485BPOS

As filed with the Securities and Exchange Commission on October 19, 2012

File No. 033-58041

File No. 811-07257

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 69

and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 70

SEI INSTITUTIONAL INVESTMENTS TRUST

(Exact Name of Registrant as Specified in Charter)

SEI Investments Company
One Freedom Valley Drive
Oaks, Pennsylvania 19456

(Address of Principal Executive Offices)

(610) 676-1000

Timothy D. Barto
SEI Investments Company
One Freedom Valley Drive
Oaks, Pennsylvania 19456

(Name and Address of Agent for Service)

Copy to:

Timothy W. Levin, Esquire
Morgan, Lewis & Bockius LLP
1701 Market Street
Philadelphia, PA 19103

Title of Securities Being Registered. . .Units of Beneficial Interest

It is proposed that this filing become effective (check appropriate box)

x immediately upon filing pursuant to paragraph (b)

o on [date] pursuant to paragraph (b)

o 60 days after filing pursuant to paragraph (a)(1)

o on [date] pursuant to paragraph (a)(1)

o 75 days after filing pursuant to paragraph (a)(2)

o on [date] pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

o This post-effective Amendment designates a new effective date for a previously filed Post-Effective Amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Post-Effective Amendment No. 69 to Registration Statement No. 033-58041 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Oaks, Commonwealth of Pennsylvania on the 19th day of October, 2012.

SEI INSTITUTIONAL INVESTMENTS TRUST
By:	/s/ Robert A. Nesher
Robert A. Nesher
Trustee, President & Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the date(s) indicated.

*			Trustee	October 19, 2012
Rosemarie B. Greco
*			Trustee	October 19, 2012
William M. Doran
*			Trustee	October 19, 2012
George J. Sullivan, Jr.
*			Trustee	October 19, 2012
Nina Lesavoy
*			Trustee	October 19, 2012
James M. Williams
*			Trustee	October 19, 2012
Mitchell A. Johnson
*			Trustee	October 19, 2012
Hubert L. Harris, Jr.
/s/ Robert A. Nesher			Trustee, President & Chief Executive Officer	October 19, 2012
Robert A. Nesher
/s/ Peter A. Rodriguez			Controller & Chief Financial Officer	October 19, 2012
Peter A. Rodriguez
*By:	/s/	Robert A. Nesher
		Robert A. Nesher
		Attorney-in-Fact

INDEX TO EXHIBITS

EXHIBIT NO.	DESCRIPTION OF EXHIBIT	PAGE NO.
	Risk/return summary of each Fund’s prospectus as an Interactive Data File using eXtensible Business Reporting Language (“XBRL”)

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Small Cap II Fund (Prospectus Summary) | SIIT Small Cap II Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SMALL CAP II FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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 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, for the period April 10, 2012 through May 31, 2012, the Fund's annualized portfolio turnover rate was 9% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	9.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
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 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 Small Cap II Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of small companies. For purposes of this Fund, a small company is a company with a market capitalization in the range of companies in the Russell 2000 Index (between $30.7 million and $3.67 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the Russell 2000 Index are subject to change. The Fund's investments in equity securities may include common and preferred stocks and, to a lesser extent, securities of real estate investment trusts (REITs) and securities of large capitalization companies. The Fund uses a multi-manager approach, relying upon one or more sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. Each Sub-Adviser, in managing its portion of the Fund's assets, generally applies a growth-oriented, a value-oriented or a blended approach to selecting investments. Growth-oriented managers generally select stocks they believe have attractive growth and appreciation potential in light of such characteristics as revenue and earnings growth, expectations from sell-side analysts and relative valuation, while value-oriented managers generally select stocks they believe are attractively valued in light of fundamental characteristics such as earnings, capital structure and/or return on invested capital.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. Investment Style Risk - The risk that the securities in which the Fund principally invests may underperform other segments of the equity markets or the equity markets as a whole. 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 equity market as a whole. 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. 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 include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties. Small Capitalization Risk - The small capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, smaller capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Small capitalization stocks may be traded over-the-counter or listed on an exchange. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund commenced operations on April 10, 2012. Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
SIIT Small Cap II Fund (Prospectus Summary) | SIIT Small Cap II Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.65%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.13%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.78%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	80
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	249

[1] Other Expenses are based on estimated amounts for the current fiscal year.

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SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund

ENHANCED LIBOR OPPORTUNITIES FUND

Investment Goal

Capital appreciation and income.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Enhanced LIBOR Opportunities Fund Class A
Management Fees		0.45%
Distribution (12b-1) Fees		none
Other Expenses		0.08%
Acquired Fund Fees and Expenses (AFFE)		0.09%
Total Annual Fund Operating Expenses	[1]	0.62%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Enhanced LIBOR Opportunities Fund Class A	63	199	346	774

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 58%
of the average value of its portfolio.

Principal Investment Strategies

The Enhanced LIBOR Opportunities Fund invests primarily in a diversified
portfolio of investment grade and non-investment grade fixed-income securities
(junk bonds), including: (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) U.S. and foreign corporate debt securities, including commercial paper,
and fully-collateralized repurchase agreements with counterparties deemed
credit-worthy by the Fund's Sub-Advisers; and (iv) securitized issues, such as
mortgage-backed securities, asset-backed securities, commercial mortgage-backed
securities and collateralized debt obligations. These securities may be fixed-,
variable- or floating-rate obligations and will be rated CCC- or higher at the
time of purchase by at least one ratings agency. There are no restrictions on
the maturity of any individual securities or on the Fund's average portfolio
maturity, although the average portfolio duration of the Fund will typically
vary between zero and two years. Duration is a measure of the expected life of a
fixed income security that is used to determine the sensitivity of a security's
price to changes in interest rates.

The Fund uses a multi-manager approach under the general supervision of SIMC,
allocating the assets among multiple Sub-Advisers that use different investment
strategies designed to produce a total return that exceeds the total return of
the 3-Month LIBOR (London Interbank Offered Rate). LIBOR is based on rates that
contributor banks in London charge each other for interbank deposits and is
typically used to set coupon rates on floating rate debt securities.

The Sub-Advisers may seek to enhance the Fund's return by actively managing the
Fund's foreign currency exposure. Up to 10% of the Fund's assets may be invested
in foreign currencies. In managing the Fund's currency exposure, the Sub-Advisers
buy and sell currencies (i.e., take long or short positions) using derivatives,
principally futures, foreign currency forward 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. In managing the Fund's currency
exposure for foreign securities, the Sub-Advisers may buy and sell currencies for
hedging or for speculative purposes.

The Fund also invests a portion of its assets in bank loans, which are generally
non-investment grade (junk bond) floating rate instruments. Up to 100% of the
bank loans in which the Fund invests may be junk bonds. The Fund may invest in
bank loans in the form of participations in the loans (participations) and
assignments of all or a portion of the loans from third parties (assignments).
The Fund may also invest in other financial instruments or use other investment
techniques, such as reverse repurchase agreements, to seek to obtain market
exposure to the securities in which the Fund primarily invests.

The Fund may also invest in futures contracts and swaps for speculative or
hedging purposes. Futures 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. Interest rate swaps are further used to manage
the Fund's yield spread sensitivity. When the Fund seeks to take an active long
or short position with respect to the likelihood of an event of default of a
security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities.

To achieve its investment goal, the Fund may invest in the SEI LIBOR Plus Portfolio
(Portfolio), which is a portfolio of SEI Alpha Strategy Portfolios, LP, a registered
open-end investment company that was established to permit certain Funds to pursue
their respective investment strategies in an efficient manner. The Fund will invest
in the Portfolio only if the Portfolio invests in securities and pursues investment
strategies that are consistent with the Fund's investment strategy. The Portfolio
has expenses associated with its operations, including advisory and administration
fees. When the Fund invests in the Portfolio, it will bear a pro rata portion of
the Portfolio's expenses,which will be reflected in the Fund's fee table as "Acquired
Fund Fees and Expenses."

Principal Risks

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.

Bank Loans Risk - With respect to bank loans, the Fund will assume the credit
risk of both the borrower of the loan and the lender that is selling the
participation in the loan. The Fund may also have difficulty disposing of bank
loans because, in certain cases, the market for such instruments is not highly
liquid.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.

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.

Currency Risk - 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.

Derivatives Risk - The Fund's use of futures contracts, forward contracts,
options and swaps is subject to market risk, leverage risk, correlation risk and
liquidity risk. Leverage risk, liquidity risk and market risk are described
below. 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 forward contracts and swap agreements is also subject to credit risk and
valuation risk. Valuation risk is the risk that the derivative may be difficult
to value and/or may be 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.
  
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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in values of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in values in such 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 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.

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, sell other securities instead or forego an investment opportunity,
any of which could have a negative effect on Fund management or performance.

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.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 5.76% (09/30/09)

Worst Quarter: -20.36% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 3.43%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT Enhanced LIBOR Opportunities Fund	Label	1 Year	5 Years	Since Inception		Inception Date
Class A	Return Before Taxes	1.19%	(2.20%)	(2.16%)	[1]	Dec. 14, 2006
Class A After Taxes on Distributions	Return After Taxes on Distributions	0.50%	(3.11%)	(3.07%)	[1]	Dec. 14, 2006
Class A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	0.77%	(2.35%)	(2.33%)	[1]	Dec. 14, 2006
BofA Merrill Lynch US Dollar 3-Month LIBOR Constant Maturity Index Return	BofA Merrill Lynch US Dollar 3-Month LIBOR Constant Maturity Index Return (reflects no deduction for fees, expenses or taxes)	0.27%	2.19%	2.24%	[1]	Dec. 14, 2006

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from December 31, 2006.

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SIIT Strategic U.S. Large Cap Equity Fund (Prospectus Summary) | SIIT Strategic U.S. Large Cap Equity Fund

STRATEGIC U.S. LARGE CAP EQUITY FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Strategic U.S. Large Cap Equity Fund Class A
Management Fees		0.40%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.15%
Total Annual Fund Operating Expenses		0.55%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT Strategic U.S. Large Cap Equity Fund Class A	56	176

PORTFOLIO TURNOVER

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.

Principal Investment Strategies

Under normal circumstances, the Strategic U.S. Large Cap Equity Fund will invest
at least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of large U.S. companies. These securities may
include common stocks, preferred stocks, warrants and ETFs based on a large
capitalization equity index. The Fund will invest primarily in common stocks of
U.S. companies with market capitalizations in the range of companies in the S&P
500 Index (between $1.22 billion and $572.4 billion as of July 31, 2012) at the
time of purchase. The market capitalization range and the composition of the S&P
500 Index are subject to change. The Fund may also, to a lesser extent, invest
in common and preferred stocks of small capitalization companies.

