Label

Element

Value

SIIT Multi-Asset Real Return Fund

Risk/Return:

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Risk/Return [Heading]

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SIIT Multi-Asset Real Return Fund

Objective [Heading]

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Investment Goal

Objective, Primary [Text Block]

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Total return exceeding the rate of inflation.

Expense [Heading]

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Fees and Expenses

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Fund shares.

Operating Expenses Caption [Text]

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ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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PORTFOLIO TURNOVER

Portfolio Turnover [Text Block]

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The Fund will pay transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual Fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 22% of the average value of its portfolio.

Portfolio Turnover, Rate

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22.00%

Expense Example [Heading]

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EXAMPLE

Expense Example Narrative [Text Block]

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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]

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Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund uses a multi-manager approach under the general supervision of SEI Investments Management Corporation (SIMC or the Adviser), allocating its assets among one or more sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) using different investment strategies designed to produce a total return that exceeds the rate of inflation in the U.S. Assets of the Fund not allocated to Sub-Advisers are managed directly by SIMC.

Under normal circumstances, the Fund will pursue its investment goal by selecting investments from a broad range of asset classes, including fixed income and equity securities and commodity linked instruments. The Fund seeks "real return" (i.e., total returns that exceed the rate of inflation over a full market cycle, regardless of market conditions). The Fund may invest in U.S. and non-U.S. dollar-denominated securities.

Fixed income securities may include: (i) securities issued or guaranteed by the U.S. Government and its agencies and instrumentalities and obligations of U.S. and foreign commercial banks, such as certificates of deposit, time deposits, bankers' acceptances and bank notes; (ii) obligations of foreign governments; (iii) Treasury Inflation-Protected Securities (TIPS) and other inflation-linked debt securities; (iv) U.S. and foreign (including emerging markets) corporate debt securities, including commercial paper, and fully-collateralized repurchase and reverse repurchase agreements with highly rated counterparties (those rated A or better); and (v) securitized issues such as residential and commercial mortgage-backed securities, asset-backed securities and collateralized debt obligations. The Fund may invest in debt securities of any credit quality, including those rated below investment grade (junk bonds) or, if unrated, of equivalent credit quality, as determined by the Fund's managers. The Fund may invest in securities with a broad range of maturities. The Fund may also enter into reverse repurchase agreements with respect to its investment in TIPS. In an attempt to generate excess returns, when the Fund enters into such a TIPS reverse repurchase agreement it will use the cash received to enter into a short position on U.S. Treasury bonds.

Equity securities may include common or preferred stocks, warrants, rights, depositary receipts, equity-linked securities and other equity interests. The Fund may invest in securities of issuers of any market capitalization and may invest in both foreign and domestic equity securities. In addition to direct investment in securities and other instruments, the Fund may invest in exchange-traded funds (ETFs). The Fund may also invest in real estate investment trusts (REITs) and U.S. and non-U.S. real estate companies.

A portion of the Fund's assets may also be invested in commodity-linked securities to provide exposure to the investment returns of the commodities markets without investing directly in physical commodities. Commodity-linked securities include notes with interest payments that are tied to an underlying commodity or commodity index, ETFs or other exchange-traded products that are tied to the performance of a commodity or commodity index or other types of investment vehicles or instruments that provide returns that are tied to commodities or commodity indexes. The Fund may also invest in equity and debt securities of issuers in commodity-related industries. The Fund may also seek to gain long and short exposure to the commodity markets, in whole or in part, through investments in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (Subsidiary). The Subsidiary, unlike the Fund, may invest to a significant extent in long and short positions in commodities, commodity contracts, commodity investments and derivative instruments. The Subsidiary may also invest in other instruments in which the Fund is permitted to invest, either as investments or to serve as margin or collateral for its derivative positions. The Fund may invest up to 25% of its total assets in the Subsidiary. The Subsidiary is advised by SIMC.

The Fund may also purchase or sell futures contracts, options, forward contracts and swaps (including swaptions) for return enhancement or hedging purposes. Futures contracts, forward contracts and swaps are used to synthetically obtain exposure to securities or baskets of securities and to manage the Fund's interest rate duration and yield curve exposure. These derivatives are also used to mitigate the Fund's overall level of risk and/or the Fund's risk to particular types of securities or market segments. The Fund may purchase or sell futures contracts and options on U.S. Government securities for return enhancement.

