Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Jan. 31, 2012
SIMT CORE FIXED INCOME FUND (Second Prospectus Summary) | SIMT CORE FIXED INCOME FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	CORE FIXED INCOME FUND
Investment Objective, Heading	rr_ObjectiveHeading	Investment Goal
investment Objective, Primary	rr_ObjectivePrimaryTextBlock	Current income consistent with the preservation of capital.
Expense, Heading	rr_ExpenseHeading	Fees and Expenses
Expense, Narrative	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Fund shares.
Shareholder Fees, Caption	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses, Caption	rr_OperatingExpensesCaption	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	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 473% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	473.00%
Expenses, Not Correlated to Ratio Due to Acquired Fund Fees	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
Expense Example, Heading	rr_ExpenseExampleHeading	EXAMPLE
Expense Example, Narrative	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	rr_ExpenseExampleByYearCaption	Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Investment Strategy, Heading	rr_StrategyHeading	Principal Investment Strategies
Investment Strategy, Narrative	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Core Fixed Income Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in fixed income securities. The Fund will invest primarily in investment and non-investment grade U.S. and foreign corporate and government fixed income securities, including emerging market, asset-backed securities and mortgage-backed securities. The Fund may invest in securities denominated in either U.S. dollars or foreign currency. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. Sub-Advisers are selected for their expertise in managing various kinds of fixed income securities, and each Sub-Adviser makes investment decisions based on an analysis of yield trends, credit ratings and other factors in accordance with its particular discipline. The Fund may also invest in futures contracts, forward contracts and swaps for speculative or hedging purposes. Futures contracts, forward contracts and swaps are used to synthetically obtain exposure to securities or baskets of securities and to manage the Fund's interest rate duration and yield curve exposure. These derivatives are also used to mitigate the Fund's overall level of risk and/or the Fund's risk to particular types of securities, currencies or market segments. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. The Fund may buy credit default swaps in an attempt to manage credit risk where the Fund has credit exposure to an issuer, and the Fund may sell credit default swaps to more efficiently gain credit exposure to such security or basket of securities. The Sub-Advisers may also engage in currency transactions using futures and foreign currency forward contracts either to seek to hedge the Fund's currency exposure or to enhance the Fund's returns. The Fund may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency. The Fund will invest primarily in investment grade securities (those rated AAA, AA, A and BBB-). However, the Fund may also invest in non-rated securities or securities rated below investment grade (BB+, B and CCC). The Fund also invests a portion of its assets in bank loans, which are, generally, non-investment grade (junk bond) floating rate instruments. The Fund may invest in bank loans in the form of participations in the loans (participations) and assignments of all or a portion of the loans from third parties (assignments). While each Sub-Adviser chooses securities of different types and maturities, the Fund in the aggregate generally will have a dollar-weighted average duration that is consistent with that of the broad U.S. fixed income market as represented by the Barclays Capital U.S. Aggregate Bond Index. The dollar-weighted average duration of the Barclays Capital U.S. Aggregate Bond Index varies significantly over time, but as of December 31, 2011 it was 4.95 years. Duration is a measure of the expected life of a fixed income security that is used to determine the sensitivity of a security's price to changes in interest rates.
Risk, Heading	rr_RiskHeading	Principal Risks
Risk, Narrative	rr_RiskNarrativeTextBlock	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, and asset-backed securities may not have the benefit of any security interest in the related assets. Bank Loans Risk - With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - Due to its active positions in currencies, the Fund will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities or by the imposition of currency controls or other political developments in the United States or abroad. Derivatives Risk - The Fund's use of futures contracts, forward contracts and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund's use of forward contracts and swap agreements is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Credit risk is described above. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Extension Risk - The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value. Fixed Income 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. 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. Foreign Investment/Emerging Markets 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. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Interest Rate Risk - The risk that the value of fixed income securities, including U.S. Government securities, will fall due to rising interest rates. Investment Style Risk - The risk that U.S. fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. Mortgage-Backed Securities Risk - Mortgage-backed securities are affected by, among other things, interest rate changes and the possibility of prepayment of the underlying mortgage loans. Mortgage-backed securities are also subject to the risk that underlying borrowers will be unable to meet their obligations. Portfolio Turnover Risk - Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and additional capital gains tax liabilities. Prepayment Risk - The risk that, with declining interest rates, 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. Short Sales Risk - A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as "covering" the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities. 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. Loss of money is a risk of investing in the Fund.
