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MainStay MacKay Total Return Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MainStay MacKay Total Return Bond 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 129 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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Feb. 28, 2021
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 100% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 100.00%
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

The Fund, under normal circumstances, invests at least 80% of its assets (net assets plus any borrowings for investment purposes) in bonds, which include all types of debt securities, such as: debt or debt-related securities issued or guaranteed by the U.S. or foreign governments, their agencies or instrumentalities; obligations of international or supranational entities; debt securities issued by U.S. or foreign corporate entities; zero coupon bonds; municipal bonds; mortgage-related and other asset-backed securities; and loan participation interests. The Fund will generally seek to maintain a weighted average duration within 2.5 years (plus or minus) of the duration of the Bloomberg Barclays U.S. Aggregate Bond Index. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates. As of December 31, 2019, the weighted average duration of the Fund and Bloomberg Barclays U.S. Aggregate Bond Index were 6.05 years and 5.85 years, respectively.


The Fund, under normal circumstances, will invest at least 65% percent of its total assets in investment grade debt securities, as rated by a nationally recognized statistical rating organization (“NRSRO”) when purchased, or if unrated, determined by MacKay Shields LLC, the Fund’s Subadvisor, to be of comparable quality. The Fund may also invest up to 30% of its total assets in securities rated below investment grade by a NRSRO (such securities rated lower than BBB- and Baa3) or, if unrated, determined by the Subadvisor to be of comparable quality. Securities that are rated below investment grade by NRSROs are commonly referred to as “high-yield securities” or "junk bonds." If NRSROs assign different ratings for the same security, the Fund will use the higher rating for purposes of determining the credit quality. The Fund may invest in mortgage dollar rolls, to-be-announced ("TBA") securities transactions, variable rate notes and floating rate notes.


The Fund may invest up to 20% of its total assets in securities denominated in foreign currencies. To the extent possible, the Fund will attempt to protect these investments against risks stemming from differences in foreign exchange rates.


The Fund may also invest in derivatives such as futures, options and swap agreements to try to enhance returns or reduce the risk of loss by hedging certain of its holdings. Commercial paper must be, when purchased, rated in the highest rating category by a NRSRO or if unrated, determined by the Subadvisor to be of comparable quality. The Fund's principal investments may have fixed or floating rates of interest.


Investment Process: In pursuing the Fund's investment strategy, the Subadvisor conducts a continuing review of yields and other information derived from a database which it maintains in managing fixed-income portfolios.


Fundamental economic cycle analysis, credit quality and interest rate trends are the principal factors considered by the Subadvisor in managing the Fund and determining whether to increase or decrease the emphasis placed upon a particular type of security or industry sector within the Fund's investment portfolio. Maturity duration shifts adjustments are based on a set of investment decisions that take into account a broad range of economic, fundamental and technical indicators.


The Subadvisor may sell a security if it no longer believes that 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, the condition of the economy, meaningful changes in the issuer's financial condition, and changes in the condition and outlook in the issuer's industry.
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.


Yield Risk: There can be no guarantee that the Fund will achieve or maintain any particular level of yield.


Debt Securities Risk: The risks of investing in debt or fixed-income securities include (without limitation): (i) credit risk, e.g., the issuer or guarantor of a debt security may be unable or unwilling (or be perceived as unable or unwilling) to make timely principal and/or interest payments or otherwise honor its obligations, or changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may affect the value of the Fund’s investments; (ii) maturity risk, e.g., a debt security with a longer maturity may fluctuate in value more than one with a shorter maturity; (iii) market risk, e.g., low demand for debt securities may negatively impact their price; (iv) interest rate risk, e.g., when interest rates go up, the value of a debt security generally goes down, and when interest rates go down, the value of a debt security generally goes up (long-term debt securities are generally more susceptible to interest rate risk than short-term debt securities); and (v) call or prepayment risk, e.g., during a period of falling interest rates, the issuer may redeem a security by repaying it early, which may reduce the Fund’s income if the proceeds are reinvested at lower interest rates.


Interest rate risk is the risk that the value of the Fund’s investments in fixed income or debt securities will change because of changes in interest rates. There is a risk that interest rates across the financial system may change, possibly significantly and/or rapidly. Changes in interest rates or a lack of market participants may lead to decreased liquidity and increased volatility in the fixed-income or debt markets, making it more difficult for the Fund to sell its fixed-income or debt holdings. Decreased liquidity in the fixed-income or debt markets also may make it more difficult to value some or all of the Fund’s fixed-income or debt holdings. For most fixed-income investments, when market interest rates fall, prices of fixed-rate debt securities rise. However, when market interest rates fall, prices of certain variable and fixed-rate debt securities may be adversely affected (i.e., falling interest rates bring the possibility of prepayment risk, as an instrument may be redeemed before maturity).


