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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
ProspectusDate rr_ProspectusDate May 31, 2011
MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST (Prospectus Summary) | MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return, Heading rr_RiskReturnHeading Fund Summary
Investment Objective, Heading rr_ObjectiveHeading Investment Objectives
investment Objective, Primary rr_ObjectivePrimaryTextBlock 
Morgan Stanley U.S. Government Money Market Trust is a money market fund that
seeks to provide security of principal, high current income and liquidity.
Expense, Heading rr_ExpenseHeading Fees and Expenses
Expense, Narrative rr_ExpenseNarrativeTextBlock 
The table below describes the fees and expenses that you may pay if you buy and
hold shares of the Fund. The Fund is a no-load fund. The Fund does not impose
any sales charges and does not impose account or exchange fees.
Operating Expenses, Caption rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Expense Example, Heading rr_ExpenseExampleHeading Example
Expense Example, Narrative rr_ExpenseExampleNarrativeTextBlock 
The example below 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, your investment has a
5% return each year, and the Fund's operating expenses remain the same. Although
your actual costs may be higher or lower, based on these assumptions your costs
would be:
Investment Strategy, Heading rr_StrategyHeading Principal Investment Strategies
Investment Strategy, Narrative rr_StrategyNarrativeTextBlock 
The Fund invests in high quality, short-term U.S. government securities. In
selecting investments, the Investment Adviser seeks to maintain the Fund's share
price at $1.00.

The U.S. government securities that the Fund may purchase include U.S. Treasury
bills, notes and bonds, all of which are direct obligations of the U.S.
Government. In addition, the Fund may purchase securities issued by agencies and
instrumentalities of the U.S. Government which are backed by the full faith and
credit of the United States. Among the agencies and instrumentalities issuing
these obligations are the Government National Mortgage Association ("Ginnie
Mae") and the Federal Housing Administration. The Fund may also purchase
securities issued by agencies and instrumentalities which are not backed by the
full faith and credit of the United States, but whose issuing agency or
instrumentality has the right to borrow, to meet its obligations, from the U.S.
Treasury. Among these agencies and instrumentalities are the Federal National
Mortgage Association ("Fannie Mae"), the Federal Home Loan Mortgage Corporation
("Freddie Mac") and the Federal Home Loan Banks. Further, the Fund may purchase
securities issued by agencies and instrumentalities, which are backed solely by
the credit of the issuing agency or instrumentality. Among these agencies and
instrumentalities is the Federal Farm Credit System. Finally, the Fund may
purchase U.S. government securities guaranteed under the Federal Deposit
Insurance Corporation ("FDIC") Temporary Liquidity Guarantee Program. The Fund
may also invest in repurchase agreements.
Risk, Heading rr_RiskHeading Principal Risks
Risk, Narrative rr_RiskNarrativeTextBlock 
There is no assurance that the Fund will achieve its investment objectives.
Although the Fund seeks to preserve the value of your investment at $1.00 per
share, if it is unable to do so, it is possible to lose money by investing in
the Fund. The principal risks of investing in this Fund include:

• U.S. Government Securities. The Fund may purchase U.S. government securities
that are not backed by the full faith and credit of the United States. With
respect to these U.S. government securities, there is the risk that the U.S.
Government will not provide financial support to such U.S. government agencies,
instrumentalities or sponsored enterprises if it is not obligated to do so by
law.

• Repurchase Agreements. Repurchase agreements are subject to risks associated
with the possibility of default by the seller at a time when the collateral has
declined in value, or insolvency of the seller, which may affect the Fund's
right to control the collateral and result in certain costs and delays.

