Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Feb. 28, 2012
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	MainStay International Equity Fund
Investment Objective, Heading	rr_ObjectiveHeading	Investment Objective
investment Objective, Primary	rr_ObjectivePrimaryTextBlock	The Fund seeks long-term growth of capital.
Expense, Heading	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense, Narrative	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 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. More information about these and other discounts is available from your financial professional and in the "Information on Sales Charges" section starting on page 91 of the Prospectus and in the "Alternative Sales Arrangements" section on page 104 of the Statement of Additional Information.
Shareholder Fees, Caption	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses, Caption	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	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 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 80% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	80.00%
Expense Breakpoint, Discounts	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	rr_ExpenseExampleNarrativeTextBlock	The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except as indicated with respect to Class B and Class C shares). The Example reflects Class B shares converting into Investor Class shares in years 9-10; fees could be lower if you are eligible to convert to Class A shares instead. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example, By Year, Caption	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Investment Strategy, Heading	rr_StrategyHeading	Principal Investment Strategies
Investment Strategy, Narrative	rr_StrategyNarrativeTextBlock	The Fund invests in those companies that meet the quality and valuation criteria of Madison Square Investors LLC, the Fund's Subadvisor. The Fund normally invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in equity securities of issuers, wherever organized, which do business mainly outside the U.S. It invests in securities of companies which do business in a variety of countries, with a minimum of five countries other than the U.S. This includes countries with established economies as well as emerging market countries that the Subadvisor believes present favorable opportunities. The Fund may also invest in exchange traded funds ("ETFs"). Investment Process: The Subadvisor seeks to identify investment opportunities through "bottom-up" analysis and fundamental research. The Subadvisor performs research to identify reasonably priced companies with competitive market advantages that it believes are able to benefit from long-term market trends and that the Subadvisor believes are able to sustainably grow earnings over time regardless of economic climate. Allocations to countries and industries are also a result of the "bottom-up" stock selection process and, as a result, may deviate from the country and industry weightings in the benchmark. The Fund may not perform as well as its peers or benchmark during periods when the stock market favors the securities of businesses with low-quality earnings. Generally, the Fund seeks to limit its investments in securities of: (i) any one company; (ii) companies in the same industry; (iii) companies located in any one country; and (iv) countries located in emerging markets. The Subadvisor may sell a security if it no longer believes the security will contribute to meeting the investment objective of the Fund. In considering whether to sell a security, the Subadvisor may evaluate, among other things, whether the security has reached its target price, if the investment thesis is invalidated, if superior opportunities to redeploy exist or emerge, or if sector weights or individual positions need to be rebalanced.
Risk, Heading	rr_RiskHeading	Principal Risks
Risk, Narrative	rr_RiskNarrativeTextBlock	Loss of Money Risk: Before considering an investment in the Fund, you should understand that you could lose money. Market Changes Risk: The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests, which could cause the Fund to underperform other funds with similar objectives. From time to time, markets may experience periods of acute stress that may result in increased volatility. Such market conditions tend to add significantly to the risk of short-term volatility in the net asset value of the Fund's shares. Management Risk: The investment strategies, practices and risk analysis used by the Fund's Subadvisor may not produce the desired results. 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 manager's ability to anticipate such changes that can adversely affect the value of the Fund's holdings. Opportunity for greater gain often comes with greater risk of loss. Foreign Securities Risk: Investments in foreign securities may be riskier than investments in U.S. securities. Differences between U.S. and foreign regulatory regimes and securities markets, including less stringent investor protections and disclosure standards of some foreign markets, less liquid trading markets, as well as political and economic developments in foreign countries, 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. 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, risk of loss resulting from problems in share registration and custody, substantial economic and political disruptions and the nationalization of foreign deposits or assets. 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. Exchange Traded Fund Risk: The risks of owning an ETF generally reflect the risks of owning the underlying securities they are designed to track, although lack of liquidity in an ETF could result in it being more volatile than the underlying portfolio of 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 that increase their costs versus the costs of owning the underlying securities directly.
Risk, Lose Money	rr_RiskLoseMoney	Before considering an investment in the Fund, you should understand that you could lose money.
Bar Chart and Performance Table, Heading	rr_BarChartAndPerformanceTableHeading	Past Performance
Performance, Narrative	rr_PerformanceNarrativeTextBlock	The following bar chart and tables 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 the last ten years. Sales loads 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) for the one-, five- and ten-year periods 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 figures for Class I, R1 and R2 shares, first offered on January 2, 2004, include the historical performance of Class B shares through January 1, 2004. Performance figures for Class R3 shares, first offered on April 28, 2006, include the historical performance of Class B shares through April 27, 2006. Performance figures for Investor Class shares, first offered on February 28, 2008, include the historical performance of Class A shares through February 27, 2008. The performance for newer share classes is adjusted for differences in fees and expenses. Unadjusted, the performance shown for the newer classes might have been lower. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Please visit mainstayinvestments.com for more recent performance information.