Not all U.S. government debt securities are guaranteed by the U.S. government—some are backed only by the issuing agency, which must rely on its own resources to repay the debt. The Fund's yield will fluctuate with changes in short-term interest rates.


Zero Coupon Bond Risk: Because zero-coupon securities bear no interest and compound semi-annually at the rate fixed at the time of issuance, their value generally is more volatile than the value of other fixed-income securities. An investment in zero-coupon and delayed interest securities may cause the Fund to recognize income, and therefore the Fund may be required to make distributions to shareholders before the Fund receives any cash payments on its investment.


Municipal Bond Risk: Municipal bond risks include the inability of the issuer to repay the obligation, the relative lack of information about certain issuers, and the possibility of future tax and legislative changes, which could affect the market for and value of municipal securities. Municipalities continue to experience economic and financial difficulties in the current economic environment. The ability of a municipal issuer to make payments and the value of municipal bonds can be affected by uncertainties in the municipal securities market. Such uncertainties could cause increased volatility in the municipal securities market and could negatively impact the Fund’s net asset value.


Loan Participation Interest Risk: There may not be a readily available market for loan participation interests, which in some cases could result in the Fund disposing of such interests at a substantial discount from face value or holding such interests until maturity. In addition, the Fund may be exposed to the credit risk of the underlying corporate borrower as well as the lending institution or other participant from whom the Fund purchased the loan participation interests. The Fund may not always have direct recourse against a borrower if the borrower fails to pay scheduled principal and/or interest and may be subject to greater delays, expenses and risks than if the Fund had purchased a direct obligation of the borrower. Substantial increases in interest rates may cause an increase in loan obligation defaults.


High-Yield Securities Risk: Investments in high-yield securities or non-investment grade securities (commonly referred to as "junk bonds") are considered speculative because investments in such securities present a greater risk of loss than investments in higher quality securities. Such securities may, under certain circumstances, be less liquid than higher rated securities. These securities pay investors a premium (a high interest rate or yield) because of the potential illiquidity and increased risk of loss. These securities can also be subject to greater price volatility. In times of unusual or adverse market, economic or political conditions, these securities may experience higher than normal default rates.


TBA Securities Risk: In a TBA securities transaction, the Fund commits to purchase certain securities for a fixed price at a future date. The principal risks of a TBA securities transaction are that the counterparty may not deliver the security as promised and/or that the value of the TBA security may decline prior to when the Fund receives the security.


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.


Mortgage-Related and Other Asset-Backed Securities Risk: Investments in mortgage-related securities (such as mortgage-backed securities) and other asset-backed securities generally involve a stream of payments based on the underlying obligations. These payments, which are often part interest and part return of principal, vary based on the rate at which the underlying borrowers repay their loans or other obligations. Asset-backed securities are subject to the risk that borrowers may default on the underlying obligations and that, during periods of falling interest rates, these obligations may be called or prepaid and, during periods of rising interest rates, obligations may be paid more slowly than expected. Impairment of the underlying obligations or collateral, such as by non-payment, will reduce the security's value. Enforcing rights against such collateral in events of default may be difficult or insufficient. The value of these securities may be significantly affected by changes in interest rates, the market's perception of issuers, and the creditworthiness of the parties involved. The ability of the Fund to successfully utilize these instruments may depend on the ability of the Subadvisor to forecast interest rates and other economic factors correctly. These securities may have a structure that makes their reaction to interest rate changes and other factors difficult to predict, making their value highly volatile.


Floating Rate Notes and Variable Rate Notes Risk: Floating and variable rate notes provide for a periodic adjustment in the interest rate paid on the securities. The rate adjustment intervals may be regular and range from daily up to annually, or may be based on an event, such as a change in the prime rate. Floating and variable rate notes may be subject to greater liquidity risk than other debt securities, meaning that there may be limitations on the Fund's ability to sell the securities at any given time. Securities with floating interest rates generally are less sensitive to interest rate changes, but may decline in value if their interest rates do not rise as much or as fast as interest rates in general. The terms of many floating rate notes and other instruments are tied to the London Interbank Offered Rate (“LIBOR”), which functions as a reference rate or benchmark. It is anticipated that LIBOR will be discontinued at the end of 2021, which may cause increased volatility and illiquidity in the markets for instruments with terms tied to LIBOR or other adverse consequences for these instruments. These events may adversely affect the Fund and its investments in such instruments.


