1,098	1,481	2,552
Class C	348	780	1,338	2,860
Class N	138	431	745	1,635
Class T	418	791	1,187	2,295
Class Y	148	476	827	1,817

If shares are not redeemed:

Expense Example, No Redemption - (AlphaSimplex Managed Futures Strategy Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	248	780	1,338	2,860

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. Due to the short-term nature of the Fund's investment portfolio, the Fund does not calculate a portfolio turnover rate.

Investments, Risks and Performance Principal Investment Strategies

The Fund seeks to generate positive absolute returns over time. Under normal market conditions, the Adviser typically will make extensive use of a variety of derivative instruments, including futures and forward contracts, to capture the exposures suggested by its absolute return strategy while also seeking to add value through volatility management. These market exposures, which are expected to change over time, may include, for example, exposures to the returns of U.S. and non-U.S. equity and fixed-income securities indices (including both broad- and narrow-based securities indices), currencies and commodities. The Adviser will have great flexibility to allocate the Fund's derivatives exposure among various securities, indices, currencies, commodities and other instruments; the amount of the Fund's assets that may be allocated to derivative strategies and among these various instruments is expected to vary over time. The Adviser uses proprietary quantitative models to identify price trends in equity, fixed-income, currency and commodity instruments across time periods of various lengths. The Adviser believes that asset prices may show persistent trending behavior due to a number of behavioral biases among market participants as well as certain risk-management policies that will identify assets to purchase in upward-trending markets and identify assets to sell in downward-trending markets. The Adviser believes that following trends across a widely diversified set of assets, combined with active risk management, may allow it to earn a positive expected return over time. The Fund may have both "short" and "long" exposures within an asset class based upon the Adviser's analysis of multiple time horizons to identify trends in a particular asset class. A "short" exposure will benefit when the underlying asset class decreases in price. A "long" exposure will benefit when the underlying asset class increases in price. The Adviser will scale the notional exposure of the Fund's futures and currency forward positions with the objective of targeting a relatively stable level of annualized volatility for the Fund's overall portfolio. The Adviser currently targets an annualized volatility level of 17% or less (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

Under normal market conditions, it is expected that no more than 25% of the Fund's total assets will be dedicated to initial and variation margin payments relating to the Fund's derivative transactions. The gross notional value of the Fund's derivative investments, however, will generally exceed 25% of the Fund's total assets, and may significantly exceed the total value of the Fund's assets. The Fund expects that under normal market conditions it will invest at least 75% of its total assets in money market and other short-term, high-quality securities (such as bankers' acceptances, certificates of deposit, commercial paper, loan participations, repurchase agreements and time deposits) (the "Money Market Portion"), although the Fund may invest less than this percentage. The Adviser will determine the percentage of the Fund's assets that will be invested in the Money Market Portion at any time. The assets allocated to the Money Market Portion will be used primarily to support the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. Although the Fund will invest a significant portion of its assets in money market instruments, the Fund is not a "money market" fund and the value of the Money Market Portion as well as the value of the Fund's shares may decrease. The Fund is not subject to the portfolio quality, maturity and net asset value requirements applicable to money market funds, and the Fund will not seek to maintain a stable net asset value. The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit, repurchase agreements and time deposits) of issuers in such industry.

The Adviser will only invest the assets of the Money Market Portion in high-quality securities which are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities ("U.S. Government Obligations"); (ii) securities issued by foreign governments, their political subdivisions, agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives by investing in a wholly-owned subsidiary organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). Under normal market conditions, no more than 10% of the Fund's total assets will be dedicated to initial and variation margin payments relating to these transactions.

Although the Fund seeks positive absolute returns over time, it is likely that the Fund's investment returns may be volatile over short periods of time. The Fund may outperform the overall securities market during periods of flat or negative market performance and may underperform during periods of strong market performance. There can be no assurance that the Fund's returns over time or during any period will be positive or that the Fund will outperform the overall security markets over time or during any particular period.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. Due to the short-term nature of the Fund's investment portfolio, the Fund does not calculate a portfolio turnover rate. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures and forward contracts) 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 futures, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time.

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. 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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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 a significant portion of its assets 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.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary is not registered under the Investment Company Act of 1940 (the "1940 Act") and is not subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Commodity Subsidiary, respectively, are organized, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) compare to those of two broad measures of market performance. The SG Trend Index is equal-weighted, reconstituted and rebalanced annually. The index calculates the net daily rate of return for a pool of Commodity Trading Advisors selected from the larger managers that are open to new investment. AlphaSimplex Group, LLC is part of this Index. 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
First Quarter 2015, 11.72%

Lowest Quarterly Return:
Second Quarter 2015, -10.57%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (AlphaSimplex Managed Futures Strategy Fund)	Past 1 Year	Past 5 Years	Life of Fund/Life of Class N	Inception Date
Class Y	8.35%	(1.14%)	3.01%	Jul. 30, 2010
Class Y | Return After Taxes on Distributions	6.29%	(1.93%)	1.69%	Jul. 30, 2010
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	4.95%	(1.14%)	1.90%	Jul. 30, 2010
Class A	1.84%	(2.54%)	2.12%	Jul. 30, 2010
Class C	6.30%	(2.13%)	1.98%	Jul. 30, 2010
Class N	8.45%		0.59%	May 01, 2017
Class T	5.38%	(1.87%)	2.48%	Jul. 30, 2010
Credit Suisse Managed Futures Liquid Index	(4.56%)	(0.77%)	1.20%	Jul. 30, 2010
Credit Suisse Managed Futures Liquid Index			(2.17%)	May 01, 2017
SG Trend Index	9.23%	(0.75%)	2.06%	Jul. 30, 2010
SG Trend Index			1.80%	May 01, 2017

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 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.

