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High Yield Portfolio  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading High Yield Portfolio
Objective [Heading] rr_ObjectiveHeading Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The High Yield Portfolio (the "Portfolio") seeks total return.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
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 Portfolio. For purchases of Class A shares, you may qualify for a sales charge discount if the cumulative net asset value per share ("NAV") of Class A shares of the Portfolio being purchased in a single transaction, together with the NAV of any Class A, Class L and Class C shares of the Portfolio of Morgan Stanley Institutional Fund Trust (the "Fund") already held in Related Accounts (as defined in the section of the Prospectus entitled "Shareholder Information—Sales Charges Applicable to Purchases of Class A Shares") as of the date of the transaction as well as Class A, Class B, Class L and Class C shares of any other Morgan Stanley Multi-Class Fund (as defined in the section of the Prospectus entitled "Shareholder Information—Exchange Privilege") and including shares of Morgan Stanley Money Market Funds (as defined in the section of the Prospectus entitled "Shareholder Information—Exchange Privilege") that you acquired in an exchange of Class A shares of the Portfolio or Class A shares of another Morgan Stanley Multi-Class Fund already held in Related Accounts as of the date of the transaction, amounts to $25,000 or more. More information about this combined purchase discount and other discounts is available from your financial intermediary, on page 58 of the Prospectus in the section entitled "Shareholder Information—Sales Charges Applicable to Purchases of Class A Shares" and in Appendix A attached to the Prospectus.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Portfolio 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 Portfolio pays transaction costs 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 Portfolio shares are held in a taxable account. These costs, which are not reflected in Total Annual Portfolio Operating Expenses or in the Example, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 74% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 74.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The example below is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds.


The example assumes that you invest $10,000 in the Portfolio, your investment has a 5% return each year and that the Portfolio's operating expenses remain the same (except that the example incorporates the fee waiver and/or expense reimbursement arrangement for only the first year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption If You SOLD Your Shares:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption If You HELD Your Shares
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal circumstances, at least 80% of the Portfolio's assets will be invested in high yield securities (commonly referred to as "junk bonds"). This policy may be changed without shareholder approval; however, you would be notified upon 60 days' notice in writing of any changes. The Portfolio seeks to achieve its investment objective by investing primarily in high yield securities which are fixed income securities rated below Baa3 by Moody's Investors Service, Inc. ("Moody's"), below BBB- by S&P Global Ratings Group, a division of S&P Global Inc. ("S&P"), below BBB- by Fitch Ratings, Inc. ("Fitch") or if unrated considered by the Adviser to be of equivalent quality. The average maturity of the Portfolio's investments varies, and there is no limit on the maturity or on the credit quality of any security held by the Portfolio. The Portfolio's securities may include distressed and defaulted securities and mezzanine investments. The Portfolio also may invest in investment grade fixed income securities, including U.S. and foreign government securities, corporate bonds and collateralized bond obligations. The Portfolio may also invest in preferred securities, equity securities and convertible securities.


The Portfolio's investment process starts with top-down macroeconomic analysis to assess the optimal positioning of the Portfolio. The team then applies a combination of quantitative and qualitative filters to identify securities that meet the team's investment criteria in terms of competitive position, franchise value and management quality. The investment team's credit analysis focuses on financial risk, business risk, management ability and intentions. Valuation analysis is used to narrow the screened investment universe to a pool of investment candidates who are then assessed in order to determine relative valuation. Finally, the Portfolio is constructed with sector allocation driven primarily from bottom-up security selection. Integral to the Portfolio construction process is the measurement and monitoring of market risk, duration and volatility and credit risk through the use of proprietary risk measures and models.


The Portfolio may invest in public bank loans made by banks or other financial institutions. Public bank loans are privately negotiated loans that are not publicly traded for which information about the issuer has been made publicly available. These public bank loans may be rated investment grade or below investment grade. The Portfolio may also invest in restricted and illiquid securities.