The Fund seeks to exceed the total return of the S&P 500 Index, with a similar
level of volatility, by investing primarily in a portfolio of common stocks
included in the S&P 500 Index, as well as other equity investments and futures
and swaps whose value is derived from the performance of the S&P 500 Index. The
Fund uses a multi-manager approach, relying on Sub-Advisers with differing
investment philosophies to manage portions of the Fund's portfolio under the
general supervision of SIMC. The Fund may employ Sub-Advisers that use a variety
of different methods to seek to outperform the Fund's benchmark, including
purchasing stocks with strong anticipated future earnings growth, selecting
stocks that the Sub-Adviser believes are undervalued, capturing returns from
natural market volatility and employing strategies that rotate among various
market sectors. The Fund may also utilize one or more additional Sub-Advisers
who manage the Fund in a complementary style with the objective to seek to add
value over the S&P 500 Index while maintaining a level of volatility similar to
the S&P 500 Index.

Principal Risks

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 and swaps is subject to market
risk, leverage risk, correlation risk and liquidity risk. Leverage risk and
liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and unpredictably.
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
swap agreements 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that large capitalization securities may
underperform other segments of the equity markets or the equity markets as a
whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment opportunity,
any of which could have a negative effect on Fund management or performance.

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.

Small Capitalization Risk - Smaller capitalization companies in which the Fund
invests may be more vulnerable to adverse business or economic events than
larger, more established companies. In particular, small capitalization
companies may have limited product lines, markets and financial resources and
may depend upon a relatively small management group. Therefore, small
capitalization stocks may be more volatile than those of larger companies.

Loss of money is a risk of investing in the Fund.

Performance Information

As of September 30, 2012, the Fund had not yet commenced operations and did not
have a performance history.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

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SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund

U.S. MANAGED VOLATILITY FUND

Investment Goal

Capital appreciation with less volatility than the broad U.S. equity markets.

Fees and Expenses

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

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

Annual Fund Operating Expenses	SIIT U.S. Managed Volatility Fund Class A
Management Fees	0.65%
Distribution (12b-1) Fees	none
Other Expenses	0.08%
Total Annual Fund Operating Expenses	0.73%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT U.S. Managed Volatility Fund Class A	75	233	406	906

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 44%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the U.S. Managed Volatility Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of U.S. companies of all capitalization ranges.
These securities may include common stocks, preferred stocks, ETFs and warrants.
The Fund may also, to a lesser extent, invest in ADRs and securities of non-U.S.
companies.

The Fund uses a multi-manager approach, relying on a number of Sub-Advisers with
differing investment philosophies to manage portions of the Fund's portfolio
under the general supervision of SIMC. The Fund is expected to achieve an absolute
return of the broad U.S. equity markets, but with a lower absolute volatility. Over
the long term, the Fund is expected to achieve a return similar to that of the
Russell 3000 Index, but with a lower level of volatility. However, given that the
Fund's investment strategy focuses on absolute return and risk, the Fund's sector
and market capitalization exposures will typically vary from the index and may cause
significant performance deviations relative to the index over shorter-term
periods. The Fund seeks to achieve lower volatility by constructing a portfolio
of securities that effectively weighs securities based on their total expected
risk and return, without regard to market capitalization and industry.

Principal Risks

American Depositary Receipts (ADRs) Risk - ADRs are certificates evidencing
ownership of shares of a foreign issuer that are issued by depositary banks and
generally trade on an established market. ADRs 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Foreign Investment Risk - The risk that non-U.S. securities may be subject to
additional risks due to, among other things, political, social and economic
developments abroad, currency movements and different legal, regulatory and tax
environments.

Hedged Strategies Risk - The Fund may employ investment strategies that involve
greater risks than the strategies used by typical mutual funds. Although some of
the Sub-Advisers use hedged strategies, there is no assurance that hedged
strategies will protect against losses or perform better than non-hedged
strategies, and some Sub-Advisers may use long-only strategies.

Investment Style Risk - The risk that equity securities of U.S. companies of all
capitalization ranges may underperform other segments of the equity markets or
the equity markets as a whole.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

Loss of money is a risk of investing in the Fund.

Performance Information

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 calendar years and by showing how the Fund's
average annual returns for 1 year, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on a full calendar year. 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.

Best Quarter: 11.39% (09/30/09)

Worst Quarter: -11.59% (03/31/09)

The Fund's total return from January 1, 2012 to June 30, 2012 was 8.68%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT U.S. Managed Volatility Fund	Label	1 Year	Since Inception		Inception Date
Class A	Return Before Taxes	10.43%	13.78%	[1]	Dec. 30, 2008
Class A After Taxes on Distributions	Return After Taxes on Distributions	8.64%	11.23%	[1]	Dec. 30, 2008
Class A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	8.32%	10.81%	[1]	Dec. 30, 2008
Russell 3000 Index Return	Russell 3000 Index Return (reflects no deduction for fees, expenses or taxes)	1.03%	14.88%	[1]	Dec. 30, 2008

[1] Index returns are shown from December 31, 2008.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Strategic U.S. Large Cap Equity Fund (Prospectus Summary) | SIIT Strategic U.S. Large Cap Equity Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	STRATEGIC U.S. LARGE CAP EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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 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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
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 Strategic U.S. Large Cap Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of large U.S. companies. These securities may include common stocks, preferred stocks, warrants and ETFs based on a large capitalization equity index. The Fund will invest primarily in common stocks of U.S. companies with market capitalizations in the range of companies in the S&P 500 Index (between $1.22 billion and $572.4 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the S&P 500 Index are subject to change. The Fund may also, to a lesser extent, invest in common and preferred stocks of small capitalization companies. The Fund seeks to exceed the total return of the S&P 500 Index, with a similar level of volatility, by investing primarily in a portfolio of common stocks included in the S&P 500 Index, as well as other equity investments and futures and swaps whose value is derived from the performance of the S&P 500 Index. The Fund uses a multi-manager approach, relying on Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund may employ Sub-Advisers that use a variety of different methods to seek to outperform the Fund's benchmark, including purchasing stocks with strong anticipated future earnings growth, selecting stocks that the Sub-Adviser believes are undervalued, capturing returns from natural market volatility and employing strategies that rotate among various market sectors. The Fund may also utilize one or more additional Sub-Advisers who manage the Fund in a complementary style with the objective to seek to add value over the S&P 500 Index while maintaining a level of volatility similar to the S&P 500 Index.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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 and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 swap agreements 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Small Capitalization Risk - Smaller capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
SIIT Strategic U.S. Large Cap Equity Fund (Prospectus Summary) | SIIT Strategic U.S. Large Cap Equity Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.55%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	56
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	176

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	INTERNATIONAL EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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, 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 59% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	59.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 International Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities. Equity securities may include common stocks, preferred stocks, warrants and depositary receipts. The Fund will invest primarily in equity securities of issuers of all capitalization ranges that are located in at least three countries other than the U.S. It is expected that at least 40% of the Fund's assets will be invested outside the U.S. The Fund will invest primarily in companies located in developed countries, but may also invest in companies located in emerging markets. Generally, the Fund will invest less than 20% of its assets in emerging markets. The Fund's benchmark is the MSCI Europe, Australasia and Far East (EAFE) Index (net of dividends). The Fund is expected to have an absolute return and risk profile similar to the international equity market. The Fund is diversified as to issuers, market capitalization, industry and country. The Fund may invest in futures contracts and forward contracts (also called "forwards") for hedging purposes, including to seek to manage the Fund's currency exposure to foreign securities and mitigate the Fund's overall risk. The Fund may purchase shares of ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase shares directly.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. Currency Risk - As a result of the Fund's investments in securities 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. Depositary Receipts - 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. Derivatives Risk - The Fund's use of futures and forward contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 over-the-counter forward contracts 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 the above risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time.    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. Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investment Style Risk - The risk that developed international equity securities may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 22.49% (06/30/09) Worst Quarter: -25.27% (09/30/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 3.13%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deduction for 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 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.
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND | MSCI EAFE Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	MSCI EAFE Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(12.14%)
5 Years	rr_AverageAnnualReturnYear05	(4.72%)
10 Years	rr_AverageAnnualReturnYear10	4.67%
Since Inception	rr_AverageAnnualReturnSinceInception	3.40%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.51%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.14%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.66%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	67
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	211
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	368
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	822
Annual Return 2002	rr_AnnualReturn2002	(15.39%)
Annual Return 2003	rr_AnnualReturn2003	34.12%
Annual Return 2004	rr_AnnualReturn2004	19.43%
Annual Return 2005	rr_AnnualReturn2005	15.04%
Annual Return 2006	rr_AnnualReturn2006	27.41%
Annual Return 2007	rr_AnnualReturn2007	8.00%
Annual Return 2008	rr_AnnualReturn2008	(48.14%)
Annual Return 2009	rr_AnnualReturn2009	24.26%
Annual Return 2010	rr_AnnualReturn2010	11.23%
Annual Return 2011	rr_AnnualReturn2011	(13.43%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.13%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.49%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.27%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.43%)
5 Years	rr_AverageAnnualReturnYear05	(7.70%)
10 Years	rr_AverageAnnualReturnYear10	2.90%
Since Inception	rr_AverageAnnualReturnSinceInception	2.57%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(13.53%)
5 Years	rr_AverageAnnualReturnYear05	(8.81%)
10 Years	rr_AverageAnnualReturnYear10	1.67%
Since Inception	rr_AverageAnnualReturnSinceInception	1.38%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(8.05%)
5 Years	rr_AverageAnnualReturnYear05	(6.44%)
10 Years	rr_AverageAnnualReturnYear10	2.45%
Since Inception	rr_AverageAnnualReturnSinceInception	1.99%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996

[1] Index returns are shown from June 30, 1996.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME

CORE FIXED INCOME FUND

Investment Goal

Current income consistent with the preservation of capital.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT CORE FIXED INCOME CLASS A
Management Fees		0.30%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.38%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT CORE FIXED INCOME CLASS A	39	122	213	480

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 386%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Core Fixed Income Fund will invest at least 80%
of its net assets (plus the amount of any borrowings for investment purposes) in
fixed income securities. The Fund will invest in investment and non-investment
grade (junk bond) U.S. and foreign corporate and government fixed income
securities, including emerging market, asset-backed securities and
mortgage-backed securities. The Fund may invest in securities denominated in
either U.S. dollars or foreign currency. The Fund uses a multi-manager approach,
relying upon a number of Sub-Advisers with differing investment philosophies to
manage portions of the Fund's portfolio under the general supervision of SIMC.
Sub-Advisers are selected for their expertise in managing various kinds of fixed
income securities and each Sub-Adviser makes investment decisions based on an
analysis of yield trends, credit ratings and other factors in accordance with
its particular discipline.

The Fund may also invest in futures contracts, forward contracts and swaps for
speculative or hedging purposes. Futures, forwards 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, currencies or market
segments. Interest rate swaps are further used to manage the Fund's yield spread
sensitivity. When the Fund seeks to take an active long or short position with
respect to the likelihood of an event of default of a security or basket of
securities, the Fund may use credit default swaps. 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 such security or basket of securities.