(AlphaSimplex Multi-Asset Fund)

Investment Goal

The Fund seeks long-term capital appreciation. The secondary goal of the Fund is the protection of capital during unfavorable market conditions.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (AlphaSimplex Multi-Asset Fund) - USD ($)	Class A		Class C	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none
Redemption fees	none		none	none	none

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

Annual Fund Operating Expenses - (AlphaSimplex Multi-Asset Fund)		Class A	Class C	Class T		Class Y
Management fees		0.70%	0.70%	0.70%		0.70%
Distribution and/or service (12b-1) fees		0.25%	1.00%	0.25%		none
Other expenses		0.67%	0.68%	0.67%	[1]	0.67%
Acquired fund fees and expenses	[2]	0.05%	0.05%	0.05%		0.05%
Total annual fund operating expenses		1.67%	2.43%	1.67%		1.42%
Fee waiver and/or expense reimbursement	[3]	0.47%	0.48%	0.47%		0.47%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.20%	1.95%	1.20%		0.95%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (AlphaSimplex Multi-Asset Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	690	1,028	1,389	2,401
Class C	298	712	1,252	2,730
Class T	369	719	1,092	2,138
Class Y	97	403	732	1,661

If shares are not redeemed:

Expense Example, No Redemption - (AlphaSimplex Multi-Asset Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	198	712	1,252	2,730

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 23% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

The Fund tactically allocates its investments across a range of asset classes and global markets. Under normal market conditions, the Adviser will typically use a variety of derivative instruments, including equity, fixed-income and currency futures contracts and currency forward contracts, as well as exchange-traded funds ("ETFs") and money market and other short-term, high-quality securities, to achieve exposures to the following asset classes: (i) U.S. equity securities; (ii) foreign developed market equity securities; (iii) emerging market equity and fixed-income securities; (iv) U.S. fixed-income securities; (v) foreign developed market fixed-income securities; and (vi) currencies. 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 will typically obtain its target allocations through the use of long and/or short positions in futures and/or forward contracts, as well as investments in ETFs, which can provide exposure to certain asset classes that may not be readily available via futures contracts (e.g., domestic and international corporate bonds). The Adviser utilizes various proprietary quantitative models to identify investment opportunities. The Fund may obtain exposure to below investment grade fixed-income securities, also known as "junk bonds," through its investments in ETFs. Below investment grade fixed-income securities are rated below investment grade quality (i.e., none of the three major rating agencies (Moody's Investors Service, Inc., Fitch Investor Services, Inc. or S&P Global Ratings) have rated the securities in one of their respective top four ratings categories).

The Adviser uses a quantitative systematic approach to identify investment opportunities. The approach consists of overweighting and/or underweighting allocations to asset classes based on a number of factors, including momentum signals (measurements of recent trends in asset prices), the relative portfolio risks of various asset classes, asset class correlations (measurements of relationships between asset class prices) and/or market volatility. For example, the Adviser may overweight an asset class that demonstrates increasing momentum relative to other asset classes.

The Adviser separately manages the Fund's investments in derivatives and ETFs (the "Multi-Asset Portion") and the Fund's investments in money market and other short-term, high-quality securities (the "Money Market Portion," described further below). The Multi-Asset Portion will obtain economic leverage through the use of derivative instruments. Leverage can vary over time based on market conditions and the net notional value of the Multi-Asset Portion's investments may significantly exceed the Fund's total assets. Because the Fund's investment exposure will often significantly exceed its total assets, it will be subject to increased risk compared to funds that do not leverage their investment exposure. While this increased investment exposure may magnify the Fund's potential for gains, it will also magnify the potential for losses. For these reasons, the Fund is intended for long-term investors.

The Adviser will seek to manage the annualized volatility (a statistical measure of the variation of returns) of the Fund's overall portfolio as part of the investment approach. The Adviser will monitor the portfolio daily and currently targets an annualized volatility level of 13% or less. The Fund's actual or realized volatility during certain periods or over time may materially exceed its target volatility for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This will increase the risk of investing in the Fund.

The Fund expects that, under normal market conditions, it will invest at least 40% of its total assets in the Money Market Portion. The Fund may invest less than this percentage in the Money Market Portion and the Adviser will determine the percentage of the Fund's assets that will be invested in the Money Market Portion at any time. The assets allocated to the Money Market Portion will be used primarily to provide collateral for the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. Although the Fund will invest a significant portion of its assets in money market instruments, the Fund is not a "money market" fund and the value of the Money Market Portion as well as the value of the Fund's shares may decrease. The Fund is not subject to the portfolio quality, maturity and net asset value requirements applicable to money market funds, and the Fund will not seek to maintain a stable net asset value. The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit, repurchase agreements and time deposits) of issuers in that industry.

The Adviser will only invest the assets of the Money Market Portion in high-quality securities which are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in: (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions, agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic banks, foreign branches of domestic banks, foreign subsidiaries of domestic banks and domestic and foreign branches of foreign banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

The Fund expects to add commodities as an available asset class for investment at a future date. Although the Fund does not intend to invest in physical commodities directly, the Fund expects to obtain investment exposure to commodities and commodity-related derivatives by investing in a wholly-owned subsidiary expected to be organized under the laws of the Cayman Islands that will make commodity-related investments (the "Commodity Subsidiary"). The Fund anticipates registering the Commodity Subsidiary upon the attainment of approximately $100 million in assets under management. The maximum exposure to commodities will be 20% of total assets.

The Fund is non-diversified, which means that it may invest a greater percentage of its assets in a particular issuer and may invest in fewer issuers. Because the Fund may invest in the securities of a limited number of issuers, an investment in the Fund may involve a higher degree of risk than would be present in a diversified portfolio.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders.

Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs which reduce fund returns.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to 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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures and forward contracts) 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 commodities markets, 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 futures, forward contracts, and other foreign currency transactions and commodity-linked derivatives involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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 (if any) required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivative 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative or the underlying assets decrease in value over time.

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. 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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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.

Allocation Risk: This is the risk that the Adviser's judgments about, and allocations between, asset classes and market exposures may adversely affect the Fund's performance. 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. This risk can be increased by the use of derivatives to increase allocations to various market exposures. This is because derivatives can create investment leverage, which will magnify the impact to the Fund of its investment in any underperforming market exposure.