Interest rate swaps are further used to manage the Fund's interest rate risk. Swaps on indexes are used to manage the inflation-adjusted return of the Fund. The Fund may buy credit default swaps in an attempt to manage credit risk where the Fund has credit exposure to an issuer, and the Fund may sell credit default swaps to more efficiently gain credit exposure to a security or basket of securities.

The Sub-Adviser(s) may seek to enhance the Fund's return by actively managing the Fund's currency exposure. In managing the Fund's currency exposure, the Sub-Adviser(s) may buy and sell currencies (i.e., take long or short positions) through the use of cash, securities and/or currency-related derivatives, including, without limitation, currency forward contracts, futures contracts, swaps and options. The Fund may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency. The Fund may also engage in currency transactions in an attempt to take advantage of certain inefficiencies in the currency exchange market, to increase their exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another.

The Sub-Adviser(s) may engage in short sales in an attempt to capitalize on equity securities that they believe will underperform the market or their peers. When a Sub-Adviser(s) sells securities short, it may invest the proceeds from the short sales in an attempt to enhance returns. This strategy may effectively result in the Fund having a leveraged investment portfolio, which results in greater potential for loss.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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The success of the Fund's investment strategy depends both on SIMC's selection of the Sub-Adviser(s) and allocation of assets to such Sub-Adviser(s). The Sub-Adviser(s) may be incorrect in assessing market trends or the value or growth capability of particular securities or asset classes. In addition, the methodology by which SIMC allocates the Fund's assets to the Sub-Adviser(s) may not achieve desired results and may cause the Fund to lose money or underperform other comparable mutual funds.

The Sub-Adviser(s) and any underlying funds in which it invests may apply any of a variety of investment strategies and may invest in a broad range of asset classes, securities and other investments to achieve those investment strategies. The principal risks of using such investment strategies and making investments in such asset classes, securities and other investments are set forth below. Because an underlying fund's use of an investment strategy or investment in an asset class, security or other investment is subject to the same or similar risks as the Fund's use of such strategy or investment in such asset class, security or other investment, the term "the Fund" in the paragraphs below collectively refers to both the Fund and each underlying fund.

Fixed Income Market Risk — The prices of the Fund's fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund's fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. In the case of foreign securities, price fluctuations will reflect international economic and political events, as well as changes in currency valuations relative to the U.S. dollar. In response to these events, the Fund's value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund's liquidity or force the Fund to sell securities into a declining or illiquid market.

Equity 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.

Inflation Protected Securities Risk — The value of inflation protected securities, including TIPS, generally will fluctuate in response to changes in "real" interest rates, generally decreasing when real interest rates rise and increasing when real interest rates fall. Real interest rates represent nominal (or stated) interest rates reduced by the expected impact of inflation. In addition, interest payments on inflation-indexed securities will generally vary up or down along with the rate of inflation.

Large Capitalization Risk — If valuations of large capitalization companies appear to be greatly out of proportion to the valuations of small or medium capitalization companies, investors may migrate to the stocks of small and medium sized companies. Additionally, larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

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.

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

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

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.

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.

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 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.

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.

Collateralized Debt Obligations (CDOs) and Collateralized Loan Obligations (CLOs) Risk — CDOs and CLOs are securities backed by an underlying portfolio of debt and loan obligations, respectively. CDOs and CLOs issue classes or "tranches" that vary in risk and yield and may experience substantial losses due to actual defaults, decrease in market value due to collateral defaults and removal of subordinate tranches, market anticipation of defaults and investor aversion to CDO and CLO securities as a class. The risks of investing in CDOs and CLOs depend largely on the tranche invested in and the type of the underlying debts and loans in the tranche of the CDO or CLO, respectively, in which the Fund invests. CDOs and CLOs also carry risks including, but not limited to, interest rate risk and credit risk, which are described below. For example, a liquidity crisis in the global credit markets could cause substantial fluctuations in prices for leveraged loans and high-yield debt securities and limited liquidity for such instruments. When the Fund invests in CDOs or CLOs, in addition to directly bearing the expenses associated with its own operations, it may bear a pro rata portion of the CDO's or CLO's expenses.

Below Investment Grade Securities (Junk Bonds) Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. Because these securities typically offer a higher rate of return to compensate investors for these risks, they are sometimes referred to as "high yield bonds," but there is no guarantee that an investment in these securities will result in a high rate of return.

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments.

Small and Medium Capitalization Risk — The small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, smaller companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter or listed on an exchange.

Investment Company Risk — When the Fund invests in an investment company, it will bear a pro rata portion of the investment company's expenses in addition to directly bearing the expenses associated with its own operations. Furthermore, 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 that of the underlying portfolio securities.

