v3.26.1
Shareholder Report
 12 Months Ended
Jan. 31, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSR
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 Jan. 31, 2026
Shareholder Report Annual or Semi-Annual Annual Shareholder Report
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 annual shareholder report contains important information about Morgan Stanley U.S. Government Money Market Trust for the period of February 1, 2025 to January 31, 2026.
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 year?

(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
$37
0.36%
Expenses Paid, Amount $ 37
Expense Ratio, Percent 0.36%
AssetsNet $ 1,138,962,377
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 1,765,243
Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets
$1,138,962,377
# of Portfolio Holdings
212
Total Advisory Fees Paid
$1,765,243
Holdings [Text Block]

Asset Allocation (% of total investments)

Credit Rating Chart
Value
Value
U.S. Agency Securities
14.8%
U.S. Treasury Securities
40.8%
Repurchase Agreements
44.4%

Maturity Schedule (% of total investments)

Group By Asset Type Chart
Value
Value
121 + Days
14.9%
91 - 120 Days
4.0%
61 - 90 Days
4.7%
31 - 60 Days
8.9%
1 - 30 Days
67.5%
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 annual shareholder report contains important information about Morgan Stanley U.S. Government Money Market Trust for the period of February 1, 2025 to January 31, 2026.
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 year?

(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
$37
0.36%
Expenses Paid, Amount $ 37
Expense Ratio, Percent 0.36%
AssetsNet $ 1,138,962,377
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 1,765,243
Additional Fund Statistics [Text Block]

Key Fund Statistics

Total Net Assets
$1,138,962,377
# of Portfolio Holdings
212
Total Advisory Fees Paid
$1,765,243
Holdings [Text Block]

Asset Allocation (% of total investments)

Credit Rating Chart
Value
Value
U.S. Agency Securities
14.8%
U.S. Treasury Securities
40.8%
Repurchase Agreements
44.4%

Maturity Schedule (% of total investments)

Group By Asset Type Chart
Value
Value
121 + Days
14.9%
91 - 120 Days
4.0%
61 - 90 Days
4.7%
31 - 60 Days
8.9%
1 - 30 Days
67.5%
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>