Performance, Information Illustrates Variability of Returns	rr_PerformanceInformationIllustratesVariabilityOfReturns	The following bar chart and tables indicate some of the risks of investing in the Fund.
Performance, Availability Website Address	rr_PerformanceAvailabilityWebSiteAddress	mainstayinvestments.com
Performance, Past Does Not Indicate Future	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 B Shares (by calendar year 2002-2011)
Bar Chart, Narrative	rr_BarChartNarrativeTextBlock	The bar chart shows you how the Fund's calendar year performance has varied over the last ten years. Sales loads are not reflected in the bar chart. If they were, returns would be less than those shown.
Bar Chart, Does Not Reflect Sales Loads	rr_BarChartDoesNotReflectSalesLoads	Sales loads are not reflected in the bar chart. If they were, returns would be less than those shown.
Bar Chart, Closing	rr_BarChartClosingTextBlock	Best Quarter     2Q/03    17.23 % Worst Quarter    3Q/11   -19.57 %
Index No Deduction for Fees, Expenses, Taxes	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 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 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.
Performance Table, One Class of after Tax Shown	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns shown are for Class B 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	rr_PerformanceTableClosingTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. 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 B shares. After-tax returns for the other share classes may vary.
Average Annual Returns, Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns (for the periods ended December 31, 2011)
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | MSCI EAFE® Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	MSCI EAFE® Index (reflects no deductions for fees, expenses, or taxes)
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(12.14%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.72%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.67%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Investor Class
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none	[1]
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.54%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.71%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	714
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	1,059
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,427
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,458
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Investor Class Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(21.47%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(5.62%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.44%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class A
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none	[1]
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.29%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.46%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	690
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	986
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,304
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,200
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class A Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(21.31%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(5.43%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.55%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class B
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	5.00%
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.54%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.46%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	749
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	1,067
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,511
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,611
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	249
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	767
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,311
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,611
Annual Return 2002	rr_AnnualReturn2002	(4.95%)
Annual Return 2003	rr_AnnualReturn2003	31.11%
Annual Return 2004	rr_AnnualReturn2004	15.74%
Annual Return 2005	rr_AnnualReturn2005	6.22%
Annual Return 2006	rr_AnnualReturn2006	29.58%
Annual Return 2007	rr_AnnualReturn2007	3.55%
Annual Return 2008	rr_AnnualReturn2008	(26.45%)
Annual Return 2009	rr_AnnualReturn2009	17.29%
Annual Return 2010	rr_AnnualReturn2010	3.44%
Annual Return 2011	rr_AnnualReturn2011	(17.56%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2003
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	17.23%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(19.57%)
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class B Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(21.61%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(5.60%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.22%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class B | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class B Return After Taxes on Distributions
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(21.48%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(6.28%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.68%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class B | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class B Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(13.35%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.56%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.79%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class C
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.54%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.46%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	349
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	767
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,311
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,796
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	249
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	767
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,311
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,796
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class C Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(18.37%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(5.27%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.23%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class I
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.29%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.21%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	123
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	384
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	665
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,466
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class I Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(16.47%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.01%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.56%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R1
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.39%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.31%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	133
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	415
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	718
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,579
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class R1 Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(16.57%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.10%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.41%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R2
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[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	1.55%
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
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class R2 Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(16.78%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.35%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.19%
MainStay International Equity Fund (Prospectus Summary) | MainStay International Equity Fund | Class R3
Risk Return [Abstract]	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_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fees (as an annual percentage of the Fund's average daily net assets)	rr_ManagementFeesOverAssets	0.92%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses	rr_OtherExpensesOverAssets	0.38%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.80%
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	183
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	566
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	975
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,116
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class R3 Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	(17.02%)
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	(4.59%)
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	4.84%

[1] A contingent deferred sales charge of 1.00% may be imposed on certain redemptions made within one year of the date of purchase on shares that were purchased without an initial sales charge.

[2] The management fee is as follows: 0.90% on assets up to $500 million and 0.85% on assets in excess of $500 million, plus a fee for fund accounting services previously provided by New York Life Investment Management LLC ("New York Life Investments") under a separate fund accounting agreement. This addition to the management fee amounted to 0.02% of the Fund's average daily net assets, but did not result in a net increase in the Fund's Total Annual Fund Operating Expenses.