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Shareholder Report
 6 Months Ended
Jul. 31, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Morgan Stanley U.S. Government Money Market Trust
Entity Central Index Key 0000356409
Entity Investment Company Type N-1A
Document Period End Date Jul. 31, 2025
C000011343  
Shareholder Report [Line Items]  
Fund Name Morgan Stanley U.S. Government Money Market Trust
Class Name R
Trading Symbol DWGXX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about  Morgan Stanley U.S. Government Money Market Trust for the period of February 1, 2025 to July 31, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.morganstanley.com/im/shareholderreports. You can also request this information by contacting us at 1-800-869-6397.
Additional Information Phone Number 1-800-869-6397
Additional Information Website <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left; text-align-last: auto; white-space-collapse: preserve-breaks;">www.morganstanley.com/im/shareholderreports</span>
Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Class R
$17
0.34%Footnote Reference1
FootnoteDescription
Footnote1
Annualized
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.34% [1]
AssetsNet $ 1,167,721,061
Holdings Count | Holding 117
Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets
$1,167,721,061
# of Portfolio Holdings
117
Holdings [Text Block]

Asset Allocation (% of total investments)

Credit Rating Chart
Value
Value
U.S. Agency Securities
12.1%
U.S. Treasury Securities
34.8%
Repurchase Agreements
53.1%

Maturity Schedule (% of total investments)

Group By Asset Type Chart
Value
Value
121+ Days
15.9%
91 - 120 Days
6.3%
61 - 90 Days
7.1%
31 - 60 Days
1.2%
1 - 30 Days
69.5%
Material Fund Change [Text Block]
Updated Prospectus Web Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left; text-align-last: auto; white-space-collapse: preserve-breaks;">www.morganstanley.com/im/shareholderreports</span>
C000171230  
Shareholder Report [Line Items]  
Fund Name Morgan Stanley U.S. Government Money Market Trust
Class Name S
Trading Symbol DGEXX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about  Morgan Stanley U.S. Government Money Market Trust for the period of February 1, 2025 to July 31, 2025.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Fund at www.morganstanley.com/im/shareholderreports. You can also request this information by contacting us at 1-800-869-6397.
Additional Information Phone Number 1-800-869-6397
Additional Information Website <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left; text-align-last: auto; white-space-collapse: preserve-breaks;">www.morganstanley.com/im/shareholderreports</span>
Expenses [Text Block]

What were the Fund costs for the last six months?

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Class S
$17
0.34%Footnote Reference1
FootnoteDescription
Footnote1
Annualized
Expenses Paid, Amount $ 17
Expense Ratio, Percent 0.34% [2]
AssetsNet $ 1,167,721,061
Holdings Count | Holding 117
Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets
$1,167,721,061
# of Portfolio Holdings
117
Holdings [Text Block]

Asset Allocation (% of total investments)

Credit Rating Chart
Value
Value
U.S. Agency Securities
12.1%
U.S. Treasury Securities
34.8%
Repurchase Agreements
53.1%

Maturity Schedule (% of total investments)

Group By Asset Type Chart
Value
Value
121+ Days
15.9%
91 - 120 Days
6.3%
61 - 90 Days
7.1%
31 - 60 Days
1.2%
1 - 30 Days
69.5%
Material Fund Change [Text Block]
Updated Prospectus Web Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left; text-align-last: auto; white-space-collapse: preserve-breaks;">www.morganstanley.com/im/shareholderreports</span>
[1] Annualized
[2] Annualized