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MainStay Winslow Large Cap Growth Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MainStay Winslow Large Cap Growth Fund (formerly known as MainStay Large Cap Growth Fund)
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital.
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 54% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 54.00%
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 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. 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

Under normal circumstances, the Fund invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in large capitalization companies, which are companies having a market capitalization in excess of $4 billion at the time of purchase. Typically, Winslow Capital Management, LLC, the Fund's Subadvisor, invests substantially all of the Fund's investable assets in domestic securities. However, the Fund is permitted to invest up to 20% of its net assets in foreign securities, which are generally securities issued by companies organized outside the United States or that trade primarily in non-U.S. securities markets.


Investment Process: The Fund invests in those companies that the Subadvisor believes will provide an opportunity for achieving superior portfolio returns (i.e., returns in excess of the returns of the average stock mutual fund) over the long term. The Subadvisor seeks to invest in companies that have the potential for above-average future earnings and cash flow growth with management focused on shareholder value.


When purchasing stocks for the Fund, the Subadvisor looks for companies typically having some or all of the following attributes: addressing markets with growth opportunities; leads or gains in market share; identifiable and sustainable competitive advantages; managed by a team that can perpetuate the firm's competitive advantages; high, and preferably rising, returns on invested capital; deploys excess cash flow to enhance shareholder return; and demonstrates sound corporate governance. The Subadvisor may give consideration to certain environmental, social, and governance (“ESG”) criteria when evaluating an investment opportunity.


The Subadvisor takes a "bottom-up" investment approach when selecting investments. This means it bases investment decisions on company specific factors, not general economic conditions.


Under normal market conditions, the Subadvisor employs a sell discipline pursuant to which it may sell some or all of its position in a stock when a stock becomes fully valued, the fundamental business prospects are deteriorating, or the position exceeds limits set by the Subadvisor.
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. The Subadvisor may give consideration to certain ESG criteria when evaluating an investment opportunity. The application of ESG criteria may result in the Fund (i) having exposure to certain securities or industry sectors that are significantly different than the composition of the Fund's benchmark; and (ii) performing differently than other funds and strategies in its peer group that do not take into account ESG criteria or the Fund's benchmark.


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.


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.


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. These risks may be greater with respect to securities of companies that conduct their business activities in emerging markets or whose securities are traded principally in emerging markets.
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 two broad-based securities market indices. The Fund has selected the Russell 1000® Growth Index as its primary benchmark. The Russell 1000® Growth Index measures the performance of the large-cap growth segment of the U.S. equity universe. It includes those Russell 1000® Index companies with higher price-to-book ratios and higher forecasted growth values. The Fund has selected the Standard & Poor’s 500® Index (“S&P 500® Index”) as its secondary benchmark. The S&P 500® Index is widely regarded as the standard index for measuring large-cap U.S. stock market performance.


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.
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 Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The Fund has selected the Standard & Poor’s 500® Index (“S&P 500® Index”) as its secondary benchmark. The S&P 500® Index is widely regarded as the standard index for measuring large-cap U.S. stock market 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 Footnotes [Text Block] rr_BarChartFootnotesTextBlock

*Previously, the bar chart presented the Fund's annual returns for Class A shares. Class I shares are presented for consistency across the MainStay Fund complex.

Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
   

Best Quarter

 

1Q/19

17.58

%

Worst Quarter

 