The Sub-Advisers may also engage in currency transactions using futures and
foreign currency forward contracts, either to seek to hedge the Fund's currency
exposure or to enhance the Fund's returns. 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 will invest primarily in investment grade
securities (those rated AAA, AA, A and BBB-). However, the Fund may invest in
non-rated securities or securities rated below investment grade (BB+, B and
CCC).

The Fund may also invest a portion of its assets in bank loans, which are
generally non-investment grade (junk bond) floating rate instruments. The Fund
may invest in bank loans in the form of participations in the loans
(participations) and assignments of all or a portion of the loans from third
parties (assignments).

While each Sub-Adviser chooses securities of different types and maturities, the
Fund, in the aggregate, generally will have a dollar-weighted average duration
that is consistent with that of the broad U.S. fixed income market, as
represented by the Barclays Capital U.S. Aggregate Bond Index. The
dollar-weighted average duration of the Barclays Capital U.S. Aggregate Bond
Index varies significantly over time, but as of July 31, 2012, it was 4.96
years. Duration is a measure of the expected life of a fixed income security
that is used to determine the sensitivity of a security's price to changes in
interest rates.

Principal Risks

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.

Bank Loans Risk - With respect to bank loans, the Fund will assume the credit
risk of both the borrower and the lender that is selling the participation. The
Fund may also have difficulty disposing of bank loans because, in certain cases,
the market for such instruments is not highly liquid.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.

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.

Currency Risk - 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.

Derivatives Risk - The Fund's use of futures, forwards and swaps is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 forwards and swap agreements 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.

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.

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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Interest Rate Risk - The risk that the value of fixed income securities,
including U.S. Government securities, will fall due to rising interest rates.

Investment Style Risk - The risk that the fixed income securities in which the
Fund invests may underperform other segments of the fixed income markets or the
fixed income markets as a whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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 ten years and by showing how the Fund's average annual
returns for 1, 5 and 10 years, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on full calendar years. The Fund's past performance (before and
after taxes) is not necessarily an indication of how the Fund will perform in
the future. For current performance information, please call 1-800-DIAL-SEI.

Best Quarter: 6.56% (09/30/09)

Worst Quarter: -2.54% (09/30/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 3.85%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT CORE FIXED INCOME	Label	1 Year	5 Years	10 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	8.00%	7.15%	6.26%	6.80%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	5.92%	4.88%	4.13%	4.38%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	5.16%	4.78%	4.09%	4.35%	[1]	Jun. 14, 1996
Barclays Capital Aggregate Bond Index Return	Barclays Capital Aggregate Bond Index Return (reflects no deduction for fees, expenses or taxes)	7.84%	6.50%	5.78%	6.44%	[1]	Jun. 14, 1996

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from June 30, 1996.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	CORE FIXED INCOME FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Current income consistent with the preservation of capital.
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, 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 386% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	386.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Core Fixed Income Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in fixed income securities. The Fund will invest in investment and non-investment grade (junk bond) U.S. and foreign corporate and government fixed income securities, including emerging market, asset-backed securities and mortgage-backed securities. The Fund may invest in securities denominated in either U.S. dollars or foreign currency. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. Sub-Advisers are selected for their expertise in managing various kinds of fixed income securities and each Sub-Adviser makes investment decisions based on an analysis of yield trends, credit ratings and other factors in accordance with its particular discipline. The Fund may also invest in futures contracts, forward contracts and swaps for speculative or hedging purposes. Futures, forwards 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, currencies or market segments. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities. The Sub-Advisers may also engage in currency transactions using futures and foreign currency forward contracts, either to seek to hedge the Fund's currency exposure or to enhance the Fund's returns. 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 will invest primarily in investment grade securities (those rated AAA, AA, A and BBB-). However, the Fund may invest in non-rated securities or securities rated below investment grade (BB+, B and CCC). The Fund may also invest a portion of its assets in bank loans, which are generally non-investment grade (junk bond) floating rate instruments. The Fund may invest in bank loans in the form of participations in the loans (participations) and assignments of all or a portion of the loans from third parties (assignments). While each Sub-Adviser chooses securities of different types and maturities, the Fund, in the aggregate, generally will have a dollar-weighted average duration that is consistent with that of the broad U.S. fixed income market, as represented by the Barclays Capital U.S. Aggregate Bond Index. The dollar-weighted average duration of the Barclays Capital U.S. Aggregate Bond Index varies significantly over time, but as of July 31, 2012, it was 4.96 years. Duration is a measure of the expected life of a fixed income security that is used to determine the sensitivity of a security's price to changes in interest rates.
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. Bank Loans Risk - With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - 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. Derivatives Risk - The Fund's use of futures, forwards and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 forwards and swap agreements 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. 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. 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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Interest Rate Risk - The risk that the value of fixed income securities, including U.S. Government securities, will fall due to rising interest rates. Investment Style Risk - The risk that the fixed income securities in which the Fund invests may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years.
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: 6.56% (09/30/09) Worst Quarter: -2.54% (09/30/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 3.85%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME | Barclays Capital Aggregate Bond Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Barclays Capital Aggregate Bond Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	7.84%
5 Years	rr_AverageAnnualReturnYear05	6.50%
10 Years	rr_AverageAnnualReturnYear10	5.78%
Since Inception	rr_AverageAnnualReturnSinceInception	6.44%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.30%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.38%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	39
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	122
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	213
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	480
Annual Return 2002	rr_AnnualReturn2002	9.19%
Annual Return 2003	rr_AnnualReturn2003	5.70%
Annual Return 2004	rr_AnnualReturn2004	4.87%
Annual Return 2005	rr_AnnualReturn2005	2.54%
Annual Return 2006	rr_AnnualReturn2006	4.71%
Annual Return 2007	rr_AnnualReturn2007	6.58%
Annual Return 2008	rr_AnnualReturn2008	(3.18%)
Annual Return 2009	rr_AnnualReturn2009	15.42%
Annual Return 2010	rr_AnnualReturn2010	9.82%
Annual Return 2011	rr_AnnualReturn2011	8.00%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.85%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.56%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(2.54%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	8.00%
5 Years	rr_AverageAnnualReturnYear05	7.15%
10 Years	rr_AverageAnnualReturnYear10	6.26%
Since Inception	rr_AverageAnnualReturnSinceInception	6.80%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	5.92%
5 Years	rr_AverageAnnualReturnYear05	4.88%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	4.38%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	5.16%
5 Years	rr_AverageAnnualReturnYear05	4.78%
10 Years	rr_AverageAnnualReturnYear10	4.09%
Since Inception	rr_AverageAnnualReturnSinceInception	4.35%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996

[1] Index returns are shown from June 30, 1996.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	HIGH YIELD BOND FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return.
Expense [Heading]	rr_ExpenseHeading	Fund 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, 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 50% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	50.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 High Yield Bond Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in high yield fixed income securities. The Fund will invest primarily in fixed income securities rated below investment grade (junk bonds), including corporate bonds and debentures, convertible and preferred securities and zero coupon obligations. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. To a limited extent, SIMC may also directly manage a portion of the Fund's portfolio. In managing the Fund's assets, the Sub-Advisers and, to the extent applicable, SIMC, select securities that offer a high current yield as well as total return potential. The Fund's securities are diversified as to issuers and industries. The Fund's average weighted maturity may vary and will generally not exceed ten years. There is no limit on the maturity or on the credit quality of any security. As noted above, the Fund will invest primarily in securities rated BB, B, CCC, CC, C and D. However, it may also invest in non-rated securities or securities rated investment grade (AAA, AA, A and BBB). The Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly. The Fund may also invest a portion of its assets in bank loans, which are generally non-investment grade (junk bond) floating rate instruments. The Fund may invest in bank loans in the form of participations in the loans (participations) and assignments of all or a portion of the loans from third parties (assignments).
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Bank Loans Risk - With respect to bank loans, the Fund will assume the credit risk of both the borrower of the loan and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. Convertible and Preferred Securities - Convertible and preferred securities have many of the same characteristics as stocks, including many of the same risks. In addition, convertible bonds may be more sensitive to changes in interest rates than stocks. Convertible bonds may also have credit ratings below investment grade, meaning that they carry a higher risk of failure by the issuer to pay principal and/or interest when due. 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. 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.    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. 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. Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in values of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in values of such securities. Investment Style Risk - The risk that high yield fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 22.79% (06/30/09) Worst Quarter: -20.84% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 7.91%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND | BofA Merrill Lynch U.S. High Yield Constrained Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	BofA Merrill Lynch U.S. High Yield Constrained Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	4.37%
5 Years	rr_AverageAnnualReturnYear05	7.54%
Since Inception	rr_AverageAnnualReturnSinceInception	8.13%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.49%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.57%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	58
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	183
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	318
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	714
Annual Return 2006	rr_AnnualReturn2006	10.63%
Annual Return 2007	rr_AnnualReturn2007	2.04%
Annual Return 2008	rr_AnnualReturn2008	(28.23%)
Annual Return 2009	rr_AnnualReturn2009	58.33%
Annual Return 2010	rr_AnnualReturn2010	17.60%
Annual Return 2011	rr_AnnualReturn2011	5.24%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	7.91%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.79%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(20.84%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.24%
5 Years	rr_AverageAnnualReturnYear05	7.49%
Since Inception	rr_AverageAnnualReturnSinceInception	8.07%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	2.36%
5 Years	rr_AverageAnnualReturnYear05	3.96%
Since Inception	rr_AverageAnnualReturnSinceInception	4.58%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	3.39%
5 Years	rr_AverageAnnualReturnYear05	4.21%
Since Inception	rr_AverageAnnualReturnSinceInception	4.75%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005

