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MainStay Epoch International Choice Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MainStay Epoch International Choice Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks total return.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may be required to pay a commission or other transaction charge to your financial intermediary for effecting transactions in a class of shares of the Fund that has no initial sales charge, contingent deferred sales charge, or other asset-based fee for sales or distribution, such as Class I or Class R6 shares. These commissions are not reflected in the fee and expense table or expense example below. 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 MainStay Funds. This amount may vary depending on the MainStay Fund in which you invest. In addition, different financial intermediary firms and financial professionals may impose different sales loads and waivers. More information about these and other discounts or waivers is available from your financial professional, in the "Information on Sales Charges" section starting on page 101 of the Prospectus and Appendix A – Intermediary-Specific Sales Charge Waivers and Discounts, and in the "Alternative Sales Arrangements" section on page 123 of the Statement of Additional Information.

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)
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 when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 47% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 47.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the MainStay Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated whether or not you redeem all of your shares at the end of those periods (except as indicated with respect to Class C shares). 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 reflects the contractual fee waiver and/or expense reimbursement arrangement, if applicable, for the current duration of the arrangement only. 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 Assuming redemption at end of period
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption Assuming no redemption
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by investing in a portfolio consisting mostly of equity securities of companies located outside the United States, which may include companies in emerging markets. Under normal circumstances, the Fund will invest at least 80% of its assets (net assets plus any borrowings for investment purposes) in equity securities of companies located outside of the United States. Equity securities include common stock, depository receipts, and securities convertible into common stock, such as warrants, rights, convertible bonds, debentures and convertible preferred stocks. The Fund will normally invest in companies located in at least three countries outside of the United States. A company is considered to be located in a particular country if it: (i) is organized under the laws of the country; (ii) has securities which are principally traded on a stock exchange in the country; (iii) derives at least 50% of its revenues from goods produced or sold, investments made, or services performed in the country; or (iv) maintains at least 50% of its assets in the country. Although the Fund is not subject to any additional geographic requirement, the Fund expects that the majority of its investments will be in the developed markets of Canada, Western Europe, Asia and Australasia. The Fund may invest more than 25% of its net assets in securities of companies located in each of the United Kingdom and Japan. In order to gain additional exposure to international markets, the Fund may also invest in exchange traded funds ("ETFs"), whose underlying securities are issued by international companies.


Investment Process: Epoch Investment Partners, Inc., the Fund's Subadvisor, invests primarily in companies that generate increasing levels of free cash flow and have management teams that the Subadvisor believes allocate free cash flow effectively to create shareholder value.


The security selection process focuses on free-cash-flow analytics as opposed to traditional accounting-based metrics. The Subadvisor seeks to identify companies with a consistent, straightforward ability to both generate free cash flow and to intelligently allocate it among internal reinvestment opportunities, acquisitions, dividends, share repurchases and/or debt reduction.


The Subadvisor may sell or reduce a position in a security when it believes its investment objectives have been met or when the security is deemed less attractive relative to another security on a return/risk basis. The Subadvisor may sell or reduce a position in a security if it sees the investment thesis failing to materialize.

Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

You can lose money by investing in the Fund. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. The investments selected by the Subadvisor may underperform the market in which the Fund invests or other investments. The Fund may receive large purchase or redemption orders which may have adverse effects on performance if the Fund were required to sell securities, invest cash or hold a relatively large amount of cash at times when it would not otherwise do so.


The principal risks of investing in the Fund are summarized below.


Market Risk: The value of the Fund’s investments may fluctuate because of changes in the markets in which the Fund invests, which could cause the Fund to underperform other funds with similar investment objectives and strategies. Such changes may be rapid and unpredictable. From time to time, markets may experience periods of stress for potentially prolonged periods that may result in: (i) increased market volatility; (ii) reduced market liquidity; and (iii) increased redemptions of Fund shares. Such conditions may add significantly to the risk of volatility in the net asset value of the Fund's shares.


Portfolio Management Risk: The investment strategies, practices and risk analyses used by the Subadvisor may not produce the desired results. In addition, the Fund may not achieve its investment objective, including during periods in which the Subadvisor takes temporary positions in response to unusual or adverse market, economic or political conditions, or other unusual or abnormal circumstances.


