v3.25.4
Label Element Value
SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk/Return [Heading] oef_RiskReturnHeading LARGE CAP INDEX FUND
Objective [Heading] oef_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] oef_ObjectivePrimaryTextBlock

Seeks to track the performance of a benchmark index that measures the investment return of large-capitalization stocks.

Expense Heading [Optional Text] oef_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] oef_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy, hold, and sell Fund shares. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table and examples below.

Operating Expenses Caption [Optional Text] oef_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Expense Example [Heading] oef_ExpenseExampleHeading EXAMPLE
Expense Example Narrative [Text Block] oef_ExpenseExampleNarrativeTextBlock

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 redeem or hold all of your 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.

Expense Example by, Year, Caption [Text] oef_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Portfolio Turnover [Heading] oef_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] oef_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual Fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 4% of the average value of its portfolio.

Portfolio Turnover, Rate oef_PortfolioTurnoverRate 4.00%
Strategy [Heading] oef_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] oef_StrategyNarrativeTextBlock

The Fund is managed using a passive investment approach designed to track, before fees and expenses, the performance of the Russell 1000 Index (the Index). Under normal circumstances, the Fund will invest substantially all of its assets (at least 80% of its net assets, plus the amount of any borrowings for investment purposes) in securities (mostly common stocks) of companies that are included in the Index. The Index

measures the performance of the large-cap segment of the U.S. equity universe and includes approximately 1000 of the largest securities based on their market capitalization. As of December 31, 2025, the market capitalization of the companies included in the Index ranged from $1.0 billion to $4.5 trillion. The market capitalization range and the composition of the Index are subject to change. The Fund may become "non-diversified," as defined in the Investment Company Act of 1940, as amended (the 1940 Act), as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index.

The Fund's sub-adviser (the Sub-Adviser) selects the Fund's securities under the general supervision of SEI Investments Management Corporation (SIMC or the Adviser). The Sub-Adviser's passive investment strategy seeks to track, before fees and expenses, the return of the index, and therefore differs from an "active" investment strategy where an investment manager buys and sells securities based on its own economic, market or financial analyses. The Sub-Adviser generally will attempt to invest in securities composing the Index in approximately the same proportions as they are represented in the Index (i.e., among other reasons, the Fund could experience high volumes of cash flows or a particular security could be difficult to obtain). In some cases, it may not be possible or practicable to purchase all of the securities composing the Index or to hold them in the same weightings as they are represented in the Index. In those circumstances, the Sub-Adviser may purchase a sampling of stocks in the Index in proportions expected to replicate generally the performance of the Index as a whole and may also use futures contracts to obtain exposure to the equity markets or to a particular security.

The Sub-Adviser may sell securities that are represented in the Index or purchase securities that are not represented in the Index, prior to or after their removal or addition to the Index.

The Fund's investment performance will depend on the Fund's tracking of the Index and the performance of the Index. The Fund's ability to replicate the performance of the Index will depend to some extent on the size and timing of cash flows into and out of the Fund, as well as on the level of the Fund's expenses. Due to these differences, the Fund's performance generally will not be identical to that of the Index.

Bar Chart and Performance Table [Heading] oef_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] oef_PerformanceNarrativeTextBlock

The bar chart and the performance 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 for the past seven calendar years and by showing how the Fund's average annual returns for 1 and 5 years and since the Fund's inception, compare

with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.

Performance Information Illustrates Variability of Returns [Text] oef_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and the performance 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 for the past seven calendar years and by showing how the Fund's average annual returns for 1 and 5 years and since the Fund's inception, compare with those of a broad measure of market performance.
Performance Availability Phone [Text] oef_PerformanceAvailabilityPhone 1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text] oef_PerformancePastDoesNotIndicateFuture The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block] oef_BarChartClosingTextBlock
Best Quarter: 21.66% (06/30/2020)
Worst Quarter: -20.21% (03/31/2020)
Highest Quarterly Return, Label [Optional Text] oef_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date oef_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return oef_BarChartHighestQuarterlyReturn 21.66%
Lowest Quarterly Return, Label [Optional Text] oef_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date oef_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return oef_BarChartLowestQuarterlyReturn (20.21%)
Performance Table Heading oef_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2025)
Index No Deduction for Fees, Expenses, or Taxes [Text] oef_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate oef_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred oef_PerformanceTableNotRelevantToTaxDeferred After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Narrative oef_PerformanceTableNarrativeTextBlock