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.

Commodity Risk: This is the risk that exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of physical commodities or commodity-linked derivative instruments may be affected by changes in overall market movements, commodity price volatility, changes in interest rates, currency fluctuations, or factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and international economic, political and regulatory developments.

Commodity Subsidiary Risk: Investing in the Commodity Subsidiary will indirectly expose the Fund to the risks associated with the Commodity Subsidiary's investments, such as commodity risk. The Commodity Subsidiary will not be registered under the Investment Company Act of 1940 (the "1940 Act") and will not be subject to all of the investor protections of the 1940 Act. Changes in the laws of the United States and/or the Cayman Islands, under which the Fund is organized and the Commodity Subsidiary is expected to be organized, respectively, could negatively affect the Fund and its shareholders.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivatives transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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 other countries (such as the United States) 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.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

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

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year and life-of-fund periods compare to those of two broad measures of market performance. The Blended Index is an unmanaged, blended index composed of the following weights: 60% MSCI World Index (Net) and 40% Bloomberg Barclays U.S. Aggregate Bond Index. The two indices composing the Blended Index measure, respectively, the performance of global equity securities and global sovereign fixed-income securities. 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
Fourth Quarter 2019, 7.43%

Lowest Quarterly Return:
Fourth Quarter 2018, -9.89%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (AlphaSimplex Multi-Asset Fund)	Past 1 Year	Life of Fund/Life of Class N	Inception Date
Class Y	16.82%	6.61%	Nov. 30, 2015
Class Y | Return After Taxes on Distributions	15.70%	5.15%	Nov. 30, 2015
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	9.95%	4.59%	Nov. 30, 2015
Class A	9.91%	4.84%	Nov. 30, 2015
Class C	14.75%	5.57%	Nov. 30, 2015
Class T	13.66%	5.70%	Nov. 30, 2015
Morningstar Global Allocation Index	18.53%	8.35%	Nov. 30, 2015
Blended Index	20.01%	7.84%	Nov. 30, 2015

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 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.

(AlphaSimplex Tactical U.S. Market Fund)

Investment Goal

The Fund seeks long-term capital appreciation, with emphasis on the protection of capital during unfavorable market conditions.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (AlphaSimplex Tactical U.S. Market Fund) - USD ($)	Class A		Class C	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	5.75%		none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none
Redemption fees	none		none	none	none

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

Annual Fund Operating Expenses - (AlphaSimplex Tactical U.S. Market Fund)		Class A	Class C	Class T		Class Y
Management fees		0.80%	0.80%	0.80%		0.80%
Distribution and/or service (12b-1) fees		0.25%	1.00%	0.25%		none
Other expenses	[1]	0.26%	0.26%	0.26%	[2]	0.26%
Total annual fund operating expenses		1.31%	2.06%	1.31%		1.06%
Fee waiver and/or expense reimbursement	[3]	0.06%	0.06%	0.06%		0.06%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.25%	2.00%	1.25%		1.00%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement 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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (AlphaSimplex Tactical U.S. Market Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	695	961	1,246	2,058
Class C	303	640	1,103	2,385
Class T	374	649	945	1,784
Class Y	102	331	579	1,289

If shares are not redeemed:

Expense Example, No Redemption - (AlphaSimplex Tactical U.S. Market Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	203	640	1,103	2,385

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 37% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

The Fund pursues its investment goal primarily through investments in equity securities that broadly represent the U.S. equities market (including common stocks, preferred stocks and exchange-traded funds ("ETFs") related to equity investments); derivative instruments related to the U.S. equities market (primarily futures contracts on U.S. equity indices); and fixed-income securities (including money market and other short-term or variable-rate, high-quality securities and related ETFs). Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investments that are tied economically to the U.S. The Adviser considers an investment to be tied economically to the U.S. if the investment is included in an index representative of the U.S., the investment's returns are linked to the performance of such an index, or the investment is exposed to the economic risks and returns of the U.S. The Adviser may use quantitative models to determine when to magnify the Fund's exposure to the U.S. equity market, for example, through the purchase of futures contracts, or, alternatively, when to decrease such exposure, for example, through the sale of futures contracts or through the purchase of ETFs that it believes may effectively hedge equity investments. The Adviser may increase the Fund's exposure to the U.S. equity market to up to 130% of the Fund's total assets when it believes that the risk of loss is justified by potential returns. The Adviser may decrease such exposure to as little as 0% of the Fund's total assets, in an attempt to limit the effects of extreme market drawdowns, when it believes that the risk of loss is not offset by potential returns. Such increases and decreases may lag changes in the market, and there is no guarantee that the Adviser's models will accurately predict market movement. Because the Fund's equity market exposure will often exceed its total assets, it will be subject to increased risk compared to funds that do not leverage their equity market exposure. While this increased exposure to equity investments may magnify the Fund's potential for gains, it also may magnify the potential for loss. For these reasons, the Fund is intended for long-term investors.

Equity Securities Investments. The equity securities portion of the Fund is managed by Natixis Advisors, L.P. (through its division, Active Index Advisors®) ("Natixis Advisors"), with the exception of any investments in ETFs, which are selected by the Adviser. Natixis Advisors utilizes a proprietary sampling system when deciding which securities to purchase, with the goal of tracking the performance of the large-capitalization U.S. equity market. In an attempt to reduce adverse tax consequences, the portion of the Fund managed by Natixis Advisors may hold securities that are not considered to represent the large-capitalization U.S. equity market, or hold securities in amounts disproportionate to their weights within the large-capitalization U.S. equity market. The portfolio may experience tracking error and is not guaranteed to replicate exactly the large-capitalization U.S. equity market.