Exchange-Traded Funds (ETFs) Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF's expenses.

Real Estate Industry Risk — Securities of companies principally engaged in the real estate industry may be subject to the risks associated with direct ownership of real estate, including fluctuations in the value of underlying properties and defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions.

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund's investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate are described above. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

Commodity-Linked Securities Risk — Investments in commodity-linked securities may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer's financial structure or the performance of unrelated businesses.

Derivatives Risk — The Fund's use of futures, forwards, options and 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 OTC forwards, 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. Both U.S. and non-U.S. regulators are in the process of adopting and implementing regulations governing derivatives markets, the ultimate impact of which remains unclear.

Investment in the Subsidiary Risk — The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the 1940 Act), and, unless otherwise noted in this prospectus, is not subject to all of the investor protections of the 1940 Act. Thus, the Fund, as an investor in the Subsidiary, will not have all of the protections offered to investors in registered investment companies. In addition, changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Subsidiary, respectively, are organized, could result in the inability of the Fund and/or the Subsidiary to operate as intended and could negatively affect the Fund and its shareholders.

Commodity Investments and Derivatives Risk — Commodity investments and derivatives may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer's financial structure or the performance of unrelated businesses. The value of a commodity investment or a derivative investment in commodities is typically based upon the price movements of a physical commodity, a commodity futures contract or commodity index or some other readily measurable economic variable that is dependent upon changes in the value of commodities or the commodities markets. The value of these securities will rise or fall in response to changes in the underlying commodity or related benchmark or investment, changes in interest rates or factors affecting a particular industry or commodity, such as natural disasters, weather and U.S. and international economic, political and regulatory developments.

Derivatives Risk — The Fund's use of futures, forwards, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Credit risk, leverage risk and liquidity 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 OTC forwards, 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. Market 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. Both U.S. and non-U.S. regulators are in the process of adopting and implementing regulations governing derivatives markets, the ultimate impact of which remains unclear.

Currency Risk — As a result of the Fund's investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies and the Fund's active management of its currency exposures, 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. Due to the Fund's active positions in currencies, it will be subject to the risk that 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.

Short Sales Risk — A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as "covering" the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities. Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund's share price. In addition, shorting a future contract may require posting only a margin that may amount to less than the notional exposure of the contract. Such a practice may exacerbate the loss in a case of adverse price action.

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 a Fund invests. A low interest rate environment may present greater interest rate risk, because there may be a greater likelihood of rates increasing and rates may increase more rapidly.

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

Non-Diversified Risk — The Fund is non-diversified, which means that it may invest in the securities of relatively few issuers. As a result, the Fund may be more susceptible to a single adverse economic or political occurrence affecting one or more of these issuers and may experience increased volatility due to its investments in those securities.

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.

Tax Risk — The Fund may gain most of its exposure to the commodities markets through its investment in the Subsidiary, which invests in commodity investments and derivative instruments. The Fund's investment in the Subsidiary is expected to provide the Fund with exposure to the commodities markets within the limitations of the federal tax requirements of Subchapter M of the Internal Revenue Code of 1986, as amended (the Code) for qualification as a regulated investment company (RIC). To the extent the Fund invests in such instruments directly, it will seek to restrict the resulting income from commodity-linked derivative instruments that do not generate qualifying income, such as commodity-linked swaps, to a maximum of 10% of its gross income (when combined with its other investments that produce non-qualifying income) to comply with certain qualifying income tests necessary for the Fund to qualify as a RIC under Subchapter M of the Code. However, the Fund may generate more non-qualifying income than anticipated, may not be able to generate qualifying income in a particular taxable year at levels sufficient to meet the qualifying income requirement, or may not be able to accurately predict the non-qualifying income from these investments. Accordingly, the extent to which the Fund invests in commodities or commodity-linked derivative instruments directly may be limited by the requirements of Subchapter M of the Code, which the Fund must continue to satisfy to maintain its status as a RIC. Failure to comply with such requirements would have significant negative tax consequences to Fund shareholders. Under certain circumstances, the Fund may be able to cure a failure to meet the qualifying income requirement, but in order to do so the Fund may incur significant Fund-level taxes, which would effectively reduce (and could eliminate) the Fund's returns. See the "Taxes" section of the SAI for additional information.

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

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

Prepayment Risk — The risk that, with declining interest rates, fixed income securities with stated interests may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

Leverage Risk — The Fund's use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) 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.