Equity Securities Risk: Investments in common stocks and other equity securities are particularly subject to the risk of changing economic, stock market, industry and company conditions and the risks inherent in the portfolio managers' ability to anticipate such changes that can adversely affect the value of the Fund's holdings.


Market Capitalization Risk: To the extent the Fund invests in securities issued by small-, mid-, or large-cap companies, the Fund will be subject to the risks associated with securities issued by companies of the applicable market capitalization.  Securities of small-cap and mid-cap companies may be subject to greater price volatility, significantly lower trading volumes, cyclical, static or moderate growth prospects and greater spreads between their bid and ask prices than securities of larger companies. Smaller capitalization companies frequently rely on narrower product lines and niche markets and may be more vulnerable to adverse business or market developments.  Securities issued by larger companies may have less growth potential and may not be able to attain the high growth rates of successful smaller companies, especially during strong economic periods.  In addition, larger companies may be less capable of responding quickly to competitive challenges and industry changes, including those resulting from improvements in technology, and may suffer sharper price declines as a result of earnings disappointments.  There is a risk that the securities issued by companies of a certain market capitalization may underperform the broader market at any given time.


Value Stock Risk: Value stocks may never reach what the Subadvisor believes is their full value or they may go down in value. In addition, different types of stocks tend to shift in and out of favor depending on market and economic conditions, and therefore the Fund's performance may be lower or higher than that of funds that invest in other types of equity securities.


Growth Stock Risk: If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns.


Focused Portfolio Risk: Because the Fund typically invests in relatively few holdings, a larger percentage of its assets may be invested in a particular issuer or in fewer companies than is typical of other mutual funds. This may increase volatility of the Fund’s NAVs. The Fund will be more susceptible to adverse economic, political, regulatory or market developments affecting a single issuer than a fund that is invested more broadly.


Foreign Securities Risk: Investments in foreign (non-U.S.) securities may be riskier than investments in U.S. securities. Foreign regulatory regimes and securities markets can have less stringent investor protections and disclosure standards and less liquid trading markets than U.S. regulatory regimes and securities markets, and can experience political, social and economic developments that may affect the value of the Fund's investments in foreign securities. Foreign securities may also subject the Fund's investments to changes in currency rates. Changes in the value of foreign currencies may make the return on an investment increase or decrease, unrelated to the quality or performance of the investment itself.


Liquidity and Valuation Risk: The Fund’s investments may be illiquid at the time of purchase or liquid at the time of purchase and subsequently become illiquid due to, among other things, events relating to the issuer of the securities, market events, operational issues, economic conditions, investor perceptions or lack of market participants. The lack of an active trading market may make it difficult to sell or obtain an accurate price for a security. If market conditions or issuer specific developments make it difficult to value securities, the Fund may value these securities using more subjective methods, such as fair value pricing. In such cases, the value determined for a security could be different than the value realized upon such security's sale. As a result, an investor could pay more than the market value when buying Fund shares or receive less than the market value when selling Fund shares. This could affect the proceeds of any redemption or the number of shares an investor receives upon purchase.


The Fund is subject to the risk that it could not meet redemption requests within the allowable time period without significant dilution of remaining investors' interests in the Fund. To meet redemption requests or to raise cash to pursue other investment opportunities, the Fund may be forced to sell securities at an unfavorable time and/or under unfavorable conditions, which may adversely affect the Fund.


Emerging Markets Risk: The risks related to investing in foreign securities are generally greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets. The risks of investing in emerging markets include the risks of illiquidity, increased price volatility, smaller market capitalizations, less government regulation, less extensive and less frequent accounting, financial and other reporting requirements, loss resulting from problems in share registration and custody, substantial economic and political disruptions and the nationalization of foreign deposits or assets.


Geographic Focus Risk: Issuers that operate in a single country, a small number of countries, or a particular geographic region can be affected similarly by the market, currency, political, economic, regulatory, geopolitical and other conditions in such country or region, and the Fund’s performance will be affected by the conditions, in the countries or regions to which the Fund is exposed. To the extent the Fund focuses its investments in a particular country or region, such as the United Kingdom or Japan, its performance will be more susceptible to adverse developments in such country or region than a more geographically diversified fund.


Depositary Receipts Risk: Investments in depositary receipts may entail the special risks of investing in foreign securities, including currency exchange fluctuations, government regulations, and the potential for political and economic instability.


Convertible Securities Risk: Convertible securities are typically subordinate to an issuer’s other debt obligations. In part, the total return for a convertible security depends upon the performance of the underlying stock into which it can be converted. Also, issuers of convertible securities are often not as strong financially as those issuing securities with higher credit ratings, are more likely to encounter financial difficulties and typically are more vulnerable to changes in the economy, such as a recession or a sustained period of rising interest rates, which could affect their ability to make interest and principal payments. If an issuer stops making interest and/or principal payments, the Fund could lose its entire investment.


Regulatory Risk: The Fund as well as the issuers of the securities and other instruments in which the Fund invests are subject to considerable regulation and the risks associated with adverse changes in laws and regulations governing their operations. For example, regulatory authorities in the United States or other countries may prohibit or restrict the ability of the Fund to short sell certain securities, either generally or with respect to certain industries or countries, which may impact the Fund's ability to fully implement its investment strategies. In addition, regulatory authorities are in the process of adopting and implementing regulations governing derivatives markets, and, although the ultimate impact of the regulations remains unclear, the regulations may adversely affect, among other things, the availability, value or performance of derivatives.


Rights and Warrants Risk: Rights and warrants may provide a greater potential for profit or loss than an equivalent investment in the underlying securities. Prices of these investments do not necessarily move in tandem with the prices of the underlying securities, and warrants are speculative investments. If a right or warrant is not exercised by the date of its expiration, the Fund will lose its entire investment in such right or warrant.


Exchange-Traded Fund Risk: The risks of owning an ETF generally reflect the risks of owning the securities in which the ETF invests or is designed to track, although lack of liquidity in an ETF could result in it being more volatile than its underlying portfolio securities. Disruptions in the markets for the securities underlying ETFs purchased or sold by the Fund could result in losses on the Fund's investment in ETFs. ETFs also have management fees and transaction costs that may make them more expensive than owning the underlying securities directly.
Risk Lose Money [Text] rr_RiskLoseMoney You can lose money by investing in the Fund.
RIsk Not Insured [Text] rr_RiskNotInsured An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following bar chart and table indicate some of the risks of investing in the Fund. The bar chart shows you how the Fund's calendar year performance has varied over time. Sales loads, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. The average annual total returns table shows how the Fund's average annual total returns (before and after taxes) compare to those of a broad-based securities market index. The Fund has selected the MSCI EAFE® Index as its primary benchmark. The MSCI EAFE® Index consists of international stocks representing the developed world outside of North America.


Performance data for the classes varies based on differences in their fee and expense structures. Performance data is not shown for classes with less than one calendar year of performance. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Please visit nylinvestments.com/funds for more recent performance information.


The Fund's subadvisor changed effective January 9, 2017, and the Fund's principal investment strategies changed effective March 13, 2017. The past performance in the bar chart and table prior to those dates reflects the Fund's prior subadvisor and principal investment strategies.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table indicate some of the risks of investing in the Fund.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess Performance data is not shown for classes with less than one calendar year of performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress nylinvestments.com/funds
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Returns, Class I Shares (by calendar year 2010-2019)
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales loads, if any, are not reflected in the bar chart. If they were, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
   

Best Quarter

 

3Q/10

17.79

%

Worst Quarter

 

