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

Preserve principal value and maintain 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, 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 [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 405% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 405.00%
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 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] 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 GNMA Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in mortgage-backed securities issued by the Government National Mortgage Association (GNMA). The Fund may also invest in U.S. Treasury securities and U.S. Government securities obligations, and repurchase agreements collateralized by such obligations. 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. Due to its investment strategy, the Fund may buy and sell securities and other instruments frequently.

Using a top-down strategy and bottom-up security selection, the sub-adviser (the Sub-Adviser) seeks attractively-valued securities that offer competitive yields. The Sub-Adviser also considers factors such as the anticipated level of interest rates, relative valuations and yield spreads, 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%.
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. Markets for fixed income securities 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. 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.

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and 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. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

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.

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

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. 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.

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.

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.

When-Issued and Delayed Delivery Securities Risk — When-issued and delayed delivery securities involve the risk that the security the Fund buys will lose value prior to its delivery.

Derivatives Risk — The Fund's use of futures contracts and forward contracts is subject to market risk, liquidity risk, correlation risk and leverage risk. Market risk is described above and liquidity risk and leverage risk are described below. Many over-the-counter 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. The Fund's use of forward contracts is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. 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 have adopted and are in the process of implementing regulations governing derivatives markets, the ultimate impact of which remains unclear.

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 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.

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.

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.

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

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.

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.

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund's performance.

LIBOR Replacement Risk — The U.K. Financial Conduct Authority stopped compelling or inducing banks to submit certain London Inter-Bank Offered Rate (LIBOR) rates and will do so for the remaining LIBOR rates immediately after June 30, 2023. The elimination of LIBOR may adversely affect the interest rates on, and value of, certain Fund 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 [Text] rr_RiskNotInsured 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 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 performance information shown is based on full calendar years. 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: 2.74% (03/31/20)
Worst Quarter: -2.85% (06/30/13)
The Fund's Class Y total return (pre-tax) from January 1, 2022 to March 31, 2022 was -4.07%.
The Fund's Class Y shares commenced operations on October 30, 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. 		 
Year to Date Return, Label rr_YearToDateReturnLabel The Fund's Class Y total return (pre-tax) from January 1, 2022 to March 31, 2022 was
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Mar. 31, 2022
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn (4.07%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 2.74%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.85%)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for the periods ended December 31, 2021)
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 Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher In some cases, the Fund's return after taxes may exceed the Fund's return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.
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. In some cases, the Fund's return after taxes may exceed the Fund's return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period.
Class Y Prospectus | SDIT GNMA FUND | Bloomberg GNMA Index Return (reflects no deduction for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Bloomberg GNMA Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (1.45%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.16%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.99%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 5.74%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 20, 1987
Class Y Prospectus | SDIT GNMA FUND | Class Y  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.09%
Distribution (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.28%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.37%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 38
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 119
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 208
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 468
Annual Return 2012 rr_AnnualReturn2012 2.47%
Annual Return 2013 rr_AnnualReturn2013 (2.68%)
Annual Return 2014 rr_AnnualReturn2014 6.70%
Annual Return 2015 rr_AnnualReturn2015 1.57%
Annual Return 2016 rr_AnnualReturn2016 1.73%
Annual Return 2017 rr_AnnualReturn2017 1.79%
Annual Return 2018 rr_AnnualReturn2018 0.92%
Annual Return 2019 rr_AnnualReturn2019 5.67%
Annual Return 2020 rr_AnnualReturn2020 4.01%
Annual Return 2021 rr_AnnualReturn2021 (1.68%)
Label rr_AverageAnnualReturnLabel Fund Return Before Taxes
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (1.68%) [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.11% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 2.02% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 5.46% [1]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 20, 1987 [1]
Class Y Prospectus | SDIT GNMA 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 (2.50%) [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.97% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.91% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.48% [1]
Class Y Prospectus | SDIT GNMA 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 (0.99%) [1]
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.12% [1]
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.07% [1]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.46% [1]
[1] The Fund's Class Y shares commenced operations on October 30, 2015. For periods prior to October 30, 2015, the performance of the Fund's Class F shares has been used. Returns for the 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.