Derivatives Risk: Derivatives are investments whose value depends on (or is derived from) the value of an underlying instrument, such as a security, asset, reference rate or index. Derivative strategies may expose the Fund to greater risk than if it had invested directly in the underlying instrument and often involve leverage, which may exaggerate a loss, potentially causing the Fund to lose more money than it originally invested and would have lost had it invested directly in the underlying instrument. For example, if the Fund is the seller of credit protection in a credit default swap, the Fund effectively adds leverage to its portfolio and is subject to the credit exposure on the full notional value of the swap. Derivatives may be difficult to sell, unwind or value. Derivatives may also be subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Fund. Futures may be more volatile than direct investments in the instrument underlying the contract, and may not correlate perfectly to the underlying instrument. Futures and other derivatives also may involve a small initial investment relative to the risk assumed, which could result in losses greater than if they had not been used. Due to fluctuations in the price of the underlying asset, the Fund may not be able to profitably exercise an option and may lose its entire investment in an option. Swaps may be subject to counterparty credit, correlation, valuation, liquidity and leveraging risks. Swap transactions tend to shift a Fund's investment exposure from one type of investment to another and may entail the risk that a party will default on its payment obligations to the Fund. Additionally, applicable regulators have adopted rules imposing certain margin requirements, including minimums on uncleared swaps, which may result in the Fund and its counterparties posting higher margin amounts for uncleared swaps. Certain standardized swaps are subject to mandatory central clearing and exchange trading. Central clearing, which interposes a central clearinghouse to each participant’s swap, and exchange trading are intended to reduce counterparty credit risk and increase liquidity but neither makes swap transactions risk-free. Derivatives may also increase the expenses of the Fund.


Mortgage Dollar Roll Transaction Risk: A mortgage dollar roll is a transaction in which the Fund sells mortgage-related securities from its portfolio to a counterparty from whom it simultaneously agrees to buy a similar security on a delayed delivery basis. Mortgage dollar roll transactions are subject to certain risks, including the risk that securities returned to the Fund at the end of the roll, while substantially similar, may be inferior to what was initially sold to the counterparty.


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.


Money Market/Short-Term Securities Risk: To the extent the Fund holds cash or invests in money market or short-term securities, the Fund may be less likely to achieve its investment objective. In addition, it is possible that the Fund's investments in these instruments could lose money.
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 Bloomberg Barclays U.S. Aggregate Bond Index as its primary benchmark. The Bloomberg Barclays U.S. Aggregate Bond Index is a broad-based benchmark that measures the investment grade, U.S. dollar-denominated, fixed-rate taxable bond market, including Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate and hybrid adjustable rate mortgage pass-throughs), asset-backed securities, and commercial mortgage-backed securities.


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 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

3.73

%

Worst Quarter

 

