XML 100 R5.htm IDEA: XBRL DOCUMENT v3.26.1
Investment Risks
May 28, 2026
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Foreign Issuer Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund's investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. 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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class F Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that short-duration U.S. Government fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class F Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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

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

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

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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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

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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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.
GNMA FUND - Class F Prospectus | SDIT GNMA FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Foreign Issuer Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund's investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. 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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
ULTRA SHORT DURATION BOND FUND - Class Y Prospectus | SDIT ULTRA SHORT DURATION BOND FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that short-duration U.S. Government fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
SHORT DURATION GOVERNMENT FUND - Class Y Prospectus | SDIT SHORT DURATION GOVERNMENT FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GNMA FUND - Class Y Prospectus | SDIT GNMA FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
GNMA FUND - Class Y Prospectus | SDIT GNMA FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] 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.
GNMA FUND - Class Y Prospectus | SDIT GNMA FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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

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

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

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.
GNMA FUND - Class Y Prospectus | SDIT GNMA FUND | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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

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

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

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

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

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

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

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

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

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.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit nor is it insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that the Fund's yield will decline due to changing interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, whereas a fall in interest rates typically results in the Fund having to invest available cash in instruments with lower interest rates than those of the current portfolio securities. During periods when interest rates are low, the Fund's yield will also be low and the Fund may not generate enough income to pay its expenses or pay a daily dividend. This could impair the Fund's ability to provide a positive yield and maintain a stable $1.00 share price. Fluctuations in interest rates may also have unpredictable effects on the markets and may affect the liquidity of the fixed-income securities held by the Fund.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund's ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT II FUND - Class F Prospectus | SDIT GOVERNMENT II FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit nor is it insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that the Fund's yield will decline due to changing interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, whereas a fall in interest rates typically results in the Fund having to invest available cash in instruments with lower interest rates than those of the current portfolio securities. During periods when interest rates are low, the Fund's yield will also be low and the Fund may not generate enough income to pay its expenses or pay a daily dividend. This could impair the Fund's ability to provide a positive yield and maintain a stable $1.00 share price. Fluctuations in interest rates may also have unpredictable effects on the markets and may affect the liquidity of the fixed-income securities held by the Fund.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund's ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
TREASURY II FUND - Class F Prospectus | SDIT TREASURY II FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit nor is it insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that the Fund's yield will decline due to changing interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, whereas a fall in interest rates typically results in the Fund having to invest available cash in instruments with lower interest rates than those of the current portfolio securities. During periods when interest rates are low, the Fund's yield will also be low and the Fund may not generate enough income to pay its expenses or pay a daily dividend. This could impair the Fund's ability to provide a positive yield and maintain a stable $1.00 share price. Fluctuations in interest rates may also have unpredictable effects on the markets and may affect the liquidity of the fixed-income securities held by the Fund.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Cash Management Risk — The value of the investments held by the Fund for cash management purposes may be affected by market risks, changing interest rates and by changes in credit ratings of the investments. To the extent that the Fund has any uninvested cash, the Fund would be subject to credit risk with respect to the depository institution holding the cash. If the Fund holds uninvested cash, the Fund will not earn income on the cash. During such periods, it may be more difficult for the Fund to achieve its investment objective.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund's ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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. Additionally, if the Fund has uninvested cash, the Fund is subject to the risk that the depository institution holding the uninvested cash will be unable to repay the cash held.
GOVERNMENT FUND - Admin Class Shares Prospectus | SDIT GOVERNMENT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit nor is it insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that the Fund's yield will decline due to changing interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, whereas a fall in interest rates typically results in the Fund having to invest available cash in instruments with lower interest rates than those of the current portfolio securities. During periods when interest rates are low, the Fund's yield will also be low and the Fund may not generate enough income to pay its expenses or pay a daily dividend. This could impair the Fund's ability to provide a positive yield and maintain a stable $1.00 share price. Fluctuations in interest rates may also have unpredictable effects on the markets and may affect the liquidity of the fixed-income securities held by the Fund.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Cash Management Risk — The value of the investments held by the Fund for cash management purposes may be affected by market risks, changing interest rates and by changes in credit ratings of the investments. To the extent that the Fund has any uninvested cash, the Fund would be subject to credit risk with respect to the depository institution holding the cash. If the Fund holds uninvested cash, the Fund will not earn income on the cash. During such periods, it may be more difficult for the Fund to achieve its investment objective.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund's ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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. Additionally, if the Fund has uninvested cash, the Fund is subject to the risk that the depository institution holding the uninvested cash will be unable to repay the cash held.
GOVERNMENT FUND - Wealth Class Shares Prospectus | SDIT GOVERNMENT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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

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.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit nor is it insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that the Fund's yield will decline due to changing interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, whereas a fall in interest rates typically results in the Fund having to invest available cash in instruments with lower interest rates than those of the current portfolio securities. During periods when interest rates are low, the Fund's yield will also be low and the Fund may not generate enough income to pay its expenses or pay a daily dividend. This could impair the Fund's ability to provide a positive yield and maintain a stable $1.00 share price. Fluctuations in interest rates may also have unpredictable effects on the markets and may affect the liquidity of the fixed-income securities held by the Fund.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Cash Management Risk — The value of the investments held by the Fund for cash management purposes may be affected by market risks, changing interest rates and by changes in credit ratings of the investments. To the extent that the Fund has any uninvested cash, the Fund would be subject to credit risk with respect to the depository institution holding the cash. If the Fund holds uninvested cash, the Fund will not earn income on the cash. During such periods, it may be more difficult for the Fund to achieve its investment objective.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund's ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Repurchase Agreement Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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. Additionally, if the Fund has uninvested cash, the Fund is subject to the risk that the depository institution holding the uninvested cash will be unable to repay the cash held.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value.
GOVERNMENT FUND - Institutional Shares Prospectus | SDIT GOVERNMENT FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

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.