[1] Index returns are shown from December 31, 2005.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LARGE CAP INDEX FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Investment results that correspond to the aggregate price and dividend performance of the securities in the Russell 1000 Index.
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, 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 12% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	12.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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	The Large Cap Index Fund invests substantially all of its assets in securities (mostly common stocks) of U.S. companies that are included at the time of purchase in the Russell 1000 Index, which is composed of the 1,000 largest U.S. companies with market capitalizations between $212.3 million and $572.4 billion as of July 31, 2012. The market capitalization range and the composition of the Russell 1000 Index are subject to change. The Fund's ability to replicate the performance of the Russell 1000 Index will depend to some extent on the size and timing of cash flows into and out of the Fund, as well as on the level of the Fund's expenses. The Sub-Adviser selects the Fund's securities under the general supervision of SIMC, but the Sub-Adviser makes no attempt to "manage" the Fund in the traditional sense (i.e., by using economic, market or financial analyses). Instead, the Sub-Adviser purchases a basket of securities that includes a representative sample of the companies in the Russell 1000 Index. However, the Fund's Sub-Adviser may, but is not required to, sell an investment if the merit of the investment has been substantially impaired by extraordinary events, such as fraud or a material adverse change in an issuer, or adverse financial conditions. In addition, for liquidity purposes, the Fund may invest in securities that are not included in the Russell 1000 Index, cash and cash equivalents or money market instruments, such as reverse repurchase agreements and money market funds. The Fund may also invest in ETFs based on a large capitalization index.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that its investment approach, which attempts to replicate the performance of the Russell 1000 Index, may underperform other segments of the equity markets or the equity markets as a whole. The Fund is also subject to the risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. Sampling Risk - The Fund may not fully replicate the benchmark index and may hold securities not included in the index. As a result, the Fund may not track the return of its benchmark index as well as it would have if the Fund purchased all of the securities in its benchmark index. Tracking Error Risk - The risk that the Fund's performance may vary substantially from the performance of the benchmark index it tracks as a result of cash flows, Fund expenses, imperfect correlation between the Fund's and benchmark's investments and other factors. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past nine years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past nine years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 16.46% (06/30/09) Worst Quarter: -22.51% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 9.31%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND | Russell 1000 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	1.50%
5 Years	rr_AverageAnnualReturnYear05	(0.02%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.02%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 01, 2002
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.17%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.25%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	26
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	80
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	141
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	318
Annual Return 2003	rr_AnnualReturn2003	29.53%
Annual Return 2004	rr_AnnualReturn2004	11.27%
Annual Return 2005	rr_AnnualReturn2005	6.18%
Annual Return 2006	rr_AnnualReturn2006	15.40%
Annual Return 2007	rr_AnnualReturn2007	5.75%
Annual Return 2008	rr_AnnualReturn2008	(37.69%)
Annual Return 2009	rr_AnnualReturn2009	28.60%
Annual Return 2010	rr_AnnualReturn2010	16.07%
Annual Return 2011	rr_AnnualReturn2011	1.47%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	9.31%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	16.46%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(22.51%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	1.47%
5 Years	rr_AverageAnnualReturnYear05	(0.04%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.29%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 01, 2002
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	1.15%
5 Years	rr_AverageAnnualReturnYear05	(0.53%)
Since Inception	rr_AverageAnnualReturnSinceInception	2.83%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 01, 2002
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	1.30%
5 Years	rr_AverageAnnualReturnYear05	(0.15%)
Since Inception	rr_AverageAnnualReturnSinceInception	2.70%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 01, 2002

[1] Index returns are shown from April 30, 2002.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	ENHANCED LIBOR OPPORTUNITIES FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation and income.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy 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, 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 58% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	58.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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	The Enhanced LIBOR Opportunities Fund invests primarily in a diversified portfolio of investment grade and non-investment grade fixed-income securities (junk bonds), including: (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) U.S. and foreign corporate debt securities, including commercial paper, and fully-collateralized repurchase agreements with counterparties deemed credit-worthy by the Fund's Sub-Advisers; and (iv) securitized issues, such as mortgage-backed securities, asset-backed securities, commercial mortgage-backed securities and collateralized debt obligations. These securities may be fixed-, variable- or floating-rate obligations and will be rated CCC- or higher at the time of purchase by at least one ratings agency. There are no restrictions on the maturity of any individual securities or on the Fund's average portfolio maturity, although the average portfolio duration of the Fund will typically vary between zero and two years. Duration is a measure of the expected life of a fixed income security that is used to determine the sensitivity of a security's price to changes in interest rates. The Fund uses a multi-manager approach under the general supervision of SIMC, allocating the assets among multiple Sub-Advisers that use different investment strategies designed to produce a total return that exceeds the total return of the 3-Month LIBOR (London Interbank Offered Rate). LIBOR is based on rates that contributor banks in London charge each other for interbank deposits and is typically used to set coupon rates on floating rate debt securities. The Sub-Advisers may seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. Up to 10% of the Fund's assets may be invested in foreign currencies. In managing the Fund's currency exposure, the Sub-Advisers buy and sell currencies (i.e., take long or short positions) using derivatives, principally futures, foreign currency forward 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. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes. The Fund also invests a portion of its assets in bank loans, which are generally non-investment grade (junk bond) floating rate instruments. Up to 100% of the bank loans in which the Fund invests may be junk bonds. The Fund may invest in bank loans in the form of participations in the loans (participations) and assignments of all or a portion of the loans from third parties (assignments). The Fund may also invest in other financial instruments or use other investment techniques, such as reverse repurchase agreements, to seek to obtain market exposure to the securities in which the Fund primarily invests. The Fund may also invest in futures contracts and swaps for speculative or hedging purposes. Futures 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. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities. To achieve its investment goal, the Fund may invest in the SEI LIBOR Plus Portfolio (Portfolio), which is a portfolio of SEI Alpha Strategy Portfolios, LP, a registered open-end investment company that was established to permit certain Funds to pursue their respective investment strategies in an efficient manner. The Fund will invest in the Portfolio only if the Portfolio invests in securities and pursues investment strategies that are consistent with the Fund's investment strategy. The Portfolio has expenses associated with its operations, including advisory and administration fees. When the Fund invests in the Portfolio, it will bear a pro rata portion of the Portfolio's expenses,which will be reflected in the Fund's fee table as "Acquired Fund Fees and Expenses."
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. Bank Loans Risk - With respect to bank loans, the Fund will assume the credit risk of both the borrower of the loan and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - 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. Derivatives Risk - The Fund's use of futures contracts, forward contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk, liquidity risk and market risk are described below. 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 forward contracts and swap agreements is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or may be 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.    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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in values of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in values in such 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 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 5.76% (09/30/09) Worst Quarter: -20.36% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 3.43%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund | BofA Merrill Lynch US Dollar 3-Month LIBOR Constant Maturity Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	BofA Merrill Lynch US Dollar 3-Month LIBOR Constant Maturity Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	0.27%
5 Years	rr_AverageAnnualReturnYear05	2.19%
Since Inception	rr_AverageAnnualReturnSinceInception	2.24%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.09%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.62%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	63
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	199
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	346
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	774
Annual Return 2007	rr_AnnualReturn2007	(0.50%)
Annual Return 2008	rr_AnnualReturn2008	(28.06%)
Annual Return 2009	rr_AnnualReturn2009	15.47%
Annual Return 2010	rr_AnnualReturn2010	6.96%
Annual Return 2011	rr_AnnualReturn2011	1.19%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.43%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.76%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(20.36%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	1.19%
5 Years	rr_AverageAnnualReturnYear05	(2.20%)
Since Inception	rr_AverageAnnualReturnSinceInception	(2.16%)	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund | Class A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	0.50%
5 Years	rr_AverageAnnualReturnYear05	(3.11%)
Since Inception	rr_AverageAnnualReturnSinceInception	(3.07%)	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund | Class A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	0.77%
5 Years	rr_AverageAnnualReturnYear05	(2.35%)
Since Inception	rr_AverageAnnualReturnSinceInception	(2.33%)	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006

[1] Index returns are shown from December 31, 2006.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Long Duration Corporate Bond Fund (Prospectus Summary) | SIIT Long Duration Corporate Bond Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LONG DURATION CORPORATE BOND FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Return characteristics similar to those of high quality corporate bonds.
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 will incur 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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
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 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 Long Duration Corporate Bond Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in long duration corporate fixed income securities, exchange-traded funds (ETFs) that track long duration corporate bond indices, and synthetic instruments or derivatives having economic characteristics similar to long duration corporate fixed income securities.    The Fund will invest primarily in U.S. and foreign investment grade fixed income instruments, including corporate bonds and unrated fixed income securities that the Adviser or Sub-Advisers determined to be equivalent in quality. The Fund may also invest a portion of its assets in municipal bonds, fixed income securities issued by both developing and emerging foreign sovereigns, obligations of supranational entities, and securities issued or guaranteed by the U.S. Government and its agencies and instrumentalities. To a lesser extent, the Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly. The Fund may also invest in futures contracts and swaps for speculative or hedging purposes. Futures 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, currencies or market segments. Interest rate swaps are further used to manage the Fund's interest rate risk and spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities. Under normal circumstances, the Fund is expected to maintain an effective average duration of between nine and sixteen years. Duration is a measure that is used to determine the sensitivity of a security's price to changes in interest rates. For each year of duration of a fixed income security, a 1% change in interest rates will result in an approximately 1% change in the value of the security. For example, a duration of ten years means that the fixed income security's price will change by approximately 10% if interest rates change by 1%. The Fund uses one or more Sub-Advisers to manage the Fund's portfolio under the general supervision of SIMC. The Sub-Advisers are selected for their expertise in managing various kinds of fixed income securities, and the Sub-Advisers make investment decisions based on an analysis of yield trends, credit ratings and other factors in accordance with their particular discipline.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. 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 and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 swap agreements 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.    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. 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. 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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. 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, due to 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. Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in values of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in values in such securities. Investment Style Risk - The risk that longer duration corporate fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. Municipal Securities Risk - Municipal securities, like other fixed income securities, rise and fall in value in response to economic and market factors, primarily changes in interest rates, and actual or perceived credit quality. Rising interest rates will generally cause municipal securities to decline in value. Longer-term securities respond more sharply to interest rate changes than do shorter-term securities. A municipal security will also lose value if, due to rating downgrades or other factors, there are concerns about the issuer's current or future ability to make principal or interest payments. State and local governments rely on taxes and, to some extent, revenues from private projects financed by municipal securities, to pay interest and principal on municipal debt. Poor statewide or local economic results or changing political sentiments may reduce tax revenues and increase the expenses of municipal issuers, making it more difficult for them to meet their obligations. Actual or perceived erosion of the creditworthiness of municipal issuers may reduce the value of the Fund's holdings. As a result, the Fund will be more susceptible to factors that adversely affect issuers of municipal obligations than a mutual fund that does not have as great a concentration in municipal obligations. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund commenced operations on June 29, 2012. Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
SIIT Long Duration Corporate Bond Fund (Prospectus Summary) | SIIT Long Duration Corporate Bond Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.30%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.10%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.40%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	41
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	128

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND

INTERNATIONAL EQUITY FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT INTERNATIONAL EQUITY FUND CLASS A
Management Fees		0.51%
Distribution (12b-1) Fees		none
Other Expenses		0.14%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.66%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT INTERNATIONAL EQUITY FUND CLASS A	67	211	368	822

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 59%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the International Equity Fund will invest at least
80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities. Equity securities may include common stocks,
preferred stocks, warrants and depositary receipts. The Fund will invest
primarily in equity securities of issuers of all capitalization ranges that are
located in at least three countries other than the U.S. It is expected that at
least 40% of the Fund's assets will be invested outside the U.S. The Fund will
invest primarily in companies located in developed countries, but may also
invest in companies located in emerging markets. Generally, the Fund will invest
less than 20% of its assets in emerging markets. The Fund's benchmark is the
MSCI Europe, Australasia and Far East (EAFE) Index (net of dividends). The Fund
is expected to have an absolute return and risk profile similar to the
international equity market. The Fund is diversified as to issuers, market
capitalization, industry and country.

The Fund may invest in futures contracts and forward contracts (also called
"forwards") for hedging purposes, including to seek to manage the Fund's
currency exposure to foreign securities and mitigate the Fund's overall risk.

The Fund may purchase shares of ETFs to gain exposure to a particular portion of
the market while awaiting an opportunity to purchase shares directly.

Principal Risks

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.

Currency Risk - As a result of the Fund's investments in securities 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.

Depositary Receipts - 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.

Derivatives Risk - The Fund's use of futures and forward contracts is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 over-the-counter forward contracts 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 the above risks could cause the Fund to lose more than the principal
amount invested in a derivative instrument.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.
  
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.

Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Investment Style Risk - The risk that developed international equity securities
may underperform other segments of the equity markets or the equity markets as a
whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

Loss of money is a risk of investing in the Fund.

Performance Information

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 ten years and by showing how the Fund's average annual
returns for 1, 5 and 10 years, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on full calendar years. The Fund's past performance (before and
after taxes) is not necessarily an indication of how the Fund will perform in
the future. For current performance information, please call 1-800-DIAL-SEI.

Best Quarter: 22.49% (06/30/09)

Worst Quarter: -25.27% (09/30/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 3.13%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT INTERNATIONAL EQUITY FUND	Label	1 Year	5 Years	10 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	(13.43%)	(7.70%)	2.90%	2.57%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	(13.53%)	(8.81%)	1.67%	1.38%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(8.05%)	(6.44%)	2.45%	1.99%	[1]	Jun. 14, 1996
MSCI EAFE Index Return	MSCI EAFE Index Return (reflects no deduction for fees, expenses or taxes)	(12.14%)	(4.72%)	4.67%	3.40%	[1]	Jun. 14, 1996

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from June 30, 1996.

XML

SIIT EMERGING MARKETS EQUITY FUND (Prospectus Summary) | SIIT EMERGING MARKETS EQUITY FUND

EMERGING MARKETS EQUITY FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT EMERGING MARKETS EQUITY FUND CLASS A
Management Fees		1.05%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.45%
Total Annual Fund Operating Expenses		1.50%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT EMERGING MARKETS EQUITY FUND CLASS A	153	474

PORTFOLIO TURNOVER

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.

Principal Investment Strategies

Under normal circumstances, the Emerging Markets Equity Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of emerging market issuers. The Fund will invest
primarily in common stocks and other equity securities of foreign companies
located in emerging market countries. The Fund normally maintains investments
in at least six emerging market countries and does not invest more than 35% of
its total assets in any one emerging market country. Emerging market countries
are countries that the World Bank classifies as low, low-middle and upper-middle
income countries.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment philosophies to manage portions of the Fund's
portfolio under the general supervision of SIMC. The Fund is diversified as to
issuers, market capitalization, industry and country. The Fund may also invest
in ETFs to gain exposure to a particular portion of the market while awaiting an
opportunity to purchase securities directly.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.
  
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.

Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Investment Style Risk - The risk that emerging market equity securities may
underperform other segments of the equity markets or the equity markets as a
whole.
  
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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

Loss of money is a risk of investing in the Fund.

Performance Information

As of September 30, 2012, the Fund had not yet commenced operations and did not
have a performance history.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Extended Market Index Fund (Prospectus Summary) | SIIT Extended Market Index Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	EXTENDED MARKET INDEX FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Seeks investment results that approximate, as closely as practicable and before expenses, the performance of the Russell Small Cap Completeness® Index.
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 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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
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 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	The Fund is managed using a passive/indexing investment approach and invests substantially all of its assets in securities (mostly common stocks) of companies that are included (at the time of purchase) in the Russell Small Cap Completeness® Index (the Index). As of July 31, 2012, the market capitalization of the companies included in the Index ranged from $30.7 million to $30.9 billion. The Index is composed of securities of the companies included in the Russell 3000® Index (which includes the largest 3,000 U.S. companies), excluding the securities of companies that are constituents of the S&P 500 Index (which includes 500 leading U.S. companies). The Index is constructed to attempt to provide a comprehensive and unbiased barometer of the extended broad market of U.S. equity securities beyond that of the 500 leading U.S. companies included in the S&P 500 Index. The market capitalization range and the composition of the Index are subject to change. The Fund generally will attempt to invest in securities (including interests of real estate investment trusts (REITs)) composing the Index in approximately the same proportions as they are represented in the Index. The Fund's ability to fully replicate the performance of the Index will depend to some extent on the size and timing of cash flows into and out of the Fund, as well as on the level of the Fund's expenses. In some cases, it may not be possible or practicable to purchase all of the securities composing the Index or to hold them in the same weightings as they are represented in the Index. In those cases, the Fund's sub-adviser (the Sub-Adviser) may employ a sampling or optimization technique to construct the Fund's portfolio. In seeking to replicate the performance of the Index, the Fund may also invest in exchange-traded funds (ETFs) and REITs that are not constituents of the Index. The Sub-Adviser selects the Fund's securities under the general supervision of SEI Investments Management Corporation, the Fund's adviser (SIMC), but the Sub-Adviser makes no attempt to "manage" the Fund in the traditional sense (i.e., by using economic, market or financial analyses). Instead, the Sub-Adviser purchases a basket of securities that includes most of the companies in the Index. However, the Sub-Adviser may sell an investment if the merit of the investment has been substantially impaired by extraordinary events or adverse financial conditions. The Fund may, at times, purchase or sell index futures contracts, or options on those futures, or engage in forward or swap transactions in lieu of investing directly in the securities making up the Index or to enhance the Fund's replication of the Index's return. In addition, for liquidity purposes, the Fund may invest in securities that are not included in the Index, cash and cash equivalents or money market instruments, such as reverse repurchase agreements and money market funds. The Fund's return may not match the return of the Index. Russell Investment Group is the source and owner of the trademarks, service marks and copyrights related to Russell Indexes. Russell Small Cap Completeness® Index and Russell 3000® Index are trademarks of Russell Investment Group.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Derivatives Risk - The Fund's use of futures, forwards, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Market risk, leverage risk and liquidity risk are described below. 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 forwards and swap agreements 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 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. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that the Fund's investment approach, which attempts to replicate the performance of the Index, may underperform other segments of the equity markets or the equity markets as a whole. The Fund is also subject to the risk that the securities in which it invests may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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 equity market as a whole. 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. 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 include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties. Sampling Risk - The Fund may not fully replicate the Index and may hold securities not included in the Index. As a result, the Fund may not track the return of the Index as well as it would have if the Fund purchased all of the securities in the Index. Small and Medium Capitalization Risk - The small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small and medium capitalization stocks may be more volatile than those of larger companies. Small and medium capitalization stocks may be traded over-the-counter or listed on an exchange. Tracking Error Risk - The risk that the Fund's performance may vary substantially from the performance of the Index as a result of cash flows, Fund expenses, imperfect correlation between the Fund's and Index's investments and other factors. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
SIIT Extended Market Index Fund (Prospectus Summary) | SIIT Extended Market Index Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.12%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.27%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	28
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	87

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND

SMALL CAP FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT SMALL CAP FUND CLASS A
Management Fees		0.65%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.73%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT SMALL CAP FUND CLASS A	75	233	406	906

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 85%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Small Cap Fund will invest at least 80% of its
net assets (plus the amount of any borrowings for investment purposes) in equity
securities (including common and preferred stocks) of small companies, including
ETFs based on small capitalization indices and securities of real estate
investment trusts (REITs). For purposes of this Fund, a small company is a
company with a market capitalization in the range of companies in the Russell
2000 Index (between $30.7 million and $3.67 billion as of July 31, 2012) or the
S&P SmallCap 600 Index (between $52.7 million and $3.41 billion as of July 31,
2012) at the time of purchase. The market capitalization range and the
composition of both the Russell 2000 Index and the S&P SmallCap 600 Index are
subject to change. The Fund may also invest in securities of large
capitalization companies.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment philosophies to manage portions of the Fund's
portfolio under the general supervision of SIMC. Each Sub-Adviser, in managing
its portion of the Fund's assets, generally applies a growth-oriented, a
value-oriented or a blended approach to selecting investments. Growth-oriented
managers generally select stocks they believe have attractive growth and
appreciation potential in light of such characteristics as revenue and earnings
growth, expectations from sell-side analysts and relative valuation, while
value-oriented managers generally select stocks they believe are attractively
valued in light of fundamental characteristics such as earnings, capital
structure and/or return on invested capital.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that small capitalization securities may
underperform other segments of the equity markets or the equity markets as a
whole.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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 include fluctuations in the
value of underlying properties, defaults by borrowers or tenants, changes in
interest rates and risks related to general or local economic conditions. Some
REITs may have limited diversification and may be subject to risks inherent in
financing a limited number of properties.

Small Capitalization Risk - Smaller capitalization companies in which the Fund
invests may be more vulnerable to adverse business or economic events than
larger, more established companies. In particular, small capitalization
companies may have limited product lines, markets and financial resources and
may depend upon a relatively small management group. Therefore, small
capitalization stocks may be more volatile than those of larger companies.

Loss of money is a risk of investing in the Fund.

Performance Information

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 ten years and by showing how the Fund's average annual
returns for 1, 5 and 10 years, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on full calendar years. The Fund's past performance (before and
after taxes) is not necessarily an indication of how the Fund will perform in
the future. For current performance information, please call 1-800-DIAL-SEI.

Best Quarter: 24.27% (06/30/09)

Worst Quarter: -28.10% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 7.28%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT SMALL CAP FUND	Label	1 Year	5 Years	10 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	(5.39%)	(1.09%)	4.86%	6.69%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	(5.53%)	(1.83%)	3.60%	5.21%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(3.40%)	(1.14%)	3.79%	5.20%	[1]	Jun. 14, 1996
Russell 2000 Index Return	Russell 2000 Index Return (reflects no deduction for fees, expenses or taxes)	(4.18%)	0.15%	5.62%	6.41%	[1]	Jun. 14, 1996

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from June 30, 1996.

XML

SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND

LARGE CAP DIVERSIFIED ALPHA FUND

Investment Goal

Long-term growth of capital and income.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT LARGE CAP DIVERSIFIED ALPHA FUND CLASS A
Management Fees		0.40%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.48%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT LARGE CAP DIVERSIFIED ALPHA FUND CLASS A	49	154	269	604

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 101%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Large Cap Diversified Alpha Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of large companies or in portfolio strategies
designed to correlate to a portfolio composed of large capitalization equity
securities. For purposes of this Fund, a large company is a company with a
market capitalization in the range of companies in the Russell 1000 Index
(between $212.3 million and $572.4 billion as of July 31, 2012) at the time of
purchase. The market capitalization range and the composition of the Russell
1000 Index are subject to change. The Fund may also, to a lesser extent, invest
in common and preferred stocks of small capitalization companies. The Fund may
also invest in ETFs based on a large capitalization index.

The Fund uses a multi-manager approach under the general supervision of SIMC,
allocating the assets among multiple Sub-Advisers that use different investment
strategies to seek to achieve returns in excess of the performance of the
Russell 1000 Index. This allocation among investment strategies aims to
diversify the sources from which Sub-Advisers seek to achieve excess returns
(i.e., returns in excess of a benchmark index or "alpha"), thereby diversifying
the relative risk of the Fund. While the Fund is expected to have an absolute
return and risk profile similar to the broad U.S. large capitalization equity
market, returns may be derived in part from investing up to 20% of the Fund in
securities outside of the large capitalization market.

Certain Sub-Advisers use portfolio strategies that are designed to correlate
with a portfolio of large capitalization equity securities, but which are
composed of futures contracts (also called "futures") and swaps backed by other
types of securities. The Fund may invest in futures and swaps either for risk
management purposes or as part of its investment strategies. These portfolio
strategies are included in the Fund's principal investment strategy described
above. The managers may purchase futures contracts or swaps, generally using
only a fraction of the assets that would be needed to purchase the equity
securities directly, so that the remainder of the assets in a portfolio may be
invested in other types of securities. Therefore, a Sub-Adviser would seek to
outperform a large capitalization benchmark by purchasing futures contracts or
swaps correlated to a broad large capitalization index and investing the
remaining assets in other types of securities to add excess return. This portion
of the Fund's assets may be invested in a wide range of asset classes other than
large capitalization equities. Pursuant to a derivatives strategy, the other
types of securities backing the futures and swaps held by the Fund may include
investments in U.S. and foreign corporate and government fixed income securities
of different types and maturities, including mortgage-backed or other
asset-backed securities, securities rated below the fourth highest rating
category by a Nationally Recognized Statistical Rating Organization (NRSRO)
(junk bonds) and repurchase or reverse repurchase agreements. In managing the
Fund's currency exposure for foreign securities, the Sub-Advisers may buy and
sell currencies for hedging or for speculative purposes. The amount of the
Fund's portfolio that may be allocated to derivative strategies is expected to
vary over time.

The Fund may also invest in futures contracts and swaps for speculative or
hedging purposes. Futures and swaps are used to synthetically obtain exposure to
securities or baskets of securities. 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. Interest rate swaps are further used to manage
the Fund's yield spread sensitivity. When the Fund seeks to take an active long
or short position with respect to the likelihood of an event of default of a
security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities.

Principal Risks

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.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.

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.

Currency Risk - 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.

Derivatives Risk - The Fund's use of futures and swaps is subject to market
risk, leverage risk, correlation risk and liquidity risk. Leverage risk and
liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 swap agreements 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Foreign Sovereign Debt Securities Risk - The risk 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, due to 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.

Investment Style Risk - The risk that large capitalization securities may
underperform other segments of the equity markets or the equity markets as a
whole. The Fund uses portfolio strategies that are designed to correlate with a
portfolio of large capitalization equity securities, but which are composed of
derivative instruments backed by other types of securities in order to seek to
generate excess return. The financial performance of the Fund will be affected,
positively or negatively, by the financial performance of the securities backing
such derivative instruments. These factors, among others, may cause the Fund to
perform differently than a fund that is invested solely in large capitalization
equity securities or other funds with similar investment objectives or cause the
Fund to underperform its benchmark.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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.
  
Short Sales Risk - 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.

Small Capitalization Risk - Smaller capitalization companies in which the Fund
invests may be more vulnerable to adverse business or economic events than
larger, more established companies. In particular, small capitalization
companies may have limited product lines, markets and financial resources and
may depend upon a relatively small management group. Therefore, small
capitalization stocks may be more volatile than those of larger 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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 17.00% (06/30/09)

Worst Quarter: -25.55% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 8.84%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT LARGE CAP DIVERSIFIED ALPHA FUND	Label	1 Year	5 Years	Since Inception	Inception Date
CLASS A	Return Before Taxes	2.27%	(1.72%)	0.30%	Feb. 28, 2006
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	2.08%	(2.18%)	(0.17%)	Feb. 28, 2006
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	1.73%	(1.58%)	0.12%	Feb. 28, 2006
Russell 1000 Index Return	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)	1.50%	(0.02%)	1.95%	Feb. 28, 2006

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund

DYNAMIC ASSET ALLOCATION FUND

Investment Goal

Long-term total return.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Dynamic Asset Allocation Fund Class A
Management Fees		0.60%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.15%
Total Annual Fund Operating Expenses	[1]	0.82%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Dynamic Asset Allocation Fund Class A	84	262	455	1,014

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 140%
of the average value of its portfolio.

Principal Investment Strategies

The Fund employs a dynamic asset allocation investment strategy, seeking to
achieve its investment objective through a risk-controlled, disciplined process
that is designed to attempt to capture returns from short- and intermediate-term
market anomalies that may arise in particular asset classes within a broad range
of possible asset classes.

The Fund seeks to generate total return over time by selecting investments from
among a broad range of asset classes based upon SEI Investments Management
Corporation's (SIMC or the Adviser) expectations of risk and return. The asset
classes used and the Fund's allocations among those asset classes are determined
based on SIMC's views of fundamental, technical or valuation measures. The Fund's
allocations among asset classes may be adjusted over short periods of time and at
any particular point in time the Fund may be diversified across many asset classes
or concentrated in a limited number of asset classes, including possibly a single
asset class.

The Fund uses a multi-manager approach under the general supervision of SIMC,
allocating its assets among one or more sub-advisers (each, a Sub-Adviser and
collectively, the Sub-Advisers) that will implement different investment strategies.
SIMC allocates Fund assets among one or more Sub-Advisers based on SIMC's
expectations of risk and return as informed by SIMC's views of fundamental,
technical or valuation measures. The Fund is also managed, in part, by SIMC.

The Fund may obtain its exposures to a particular asset class by investing
directly (e.g., in equity and fixed income securities and other instruments) or
indirectly (e.g., through the use of other pooled investment vehicles and
derivative instruments, principally futures contracts, forward contracts,
options and swaps). The particular types of securities and other instruments
that the Fund may invest in within a particular asset class are further
described below. The Fund may invest in particular securities or instruments
that are not specifically listed below, but which have similar characteristics
or represent similar exposures as those described below.

Equity Securities. The Fund may invest in equity securities, including common
stocks, preferred stocks, convertible securities, warrants and depositary
receipts of U.S. and non-U.S. issuers (including emerging markets) of various
market capitalizations and industries.

Fixed Income Securities. The Fund may invest in fixed income securities that are
investment or non-investment grade (also known as "junk bonds"), U.S.- or
foreign-issued (including emerging markets), and corporate- or government-issued.
The Fund's fixed income investments may include asset-backed securities,
mortgage-backed securities, collateralized debt obligations (CDOs) and
collateralized loan obligations (CLOs), corporate bonds and debentures, commercial
paper, exchange traded notes (ETNs), money market instruments, mortgage dollar
rolls, repurchase and reverse repurchase agreements, when issued/delayed delivery
securities, zero coupon bonds, obligations of foreign governments, and obligations
of either supranational entities issued or guaranteed by certain banks and entities
organized to restructure the outstanding debt of such issuers.

The Fund's fixed income investments may also include U.S. Treasury obligations,
obligations issued by agencies or instrumentalities of the U.S. Government
(including obligations not guaranteed by the U.S. Treasury), such as obligations
issued by U.S. Government sponsored entities, and Treasury Inflation Protected
Securities (TIPS) and other inflation-linked debt securities of both U.S. and
non-U.S. governments and corporations.
  
The Fund may also invest a portion of its assets in bank loans, which are,
generally, non-investment grade floating rate instruments, in the form of
participations in the loans (participations) and assignments of all or a portion
of the loans from third parties (assignments).

The Fund may invest in fixed, variable and floating rate fixed income
instruments. The Fund's portfolio and the Fund's investments in particular fixed
income securities are not subject to any maturity or duration restrictions.

Other Instruments. The Fund may also invest in real estate investment trusts
(REITs) and securities issued by U.S. and non-U.S. real estate companies.

Pooled Investment Vehicles. In addition to direct investment in securities and
other instruments, the Fund may invest in affiliated and unaffiliated funds,
including open-end funds, money market funds, closed-end funds and
exchange-traded funds (ETFs), to obtain the Fund's desired exposure to a
particular asset class.

Derivative Instruments. The Fund may also purchase or sell futures contracts,
forward contracts, options and swaps (including swaptions, caps, floors or
collars) for return enhancement or hedging purposes or to obtain the Fund's
desired exposure to a particular asset class. Futures contracts, forward
contracts, options and swaps may be 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 may also be used to
mitigate the Fund's overall level of risk and/or the Fund's exposure to the risk
of particular types of securities or market segments. The Fund may purchase or
sell futures contracts on U.S. Government securities for return enhancement and
hedging purposes. The Fund may purchase and sell forward contracts on currencies
or securities for return enhancement and hedging purposes. Interest rate swaps
are further used to manage the Fund's yield spread sensitivity. Currency swaps
may be used for return enhancement or hedging purposes. Securities index and
single-security swaps may be used to manage the inflation-adjusted return of the
Fund or to more efficiently gain exposure to a particular security or basket of
securities. 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.

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 marketable securities issued by companies that own or invest
in commodities or commodities contracts, equity and debt securities of issuers
in commodity-related industries, 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 indices.

The Fund may invest in U.S. dollar and non-U.S. dollar denominated securities.
SIMC or the Sub-Advisers may also seek to enhance the Fund's return by actively
managing the Fund's foreign currency exposure. In managing the Fund's currency
exposure, SIMC or the Sub-Advisers may buy and sell currencies (i.e., take long
or short positions) using futures and foreign currency forward contracts. 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 its exposure to a foreign currency
or to shift exposure to foreign currency fluctuations from one currency to another.
In managing the Fund's currency exposure for foreign securities, SIMC or the
Sub-Advisers may buy and sell currencies for hedging or for speculative purposes.

The Sub-Advisers may engage in short sales in an attempt to capitalize on equity
securities that they believe will underperform the market or their peers. When
the Sub-Advisers sell securities short, they 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.

Due to its investment strategy, the Fund may buy and sell securities and other
instruments frequently.

The goal of the Fund is to serve as a dynamic overlay to broader strategic
allocations. This Fund is intended to be used by shareholders seeking to add a
dynamic component to their broader overall investment strategy. An investment in
the Fund should not constitute a shareholder's complete investment program.

Principal Risks

American Depositary Receipts (ADRs) Risk - ADRs are certificates evidencing
ownership of shares of a foreign issuer that are issued by depositary banks and
generally trade on an established market. ADRs 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.

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.

Bank Loans Risk - With respect to bank loans, the Fund will assume the credit
risk of both the borrower and the lender that is selling the participation in
the loan. The Fund may also have difficulty disposing of bank loans because, in
certain cases, the market for such instruments is not highly liquid.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

CDOs and 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 of 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 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.

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.