3Q/11

-19.16

%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 17.79%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.16%)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2019)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deductions for fees, expenses, or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest individual federal marginal income tax rates in effect at the time of each distribution or capital gain or upon the sale of Fund shares, and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred After-tax returns are not relevant if you hold your shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns shown are for Class I shares. After-tax returns for the other share classes may vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher In some cases, the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of shares at the end of the measurement period.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest individual federal marginal income tax rates in effect at the time of each distribution or capital gain or upon the sale of Fund shares, and do not reflect the impact of state and local taxes. In some cases, the return after taxes may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of shares at the end of the measurement period. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns are not relevant if you hold your shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns shown are for Class I shares. After-tax returns for the other share classes may vary.
MainStay Epoch International Choice Fund | MSCI EAFE® Index (reflects no deductions for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 22.01%
5 Years rr_AverageAnnualReturnYear05 5.67%
10 Years rr_AverageAnnualReturnYear10 5.50%
MainStay Epoch International Choice Fund | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none [1]
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.20%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock No initial sales charge applies on investments of $1 million or more (and certain other qualified purchases). However, a contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within 18 months of the date of purchase on shares that were purchased without an initial sales charge.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 666
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 910
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,173
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,925
1 Year rr_AverageAnnualReturnYear01 16.53%
5 Years rr_AverageAnnualReturnYear05 3.17%
10 Years rr_AverageAnnualReturnYear10 3.91%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 2006
MainStay Epoch International Choice Fund | Investor Class  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none [1]
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.38%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.43%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock No initial sales charge applies on investments of $1 million or more (and certain other qualified purchases). However, a contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within 18 months of the date of purchase on shares that were purchased without an initial sales charge.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 688
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 978
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,289
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,169
1 Year rr_AverageAnnualReturnYear01 16.27%
5 Years rr_AverageAnnualReturnYear05 2.98%
10 Years rr_AverageAnnualReturnYear10 3.73%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 29, 2008
MainStay Epoch International Choice 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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.38%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.18%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 321
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 682
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,169
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,513
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 221
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 682
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,169
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,513
1 Year rr_AverageAnnualReturnYear01 21.11%
5 Years rr_AverageAnnualReturnYear05 3.31%
10 Years rr_AverageAnnualReturnYear10 3.51%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 2006
MainStay Epoch International Choice Fund | Class I  
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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 303
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 525
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,166
Annual Return 2010 rr_AnnualReturn2010 5.65%
Annual Return 2011 rr_AnnualReturn2011 (9.10%)
Annual Return 2012 rr_AnnualReturn2012 16.78%
Annual Return 2013 rr_AnnualReturn2013 20.72%
Annual Return 2014 rr_AnnualReturn2014 (5.74%)
Annual Return 2015 rr_AnnualReturn2015 (4.59%)
Annual Return 2016 rr_AnnualReturn2016 (2.12%)
Annual Return 2017 rr_AnnualReturn2017 25.59%
Annual Return 2018 rr_AnnualReturn2018 (13.60%)
Annual Return 2019 rr_AnnualReturn2019 23.64%
1 Year rr_AverageAnnualReturnYear01 23.64%
5 Years rr_AverageAnnualReturnYear05 4.61%
10 Years rr_AverageAnnualReturnYear10 4.81%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 1997
MainStay Epoch International Choice Fund | Class I | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 23.10%
5 Years rr_AverageAnnualReturnYear05 4.31%
10 Years rr_AverageAnnualReturnYear10 4.57%
MainStay Epoch International Choice Fund | Class I | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 14.82%
5 Years rr_AverageAnnualReturnYear05 3.76%
10 Years rr_AverageAnnualReturnYear10 4.03%
MainStay Epoch International Choice Fund | Class R1  
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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.05%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 334
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 579
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,283
1 Year rr_AverageAnnualReturnYear01 23.53%
5 Years rr_AverageAnnualReturnYear05 4.51%
10 Years rr_AverageAnnualReturnYear10 4.69%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 2006
MainStay Epoch International Choice Fund | Class R2  
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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 132
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 412
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 713
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,568
1 Year rr_AverageAnnualReturnYear01 23.23%
5 Years rr_AverageAnnualReturnYear05 4.25%
10 Years rr_AverageAnnualReturnYear10 4.39%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 2006
MainStay Epoch International Choice Fund | Class R3  
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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 158
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 490
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,845
1 Year rr_AverageAnnualReturnYear01 22.89%
5 Years rr_AverageAnnualReturnYear05 3.97%
10 Years rr_AverageAnnualReturnYear10 4.12%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 01, 2006
MainStay Epoch International Choice Fund | Class R6  
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 the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.80% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.08%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.88%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 90
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 281
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 488
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,084
[1] No initial sales charge applies on investments of $1 million or more (and certain other qualified purchases). However, a contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within 18 months of the date of purchase on shares that were purchased without an initial sales charge.
[2] The management fee is as follows: 0.80% on assets up to $5 billion; 0.775% on assets from $5 billion to $7.5 billion; and 0.75% on assets over $7.5 billion.