Derivative Investments. As discussed above, the Adviser seeks to complement the equity portion of the Fund with investments in derivative instruments intended to enhance return and, during times of significant market decline, mitigate losses. In addition, the Adviser uses futures contracts to manage volatility and adjusts the Fund's exposure to equity investments in times of significantly increased volatility (including, when volatility is more than double the long-term average volatility of the U.S. equity markets). As of March 31, 2020, the long-term average annualized volatility of the U.S. equity markets was 19.1%. The Fund's actual or realized volatility during certain periods or over time may materially exceed the long-term average annualized volatility of the U.S. equity markets, for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. The Fund may have both "short" and "long" exposures to equity investments simultaneously. The Fund will benefit from a "short" exposure when equity and equity-related investments decrease in price, and will benefit from a "long" exposure when equity and equity-related investments increase in price.

Fixed-Income Investments. The assets allocated to the fixed-income portion will be used primarily to support the Fund's investments in derivatives and, secondarily, to provide the Fund with incremental income and liquidity. The fixed-income portion of the Fund will only invest in high-quality securities that are denominated in U.S. dollars, and will select securities for investment based on various factors, including the security's maturity and rating. The Adviser will invest primarily in (i) short-term obligations issued or guaranteed by the United States government, its agencies or instrumentalities; (ii) securities issued by foreign governments, their political subdivisions or agencies or instrumentalities; (iii) certificates of deposit, time deposits and bankers' acceptances issued by domestic and foreign banks, including domestic or foreign branches or subsidiaries of such banks; (iv) variable amount master demand notes; (v) participation interests in loans extended by banks to companies; (vi) commercial paper or similar debt obligations; and (vii) repurchase agreements.

When buying and selling securities and other instruments for the Fund, and when allocating assets to Natixis Advisors, the Adviser may consider: (i) the Adviser's proprietary quantitative models, including the outlook on volatility and market decline; (ii) the Fund's obligations under its various derivative positions; (iii) redemption requests; (iv) yield management; (v) credit management; and (vi) volatility management.

The Fund will concentrate its investments in the financial services industry, which means it will normally invest at least 25% of its total assets in securities and other obligations (for example, bank certificates of deposit) of issuers in such industry.

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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance. The Fund's trading in derivatives is active and frequent. Active and frequent trading of derivatives, like active and frequent trading of securities, will result in transaction costs that reduce Fund returns.

With the exception of the Fund's 80% policy, the percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to time. In accordance with applicable requirements of the U.S. Securities and Exchange Commission (the "SEC"), the Fund will notify shareholders prior to any change to the 80% policy discussed above taking effect.

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result 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. 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.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures contracts) 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 futures contracts, involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward contracts 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time.

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

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

Index/Tracking Error Risk: This is the risk that, to the extent the Fund's principal investment strategies utilize indices, the Fund's performance may not track the performance of such indices. For example, the equity securities in which the Fund invests may not provide investment performance matching the performance of broad-based large capitalization U.S. equity indices. Similarly, changes in the value of the derivatives in which the Fund invests may not correlate perfectly with the underlying assets or indices associated with such derivatives. Moreover, the ETFs in which the Fund invests may not replicate the performance of the indices they track and may, therefore, result in loss to the Fund.

Concentrated Investment Risk: The Fund is particularly vulnerable to events affecting companies in the financial services industry because the Fund concentrates its investments in securities and other obligations of issuers in such industry. Examples of risks affecting the financial services industry include changes in governmental regulation, issues relating to the availability and cost of capital, changes in interest rates and/or monetary policy and price competition. In addition, financial services companies are often more highly leveraged than other companies, making them inherently riskier. As a result, the Fund's shares may rise and fall in value more rapidly and to a greater extent than shares of a fund that does not concentrate or focus in a particular industry or economic sector.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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. Potential future changes in government monetary policy may affect the level of interest rates.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies, including ETFs, in which it invests in addition to its own expenses.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

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. The Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Short Exposure Risk: A short exposure through a derivative or short sale may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. The Fund may be unable to borrow securities in connection with a short sale or to enter into a short position at an advantageous time or price, which could limit its ability to obtain the desired short exposure. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

U.S. Government Securities Risk: Investments in certain U.S. government securities may not be supported by the full faith and credit of the U.S. government. Accordingly, no assurance can be given that the U.S. government will provide financial support to U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. The maximum potential liability of the issuers of some U.S. government securities held by the Fund may greatly exceed their current resources, and it is possible that these issuers will not have the funds to meet their payment obligations in the future. In such a case, the Fund would have to look principally to the agency, instrumentality or sponsored enterprise issuing or guaranteeing the security for ultimate repayment, and the Fund may not be able to assert a claim against the U.S. government itself in the event the agency, instrumentality or sponsored enterprise does not meet its commitment. Concerns about the capacity of the U.S. government to meet its obligations may raise the interest rates payable on its securities, negatively impacting the price of such securities already held by the Fund.

Valuation Risk: This is the risk that the Fund has valued certain securities or positions at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as derivatives, that may be illiquid or may become illiquid.

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 compare to those of two broad measures of market performance. The Barclay Equity Long/Short Index is comprised of equity-oriented hedge funds which hold both long and short stock positions and tend to tactically vary their net market exposure, i.e., market beta, based on their assessment of market risk and expected return. Index returns are recalculated by Barclay Hedge Ltd. throughout each month. The Fund does not expect to update the index returns provided if subsequent recalculations cause such returns to change. In addition, because of these recalculations, the Barclay Equity Long/Short Index returns reported by the Fund may differ from the index returns for the same period published by others. 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
Fourth Quarter 2019, 10.28%

Lowest Quarterly Return:
Fourth Quarter 2018, -12.94%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (AlphaSimplex Tactical U.S. Market Fund)	Past 1 Year	Past 5 Years	Life of Fund/Life of Class N	Inception Date
Class Y	23.34%	8.68%	11.46%	Sep. 30, 2013
Class Y | Return After Taxes on Distributions	23.05%	8.12%	10.54%	Sep. 30, 2013
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	13.97%	6.76%	8.97%	Sep. 30, 2013
Class A	15.84%	7.12%	10.11%	Sep. 30, 2013
Class C	21.04%	7.58%	10.34%	Sep. 30, 2013
Class T	19.86%	7.85%	10.71%	Sep. 30, 2013
S&P 500® Index	31.49%	11.70%	13.26%	Sep. 30, 2013
Barclay Equity Long/Short Index	7.08%	3.25%	3.83%	Sep. 30, 2013

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 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 Fund 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.

