Label	Element	Value
SIIT Ultra Short Duration Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SIIT Ultra Short Duration Bond Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Provide higher current income than that typically offered by a money market fund while maintaining a high degree of liquidity and a correspondingly higher risk of principal volatility.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Fund shares.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs affect the Fund's performance. During the most recent fiscal year, the Fund's annualized portfolio turnover rate was 112% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	112.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Ultra Short Duration Bond Fund invests at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in investment grade U.S. dollar-denominated debt instruments, including: (i) commercial paper and other corporate obligations; (ii) certificates of deposit, time deposits, bankers' acceptances, bank notes and other obligations of U.S. savings and loan and thrift institutions, U.S. commercial banks (including foreign branches of such banks) and foreign banks that meet certain asset requirements; (iii) U.S. Treasury obligations and obligations issued or guaranteed as to principal and interest by agencies or instrumentalities of the U.S. Government; (iv) mortgage-backed securities; (v) asset-backed securities; (vi) fully-collateralized repurchase agreements involving any of the foregoing obligations; and (vii) U.S. dollar-denominated instruments of foreign issuers. In addition, the Fund may invest in futures contracts, options, swaps and other similar instruments. The primary derivatives used by the Fund are futures contracts, options, interest rate swaps and credit default swaps. The Fund will primarily use futures contracts for hedging purposes to manage the Fund's exposure to interest rate risk. There will be times when the Fund utilizes futures contracts to take an active position to either add or reduce the interest rate sensitivity of the Fund. The Fund will primarily use options and swaps to either mitigate the Fund's overall level of risk or to gain exposure to a particular fixed income security or segment of the fixed income market. Using a top-down strategy and bottom-up security selection, the Sub-Adviser seeks attractively-valued securities that offer competitive yields and that are issued by issuers that are on a sound financial footing. The Sub-Adviser also considers factors such as the anticipated level of interest rates, relative valuations and yield spreads among various sectors and the duration of the Fund's entire portfolio. Duration measures the price sensitivity of a fixed income security to changes in interest rates. For example, a five-year duration means that the fixed income security will decrease in value by 5% if interest rates rise 1% and increase in value by 5% if interest rates fall 1%. While the Fund may invest in securities with any maturity or duration, the Fund will maintain a portfolio duration of 18 months or less under normal market conditions. To achieve its investment goal, the Fund may invest in one or more SEI-sponsored funds to pursue its investment strategies in an efficient manner. The Fund may invest in a SEI-sponsored fund only if the SEI-sponsored fund invests in securities and pursues investment strategies that are consistent with the Fund's investment goal and strategy.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities, and asset-backed securities may not have the benefit of any security interest in the related assets. Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation. Derivatives Risk — The Fund's use of futures contracts, options, interest rate swaps and credit default swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage, liquidity and market risk are described below. Many over-the-counter ("OTC") derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund's use of options and swaps is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Credit risk is described above. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. 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. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation are not yet fully known and may not be for some time. New regulation of derivatives may make them more costly, may limit their availability or may otherwise adversely affect their value or performance. Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security's value. Fixed Income Market Risk — The prices of the Fund's fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund's fixed income securities will decrease in value if interest rates rise and vice versa. In the case of foreign securities, price fluctuations will reflect international economic and political events, as well as changes in currency valuations relative to the U.S. dollar. Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risk due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. Interest Rate Risk — The risk that a rise in interest rates will cause a fall in the value of fixed income securities, including U.S. Government Securities, in which the Fund invests. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates. A low interest rate environment may present greater interest rate risk, because there may be a greater likelihood of rates increasing and rates may increase more rapidly. Investment Company Risk — When the Fund invests in an investment company, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the investment company's expenses. In addition, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. Investment Style Risk — The risk that short-duration fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk — The Fund's use of derivatives may result in the Fund's total investment exposure substantially exceeding the value of its portfolio securities and the Fund's investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund's share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund's use of leverage may result in a heightened risk of investment loss. Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the seller would like. The seller may have to lower the price, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on fund management or performance. Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the bond market as a whole. Mortgage-Backed Securities Risk — Mortgage-backed securities are affected by, among other things, interest rate changes and the possibility of prepayment of the underlying mortgage loans. Mortgage-backed securities are also subject to the risk that underlying borrowers will be unable to meet their obligations. Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments. Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and additional capital gains tax liabilities. Prepayment Risk — The risk that with declining interest rates, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates. U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency's own resources. Investing in the Fund involves risk, and there is no guarantee that the Fund will achieve its investment goal. You could lose money on your investment in the Fund, just as you could with other investments.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money on your investment in the Fund, just as you could with other investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund commenced operations on February 28, 2011. The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past three years, and by showing how the Fund's average annual returns for 1 year and since the Fund's inception compare with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past three years, and by showing how the Fund's average annual returns for 1 year and since the Fund's inception compare with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 1.19% (9/30/12) Worst Quarter: -0.04% (6/30/13) The Fund's total return from January 1, 2015 to June 30, 2015 was 0.61%.
Year to Date Return, Label	rr_YearToDateReturnLabel	total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2015
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.61%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	1.19%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(0.04%)
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2014)
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	(reflects no deduction for fees, expenses or taxes)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Your actual after-tax returns will depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Explanation after Tax Higher	rr_PerformanceTableExplanationAfterTaxHigher	In the event of negative performance, the Fund's returns after taxes on distributions and sale of Fund Shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund Shares. As a result, the Fund's returns after taxes on distributions and sale of Fund Shares may exceed the Fund's returns before taxes and/or returns after taxes on distributions.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. In the event of negative performance, the Fund's returns after taxes on distributions and sale of Fund Shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund Shares. As a result, the Fund's returns after taxes on distributions and sale of Fund Shares may exceed the Fund's returns before taxes and/or returns after taxes on distributions.
SIIT Ultra Short Duration Bond Fund \| Barclays Capital Short U.S. Treasury 9-12 Month Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Barclays Capital Short U.S. Treasury 9-12 Month Index (reflects no deduction for fees, expenses or taxes)
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	0.17%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	0.27%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2011
SIIT Ultra Short Duration Bond Fund \| SIIT Ultra Short Duration Bond Fund - Class A
Risk/Return:	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.15%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.22%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 23
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	71
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	124
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 280
Annual Return 2012	rr_AnnualReturn2012	2.80%
Annual Return 2013	rr_AnnualReturn2013	0.92%
Annual Return 2014	rr_AnnualReturn2014	0.74%
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	0.74%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	1.19%
Average Annual Returns, Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2011
SIIT Ultra Short Duration Bond Fund \| SIIT Ultra Short Duration Bond Fund - Class A \| After Taxes on Distributions
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	0.29%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	0.73%
SIIT Ultra Short Duration Bond Fund \| SIIT Ultra Short Duration Bond Fund - Class A \| After Taxes on Distributions and Sale of Fund Shares
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Returns, 1 Year	rr_AverageAnnualReturnYear01	0.42%
Average Annual Returns, Since Inception	rr_AverageAnnualReturnSinceInception	0.73%

If the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Form

-Number N-1A

-Chapter A

-Section 4

-Subsection b

-Paragraph 2

-Subparagraph ii