The Portfolio may, but it is not required to, use derivative instruments for a variety of purposes, including hedging, risk management, portfolio management or to earn income. The Portfolio's use of derivatives may involve the purchase and sale of derivative instruments such as futures, options, swaps and other related instruments and techniques. The Portfolio may utilize foreign currency forward exchange contracts, which are also derivatives, in connection with its investments in foreign securities. Derivative instruments used by the Portfolio will be counted towards the 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

There is no assurance that the Portfolio will achieve its investment objective, and you can lose money investing in this Portfolio. The principal risks of investing in the Portfolio include:


•  Fixed Income Securities. Fixed income securities are subject to the risk of the issuer's inability to meet principal and interest payments on its obligations (i.e., credit risk) and are subject to price volatility resulting from, among other things, interest rate sensitivity, market perception of the creditworthiness of the issuer and general market liquidity (i.e., market risk). The historically low interest rate environment increases the risk associated with rising interest rates, including the potential for periods of volatility and increased redemptions. The Portfolio may face a heightened level of interest rate risk, especially since the Federal Reserve Board has ended its quantitative easing program and has begun to raise rates. The Portfolio is not limited as to the maturities of the securities in which it may invest. The Portfolio may be subject to certain liquidity risks that may result from the lack of an active market and the reduced number and capacity of traditional market participants to make a market in fixed-income securities. Securities with longer durations are likely to be more sensitive to changes in interest rates, generally making them more volatile than securities with shorter durations. Lower rated fixed income securities have greater volatility because there is less certainty that principal and interest payments will be made as scheduled. A portion of the Portfolio's fixed income securities may be rated below investment grade. To the extent that the Portfolio invests in convertible securities, and the convertible security's investment value is greater than its conversion value, its price will be likely to increase when interest rates fall and decrease when interest rates rise. If the conversion value exceeds the investment value, the price of the convertible security will tend to fluctuate directly with the price of the underlying security.


•  High Yield Securities ("Junk Bonds"). High yield securities offer a higher yield than other, higher rated securities, but they carry a greater degree of risk and are considered speculative by the major credit rating agencies. High yield securities may be issued by companies that are restructuring, are smaller and less creditworthy, or are more highly indebted than other companies. This means that they may have more difficulty making scheduled payments of principal and interest.


  Changes in the value of high yield securities are influenced more by changes in the financial and business position of the issuing company than by changes in interest rates when compared to investment grade securities. Lower rated fixed income securities have greater volatility because there is less certainty that principal and interest payments will be made as scheduled. Prices of fixed income securities generally will move in correlation to changes in an issuer's credit rating and inversely to movements in interest rates. The Portfolio's investments in high yield securities expose it to a substantial degree of credit risk. Prices of high yield securities will rise and fall primarily in response to actual or perceived changes in the issuer's financial health, although changes in market interest rates also will affect prices. High yield securities may experience reduced liquidity and sudden and substantial decreases in price. An economic downturn affecting an issuer of high yield securities may result in an increased incidence of default. In the event of a default, the Portfolio may incur additional expenses to seek recovery.


•  Foreign and Emerging Market Securities. Investments in foreign markets entail special risks such as currency, political, economic and market risks. There also may be greater market volatility, less reliable financial information, higher transaction and custody costs, decreased market liquidity and less government and exchange regulation associated with investments in foreign markets. In addition, investments in certain foreign markets that have historically been considered stable may become more volatile and subject to increased risk due to ongoing developments and changing conditions in such markets. Moreover, the growing interconnectivity of global economies and financial markets has increased the probability that adverse developments and conditions in one country or region will affect the stability of economies and financial markets in other countries or regions. The risks of investing in emerging market countries are greater than risks associated with investments in foreign developed countries. Certain emerging market or developing countries are among the largest debtors to commercial banks and foreign governments. The issuer or governmental authority that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or pay interest when due in accordance with the terms of such obligations. In addition, foreign governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments. Moreover, there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part. In addition, the Portfolio's investments in foreign issuers may be denominated in foreign currencies and therefore, to the extent unhedged, the value of the investment will fluctuate with the U.S. dollar exchange rates. To the extent hedged by the use of foreign currency forward exchange contracts, the precise matching of the foreign currency forward exchange contract amounts and the value of the securities involved will not generally be possible because the future value of such securities in foreign currencies will change as a consequence of market movements in the value of those securities between the date on which the contract is entered into and the date it matures. There is additional risk that such transactions may reduce or preclude the opportunity for gain if the value of the currency should move in the direction opposite to the position taken and that foreign currency forward exchange contracts create exposure to currencies in which the Portfolio's securities are not denominated. The use of foreign currency forward exchange contracts involves the risk of loss from the insolvency or bankruptcy of the counterparty to the contract or the failure of the counterparty to make payments or otherwise comply with the terms of the contract.