4Q/18

-15.98

%
Bar Chart, Reason Selected Class Different from Immediately Preceding Period [Text] rr_BarChartReasonSelectedClassDifferentFromImmediatelyPrecedingPeriod Previously, the bar chart presented the Fund's annual returns for Class A shares. Class I shares are presented for consistency across the MainStay Fund complex.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 17.58%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (15.98%)
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 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 [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 Winslow Large Cap Growth Fund | Russell 1000® Growth Index (reflects no deductions for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 36.39%
5 Years rr_AverageAnnualReturnYear05 14.63%
10 Years or Since Inception rr_AverageAnnualReturnYear10 15.22%
MainStay Winslow Large Cap Growth Fund | S&P 500® Index (reflects no deductions for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years or Since Inception rr_AverageAnnualReturnYear10 13.56%
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.12%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.99%
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 $ 645
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 848
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,067
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,696
1 Year rr_AverageAnnualReturnYear01 26.06%
5 Years rr_AverageAnnualReturnYear05 12.20%
10 Years or Since Inception rr_AverageAnnualReturnYear10 13.24%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 01, 1995
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.23%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.10%
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 $ 656
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 880
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,123
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,816
1 Year rr_AverageAnnualReturnYear01 25.83%
5 Years rr_AverageAnnualReturnYear05 12.07%
10 Years or Since Inception rr_AverageAnnualReturnYear10 13.15%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 28, 2008
MainStay Winslow Large Cap Growth Fund | Class B  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [3]
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 5.00% [3]
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.62% [2],[3]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00% [3]
Other Expenses rr_OtherExpensesOverAssets 0.23% [3]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.85% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 688
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 882
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,201
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,973
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 188
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 582
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,001
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,973
1 Year rr_AverageAnnualReturnYear01 27.07%
5 Years rr_AverageAnnualReturnYear05 12.32%
10 Years or Since Inception rr_AverageAnnualReturnYear10 12.96%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 01, 2005
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.23%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.85%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 288
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 582
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,001
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,169
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 188
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 582
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,001
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,169
1 Year rr_AverageAnnualReturnYear01 31.18%
5 Years rr_AverageAnnualReturnYear05 12.51%
10 Years or Since Inception rr_AverageAnnualReturnYear10 12.95%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 01, 2005
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.12%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 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 2010 rr_AnnualReturn2010 15.65%
Annual Return 2011 rr_AnnualReturn2011 (0.19%)
Annual Return 2012 rr_AnnualReturn2012 13.21%
Annual Return 2013 rr_AnnualReturn2013 36.94%
Annual Return 2014 rr_AnnualReturn2014 10.54%
Annual Return 2015 rr_AnnualReturn2015 6.17%
Annual Return 2016 rr_AnnualReturn2016 (2.28%)
Annual Return 2017 rr_AnnualReturn2017 32.39%
Annual Return 2018 rr_AnnualReturn2018 3.74%
Annual Return 2019 rr_AnnualReturn2019 33.67%
1 Year rr_AverageAnnualReturnYear01 33.67%
5 Years rr_AverageAnnualReturnYear05 13.75%
10 Years or Since Inception rr_AverageAnnualReturnYear10 14.19%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 01, 2005
MainStay Winslow Large Cap Growth Fund | Class I | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 30.54%
5 Years rr_AverageAnnualReturnYear05 10.30%
10 Years or Since Inception rr_AverageAnnualReturnYear10 12.02%
MainStay Winslow Large Cap Growth Fund | Class I | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 22.00%
5 Years rr_AverageAnnualReturnYear05 10.22%
10 Years or Since Inception rr_AverageAnnualReturnYear10 11.37%
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.22%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.84%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 86
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 268
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 466
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,037
1 Year rr_AverageAnnualReturnYear01 33.46%
5 Years rr_AverageAnnualReturnYear05 13.64%
10 Years or Since Inception rr_AverageAnnualReturnYear10 14.05%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 01, 2005
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.22%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.09%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 111
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 347
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 601
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,329
1 Year rr_AverageAnnualReturnYear01 33.16%
5 Years rr_AverageAnnualReturnYear05 13.33%
10 Years or Since Inception rr_AverageAnnualReturnYear10 13.78%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 01, 2005
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.22%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 136
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 425
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 734
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,613
1 Year rr_AverageAnnualReturnYear01 32.82%
5 Years rr_AverageAnnualReturnYear05 13.06%
10 Years or Since Inception rr_AverageAnnualReturnYear10 13.48%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 28, 2006
MainStay Winslow Large Cap Growth 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 0.62% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.02%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.64%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 65
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 357
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 798
1 Year rr_AverageAnnualReturnYear01 33.87%
5 Years rr_AverageAnnualReturnYear05 13.87%
10 Years or Since Inception rr_AverageAnnualReturnYear10 15.51%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 17, 2013
[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: 0.75% on assets up to $500 million; 0.725% on assets from $500 million to $750 million; 0.71% on assets from $750 million to $1 billion; 0.70% on assets from $1 billion to $2 billion; 0.66% on assets from $2 billion to $3 billion; 0.61% on assets from $3 billion to $7 billion; 0.585% on assets from $7 billion to $9 billion; and 0.575% on assets over $9 billion.
[3] Class B shares are closed to all new purchases as well as additional investments by existing Class B shareholders.