Convertible and Preferred Securities Risk - Convertible and preferred securities
have many of the same characteristics as stocks, including many of the same
risks. In addition, convertible securities may be more sensitive to changes in
interest rates than stocks. Convertible securities may also have credit ratings
below investment grade, meaning that they carry a higher risk of failure by the
issuer to pay principal and/or interest when due.

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.

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.

Currency Risk - 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.

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 risk, liquidity risk and market risk are described below. 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 forwards
and swap agreements 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.

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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

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. 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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal, regulatory
and tax environments. These additional risks may be heightened with respect to
emerging market countries since political turmoil and rapid changes in economic
conditions are more likely to occur in these countries.

Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in values of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in values of such securities.

Investment Company Risk - When the Fund invests in an investment company,
including closed-end funds and ETFs, 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. Further, 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.
Closed-end investment companies issue a fixed number of shares that trade on a
stock exchange or over-the-counter at a premium or a discount to their net asset
value. As a result, a closed-end fund's share price fluctuates based on what
another investor is willing to pay rather than on the market value of the
securities in the fund.

Leverage Risk - 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.

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 equity or 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.

Private Placements Risk - Investment in privately placed securities may be less
liquid than in publicly traded securities. Although these securities may be
resold in privately negotiated transactions, the prices realized from these sales
could be less than those originally paid by the Fund or less than what may be
considered the fair value of such securities. Further, companies whose securities
are not publicly traded may not be subject to the disclosure and other investor
protection requirements that might be applicable if their securities were publicly
traded.

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. Risks commonly associated with the direst ownership of real estate
include fluctuations in the value of underlying properties, 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 are subject to the
risks associated with the direct ownership of real estate, which are discussed
above. Some REITs may have limited diversification and may be subject to risks
inherent in financing a limited number of properties.

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.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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 for
each calendar year since its inception and by showing how the Fund's average
annual returns for 1 year, and since the Fund's inception, compared 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.

Best Quarter: 5.36% (12/31/11)

Worst Quarter: -5.05% (09/30/11)

The Fund's total return from January 1, 2012 to June 30, 2012 was 9.72%.

Average Annual Total Returns (for the periods ended December 31, 2011)

This table compares the Fund's average annual total returns to those of a
broad-based index and the Fund's 80/10/10 Blended Benchmark, which consists
of the S&P 500 Index (80%), the iBoxx $ Liquid High Yield Index (10%) and
the J.P. Morgan EMBI Global Core Index (10%). The Fund's Blended Benchmark
is designed to provide a useful comparison to the Fund's overall performance
and more accurately reflects the Fund's investment strategy than the
broad-based index.

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.

Average Annual Total Returns SIIT Dynamic Asset Allocation Fund	Label	1 Year	Since Inception	Inception Date
Class A	Return Before Taxes	2.58%	7.58%	Jul. 30, 2010
Class A After Taxes on Distributions	Return After Taxes on Distributions	1.50%	6.48%	Jul. 30, 2010
Class A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	2.26%	6.08%	Jul. 30, 2010
The Fund's Blended Benchmark Return	The Fund's Blended Benchmark Return (reflects no deduction for frees, expenses or taxes)	7.71%	10.45%	Jul. 30, 2010
S&P 500 Index Return	S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)	2.11%	12.14%	Jul. 30, 2010

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND

SMALL/MID CAP EQUITY FUND

Investment Goal

Long-term capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT SMALL MID CAP EQUITY FUND CLASS A
Management Fees		0.65%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.73%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT SMALL MID CAP EQUITY FUND CLASS A	75	233	406	906

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 84%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Small/Mid Cap Equity Fund will invest at least
80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of small- and medium-sized companies. The Fund
will invest primarily in common stocks of U.S. companies with market
capitalizations in the range of companies in the Russell 2500 Index (between
$30.7 million and $7.73 billion as of July 31, 2012) at the time of purchase.
The market capitalization range and the composition of the Russell 2500 Index
are subject to change. The Fund uses a multi-manager approach, relying on a
number of Sub-Advisers with differing investment philosophies to manage portions
of the Fund's portfolio under the general supervision of SIMC. For example, the
Sub-Advisers may include both value managers (i.e., managers that select stocks
they believe are undervalued in light of such fundamental characteristics as
earnings, cash flow or book value) and growth managers (i.e., managers that
select stocks they believe have significant earnings growth potential based on
new product introductions, revenue growth and/or margin improvement and other
factors). The Fund may also invest in ETFs to gain exposure to a particular
portion of the market while awaiting an opportunity to purchase securities
directly and REITs.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that smaller and medium capitalization
securities may underperform other segments of the equity market or the equity
markets as a whole.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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 include fluctuations in the
value of underlying properties, defaults by borrowers or tenants, changes in
interest rates and risks related to general or local economic conditions. Some
REITs may have limited diversification and may be subject to risks inherent in
financing a limited number of properties.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 22.03% (06/30/09)

Worst Quarter: -27.32% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 8.31%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT SMALL MID CAP EQUITY FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	(4.52%)	(0.31%)	5.47%	[1]	Dec. 15, 2003
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	(4.71%)	(0.85%)	4.66%	[1]	Dec. 15, 2003
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(2.88%)	(0.49%)	4.41%	[1]	Dec. 15, 2003
Russell 2500 Index Return	Russell 2500 Index Return (reflects no deduction for fees, expenses or taxes)	(2.51%)	1.24%	5.89%	[1]	Dec. 15, 2003

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from December 31, 2003.

XML

SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND

LARGE CAP FUND

Investment Goal

Long-term growth of capital and income.

Fees and Expenses

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

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

Annual Fund Operating Expenses	SIIT LARGE CAP FUND CLASS A
Management Fees	0.40%
Distribution (12b-1) Fees	none
Other Expenses	0.07%
Total Annual Fund Operating Expenses	0.47%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT LARGE CAP FUND CLASS A	48	151	263	591

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 83%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Large Cap Fund will invest at least 80% of its
net assets (plus the amount of any borrowings for investment purposes) in equity
securities of large companies. For purposes of this Fund, a large company is a
company with a market capitalization in the range of companies in the Russell
1000 Index (between $212.3 million and $572.4 billion as of July 31, 2012) at
the time of purchase. The market capitalization range and the composition of the
Russell 1000 Index are subject to change. These securities may include common
stocks, preferred stocks, warrants and exchange-traded funds (ETFs). The Fund may
also, to a lesser extent, invest in common and preferred stocks of small
capitalization companies. The Fund uses a multi-manager approach, relying on a
number of sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers)
with differing investment philosophies and strategies to manage portions of the
Fund's portfolio under the general supervision of SEI Investments Management
Corporation (SIMC).

The Sub-Advisers may engage in short sales in an amount up to 20% of the Fund's
value (measured at the time of investment) in an attempt to capitalize on equity
securities that they believe will underperform the market or their peers. When
the Sub-Advisers sell securities short, they may use the proceeds from the sales
to purchase long positions in additional equity securities that they believe
will outperform the market or their peers. This strategy may effectively result
in the Fund having a leveraged investment portfolio, which increases the
potential for loss.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that large capitalization securities may
underperform other segments of the equity markets or the equity markets as a
whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Short Sales Risk - 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. Reinvesting proceeds received from short selling may
create leverage, which can amplify the effects of market volatility on the
Fund's share price.

Small Capitalization Risk - Smaller capitalization companies in which the Fund
invests may be more vulnerable to adverse business or economic events than
larger, more established companies. In particular, small capitalization
companies may have limited product lines, markets and financial resources and
may depend upon a relatively small management group. Therefore, small
capitalization stocks may be more volatile than those of larger companies.

Loss of money is a risk of investing in the Fund.

Performance Information

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 ten years and by showing how the Fund's average annual
returns for 1, 5 and 10 years, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on full calendar years. The Fund's past performance (before and
after taxes) is not necessarily an indication of how the Fund will perform in
the future. For current performance information, please call 1-800-DIAL-SEI.

Best Quarter: 17.27% (06/30/09)

Worst Quarter: -21.67% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 9.09%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT LARGE CAP FUND	Label	1 Year	5 Years	10 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	0.74%	(0.31%)	2.99%	5.86%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	(0.14%)	(0.71%)	2.64%	5.21%	[1]	Jun. 14, 1996
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	1.61%	(0.30%)	2.52%	4.92%	[1]	Jun. 14, 1996
Russell 1000 Index Return	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)	1.50%	(0.02%)	3.34%	6.23%	[1]	Jun. 14, 1996

[1] Index returns are shown from June 30, 1996.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SMALL/MID CAP EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Long-term capital appreciation.
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, 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 84% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	84.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Small/Mid Cap Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of small- and medium-sized companies. The Fund will invest primarily in common stocks of U.S. companies with market capitalizations in the range of companies in the Russell 2500 Index (between $30.7 million and $7.73 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the Russell 2500 Index are subject to change. The Fund uses a multi-manager approach, relying on a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. For example, the Sub-Advisers may include both value managers (i.e., managers that select stocks they believe are undervalued in light of such fundamental characteristics as earnings, cash flow or book value) and growth managers (i.e., managers that select stocks they believe have significant earnings growth potential based on new product introductions, revenue growth and/or margin improvement and other factors). The Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly and REITs.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that smaller and medium capitalization securities may underperform other segments of the equity market or the equity markets as a whole. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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 include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past eight years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past eight years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 22.03% (06/30/09) Worst Quarter: -27.32% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 8.31%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND | Russell 2500 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 2500 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(2.51%)
5 Years	rr_AverageAnnualReturnYear05	1.24%
Since Inception	rr_AverageAnnualReturnSinceInception	5.89%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 15, 2003
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.65%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.73%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	75
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	233
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	406
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	906
Annual Return 2004	rr_AnnualReturn2004	19.07%
Annual Return 2005	rr_AnnualReturn2005	8.90%
Annual Return 2006	rr_AnnualReturn2006	15.30%
Annual Return 2007	rr_AnnualReturn2007	0.13%
Annual Return 2008	rr_AnnualReturn2008	(40.68%)
Annual Return 2009	rr_AnnualReturn2009	38.78%
Annual Return 2010	rr_AnnualReturn2010	25.08%
Annual Return 2011	rr_AnnualReturn2011	(4.52%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	8.31%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.03%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(27.32%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(4.52%)
5 Years	rr_AverageAnnualReturnYear05	(0.31%)
Since Inception	rr_AverageAnnualReturnSinceInception	5.47%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 15, 2003
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(4.71%)
5 Years	rr_AverageAnnualReturnYear05	(0.85%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.66%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 15, 2003
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(2.88%)
5 Years	rr_AverageAnnualReturnYear05	(0.49%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.41%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 15, 2003