This table compares the Fund's average annual total returns to those of a broad-based securities market index and an additional index with characteristics relevant to the Fund's investment strategy.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Risk Not Insured [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Risk Lose Money [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock You could lose money on your investment in the Fund, just as you could with other investments.
SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Market Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity or bond market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Large Capitalization Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Investment Style Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Investment Style Risk — The risk that its investment approach, which attempts to replicate the performance of the Russell 1000 Index, may underperform other segments of the equity markets or the equity markets as a whole. The Fund is also subject to the risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Tracking Error Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Tracking Error Risk — The risk that the Fund's performance may vary substantially from the performance of the benchmark index it tracks as a result of cash flows, Fund expenses, imperfect correlation between the Fund's investments and the index's components and other factors.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Derivatives Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Derivatives Risk — The Fund's use of futures contracts is subject to leverage risk, correlation risk, liquidity risk and market risk. Market risk is described above, and leverage risk and liquidity risk are described below. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. The Fund's use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Liquidity Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Medium Capitalization Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Medium Capitalization Risk — The risk that medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, medium capitalization stocks may be more volatile than those of larger companies. Medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange-listed stocks and may have more price volatility than that of exchange-listed stocks.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Leverage Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Leverage Risk — The Fund's use of derivatives may result in the Fund's total investment exposure substantially exceeding the value of its portfolio securities and the Fund's investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund's share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund's use of leverage may result in a heightened risk of investment loss.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Non-Diversified Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Non-Diversification Risk — In seeking to track the Index, the Fund may become non-diversified as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index. A non-diversified fund generally invests a greater portion of its assets in the securities of one or more issuers and invests overall in a smaller number of issuers than a diversified fund. When it is non-diversified, the Fund may be more sensitive to a single economic, business, political, regulatory, or other occurrence, which may negatively impact the Fund's performance and result in greater fluctuation in the value of the Fund's shares.

SIMT Large Cap Index Fund | LARGE CAP INDEX FUND - Class F Prospectus | Class F  
Prospectus [Line Items] oef_ProspectusLineItems  
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.05%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.59%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.64%
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 65
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 357
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 798
LARGE CAP INDEX FUND - Class F Prospectus | Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Return, Percent oef_AvgAnnlRtrPct 17.37%
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.59%
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.43%
LARGE CAP INDEX FUND - Class F Prospectus | S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Return, Percent oef_AvgAnnlRtrPct 17.88%
Average Annual Return, Percent oef_AvgAnnlRtrPct 14.42%
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.68%
LARGE CAP INDEX FUND - Class F Prospectus | Class F  
Prospectus [Line Items] oef_ProspectusLineItems  
Annual Return [Percent] oef_AnnlRtrPct 31.08%
Annual Return [Percent] oef_AnnlRtrPct 20.64%
Annual Return [Percent] oef_AnnlRtrPct 26.16%
Annual Return [Percent] oef_AnnlRtrPct (19.33%)
Annual Return [Percent] oef_AnnlRtrPct 26.27%
Annual Return [Percent] oef_AnnlRtrPct 24.09%
Annual Return [Percent] oef_AnnlRtrPct 17.04%
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Return Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 17.04%
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.29%
Average Annual Return, Percent oef_AvgAnnlRtrPct 13.12%
Performance Inception Date oef_PerfInceptionDate Jan. 31, 2018
LARGE CAP INDEX FUND - Class F Prospectus | Class F | After Taxes on Distributions  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Return After Taxes on Distributions
Average Annual Return, Percent oef_AvgAnnlRtrPct 15.50%
Average Annual Return, Percent oef_AvgAnnlRtrPct 12.53%
Average Annual Return, Percent oef_AvgAnnlRtrPct 12.46%
LARGE CAP INDEX FUND - Class F Prospectus | Class F | After Taxes on Distributions and Sales  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent oef_AvgAnnlRtrPct 11.07%
Average Annual Return, Percent oef_AvgAnnlRtrPct 10.55%
Average Annual Return, Percent oef_AvgAnnlRtrPct 10.68%