•  Public Bank Loans. Certain public bank loans are illiquid, meaning the Portfolio may not be able to sell them quickly at a fair price. To the extent a bank loan has been deemed illiquid, it will be subject to the Portfolio's restrictions on investment in illiquid securities. The secondary market for bank loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods. Bank loans are subject to the risk of default in the payment of interest or principal on a loan, which will result in a reduction of income to the Portfolio, and a potential decrease in the Portfolio's NAV. The risk of default will increase in the event of an economic downturn or a substantial increase in interest rates. Because public bank loans usually rank lower in priority of payment to senior loans, they present a greater degree of investment risk. These bank loans may exhibit greater price volatility as well.


•  Equity Securities. In general, prices of equity securities are more volatile than those of fixed income securities. The prices of equity securities fluctuate, and sometimes widely fluctuate, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic and political conditions. To the extent that the Portfolio invests in convertible securities, and the convertible security's investment value is greater than its conversion value, its price will be likely to increase when interest rates fall and decrease when interest rates rise. If the conversion value exceeds the investment value, the price of the convertible security will tend to fluctuate directly with the price of the underlying security.


•  Preferred Securities. Preferred stock is issued with a fixed par value and pays dividends based on a percentage of that par value at a fixed rate. As with fixed income securities, which also make fixed payments, the market value of preferred stock is sensitive to changes in interest rates. Preferred stock generally decreases in value if interest rates rise and increases in value if interest rates fall.


•  Mezzanine Investments. Mezzanine investments are subordinated debt securities that receive payments of interest and principal after other more senior security holders are paid. Mezzanine investments carry the risk that the issuer will not be able to meet its obligations and that the mezzanine investments may lose value.


•  Distressed and Defaulted Securities. Distressed and defaulted securities are speculative and involve substantial risks in addition to the risks of investing in high yield securities. The Portfolio will generally not receive interest payments on the distressed securities and the principal may also be at risk. These securities may present a substantial risk of default or may be in default at the time of investment, requiring the Portfolio to incur additional costs. The repayment of defaulted securities is also subject to significant uncertainties.


•  Liquidity. The Portfolio's investments in restricted and illiquid securities may entail greater risk than investments in other types of securities. These securities may be more difficult to sell, particularly in times of market turmoil. Additionally, the market for certain investments deemed liquid at the time of purchase may become illiquid under adverse market or economic conditions. Liquidity risk may be magnified in a rising interest rate environment or in other circumstances where investor redemptions from fixed income mutual funds may be higher than normal. Illiquid securities may be more difficult to value. If the Portfolio is forced to sell an illiquid security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss.


•  Derivatives. A derivative instrument often has risks similar to its underlying asset and may have additional risks, including imperfect correlation between the value of the derivative and the underlying asset, risks of default by the counterparty to certain transactions, magnification of losses incurred due to changes in the market value of the securities, instruments, indices or interest rates to which the derivative instrument relates and risks that the transactions may not be liquid. Certain derivative transactions may give rise to a form of leverage. Leverage magnifies the potential for gain and the risk of loss.


Shares of the Portfolio are not bank deposits and are not guaranteed or insured by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney There is no assurance that the Portfolio will achieve its investment objective, and you can lose money investing in this Portfolio.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution Shares of the Portfolio are not bank deposits and are not guaranteed or insured by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing the Portfolio's Class I shares' performance from year-to-year and by showing how the Portfolio's average annual returns for the past one year period and since inception compare with those of a broad measure of market performance, as well as an index that represents a group of similar mutual funds, over time. The performance of the other Classes, which is shown in the table below, will differ because the Classes have different ongoing fees. The Portfolio's returns in the table include the maximum applicable sales charge for Class A and Class C and assume you sold your shares at the end of each period (unless otherwise noted). The Portfolio's past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future. Updated performance information is available online at www.morganstanley.com/im or by calling toll-free (800) 548-7786.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing the Portfolio's Class I shares' performance from year-to-year and by showing how the Portfolio's average annual returns for the past one year period and since inception compare with those of a broad measure of market performance, as well as an index that represents a group of similar mutual funds, over time.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone (800) 548-7786
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.morganstanley.com/im
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Portfolio's past performance, before and after taxes, is not necessarily an indication of how the Portfolio will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns—Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

High Quarter

  

9/30/16

    

6.02

%

  

Low Quarter

  

12/31/14

    

–3.64

%

  
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel High Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.02%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Low Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2014
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.64%)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The Portfolio's returns in the table include the maximum applicable sales charge for Class A and Class C and assume you sold your shares at the end of each period (unless otherwise noted).
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate The after-tax returns shown in the table above are calculated using the historical highest individual federal marginal income tax rates during the period shown 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 the investor's tax situation and may differ from those shown, and after-tax returns are not relevant to investors who hold their Portfolio 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 for the Portfolio's other Classes will vary from Class I shares' returns.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher After-tax returns may be higher than before-tax returns due to foreign tax credits and/or an assumed benefit from capital losses that would have been realized had Portfolio shares been sold at the end of the relevant periods, as applicable.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

The after-tax returns shown in the table above are calculated using the historical highest individual federal marginal income tax rates during the period shown and do not reflect the impact of state and local taxes. After-tax returns for the Portfolio's other Classes will vary from Class I shares' returns. Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and after-tax returns are not relevant to investors who hold their Portfolio shares through tax deferred arrangements such as 401(k) plans or individual retirement accounts. After-tax returns may be higher than before-tax returns due to foreign tax credits and/or an assumed benefit from capital losses that would have been realized had Portfolio shares been sold at the end of the relevant periods, as applicable.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (for periods ended December 31, 2016)
High Yield Portfolio | Bloomberg Barclays U.S. Corporate High Yield Index (reflects no deduction for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 17.13% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 6.70% [1],[2]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 07, 2012 [1]
High Yield Portfolio | Lipper High Current Yield Bond Funds Index (reflects no deduction for taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 14.54% [3]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 5.97% [2],[3]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 07, 2012 [3]
High Yield Portfolio | 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 based on the lesser of the offering price or NAV at redemption) rr_MaximumDeferredSalesChargeOverOther none
Advisory Fee rr_ManagementFeesOverAssets 0.60%
Distribution and/or Shareholder Service (12b-1) Fee rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.42%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 1.02% [4]
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.37% [4]
Total Annual Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 0.65% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 288
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 527
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,214
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 66
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 288
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 527
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,214
Annual Return 2013 rr_AnnualReturn2013 13.22%
Annual Return 2014 rr_AnnualReturn2014 1.11%
Annual Return 2015 rr_AnnualReturn2015 (1.71%)
Annual Return 2016 rr_AnnualReturn2016 15.49%
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 15.49%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.75%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 07, 2012
High Yield Portfolio | Class I | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 12.04%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 5.01%
High Yield Portfolio | Class I | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 8.63%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 5.08%
High Yield Portfolio | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.25%
Maximum deferred sales charge (load) (as a percentage based on the lesser of the offering price or NAV at redemption) rr_MaximumDeferredSalesChargeOverOther none [5]
Advisory Fee rr_ManagementFeesOverAssets 0.60%
Distribution and/or Shareholder Service (12b-1) Fee rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.48%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 1.33% [4]
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.33% [4]
Total Annual Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 1.00% [4]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock Investments that are not subject to any sales charges at the time of purchase are subject to a contingent deferred sales charge ("CDSC") of 0.50% that will be imposed if you sell your shares within 18 months after the last day of the month of purchase, except for certain specific circumstances. See "Shareholder Information—How to Redeem Portfolio Shares" for further information about the CDSC waiver categories.
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts For purchases of Class A shares, you may qualify for a sales charge discount if the cumulative net asset value per share ("NAV") of Class A shares of the Portfolio being purchased in a single transaction, together with the NAV of any Class A, Class L and Class C shares of the Portfolio of Morgan Stanley Institutional Fund Trust (the "Fund") already held in Related Accounts (as defined in the section of the Prospectus entitled "Shareholder Information—Sales Charges Applicable to Purchases of Class A Shares") as of the date of the transaction as well as Class A, Class B, Class L and Class C shares of any other Morgan Stanley Multi-Class Fund (as defined in the section of the Prospectus entitled "Shareholder Information—Exchange Privilege") and including shares of Morgan Stanley Money Market Funds (as defined in the section of the Prospectus entitled "Shareholder Information—Exchange Privilege") that you acquired in an exchange of Class A shares of the Portfolio or Class A shares of another Morgan Stanley Multi-Class Fund already held in Related Accounts as of the date of the transaction, amounts to $25,000 or more.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 25,000