(Loomis Sayles Intermediate Municipal Bond Fund)

Investment Goal

The Fund seeks a high level of federal tax-exempt current income, consistent with the preservation of capital.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 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 Intermediate Municipal Bond Fund) - USD ($)	Class A		Class C	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	3.00%		none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none
Redemption fees	none		none	none	none

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

Annual Fund Operating Expenses - (Loomis Sayles Intermediate Municipal Bond Fund)		Class A	Class C	Class T		Class Y
Management fees		0.40%	0.40%	0.40%		0.40%
Distribution and/or service (12b-1) fees		0.25%	1.00%	0.25%		none
Other expenses		1.19%	1.20%	1.19%	[1]	1.20%
Acquired fund fees and expenses	[2]	0.01%	0.01%	0.01%		0.01%
Total annual fund operating expenses		1.85%	2.61%	1.85%		1.61%
Fee waiver and/or expense reimbursement	[3]	1.14%	1.15%	1.14%		1.15%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.71%	1.46%	0.71%		0.46%

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (Loomis Sayles Intermediate Municipal Bond Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	370	757	1,167	2,313
Class C	249	702	1,282	2,859
Class T	321	709	1,122	2,274
Class Y	47	395	767	1,814

If shares are not redeemed:

Expense Example, No Redemption - (Loomis Sayles Intermediate Municipal Bond Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	149	702	1,282	2,859

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 11% 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 borrowings made for investment purposes) in municipal securities that pay interest exempt from federal income taxes. Municipal securities are debt instruments typically issued by or on behalf of state and local governments, territories or possessions of the United States, including the District of Columbia, and their political subdivisions, agencies and instrumentalities and may include general obligation, revenue and private activity bonds and notes. In addition, the Fund may invest up to 20% of its assets in securities that pay interest subject to federal income taxation. The Fund may invest up to 20% of its assets in debt securities subject to the federal alternative minimum tax. The Fund's investments may include securities issued by the U.S. government, its agencies and instrumentalities and corporate debt securities. The Fund will invest primarily in investment grade fixed-income 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., Fitch Investors Services, Inc. or S&P Global Ratings), or, if unrated, are determined by Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Subadviser") to be of comparable quality. The Subadviser considers pre-refunded bonds and municipal securities escrowed to maturity using U.S. Treasury securities or U.S. government agency securities to be investment grade securities, regardless of rating. The Fund may also invest up to 10% of its assets in securities that are not investment grade (commonly known as "junk bonds"). Under normal circumstances, the dollar-weighted average maturity of the Fund's portfolio is expected to be between 3 and 10 years although the Fund may invest in securities of any maturity.

The portfolio management team seeks to build a portfolio based on a number of factors including sector, duration and maturity distribution, yield, expected return, credit momentum outlook (sector and security level), credit quality, security structure, issue size and liquidity. Through the use of quantitative and fundamental analysis, the pool of possible portfolio investments is screened using these factors to arrive at a narrower universe of securities that the Subadviser believes are suitable for the Fund's portfolio. Potential investments are also subject to a portfolio risk assessment that may include the following:

• Determining the ability of creditors to fully repay debt obligations in a timely manner.
• Use of a wide variety of internal and external quantitative and analytical and informational sources to assess likelihood of repayment.
• Monitoring rating agency and third party surveillance sources with an emphasis on core holdings.

The Subadviser may sell a security for a variety of reasons, including duration management, yield curve positioning, sector rotation, a change in credit momentum outlook or if more attractive investment opportunities are identified.

The Fund may also:

• Invest in when-issued securities and securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities").
• Enter into futures transactions for hedging and investment purposes.
• Invest in other investment companies to the extent permitted by the Investment Company Act of 1940.

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to the Fund.

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.

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. Potential future changes in government monetary policy may affect the level of interest rates.

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

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. Derivatives, and particularly OTC derivatives, are generally subject to liquidity risk as well. Liquidity issues may also make it difficult to value the Fund's investments.

Investments in Other Investment Companies Risk: The Fund will indirectly bear the management, service and other fees of any other investment companies in which it invests in addition to its own expenses.

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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

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, such as options, foreign currency transactions, 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 over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate 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.

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.

Municipal Securities Risk: Municipal bonds are investments issued by states, cities, public authorities or political subdivisions to raise money for public purposes, including general obligation bonds and revenue obligations. Municipal securities are subject to information risk, liquidity risk, credit risk and the risks that economic, political, fiscal or regulatory events, legislative changes and the enforceability of rights of municipal bond holders could adversely affect the values of municipal bonds. Municipal obligations may be susceptible to downgrades or defaults during recessions or similar periods of economic stress and insolvent municipalities may file for bankruptcy, which could significantly affect the rights of creditors and the value of the municipal securities. In addition, if the municipal securities held by the Fund fail to meet certain legal requirements allowing interest distributed from such securities to be tax-exempt, the interest received and distributed to shareholders by the Fund may be taxable.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year and life-of-fund periods (as applicable) 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
First Quarter 2019, 2.66%

Lowest Quarterly Return:
Fourth Quarter 2016, -3.76%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (Loomis Sayles Intermediate Municipal Bond Fund)	Past 1 Year	Past 5 Years	Life of Fund/Life of Class N	Inception Date
Class Y	6.80%	2.88%	2.61%	Dec. 31, 2012
Class Y | Return After Taxes on Distributions	6.79%	2.88%	2.61%	Dec. 31, 2012
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	5.11%	2.69%	2.44%	Dec. 31, 2012
Class A	3.33%	1.96%	1.86%	Dec. 31, 2012
Class C	4.64%	1.85%	1.55%	Dec. 31, 2012
Class T	3.83%	2.06%	1.95%	Dec. 31, 2012
Bloomberg Barclays Municipal Bond Index	7.54%	3.53%	3.39%	Dec. 31, 2012

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 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.