Investing in the Fund involves risk, and there is no guarantee that the Fund will achieve its investment goal. You could lose money on your investment in the Fund, just as you could with other investments. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Lose Money [Text]

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You could lose money on your investment in the Fund, just as you could with other investments.

Risk Nondiversified Status [Text]

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The Fund is non-diversified, which means that it may invest in the securities of relatively few issuers. As a result, the Fund may be more susceptible to a single adverse economic or political occurrence affecting one or more of these issuers and may experience increased volatility due to its investments in those securities.

RIsk Not Insured [Text]

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An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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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 seven calendar years, and by showing how the Fund's average annual returns for 1 and 5 years and since the Fund's inception compare with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.

Performance Information Illustrates Variability of Returns [Text]

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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 seven calendar years, and by showing how the Fund's average annual returns for 1 and 5 years and since the Fund's inception compare with those of a broad measure of market performance.

Performance Availability Phone [Text]

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1-800-DIAL-SEI

Performance Past Does Not Indicate Future [Text]

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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]

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Best Quarter: 4.55% (6/30/16)
Worst Quarter: -5.51% (6/30/13)
The Fund's total return from January 1, 2019 to June 30, 2019 was 4.11%.

Year to Date Return, Label

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total return

Bar Chart, Year to Date Return, Date

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Jun. 30, 2019

Bar Chart, Year to Date Return

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4.11%

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Jun. 30, 2016

Highest Quarterly Return

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4.55%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Jun. 30, 2013

Lowest Quarterly Return

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(5.51%)

Performance Table Heading

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Average Annual Total Returns (for the periods ended December 31, 2018)

Index No Deduction for Fees, Expenses, Taxes [Text]

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(reflects no deduction for fees, expenses or taxes)

Performance Table Uses Highest Federal Rate

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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

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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

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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

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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 Multi-Asset Real Return Fund | Bloomberg Barclays 1-5 Year U.S. TIPS Index Return (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Bloomberg Barclays 1-5 Year U.S. TIPS Index Return (reflects no deduction for fees, expenses or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.41%

5 Years

rr_AverageAnnualReturnYear05

0.60%

Since Inception

rr_AverageAnnualReturnSinceInception

0.38%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 28, 2011

SIIT Multi-Asset Real Return Fund | SIIT Multi-Asset Real Return Fund - Class A

Risk/Return:

rr_RiskReturnAbstract

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses of the Fund

rr_Component1OtherExpensesOverAssets

0.07%

Other Expenses of the Subsidiary

rr_Component2OtherExpensesOverAssets

none

Dividends on Shorts

rr_Component3OtherExpensesOverAssets

0.29%

Total Other Expenses

rr_OtherExpensesOverAssets

0.88%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.43%

Total Management Fees

rr_NetExpensesOverAssets

0.55%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 146

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

452

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

782

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,713

Annual Return 2012

rr_AnnualReturn2012

2.01%

Annual Return 2013

rr_AnnualReturn2013

(5.53%)

Annual Return 2014

rr_AnnualReturn2014

(4.01%)

Annual Return 2015

rr_AnnualReturn2015

(4.09%)

Annual Return 2016

rr_AnnualReturn2016

4.24%

Annual Return 2017

rr_AnnualReturn2017

(1.13%)

Annual Return 2018

rr_AnnualReturn2018

(2.92%)

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(2.92%)

5 Years

rr_AverageAnnualReturnYear05

(1.63%)

Since Inception

rr_AverageAnnualReturnSinceInception

(2.31%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 28, 2011

Management Fees of the Fund

ck0000939934_Componenet1ManagementFeesOverAssets

0.55%

Management Fees of the Subsidiary

ck0000939934_Componenet2ManagementFeesOverAssets

none

Interest Expense on Reverse Repurchase Agreements

ck0000939934_Component4OtherExpensesOverAssets

0.52%

SIIT Multi-Asset Real Return Fund | SIIT Multi-Asset Real Return Fund - Class A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(4.23%)

5 Years

rr_AverageAnnualReturnYear05

(2.39%)

Since Inception

rr_AverageAnnualReturnSinceInception

(2.84%)

SIIT Multi-Asset Real Return Fund | SIIT Multi-Asset Real Return 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

1 Year

rr_AverageAnnualReturnYear01

(1.64%)

5 Years

rr_AverageAnnualReturnYear05

(1.52%)

Since Inception

rr_AverageAnnualReturnSinceInception

(1.91%)