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 523
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 797
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,093
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,931
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 523
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 797
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,093
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,931
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 10.10%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 7.43%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 07, 2012
High Yield Portfolio | Class L  
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 based on the lesser of the offering price or NAV at redemption) rr_MaximumDeferredSalesChargeOverOther none
Advisory Fee rr_ManagementFeesOverAssets 0.60%
Distribution and/or Shareholder Service (12b-1) Fee rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 0.73%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 1.83% [4]
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.58% [4]
Total Annual Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 1.25% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 127
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 519
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 936
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,100
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 127
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 519
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 936
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,100
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 14.69%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.12%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 07, 2012
High Yield Portfolio | 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 based on the lesser of the offering price or NAV at redemption) rr_MaximumDeferredSalesChargeOverOther 1.00% [6]
Advisory Fee rr_ManagementFeesOverAssets 0.60%
Distribution and/or Shareholder Service (12b-1) Fee rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.52%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 2.12% [4]
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.37% [4]
Total Annual Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 1.75% [4]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock The Class C CDSC is only applicable if you sell your shares within one year after purchase. See "Shareholder Information—How to Redeem Portfolio Shares" for a complete discussion of the CDSC.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 278
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 628
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,105
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,423
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 178
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 628
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,105
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,423
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 13.16%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.56%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 2015
High Yield Portfolio | Class IS  
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 based on the lesser of the offering price or NAV at redemption) rr_MaximumDeferredSalesChargeOverOther none
Advisory Fee rr_ManagementFeesOverAssets 0.60%
Distribution and/or Shareholder Service (12b-1) Fee rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.33%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 0.93% [4]
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets 0.31% [4]
Total Annual Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 0.62% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 63
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 265
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 484
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,115
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 63
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 265
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 484
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,115
Average Annual Returns, Past 1 Year rr_AverageAnnualReturnYear01 15.52%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.62%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 28, 2014
[1] The Bloomberg Barclays U.S. Corporate High Yield Index measures the market of USD-denominated, non-investment grade, fixed-rate, taxable corporate bonds. Securities are classified as high yield if the middle rating of Moody's, Fitch and S&P is Ba1/BB+/BB+ or below. The index excludes emerging market debt. It is not possible to invest directly in an index.
[2] Since Inception reflects the inception date of Class I.
[3] The Lipper High Current Yield Bond Funds Index is an equally weighted performance index of the largest qualifying funds (based on net assets) in the Lipper High Current Yield Bond Funds classification. There are currently 30 funds represented in this Index.
[4] The Portfolio's "Adviser," Morgan Stanley Investment Management Inc., has agreed to reduce its advisory fee and/or reimburse the Portfolio so that Total Annual Portfolio Operating Expenses, excluding certain investment related expenses, taxes, interest and other extraordinary expenses (including litigation) will not exceed 0.65% for Class I, 1.00% for Class A, 1.25% for Class L, 1.75% for Class C and 0.62% for Class IS. The fee waivers and/or expense reimbursements will continue for at least one year or until such time as the Fund's Board of Trustees acts to discontinue all or a portion of such waivers and/or reimbursements when it deems such action is appropriate.
[5] Investments that are not subject to any sales charges at the time of purchase are subject to a contingent deferred sales charge ("CDSC") of 0.50% that will be imposed if you sell your shares within 18 months after the last day of the month of purchase, except for certain specific circumstances. See "Shareholder Information-How to Redeem Portfolio Shares" for further information about the CDSC waiver categories.
[6] The Class C CDSC is only applicable if you sell your shares within one year after purchase. See "Shareholder Information-How to Redeem Portfolio Shares" for a complete discussion of the CDSC.