2Q/13

-2.72

%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.73%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.72%)
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 MacKay Total Return Bond Fund | Bloomberg Barclays U.S. Aggregate Bond Index (reflects no deductions for fees, expenses, or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.72%
5 Years or Since Inception rr_AverageAnnualReturnYear05 3.05%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.75%
MainStay MacKay Total Return Bond Fund | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
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 0.49% [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 0.89%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 0.88% [3]
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 $ 536
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 720
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 920
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,496
1 Year rr_AverageAnnualReturnYear01 4.26%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.84%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.51%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 02, 2004
MainStay MacKay Total Return Bond Fund | Investor Class  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
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 0.49% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.06%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 1.05% [3]
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 $ 552
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 771
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,008
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,685
1 Year rr_AverageAnnualReturnYear01 4.04%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.79%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.42%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 28, 2008
MainStay MacKay Total Return Bond Fund | Class B  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [4]
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOther 5.00% [4]
Management Fees (as an annual percentage of the Fund's average daily net assets) rr_ManagementFeesOverAssets 0.49% [2],[4]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00% [4]
Other Expenses rr_OtherExpensesOverAssets 0.32% [4]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.81% [4]
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3],[4]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 1.80% [3],[4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 683
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 868
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,179
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,929
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 183
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 568
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 979
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,929
1 Year rr_AverageAnnualReturnYear01 3.16%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.60%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.13%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 02, 2004
MainStay MacKay Total Return Bond 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 0.49% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.81%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 1.80% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 283
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 568
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 979
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,126
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 183
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 568
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 979
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,126
1 Year rr_AverageAnnualReturnYear01 7.05%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.97%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.12%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 02, 2004
MainStay MacKay Total Return Bond 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 0.49% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.64%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.04%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 0.60% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 61
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 201
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 353
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 795
Annual Return 2010 rr_AnnualReturn2010 8.40%
Annual Return 2011 rr_AnnualReturn2011 7.37%
Annual Return 2012 rr_AnnualReturn2012 8.08%
Annual Return 2013 rr_AnnualReturn2013 (0.79%)
Annual Return 2014 rr_AnnualReturn2014 4.76%
Annual Return 2015 rr_AnnualReturn2015 (1.46%)
Annual Return 2016 rr_AnnualReturn2016 4.80%
Annual Return 2017 rr_AnnualReturn2017 4.63%
Annual Return 2018 rr_AnnualReturn2018 (1.23%)
Annual Return 2019 rr_AnnualReturn2019 9.38%
1 Year rr_AverageAnnualReturnYear01 9.38%
5 Years or Since Inception rr_AverageAnnualReturnYear05 3.14%
10 Years or Since Inception rr_AverageAnnualReturnYear10 4.32%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 02, 1991
MainStay MacKay Total Return Bond Fund | Class I | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.10%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.91%
10 Years or Since Inception rr_AverageAnnualReturnYear10 2.86%
MainStay MacKay Total Return Bond Fund | Class I | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years or Since Inception rr_AverageAnnualReturnYear05 1.84%
10 Years or Since Inception rr_AverageAnnualReturnYear10 2.74%
MainStay MacKay Total Return Bond 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 0.49% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.74%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 0.73% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 75
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 236
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 410
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 917
1 Year rr_AverageAnnualReturnYear01 9.36%
5 Years or Since Inception rr_AverageAnnualReturnYear05 3.04%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.06%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2012
MainStay MacKay Total Return Bond 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 0.49% [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 0.99%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 0.98% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 100
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 314
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 546
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,212
1 Year rr_AverageAnnualReturnYear01 9.00%
5 Years or Since Inception rr_AverageAnnualReturnYear05 2.74%
10 Years or Since Inception rr_AverageAnnualReturnYear10 2.79%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 29, 2012
MainStay MacKay Total Return Bond 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 0.49% [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 1.24%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 1.23% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 125
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 392
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 680
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,499
1 Year rr_AverageAnnualReturnYear01 8.83%
5 Years or Since Inception rr_AverageAnnualReturnYear05 3.59%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 29, 2016
MainStay MacKay Total Return Bond 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 0.49% [2]
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.05%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.54%
Waivers / Reimbursements rr_FeeWaiverOrReimbursementOverAssets none [3]
Total Annual Fund Operating Expenses After Waivers / Reimbursements rr_NetExpensesOverAssets 0.54% [3]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 55
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 173
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 302
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 677
1 Year rr_AverageAnnualReturnYear01 9.55%
5 Years or Since Inception rr_AverageAnnualReturnYear05 3.21%
10 Years or Since Inception rr_AverageAnnualReturnYear10 3.23%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 29, 2014
[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: 0.50% on assets up to $1 billion; 0.475% on assets from $1 billion to $3 billion; and 0.465% on assets over $3 billion.
[3] New York Life Investment Management LLC ("New York Life Investments") has contractually agreed to waive fees and/or reimburse expenses so that Total Annual Fund Operating Expenses (excluding taxes, interest, litigation, extraordinary expenses, brokerage and other transaction expenses relating to the purchase or sale of portfolio investments, and acquired (underlying) fund fees and expenses) of a class do not exceed the following percentages of its average daily net assets: Class A, 0.88%; and Class I, 0.60%. New York Life Investments will apply an equivalent waiver or reimbursement, in an equal number of basis points of the Class A shares waiver/reimbursement to Investor Class shares, Class B shares, Class C shares, Class R1 shares, Class R2 shares and Class R3 shares. In addition, New York Life Investments will waive fees and/or reimburse expenses so that Total Annual Fund Operating Expenses (excluding taxes, interest, litigation, extraordinary expenses, brokerage and other transaction expenses relating to the purchase or sale of portfolio investments, and acquired (underlying) fund fees and expenses) of Class R6 do not exceed those of Class I. This agreement will remain in effect until February 28, 2021, and shall renew automatically for one-year terms unless New York Life Investments provides written notice of termination prior to the start of the next term or upon approval of the Board of Trustees of the Fund.
[4] Class B shares are closed to all new purchases as well as additional investments by existing Class B shareholders.