State Street Institutional US Government Money Market Fund Fees and Expenses - State Street Institutional US Government Money Market Fund	Dec. 31, 2025
Prospectus [Line Items]
Expense Heading [Optional Text]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Fees and Expenses of the Fund</span>
Expense Narrative [Text Block]	The tables below describe the fees and expenses that you may pay if you buy, hold, and sell shares of the U.S. Government Fund (“Fund Shares”). You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. The expenses shown in the table and the Example reflect the expenses of the Fund and the Fund's proportionate share of the expenses of the State Street U.S. Government Money Market Portfolio (the “U.S. Government Portfolio” or sometimes referred to in context as the “Portfolio”).
Shareholder Fees Caption [Optional Text]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Shareholder Fees</span><span style="color:#000000;font-family:Arial;font-size:10.02pt;line-height:12.02pt;"> </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">(fees paid directly from your investment)</span>
Operating Expenses Caption [Optional Text]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Annual Fund Operating Expenses</span><span style="color:#000000;font-family:Arial;font-size:10.02pt;line-height:12.02pt;"> </span><span style="color:#000000;font-family:Arial;font-size:10.02pt;">(expenses that you pay each year as a percentage of the value of your investment)</span>
Expense Example [Heading]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">Example:</span>
Expense Example Narrative [Text Block]	This Example 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 for the time periods indicated, and then sell or hold all of your Fund Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that 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:

State Street Institutional US Government Money Market Fund Fees and Expenses - State Street Institutional US Government Money Market Fund

Dec. 31, 2025

Fees and Expenses of the Fund

Expense Narrative [Text Block]

The tables below describe the fees and expenses that you may pay if you buy, hold, and sell shares of the U.S. Government Fund (“Fund Shares”). You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. The expenses shown in the table and the Example reflect the expenses of the Fund and the Fund's proportionate share of the expenses of the State Street U.S. Government Money Market Portfolio (the “U.S. Government Portfolio” or sometimes referred to in context as the “Portfolio”).

Shareholder Fees Caption [Optional Text]

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Optional Text]

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Expense Example [Heading]

Example:

Expense Example Narrative [Text Block]

This Example 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 for the time periods indicated, and then sell or hold all of your Fund Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that 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: