Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Natixis Funds Trust II
Prospectus Date	rr_ProspectusDate	Sep. 30, 2013
ASG Tactical U.S. Market Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	ASG Tactical U.S. Market Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks long-term capital appreciation, with emphasis on 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 and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section “How Sales Charges Are Calculated” on page 14 of the Prospectus and on page 72 in the section “Reduced Sales Charges” of the Statement of Additional Information (“SAI”).
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	April 30, 2015
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.
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Natixis Fund Complex.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same, except that the example is based on the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first nineteen months and on the Total Annual Fund Operating Expenses for the remaining years. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	If shares are redeemed:
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	If shares are not redeemed:
Strategy [Heading]	rr_StrategyHeading	Investments, Risks and Performance Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund 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. Additionally, while the Fund’s 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 NGAM Advisors, L.P. (through its division, Active Investment Advisors) (“NGAM Advisors”), with the exception of any investments in ETFs, which are selected by the Adviser. NGAM 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 NGAM 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 August 31, 2013, the long-term average annualized volatility of the U.S. equity markets was 18.2%. 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. 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 fixed-income portion of the Fund is managed by Reich & Tang Asset Management, LLC (“Reich & Tang”), with the exception of any investments in ETFs, which are selected by the Adviser. 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 portion of the Fund managed by Reich & Tang 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. Reich & Tang 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 NGAM Advisors or Reich & Tang, 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 to shareholders who are individuals as ordinary income. 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 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]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. 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. Although the Fund’s investments in the financial services industry typically involve short-term obligations in money-market securities that tend to experience lower volatility than certain other investments, the Fund’s shares may nevertheless 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. As a result, the risk associated with investing in the Fund may be increased as compared to a fund that does not concentrate in the financial services industry. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. Derivatives Risk: Derivative instruments (such as those in which the Fund may invest) can be used to acquire or to transfer the risk and returns of a security or other asset without buying or selling the security or asset. Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund’s exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund’s liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives, such as futures contracts, may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund’s use of derivatives may involve other risks, such as the credit risk relating to a broker, futures commission merchant or the other party to a derivative contract, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is a risk that the Adviser’s use of derivatives 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 at the same 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. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security’s value or periods of below-average performance in a given security or in the securities market as a whole. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce the Fund’s ability to sell them. Index/Tracking Error/Correlation Risk: This is the risk that, to the extent the Fund’s principal investment strategies utilize indices, the Fund’s performance may not track that of such indices. For example, the equity securities selected by the Fund may not provide investment performance matching that 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 index 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. Interest Rate Risk: Changes in interest rates may cause the value of the Fund’s investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A prolonged period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. 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. In addition, investments in ETFs have unique characteristics, including, but not limited to, the expense structure and additional expenses associated with investing in ETFs. Issuer Risk: The value of the Fund’s investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services. 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, 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. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund’s returns, and may lead to significant losses if investments are not successful. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund’s portfolio managers may fail to produce the intended result. 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, they may incorrectly identify opportunities and these misidentified opportunities may lead to substantial losses. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer’s financial condition, as well as overall market and economic conditions. There is no guarantee that any strategies or techniques used by the Fund’s Adviser to reduce such risk will produce the intended result. 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 like a stock, bond or exchange-traded fund, 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 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 at a higher price than the price at which they can be sold. This risk may be especially pronounced for investments, such as over-the-counter (“OTC”) 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	Because the Fund is new and has not yet completed a full calendar year, information related to Fund performance, including a bar chart showing annual returns, has not been included in this Prospectus. The performance information provided by the Fund in the future will give some indication of the risks of an investment in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns compare against those of a broad measure of market performance.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The performance information provided by the Fund in the future will give some indication of the risks of an investment in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns compare against those of a broad measure of market performance.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund is new and has not yet completed a full calendar year, information related to Fund performance, including a bar chart showing annual returns, has not been included in this Prospectus.
ASG Tactical U.S. Market Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	5.75%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Redemption fees	rr_RedemptionFeeOverRedemption	none
Management fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other expenses (estimated for the current fiscal year)	rr_OtherExpensesOverAssets	1.79%
Acquired fund fees and expenses (estimated for the current fiscal year)	rr_AcquiredFundFeesAndExpensesOverAssets	0.03%
Total annual fund operating expenses	rr_ExpensesOverAssets	2.87%
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	1.44%	[1]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	1.43%
1 year	rr_ExpenseExampleYear01	712
3 years	rr_ExpenseExampleYear03	1,206
ASG Tactical U.S. Market Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Redemption fees	rr_RedemptionFeeOverRedemption	none
Management fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other expenses (estimated for the current fiscal year)	rr_OtherExpensesOverAssets	1.79%
Acquired fund fees and expenses (estimated for the current fiscal year)	rr_AcquiredFundFeesAndExpensesOverAssets	0.03%
Total annual fund operating expenses	rr_ExpensesOverAssets	3.62%
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	1.44%	[1]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	2.18%
1 year	rr_ExpenseExampleYear01	321
3 years	rr_ExpenseExampleYear03	894
1 year	rr_ExpenseExampleNoRedemptionYear01	221
3 years	rr_ExpenseExampleNoRedemptionYear03	894
ASG Tactical U.S. Market Fund | Class Y
Risk/Return:	rr_RiskReturnAbstract
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Redemption fees	rr_RedemptionFeeOverRedemption	none
Management fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses (estimated for the current fiscal year)	rr_OtherExpensesOverAssets	1.79%
Acquired fund fees and expenses (estimated for the current fiscal year)	rr_AcquiredFundFeesAndExpensesOverAssets	0.03%
Total annual fund operating expenses	rr_ExpensesOverAssets	2.62%
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	1.44%	[1]
Total annual fund operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	1.18%
1 year	rr_ExpenseExampleYear01	120
3 years	rr_ExpenseExampleYear03	$ 593

[1] 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 1.40%, 2.15% and 1.15% of the Fund's average daily net assets for Class A, C and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through April 30, 2015 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 1.40%, 2.15% and 1.15% of the Fund's average daily net assets for Class A, C and Y shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fee/expense was waived/reimbursed.