Investment Strategy - Morgan Stanley U.S. Government Money Market Trust - Classes R and S - U.S. Government Money Market Trust	Jan. 31, 2026
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies
Strategy Narrative [Text Block]	The Fund has adopted a policy to invest exclusively in obligations issued or guaranteed by the U.S. Government and its agencies and instrumentalities and in repurchase agreements collateralized by such securities, and, accordingly, qualifies as a “government money market fund” under federal regulations. The Fund may also hold cash from time to time. A “government money market fund” is a money market fund that invests at least 99.5% of its total assets in cash, securities issued or guaranteed by the United States or certain U.S. government agencies or instrumentalities and/or repurchase agreements that are collateralized fully by the foregoing. A “government money market fund” is exempt from requirements that permit and, under certain circumstances, require money market funds to impose a “liquidity fee” on redemptions. In selecting investments, Morgan Stanley Investment Management Inc. (the “Adviser”) seeks to maintain the Fund’s share price at $1.00. The share price remaining stable at $1.00 means that the Fund would preserve the principal value of your investment. 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 or instrumentalities of the U.S. Government which are backed by the full faith and credit of the United States. Among the agencies or 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 or 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 or 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 or instrumentalities which are backed solely by the credit of the issuing agency or instrumentality. Among these agencies or instrumentalities is the Federal Farm Credit System. The Fund may also invest in repurchase agreements. In addition, the Fund has adopted a policy that provides, under normal circumstances, that at least 80% of the Fund’s assets will be invested in obligations issued or guaranteed by the U.S. Government and its agencies and instrumentalities and in repurchase agreements collateralized by such securities. This policy may be changed without shareholder approval; however, shareholders would be notified upon 60 days’ notice in writing of any changes. As a “government money market fund,” the Fund may value its securities using the amortized cost method as permitted by Rule 2a-7 under the Investment Company Act of 1940, as amended (“Rule 2a-7” under the “1940 Act”), to seek to maintain a stable net asset value per share of $1.00. The Fund’s investments are subject to the quality, diversification, maturity, liquidity and other requirements of Rule 2a-7.

The Fund has adopted a policy to invest exclusively in obligations issued or guaranteed by the U.S. Government and its agencies and instrumentalities and in repurchase agreements collateralized by such securities, and, accordingly, qualifies as a “government money market fund” under federal regulations. The Fund may also hold cash from time to time. A “government money market fund” is a money market fund that invests at least 99.5% of its total assets in cash, securities issued or guaranteed by the United States or certain U.S. government agencies or instrumentalities and/or repurchase agreements that are collateralized fully by the foregoing. A “government money market fund” is exempt from requirements that permit and, under certain circumstances, require money market funds to impose a “liquidity fee” on redemptions. In selecting investments, Morgan Stanley Investment Management Inc. (the “Adviser”) seeks to maintain the Fund’s share price at $1.00. The share price remaining stable at $1.00 means that the Fund would preserve the principal value of your investment.

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 or instrumentalities of the U.S. Government which are backed by the full faith and credit of the United States. Among the agencies or 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 or 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 or 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 or instrumentalities which are backed solely by the credit of the issuing agency or instrumentality. Among these agencies or instrumentalities is the Federal Farm Credit System. The Fund may also invest in repurchase agreements.

As a “government money market fund,” the Fund may value its securities using the amortized cost method as permitted by Rule 2a-7 under the Investment Company Act of 1940, as amended (“Rule 2a-7” under the “1940 Act”), to seek to maintain a stable net asset value per share of $1.00. The Fund’s investments are subject to the quality, diversification, maturity, liquidity and other requirements of Rule 2a-7.