(Loomis Sayles Strategic Alpha Fund)

Investment Goal

The Fund seeks to provide an attractive absolute total return, complemented by prudent investment management designed to manage risks and protect investor capital. The secondary goal of the Fund is to achieve these returns with relatively low volatility.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Funds Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 76 of the Prospectus, in Appendix A to the Prospectus and on page 124 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - (Loomis Sayles Strategic Alpha Fund) - USD ($)	Class A		Class C	Class N	Class T	Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.25%		none	none	2.50%	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	[1]	1.00%	none	none	none
Redemption fees	none		none	none	none	none

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

Annual Fund Operating Expenses - (Loomis Sayles Strategic Alpha Fund)		Class A	Class C	Class N	Class T		Class Y
Management fees		0.59%	0.59%	0.59%	0.59%		0.59%
Distribution and/or service (12b-1) fees		0.25%	1.00%	none	0.25%		none
Other expenses	[1]	0.15%	0.15%	0.08%	0.15%	[2]	0.15%
Total annual fund operating expenses		0.99%	1.74%	0.67%	0.99%		0.74%
Fee waiver and/or expense reimbursement	[3]	none	none	none	none		none
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.99%	1.74%	0.67%	0.99%		0.74%

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. The example does not take into account brokerage commissions and other fees to financial intermediaries that you may pay on your purchases and sales of shares of the Fund. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If shares are redeemed:

Expense Example - (Loomis Sayles Strategic Alpha Fund) - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	522	727	949	1,586
Class C	277	548	944	2,052
Class N	68	214	373	835
Class T	348	557	783	1,433
Class Y	76	237	411	918

If shares are not redeemed:

Expense Example, No Redemption - (Loomis Sayles Strategic Alpha Fund)	1 Year	3 Years	5 Years	10 Years
Class C | USD ($)	177	548	944	2,052

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 414% of the average value of its portfolio.

Investments, Risks and Performance Principal Investment Strategies

The Fund has an absolute total return investment objective, which means that it is not managed relative to an index and that it attempts to achieve positive total returns over a full market cycle. The Fund intends to pursue its objective by utilizing a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies to mitigate downside risk. The Fund may invest up to 100% of its total assets in below investment grade fixed-income securities (also known as "junk bonds") and derivatives that have returns related to the returns on below investment grade fixed-income securities, although it is expected that, under normal market conditions, the Fund's net exposure (i.e., long exposures obtained through direct investments in securities and in derivatives minus short exposures obtained through derivatives) to below investment grade fixed-income assets generally will not exceed 50% of the Fund's total assets. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major rating agencies (Moody's Investors Service, Inc. ("Moody's"), Fitch Investor Services, Inc. or S&P Global Ratings ("S&P")) have rated the securities in one of their respective top four ratings categories). Under normal market conditions, the Fund also may invest up to 50% of its total assets in investments denominated in non-U.S. currencies and related derivatives, including up to 20% in investments denominated in emerging market currencies and related derivatives. The Fund expects that its exposure to these asset classes will often be obtained substantially through the use of derivative instruments. The Fund defines an "emerging market currency" as a currency of a country that carries a sovereign debt quality rating that is rated below investment grade by either S&P or Moody's, or is unrated by both S&P and Moody's. Currency positions that are intended to hedge the Fund's non-U.S. currency exposure (i.e., currency positions that are not made for investment purposes) will offset positions in the same currency that are made for investment purposes when calculating the limitation on investments in non-U.S. and emerging market currency investments because the Fund believes that hedging a currency position is likely to negate some or all of the currency risk associated with the original currency position. The Fund does not have limits on the duration of its portfolio, and the Fund's duration will change over time. The Fund also may invest in equity securities (including preferred stocks) as well as derivatives whose returns are linked to the returns of equity securities.

In selecting investments for the Fund, the Adviser develops long-term portfolio themes driven by macro-economic indicators. These include global economic trends, demographic trends and labor supply, analysis of global capital flows and assessments of geopolitical factors. The Adviser then develops shorter-term portfolio strategies based on factors including, but not limited to, economic, credit and Federal Reserve cycles, and top-down sector valuations and bottom-up security valuations. The Adviser seeks to actively manage risk, with a focus on managing the Fund's exposure to credit, interest rate and currency risks in relation to the market. Additionally, the portfolio managers will use risk management tools, such as models that evaluate risk correlation to various market factors or asset classes, to seek to manage risk on an ongoing basis. 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 Adviser incorporates systematic and quantitative models with respect to selection of certain investments.

The Adviser currently targets an annualized volatility range of 4% to 6% (as measured by the standard deviation of the Fund's returns). The Fund's actual or realized volatility during certain periods or over time may materially exceed or be lower than its target volatility range for various reasons, including changes in market levels of volatility and because the Fund's portfolio may include instruments that are inherently volatile. This would increase the risk of investing in the Fund.

The Fund will pursue its investment goal by obtaining long investment exposures through investments in securities and derivatives and short investment exposures substantially through derivatives. A "long" investment exposure is an investment that rises in value with a rise in the value of an asset, asset class or index and declines in value with a decline in the value of that asset, asset class or index. A "short" investment exposure is an investment that rises in value with a decline in the value of an asset, asset class or index and declines in value with a rise in the value of that asset, asset class or index. The value of the Fund's long and short investment exposures may, at times, each reach 100% of the assets invested in the Fund (excluding instruments primarily used for duration management or yield curve management and short-term investments (such as cash and money market instruments)), although these exposures may be higher or lower at any given time.

Fixed-Income Investments. In connection with its principal investment strategies, the Fund may invest in a broad range of U.S. and non-U.S. fixed-income securities, including, but not limited to, corporate bonds, municipal securities, U.S. and non-U.S. government securities (including their agencies, instrumentalities and sponsored entities), securities of supranational entities, emerging market securities, commercial and residential mortgage-backed securities, collateralized mortgage obligations, other mortgage-related securities (such as adjustable rate mortgage securities), asset-backed securities, collateralized loan obligations, bank loans, convertible bonds, securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"), real estate investment trusts ("REITs"), zero-coupon securities, step coupon securities, pay-in-kind ("PIK") securities, inflation-linked bonds, variable and floating rate securities, private placements and commercial paper.

Non-U.S. Currency Investments. Under normal market conditions, the Fund may engage in a broad range of transactions involving non-U.S. and emerging market currencies, including, but not limited to, purchasing and selling forward currency exchange contracts in non-U.S. or emerging market currencies, investing in non-U.S. currency futures contracts, investing in options on non-U.S. currencies and non-U.S. currency futures, investing in cross-currency instruments (such as swaps), investing directly in non-U.S. currencies and investing in securities denominated in non-U.S. currencies. The Fund may engage in non-U.S. currency transactions for investment or for hedging purposes.

Derivative Investments. For investment and hedging purposes, the Fund may invest substantially in a broad range of derivatives instruments and sometimes the majority of its investment returns will derive from its derivative investments. These derivative instruments include, but are not limited to, futures contracts (such as treasury futures and index futures), forward contracts, options (such as options on futures contracts, options on securities, interest rate/bond options, currency options, options on swaps and over-the-counter ("OTC") options), warrants (such as non-U.S. currency warrants), swap transactions (such as interest rate swaps, total return swaps and index swaps) and structured notes (such as equity-linked notes). In addition, the Fund may invest in credit derivative products that may be used to manage default risk and credit exposure. Examples of such products include, but are not limited to, credit default swap index products (such as LCDX, CMBX and ABX index products), single name credit default swaps, loan credit default swaps and asset-backed credit default swaps. The Fund may, at times, invest substantially all of its assets in derivatives and securities used to support its obligations under those derivatives. The Fund's strategy may be highly dependent on the use of derivatives, and to the extent that they become unavailable or unattractive the Fund may be unable to fully implement its investment strategy.

Equity Investments. In connection with its principal investment strategies, the Fund may invest in common stocks, preferred stocks and convertible preferred stocks.

The Fund is non-diversified, which means it may invest a greater portion of its assets in a particular issuer and may invest in fewer issuers. Because the Fund may invest in the securities of fewer issuers, an investment in the Fund may involve a higher degree of risk than would be present in a diversified portfolio.

The Fund expects to 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 return, and realization of greater short-term capital gains, distributions of which are taxable as ordinary income to taxable shareholders. Trading costs and tax effects associated with frequent trading may adversely affect the Fund's performance.

The percentage limitations set forth herein are not investment restrictions and the Fund may exceed these limits from time to time. In addition, when calculating these exposures, the Fund may use the market value, the notional value, an adjusted notional value or some other measure of the value of a derivative in order to reflect what the Adviser believes to be the most accurate assessment of the Fund's real economic exposure. The total notional value of the Fund's derivative instruments may significantly exceed the total value of the Fund's assets.

Although the Fund seeks positive total returns over time, the Fund's investment returns may be volatile over short periods of time. The Fund may outperform the overall securities market during periods of flat or negative performance and may underperform during periods of strong market performance. There can be no assurance that the Fund's returns over time or during any period will be positive.

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.

The significance of any specific risk to an investment in the Fund will vary over time, depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information presented below carefully, because any one or more of these risks may result in losses to 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.

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.

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. The value of zero-coupon and PIK bonds may be more sensitive to fluctuations in interest rates 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, negatively impacting the performance of the Fund. Potential future changes in government monetary policy may affect the level of interest rates.

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.

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 other countries (such as the United States) 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.

Agency Securities Risk: Certain debt securities issued or guaranteed by agencies of the U.S. government are guaranteed as to the payment of principal and interest by the relevant entity but have not been backed by the full faith and credit of the U.S. government. Instead, they have been supported only by the discretionary authority of the U.S. government to purchase the agency's obligations. An event affecting the guaranteeing entity could adversely affect the payment of principal or interest or both on the security and, therefore, these types of securities should be considered to be riskier than U.S. government securities.

Credit/Counterparty Risk: Credit/counterparty risk is the risk that the issuer or guarantor of a fixed-income security, or the counterparty to a derivative 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 risk with respect to the counterparties to its derivative transactions. Many of the protections afforded to participants on organized exchanges, such as the performance guarantee given by a central 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. This risk will be heightened to the extent the Fund enters into derivative transactions with a single counterparty (or affiliated counterparties that are part of the same organization), causing the Fund to have significant exposure to such counterparty.

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 a significant portion of its assets 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.

Cybersecurity and Technology Risk: The Fund, its service providers, and other market participants increasingly depend on complex information technology and communications systems, which are subject to a number of different threats and risks that could adversely affect the Fund and its shareholders. Cybersecurity and other operational and technology issues may result in financial losses to the Fund and its shareholders.

Derivatives Risk: Derivative instruments (such as those in which the Fund may invest, including futures contracts, forward contracts, options, warrants 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, such as futures, forward contracts, options, warrants, foreign currency transactions, swaps, credit default swaps and equity-linked and other structured notes, involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward 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. There is a risk that the Adviser's use of derivatives, such as futures and forward contracts, to manage the Fund's volatility may be ineffective or may exacerbate losses, for example, if the derivative and the underlying assets decrease in value over time. When used, derivatives may affect the amount, timing or character of distributions payable to, and thus taxes payable by, shareholders. Similarly, for accounting and performance reporting purposes, income and gain characteristics may be different than if the Fund held the underlying securities or assets directly.

Equity Securities Risk: The value of the Fund's investments in preferred stocks 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. 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.

Inflation/Deflation Risk: Inflation risk is the risk that the value of assets or income from investments will be worth less in the future as inflation decreases the present value of future payments. Deflation risk is the risk that prices throughout the economy decline over time (the opposite of inflation). Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of the Fund's portfolio. Because the Fund seeks positive returns that exceed the rate of inflation over time, if the portfolio managers' inflation forecasts are incorrect, the Fund may be more severely impacted than other funds.

