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Class Y Prospectus | SIMT Conservative Income Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading SIMT Conservative Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Principal preservation and a high degree of liquidity while providing current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Fund shares.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_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 0% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate none
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE
Expense Example Narrative [Text Block] rr_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 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] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal circumstances, the Conservative Income Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in U.S. dollar-denominated debt securities that the Fund's sub-adviser (the Sub-Adviser) believes present minimal credit risks to the Fund.


Under normal market conditions, the Fund will primarily invest in short-term US dollar denominated debt securities, including: (i) commercial paper, corporate bonds and asset-based securities of U.S. and foreign issuers; (ii) certificates of deposit, time deposits, bankers' acceptances, bank notes, and other obligations of U.S. savings and loan and thrift institutions, US banks or US branches or non-US branches of foreign banks; (iii) short-term obligations issued by state and local governments; (iv) U.S. Treasury obligations and obligations issued or guaranteed as to principal and interest by agencies or instrumentalities of the U.S. Government; and (v) obligations of foreign governments (including Canadian and Provincial Government and Crown Agency obligations). The Fund may also enter into fully-collateralized repurchase agreements. Although the Fund may invest in securities with any maturity or duration, the Fund generally seeks to maintain a weighted average maturity of 90 days or less.


Under normal circumstances, the Fund will invest at least 25% of its assets in securities issued by companies in the financial services industry, but may invest less than 25% of its assets in this industry as a temporary defensive measure.


The Fund uses a Sub-Adviser to manage the Fund's portfolio under the general supervision of SEI Investments Management Corporation, the Fund's adviser (SIMC or the Adviser). Through analysis of both macroeconomic factors and individual company attributes, the Sub-Adviser seeks to invest in securities that are marketable and liquid, offer competitive yields, and are of issuers that represent low credit risk. In selecting securities, the Sub-Adviser also considers factors such as the anticipated level of interest rates and the maturity of individual securities relative to the maturity of the Fund as a whole.


The Fund is not a money market fund and does not seek to maintain a stable net asset value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Market Risk — The prices of the Fund's fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund's fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. In the case of foreign securities, price fluctuations will reflect international economic and political events, as well as changes in currency valuations relative to the U.S. dollar. In response to these events, the Fund's value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund's liquidity or force the Fund to sell securities into a declining or illiquid market.


Interest Rate Risk — The risk that a rise in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which the Fund invests. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates. A low interest rate environment may present greater interest rate risk because there may be a greater likelihood of rates increasing and rates may increase more rapidly.


Duration Risk — The longer-term securities in which the Fund may invest tend to be more volatile than shorter-term securities. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.


Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.


Concentration Risk — A downturn in the financial services industry would impact the Fund more than a portfolio that does not concentrate in securities issued by companies in the financial services industry.


Financial Services Industry Risk — The Fund's portfolio is concentrated in investments in securities issued by companies in the financial services industry. The financial services industry is subject to extensive government regulation. Profitability is largely dependent on the availability and cost of capital, and can fluctuate significantly when interest rates change. Financial services companies are highly dependent on short-term interest rates and typically will be adversely affected by economic downturns or changes in banking regulations.


Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such issuer's underlying asset portfolio and the issuer's ability to issue new asset-backed commercial paper.


Repurchase Agreement Risk — Although the Fund's repurchase agreement transactions will be fully collateralized at all times, they generally create leverage and involve some counterparty risk to the Fund whereby a defaulting counterparty could delay or prevent the Fund's recovery of collateral.


Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.


Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than the receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.


U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency's own resources.


Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments.


Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value.


Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.


Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.


Investing in the Fund involves risk, and there is no guarantee that the Fund will achieve its investment goal. You could lose money on your investment in the Fund, just as you could with other investments. 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.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money on your investment in the Fund, just as you could with other investments.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_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 two calendar years and by showing how the Fund's average annual returns for 1 year 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] rr_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 two calendar years and by showing how the Fund's average annual returns for 1 year and since the Fund's inception compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text] rr_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] rr_BarChartClosingTextBlock
Best Quarter: 0.57% (12/31/18)
Worst Quarter: 0.13% (09/30/16)






Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2018
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.57%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.13%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2018)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate rr_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 rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

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.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

Although the Fund's performance is benchmarked against the return of the BofA Merrill Lynch 3-Month U.S. Treasury Bills Index, an investment in the Fund is substantially different from an investment in U.S. Treasury bills. Among other things, Treasury bills are backed by the full faith and credit of the U.S. Government and have a fixed rate of return. Investors in Treasury bills do not risk losing their investment, whereas loss of money is a risk of investing in the Fund. Further, an investment in the Fund is expected to be more volatile than an investment in Treasury bills because of the breadth and types of securities and other instruments in which the Fund may invest.
Class Y Prospectus | SIMT Conservative Income Fund | BofA Merrill Lynch 3-Month U.S. Treasury Bills Index (reflects no deduction for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel BofA Merrill Lynch 3-Month U.S. Treasury Bills Index (reflects no deduction for fees, expenses or taxes)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.87%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 1.10%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Apr. 22, 2016
Class Y Prospectus | SIMT Conservative Income Fund | Class Y  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.10%
Distribution (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.24%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 35
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 109
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 191
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 431
Annual Return 2017 rr_AnnualReturn2017 1.10%
Annual Return 2018 rr_AnnualReturn2018 1.96%
Label rr_AverageAnnualReturnLabel Return Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.96%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 1.27%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Apr. 22, 2016
Class Y Prospectus | SIMT Conservative Income Fund | Class Y | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.23%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.76%
Class Y Prospectus | SIMT Conservative Income Fund | Class Y | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.23%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 0.76%