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Class Y Shares Prospectus | SDIT ULTRA SHORT DURATION BOND FUND  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading SDIT ULTRA SHORT DURATION BOND FUND
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Provide higher current income than that typically offered by a money market fund while maintaining a high degree of liquidity and a correspondingly higher risk of principal volatility.
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.
Operating Expenses Caption [Text] 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 [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 89% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 89.00%
Expenses Restated to Reflect Current [Text] rr_ExpensesRestatedToReflectCurrent Other Expenses have been restated to reflect estimated fees and expenses for the upcoming fiscal year.
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 period indicated. The below estimates would be the same whether you redeemed your shares or continued to hold them at the end of the applicable period. 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 Ultra Short Duration Bond Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in investment grade U.S. dollar-denominated debt instruments, including: (i) commercial paper and other corporate obligations; (ii) certificates of deposit, time deposits, bankers' acceptances, bank notes, and other obligations of U.S. savings and loan and thrift institutions, U.S. commercial banks (including foreign branches of such banks) and foreign banks that meet certain asset requirements; (iii) U.S. Treasury obligations and obligations issued or guaranteed as to principal and interest by agencies or instrumentalities of the U.S. Government; (iv) mortgage-backed securities; (v) asset-backed securities; (vi) fully-collateralized repurchase agreements involving any of the foregoing obligations; and (vii) U.S. dollar-denominated instruments of foreign issuers. In addition, the Fund may enter into dollar roll transactions with selected banks and broker-dealers and invest in to-be-announced mortgage-backed securities, futures contracts and forward contracts. The Fund will primarily use futures contracts for hedging purposes to manage the Fund's exposure to interest rate risk. There may also be times when the Fund utilizes futures contracts to take an active position on interest rates to either increase or reduce the interest rate sensitivity of the Fund.


Using a top-down strategy and bottom-up security selection, the sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) seek attractively-valued securities that offer competitive yields and that are issued by issuers that are on a sound financial footing. The Sub-Advisers also consider factors such as the anticipated level of interest rates, relative valuations and yield spreads among various sectors, and the duration of the Fund's entire portfolio. Duration measures the price sensitivity of a fixed income security to changes in interest rates. For example, a five-year duration means that the fixed income security will decrease in value by 5% if interest rates rise 1% and increase in value by 5% if interest rates fall 1%. While the Fund may invest in securities with any maturity or duration, the Sub-Advisers will strive to maintain a portfolio duration for the Fund of 18 months or less under normal market conditions. Due to its investment strategy, the Fund may buy and sell securities and other instruments frequently.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] 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. 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.


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 an issuer's underlying asset portfolio and the issuer's ability to issue new asset-backed commercial paper.


Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as to 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.


Derivatives Risk — The Fund's use of futures contracts and forward contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk, liquidity risk and market risk are described below. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative instrument 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. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund's initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund's use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators are in the process of adopting and implementing regulations governing derivatives markets, the ultimate impact of which remains unclear.


Dollar Rolls Risk — The Fund's investments in dollar rolls may subject the Fund to leverage risk and liquidity risk, both of which are described below.


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. 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.


Foreign Issuer Risk — The risk that issuers in foreign countries face political and economic events unique to such countries. These events will not necessarily affect the U.S. economy or similar issuers located in the U.S.


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.


Investment Style Risk — The risk that short-duration fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.


Leverage Risk — The Fund's use of derivatives or investments in repurchase agreements 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.


Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the seller would like. The seller 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.


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 bond market as a whole.


Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund's actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund's expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.


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.


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, 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.


Repurchase Agreement Risk — Although repurchase agreement transactions must 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.


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.


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.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money on your investment in the Fund, just as you could with other investments.
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 Class Y shares of 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.
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 Class Y shares of 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 [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: 4.94% (06/30/09)


Worst Quarter: -7.40% (12/31/08)


The Fund's Class Y total return (pre-tax) from January 1, 2017 to March 31, 2017 was 0.66%.
Bar Chart, Returns for Class Not Offered in Prospectus [Text] rr_BarChartReturnsForClassNotOfferedInProspectus The Fund's Class F shares are offered in a separate prospectus.
Year to Date Return, Label rr_YearToDateReturnLabel The Fund's Class Y total return (pre-tax) from January 1, 2017 to March 31, 2017
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.66%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.94%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.40%)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2016)
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

The Fund's Class Y shares commenced operations on August 31, 2015. For full calendar years through December 31, 2015, the performance of the Fund's Class F shares is shown. The Fund's Class F shares are offered in a separate prospectus. Because Class Y shares are invested in the same portfolio of securities, returns for Class Y shares would have been substantially similar to those of Class F shares, shown here, and would have differed only to the extent that Class Y shares have lower total annual fund operating expenses than Class F shares.


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.
Class Y Shares Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Bloomberg Barclays Short U.S. Treasury 9-12 Month Index Return (reflects no deduction for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Bloomberg Barclays Short U.S. Treasury 9-12 Month Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.79% [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.33% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.39% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.14% [1],[2]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 1993 [1]
Class Y Shares Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Class Y  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.10%
Distribution (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.23% [3]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.33%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 34
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 106
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 185
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 418
Annual Return 2007 rr_AnnualReturn2007 1.69%
Annual Return 2008 rr_AnnualReturn2008 (9.95%)
Annual Return 2009 rr_AnnualReturn2009 11.94%
Annual Return 2010 rr_AnnualReturn2010 3.82%
Annual Return 2011 rr_AnnualReturn2011 0.38%
Annual Return 2012 rr_AnnualReturn2012 2.66%
Annual Return 2013 rr_AnnualReturn2013 0.76%
Annual Return 2014 rr_AnnualReturn2014 0.49%
Annual Return 2015 rr_AnnualReturn2015 0.43%
Annual Return 2016 rr_AnnualReturn2016 1.50%
Label rr_AverageAnnualReturnLabel Fund Return Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 1.50% [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.17% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.25% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.15% [1]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 31, 2015 [1]
Class Y Shares Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Class Y | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Fund Return After Taxes on Distributions
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.99% [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.76% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.53% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 1.82% [1]
Class Y Shares Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Class Y | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Fund Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.85% [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.72% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.69% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 1.90% [1]
[1] The Fund's Class Y shares commenced operations on August 31, 2015. For periods prior to August 31, 2015, the performance of the Fund's Class F shares has been used. Returns for Class Y shares would have been substantially similar to those of Class F shares and would have differed only to the extent that Class Y shares have lower total annual fund operating expenses than Class F shares.
[2] Index returns are shown from September 30, 1993.
[3] Other Expenses have been restated to reflect estimated fees and expenses for the upcoming fiscal year.