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.

Leverage Risk: Use of derivative instruments may involve leverage. Taking short positions in securities also results in a form of 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 the Fund's returns, and may lead to significant losses if investments are not successful.

LIBOR Risk: LIBOR risk is the risk that the transition away from the London Interbank Offered Rate ("LIBOR") may lead to increased volatility and illiquidity in markets that are tied to LIBOR. LIBOR is a benchmark interest rate that is used extensively as a "reference rate" for financial instruments, including many corporate and municipal bonds, bank loans, asset-backed and mortgage-related securities, interest rate swaps and other derivatives. Additionally, the Fund may borrow money at rates that are based on LIBOR. In July 2017, the head of the United Kingdom Financial Conduct Authority, the agency that oversees LIBOR, announced that after 2021 it will cease its active encouragement of banks to provide the quotations needed to sustain LIBOR. That announcement suggests that LIBOR may cease to be published after that time. The transition away from LIBOR poses a number of other risks, including changed values of LIBOR-related investments and reduced effectiveness of hedging strategies, each of which may adversely affect the Fund's performance.

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. Derivatives, and particularly OTC derivatives, are generally subject to 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. The Fund's Adviser will attempt to reduce this risk by implementing various volatility management strategies and techniques. However, there is no guarantee that such strategies and techniques will produce the intended result.

Models and Data Risk: The Adviser utilizes various proprietary quantitative models to identify investment opportunities. There is a possibility that one or all of the quantitative models may fail to identify profitable opportunities at any time. Furthermore, the models may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses for the Fund. Models may be predictive in nature and such models may result in an incorrect assessment of future events. Data used in the construction of models may prove to be inaccurate or stale, which may result in losses for the Fund.

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

Short Exposure Risk: A short exposure through a derivative may present various risks, including credit/counterparty risk and leverage risk. If the value of the asset, asset class or index on which the Fund has obtained a short investment exposure increases, the Fund will incur a loss. Unlike a direct cash investment such as a stock, bond or ETF, where the potential loss is limited to the purchase price, the potential risk of loss from a short exposure is theoretically unlimited. Moreover, there can be no assurance that securities necessary to cover (repurchase in order to close) a short position will be available for purchase.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual returns for the one-year, five-year, life-of-fund and life-of-class periods (as applicable) compare to those of two broad measures of market performance. The 3-Month LIBOR +300 basis points represents the average rate at which a leading bank, for a given currency (in this case, U.S. dollars), can obtain unsecured funding, and is representative of short-term interest rates. 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 im.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

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

Total Returns for Class Y Shares

Highest Quarterly Return:
First Quarter 2012, 5.54%

Lowest Quarterly Return:
Third Quarter 2011, -4.71%

Average Annual Total Returns (for the periods ended December 31, 2019)

Average Annual Total Returns - (Loomis Sayles Strategic Alpha Fund)	Past 1 Year	Past 5 Years	Life of Fund/Life of Class N	Inception Date
Class Y	3.96%	2.62%	2.80%	Dec. 15, 2010
Class Y | Return After Taxes on Distributions	2.69%	1.28%	1.54%	Dec. 15, 2010
Class Y | Return After Taxes on Distributions and Sale of Fund Shares	2.35%	1.41%	1.62%	Dec. 15, 2010
Class A	(0.85%)	1.47%	2.06%	Dec. 15, 2010
Class C	1.87%	1.59%	1.77%	Dec. 15, 2010
Class N	3.92%		2.47%	May 01, 2017
Class T	0.96%	1.83%	2.26%	Dec. 15, 2010
3-Month LIBOR	2.33%	1.39%	0.91%	Dec. 15, 2010
3-Month LIBOR			2.07%	May 01, 2017
3-month LIBOR +300 basis points	5.33%	4.39%	3.89%	Dec. 15, 2010
3-month LIBOR +300 basis points			5.06%	May 01, 2017

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 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 Fund 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] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[3] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.54%, 2.29%, 1.24%, 1.54% and 1.29% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, substitute dividend expenses on securities sold short, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y 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 fee/expense was waived/reimbursed.

[4] Natixis Advisors, L.P. ("Natixis Advisors") has given a binding contractual undertaking to the Fund to reimburse any and all transfer agency expenses for Class N shares. This undertaking is in effect through April 30, 2021 and may be terminated before then only with the consent of the Fund's Board of Trustees.

[1] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.70%, 2.45%, 1.40%, 1.70% and 1.45% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fee/expense was waived/reimbursed.

[1] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[3] AlphaSimplex Group, LLC ("AlphaSimplex" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.15%, 1.90%, 1.15% and 0.90% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

[1] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[1] The expense information shown in the table above includes acquired fund fees and expenses of less than 0.01%; the ratios may differ from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

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

[3] AlphaSimplex Group, LLC ("AlphaSimplex" 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 1.24%, 1.99%, 1.24% and 0.99% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

[1] A 0.75% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $500,000 or more that are redeemed within eighteen months of the date of purchase.

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

[2] The expense information shown in the table above differs from the expense information disclosed in the Fund's financial highlights table because the financial highlights table reflects the operating expenses of the Fund and does not include acquired fund fees and expenses.

[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 0.70%, 1.45%, 0.70% and 0.45% of the Fund's average daily net assets for Class A, Class C, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class T and Class Y 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 fee/expense was waived/reimbursed.

[1] A 1.00% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $1,000,000 or more that are redeemed within eighteen months of the date of purchase.

[1] The expense information shown in the table above includes acquired fund fees and expenses of less than 0.01%.

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

[3] Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 1.00%, 1.75%, 0.70%, 1.00% and 0.75% of the Fund's average daily net assets for Class A, Class C, Class N, Class T and Class Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2021 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 limitations for Class A, Class C, Class N, Class T and Class Y 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 fee/expense was waived/reimbursed.