Risk, Lose Money	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table, Heading	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance, Narrative	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 ten calendar years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared 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. The Fund's Class I Shares commenced operations on August 6, 2001. Therefore, performance and average annual total returns for the periods prior to August 6, 2001 are calculated using the performance and average annual total returns of the Fund's Class A Shares, adjusted for the higher expenses of the Class I Shares. The Fund's Class A Shares commenced operations on May 1, 1987.
Performance, Information Illustrates Variability of Returns	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 ten calendar years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance, Availability Phone Number	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance, Past Does Not Indicate Future	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	rr_BarChartClosingTextBlock	Best Quarter: 7.96% (09/30/09) Worst Quarter: -3.39% (09/30/08)
Performance Table, Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
Index No Deduction for Fees, Expenses, Taxes	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	As noted above, the Fund's Class I Shares commenced operations on August 6, 2001. Therefore, the Fund's average annual total returns for the periods prior to that time are based on the average annual total returns of the Class A Shares, adjusted for the higher expenses of the Class I Shares. The Fund's Class A Shares commenced operations on May 1, 1987. 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 CORE FIXED INCOME FUND (Second Prospectus Summary) | SIMT CORE FIXED INCOME FUND | Barclays Capital U.S. Aggregate Bond Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Barclays Capital U.S. Aggregate Bond Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	7.84%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	6.50%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.78%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	7.37%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	May 01, 1987	[1]
SIMT CORE FIXED INCOME FUND (Second Prospectus Summary) | SIMT CORE FIXED INCOME FUND | Class I
Risk Return [Abstract]	rr_RiskReturnAbstract
Redemption Fee (applies to a redemption, or series of redemptions, from a single identifiable source that, in the aggregate, exceeds $50 million within any thirty (30) day period)	rr_RedemptionFeeOverRedemption	(0.60%)
Management Fees	rr_ManagementFeesOverAssets	0.28%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.86%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.15%	[2]
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	117
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	365
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	633
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,398
Annual Return 2002	rr_AnnualReturn2002	8.83%
Annual Return 2003	rr_AnnualReturn2003	5.06%
Annual Return 2004	rr_AnnualReturn2004	4.41%
Annual Return 2005	rr_AnnualReturn2005	1.83%
Annual Return 2006	rr_AnnualReturn2006	4.39%
Annual Return 2007	rr_AnnualReturn2007	3.78%
Annual Return 2008	rr_AnnualReturn2008	(7.35%)
Annual Return 2009	rr_AnnualReturn2009	18.11%
Annual Return 2010	rr_AnnualReturn2010	10.88%
Annual Return 2011	rr_AnnualReturn2011	7.00%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.96%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.39%)
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class I Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	7.00%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	6.15%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	5.51%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	6.45%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	May 01, 1987
SIMT CORE FIXED INCOME FUND (Second Prospectus Summary) | SIMT CORE FIXED INCOME FUND | Class I | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class I Return After Taxes on Distributions
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	5.54%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.49%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.82%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	4.20%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	May 01, 1987
SIMT CORE FIXED INCOME FUND (Second Prospectus Summary) | SIMT CORE FIXED INCOME FUND | Class I | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Average Annual Returns, Label	rr_AverageAnnualReturnLabel	Class I Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	4.53%
Average Annual Returns, 5 Years	rr_AverageAnnualReturnYear05	4.26%
Average Annual Returns, 10 Years	rr_AverageAnnualReturnYear10	3.72%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	4.17%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	May 01, 1987

[1] Index returns are shown from May 31, 1987.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.