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SDIT GNMA FUND | GNMA FUND - Class Y Prospectus  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk/Return [Heading] oef_RiskReturnHeading GNMA FUND
Objective [Heading] oef_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] oef_ObjectivePrimaryTextBlock

Preserve principal value and maintain a high degree of liquidity while providing current income.
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 28% of the average value of its portfolio.
Portfolio Turnover, Rate oef_PortfolioTurnoverRate 28.00%
Strategy [Heading] oef_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] oef_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%.
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 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] oef_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] 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: 6.71% (12/31/23)
Worst Quarter: -5.04% (09/30/22)
The Fund's Class Y total return (pre-tax) from January 1, 2026 to March 31, 2026 was 0.76%.
Year to Date Return, Label [Optional Text] oef_YearToDateReturnLabel The Fund's Class Y total return (pre-tax) from January 1, 2026 to March 31, 2026 was
Bar Chart, Year to Date Return, Date oef_BarChartYearToDateReturnDate Mar. 31, 2026
Bar Chart, Year to Date Return oef_BarChartYearToDateReturn 0.76%
Highest Quarterly Return, Label [Optional Text] oef_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date oef_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return oef_BarChartHighestQuarterlyReturn 6.71%
Lowest Quarterly Return, Label [Optional Text] oef_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date oef_BarChartLowestQuarterlyReturnDate Sep. 30, 2022
Lowest Quarterly Return oef_BarChartLowestQuarterlyReturn (5.04%)
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 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 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.

SDIT GNMA FUND | GNMA FUND - Class Y 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.
SDIT GNMA FUND | GNMA FUND - Class Y 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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Market Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | U.S. Government Securities Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Repurchase Agreement Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Investment Style Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Interest Rate Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which the Fund invests. Generally, the value of the Fund's fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments

held by the Fund. 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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Dollar Rolls Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | When-Issued and Delayed Delivery Securities Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Derivatives Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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 implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.
SDIT GNMA FUND | GNMA FUND - Class Y 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 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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Credit Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Duration Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Extension Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Leverage Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Prepayment Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Opportunity Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Portfolio Turnover Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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.
SDIT GNMA FUND | GNMA FUND - Class Y Prospectus | Class Y  
Prospectus [Line Items] oef_ProspectusLineItems  
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.10%
Distribution and Service (12b-1) Fees oef_DistributionAndService12b1FeesOverAssets 0.00%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.41%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.51%
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 52
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 164
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 285
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 640
GNMA FUND - Class Y Prospectus | Bloomberg GNMA Index Return (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Bloomberg GNMA Index Return (reflects no deduction for fees, expenses or taxes)
Average Annual Return, Percent oef_AvgAnnlRtrPct 8.08% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 0.23% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 1.50% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.21% [1]
GNMA FUND - Class Y Prospectus | Bloomberg U.S. Aggregate Bond Index (TR) (USD) (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Bloomberg U.S. Aggregate Bond Index (TR) (USD) (reflects no deduction for fees, expenses or taxes)
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.30% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct (0.36%) [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 2.01% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.29% [1],[2]
GNMA FUND - Class Y Prospectus | Class Y  
Prospectus [Line Items] oef_ProspectusLineItems  
Annual Return [Percent] oef_AnnlRtrPct 1.73%
Annual Return [Percent] oef_AnnlRtrPct 1.79%
Annual Return [Percent] oef_AnnlRtrPct 0.92%
Annual Return [Percent] oef_AnnlRtrPct 5.67%
Annual Return [Percent] oef_AnnlRtrPct 4.01%
Annual Return [Percent] oef_AnnlRtrPct (1.68%)
Annual Return [Percent] oef_AnnlRtrPct (10.76%)
Annual Return [Percent] oef_AnnlRtrPct 5.21%
Annual Return [Percent] oef_AnnlRtrPct 1.38%
Annual Return [Percent] oef_AnnlRtrPct 7.40%
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Fund Return Before Taxes
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.40% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 0.10% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 1.45% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.94% [1]
Performance Inception Date oef_PerfInceptionDate Mar. 20, 1987
GNMA FUND - Class Y Prospectus | Class Y | After Taxes on Distributions  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Fund Return After Taxes on Distributions
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.84% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct (1.09%) [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 0.21% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 3.04% [1]
GNMA FUND - Class Y Prospectus | Class Y | After Taxes on Distributions and Sales  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Label [Optional Text] oef_AverageAnnualReturnLabel Fund Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.36% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct (0.44%) [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 0.57% [1]
Average Annual Return, Percent oef_AvgAnnlRtrPct 3.08% [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.
[2] Benchmark returns since inception do not include the return for the partial month following inception date of the Fund (3/20/1987 — 3/31/1987). Annualization calculation of the inception to date returns is based on the actual inception date (3/20/1987).