Shares of the Fund are not bank deposits and are not guaranteed or insured by
the FDIC or any other government agency.
Risk, Money Market Fund rr_RiskMoneyMarketFund Although the Fund seeks to preserve the value of your investment at $1.00 per share, if it is unable to do so, it is possible to lose money by investing in the Fund.
Risk, Not Insured Depository Institution rr_RiskNotInsuredDepositoryInstitution Shares of the Fund are not bank deposits and are not guaranteed or insured by the FDIC or any other government agency.
Bar Chart and Performance Table, Heading rr_BarChartAndPerformanceTableHeading Past Performance
Performance, Narrative rr_PerformanceNarrativeTextBlock 
The bar chart and table below provide some indication of the risks of investing
in the Fund by showing changes in the Fund's performance from year to year and
by showing the Fund's average annual returns for the one, five and 10 year
periods. The Fund's past performance does not indicate how the Fund will perform
in the future. Updated performance information is available online at
www.morganstanley.com/im or by calling toll-free (800) 869-NEWS.
Performance, Information Illustrates Variability of Returns rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing the Fund's average annual returns for the one, five and 10 year periods.
Performance, Availability Phone Number rr_PerformanceAvailabilityPhone (800) 869-NEWS
Performance, Availability Website Address rr_PerformanceAvailabilityWebSiteAddress www.morganstanley.com/im
Performance, Past Does Not Indicate Future rr_PerformancePastDoesNotIndicateFuture The Fund's past performance does not indicate how the Fund will perform in the future.
Bar Chart, Heading rr_BarChartHeading Annual Total Returns-Calendar Years
Bar Chart, Closing rr_BarChartClosingTextBlock 
The year-to-date total return as of March 31, 2011 was 0.00%.

Best Quarter (ended March 31, 2001) : 1.33%
Worst Quarter (ended March 31, 2010) : 0.00%
Performance Table, Closing rr_PerformanceTableClosingTextBlock 
For the Fund's most recent 7-day annualized yield, you may call toll-free (800)
869-NEWS.
Average Annual Returns, Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For Periods Ended December 31, 2010
Money Market, Seven Day Yield, Phone Number rr_MoneyMarketSevenDayYieldPhone (800) 869-NEWS
MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST (Prospectus Summary) | MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST | MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST
  
Risk/Return: rr_RiskReturnAbstract  
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination These fee waivers and/or expense reimbursements are expected to continue for 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 expense reimbursements when it deems that such action is appropriate.
Year to Date Return, Label rr_YearToDateReturnLabel The year-to-date total return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2011
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.00%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2001
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.33%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST | MORGAN STANLEY US GOVERNMENT MONEY MARKET TRUST
  
Risk/Return: rr_RiskReturnAbstract  
Advisory fee rr_ManagementFeesOverAssets 0.44%
Shareholder servicing fees rr_Component1OtherExpensesOverAssets 0.10%
Other expenses rr_OtherExpensesOverAssets 0.16%
Total annual Fund operating expenses rr_ExpensesOverAssets 0.70% [1]
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.49%) [1]
Total annual Fund operating expenses after fee waiver and/or expense reimbursement rr_NetExpensesOverAssets 0.21% [1]
Expense Example, With Redemption, 1 Year rr_ExpenseExampleYear01 545
Expense Example, With Redemption, 3 Years rr_ExpenseExampleYear03 589
Expense Example, With Redemption, 5 Years rr_ExpenseExampleYear05 637
Expense Example, With Redemption, 10 Years rr_ExpenseExampleYear10 779
Annual Return 2001 rr_AnnualReturn2001 3.67%
Annual Return 2002 rr_AnnualReturn2002 1.12%
Annual Return 2003 rr_AnnualReturn2003 0.47%
Annual Return 2004 rr_AnnualReturn2004 0.68%
Annual Return 2005 rr_AnnualReturn2005 2.52%
Annual Return 2006 rr_AnnualReturn2006 4.39%
Annual Return 2007 rr_AnnualReturn2007 4.60%
Annual Return 2008 rr_AnnualReturn2008 1.86%
Annual Return 2009 rr_AnnualReturn2009 0.02%
Annual Return 2010 rr_AnnualReturn2010 0.01%
Average Annual Returns, Label rr_AverageAnnualReturnLabel U.S. Government Money Market Trust
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.01%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.16%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.92%
[1] The Fund's distributor has agreed to waive a portion of the Fund's shareholder servicing fee except for 0.05%. Following any such waiver by the distributor, the Fund's "Investment Adviser," Morgan Stanley Investment Advisors Inc., and its administrator have agreed to reduce all or a portion of the Fund's advisory fees and administration fees and/or reimburse other expenses to the extent that total expenses exceed total income on a daily basis. These fee waivers and/or expense reimbursements are expected to continue for 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 expense reimbursements when it deems that such action is appropriate.