[1] Index returns are shown from December 31, 2003.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT GLOBAL EQUITY FUND (Prospectus Summary) | SIIT GLOBAL EQUITY FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	GLOBAL EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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 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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
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 Global Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities. The Fund also may invest in futures contracts, foreign currency forward contracts, swaps and options, either for hedging and risk management purposes, including to seek to manage the Fund's currency exposure to foreign securities and mitigate the Fund's overall risk, or as part of its investment strategies. The Fund will invest primarily in common stocks and other equity securities of issuers located in developed market countries, including the U.S. Under normal circumstances, the Fund will invest in at least four countries outside of the U.S., but will typically invest much more broadly. At least 30% of the Fund's assets will be invested in non-U.S. issuers at any time and it is generally expected that approximately 50% of the Fund's assets will be invested in non-U.S. issuers consistent with the Fund's benchmark. However, the Fund's investments in non-U.S. issuers will vary depending on market conditions and implementation of the Fund's investment strategy at a particular point in time. The Fund may also invest, to a limited extent, in securities of issuers located in emerging market countries. The Fund will not invest more than 15% of its assets in the common stock or other equity securities of issuers located in emerging market countries. Emerging market countries are countries that the World Bank classifies as low, low-middle and upper-middle income countries. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund is diversified as to issuers, market capitalization, industry and country. The Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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, forward contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk, liquidity risk and market risk are described below. 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 forward contracts and swap agreements is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or may be 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries.    Investment Style Risk - The risk that investments in securities pursuant to a global strategy may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, 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. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
SIIT GLOBAL EQUITY FUND (Prospectus Summary) | SIIT GLOBAL EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.25%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.85%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	87
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	271

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	REAL RETURN FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return exceeding the rate of inflation.
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, 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 96% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	96.00%
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	The Fund uses a multi-manager approach under the general supervision of SIMC, allocating the assets among multiple Sub-Advisers using different investment strategies designed to produce a total return that exceeds the rate of inflation in the U.S. To a limited extent, SIMC may also directly manage a portion of the Fund's portfolio. Under normal circumstances, the Fund will invest a significant portion of its assets in investment grade fixed income securities, including inflation-indexed bonds of varying maturities issued by the U.S. Treasury, other U.S. Government agencies and instrumentalities, and non-government entities such as corporations. An inflation-indexed bond is a bond that is structured so that its principal value will change with inflation. Treasury Inflation-Protected Securities (TIPS) are a type of inflation-indexed bond in which the Fund may invest. The Fund's exposure to fixed income securities is not restricted by maturity requirements. The Fund may also invest in futures contracts, forward contracts and swaps for speculative or hedging purposes. Futures, forwards 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. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. Securities index swaps are used to manage the inflation adjusted return of the Fund. The Fund may also invest in other financial instruments or use other investment techniques, such as reverse repurchase agreements, to seek to obtain market exposure to the securities in which the Fund primarily invests. The Fund may also invest in: (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) U.S. and foreign corporate debt securities, including commercial paper, and fully-collateralized repurchase agreements with highly rated counterparties (those rated A or better); and (iv) securitized issues, such as mortgage-backed securities issued by U.S. Government agencies.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. 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. Currency Risk - As a result of the Fund's investments in securities 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. Derivatives Risk - The Fund's use of futures, forwards and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 forwards 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.    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 risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. Foreign Sovereign Debt Securities Risk - The risk 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, due to 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. 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. Interest Rate Risk - The risk that the value of fixed income securities, including U.S. Government securities, will fall due to rising interest rates. Investment Style Risk - The Fund is also subject to the risk that the Fund's securities may underperform other segments of the markets or the markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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 interests 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 5.47% (03/31/08) Worst Quarter: -4.42% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 0.97%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Barclays Capital U.S. Treasury Inflation Notes 1-5 Year Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Barclays Capital U.S. Treasury Inflation Notes 1-5 Year Index
1 Year	rr_AverageAnnualReturnYear01	4.88%
5 Years	rr_AverageAnnualReturnYear05	5.48%
Since Inception	rr_AverageAnnualReturnSinceInception	5.48%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Barclays Capital U.S. Treasury Inflation Notes 1-10 Year Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Barclays Capital U.S. Treasury Inflation Notes 1-10 Year Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	8.93%
5 Years	rr_AverageAnnualReturnYear05	6.90%
Since Inception	rr_AverageAnnualReturnSinceInception	6.90%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.22%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.06%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.28%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	29
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	90
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	157
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	356
Annual Return 2007	rr_AnnualReturn2007	12.00%
Annual Return 2008	rr_AnnualReturn2008	(1.72%)
Annual Return 2009	rr_AnnualReturn2009	9.75%
Annual Return 2010	rr_AnnualReturn2010	3.88%
Annual Return 2011	rr_AnnualReturn2011	5.06%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.97%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.47%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.42%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.06%
5 Years	rr_AverageAnnualReturnYear05	5.68%
Since Inception	rr_AverageAnnualReturnSinceInception	5.59%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Class A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	3.06%
5 Years	rr_AverageAnnualReturnYear05	3.92%
Since Inception	rr_AverageAnnualReturnSinceInception	3.84%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Class A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	3.59%
5 Years	rr_AverageAnnualReturnYear05	3.87%
Since Inception	rr_AverageAnnualReturnSinceInception	3.80%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 14, 2006

[1] Index returns are shown from December 31, 2006.

XML

SIIT Long Duration Corporate Bond Fund (Prospectus Summary) | SIIT Long Duration Corporate Bond Fund

LONG DURATION CORPORATE BOND FUND

Investment Goal

Return characteristics similar to those of high quality corporate bonds.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Long Duration Corporate Bond Fund Class A
Management Fees		0.30%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.10%
Total Annual Fund Operating Expenses		0.40%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT Long Duration Corporate Bond Fund Class A	41	128

PORTFOLIO TURNOVER

The Fund will incur 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.

Principal Investment Strategies

Under normal circumstances, the Long Duration Corporate Bond Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in long duration corporate fixed income securities, exchange-traded
funds (ETFs) that track long duration corporate bond indices, and synthetic
instruments or derivatives having economic characteristics similar to long
duration corporate fixed income securities.
  
The Fund will invest primarily in U.S. and foreign investment grade fixed income
instruments, including corporate bonds and unrated fixed income securities that
the Adviser or Sub-Advisers determined to be equivalent in quality. The Fund may
also invest a portion of its assets in municipal bonds, fixed income securities
issued by both developing and emerging foreign sovereigns, obligations of
supranational entities, and securities issued or guaranteed by the U.S. Government
and its agencies and instrumentalities. To a lesser extent, the Fund may also
invest in ETFs to gain exposure to a particular portion of the market while
awaiting an opportunity to purchase securities directly.

The Fund may also invest in futures contracts and swaps for speculative or
hedging purposes. Futures 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, currencies or market segments. Interest rate swaps are further used
to manage the Fund's interest rate risk and spread sensitivity. When the Fund
seeks to take an active long or short position with respect to the likelihood of
an event of default of a security or basket of securities, the Fund may use
credit default swaps. 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 such
security or basket of securities.

Under normal circumstances, the Fund is expected to maintain an effective
average duration of between nine and sixteen years. Duration is a measure that is
used to determine the sensitivity of a security's price to changes in interest
rates. For each year of duration of a fixed income security, a 1% change in
interest rates will result in an approximately 1% change in the value of the
security. For example, a duration of ten years means that the fixed income
security's price will change by approximately 10% if interest rates change by 1%.

The Fund uses one or more Sub-Advisers to manage the Fund's portfolio under the
general supervision of SIMC. The Sub-Advisers are selected for their expertise
in managing various kinds of fixed income securities, and the Sub-Advisers make
investment decisions based on an analysis of yield trends, credit ratings and
other factors in accordance with their particular discipline.

Principal Risks

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.

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 and swaps is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and unpredictably.
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
swap agreements 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.
  
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.

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.

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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements and different legal, regulatory
and tax environments. These additional risks may be heightened with respect to
emerging market countries since political turmoil and rapid changes in economic
conditions are more likely to occur in these countries.

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, due to 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.

Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in values of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in values in such securities.

Investment Style Risk - The risk that longer duration corporate fixed income
securities may underperform other segments of the fixed income markets or the
fixed income markets as a whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment opportunity,
any of which could have a negative effect on Fund management or performance.

Municipal Securities Risk - Municipal securities, like other fixed income securities,
rise and fall in value in response to economic and market factors, primarily changes
in interest rates, and actual or perceived credit quality. Rising interest rates will
generally cause municipal securities to decline in value. Longer-term securities
respond more sharply to interest rate changes than do shorter-term securities. A
municipal security will also lose value if, due to rating downgrades or other factors,
there are concerns about the issuer's current or future ability to make principal or
interest payments. State and local governments rely on taxes and, to some extent,
revenues from private projects financed by municipal securities, to pay interest and
principal on municipal debt. Poor statewide or local economic results or changing
political sentiments may reduce tax revenues and increase the expenses of municipal
issuers, making it more difficult for them to meet their obligations. Actual or
perceived erosion of the creditworthiness of municipal issuers may reduce the value
of the Fund's holdings. As a result, the Fund will be more susceptible to factors
that adversely affect issuers of municipal obligations than a mutual fund that does
not have as great a concentration in municipal obligations.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

The Fund commenced operations on June 29, 2012. Because the Fund did not have a
full calendar year of performance as of September 30, 2012, performance results
have not been provided.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SMALL CAP FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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, 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 85% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	85.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Small Cap Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities (including common and preferred stocks) of small companies, including ETFs based on small capitalization indices and securities of real estate investment trusts (REITs). For purposes of this Fund, a small company is a company with a market capitalization in the range of companies in the Russell 2000 Index (between $30.7 million and $3.67 billion as of July 31, 2012) or the S&P SmallCap 600 Index (between $52.7 million and $3.41 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of both the Russell 2000 Index and the S&P SmallCap 600 Index are subject to change. The Fund may also invest in securities of large capitalization companies. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. Each Sub-Adviser, in managing its portion of the Fund's assets, generally applies a growth-oriented, a value-oriented or a blended approach to selecting investments. Growth-oriented managers generally select stocks they believe have attractive growth and appreciation potential in light of such characteristics as revenue and earnings growth, expectations from sell-side analysts and relative valuation, while value-oriented managers generally select stocks they believe are attractively valued in light of fundamental characteristics such as earnings, capital structure and/or return on invested capital.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that small capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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 include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties. Small Capitalization Risk - Smaller capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 24.27% (06/30/09) Worst Quarter: -28.10% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 7.28%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND | Russell 2000 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 2000 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(4.18%)
5 Years	rr_AverageAnnualReturnYear05	0.15%
10 Years	rr_AverageAnnualReturnYear10	5.62%
Since Inception	rr_AverageAnnualReturnSinceInception	6.41%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.65%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.73%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	75
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	233
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	406
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	906
Annual Return 2002	rr_AnnualReturn2002	(21.77%)
Annual Return 2003	rr_AnnualReturn2003	49.20%
Annual Return 2004	rr_AnnualReturn2004	17.27%
Annual Return 2005	rr_AnnualReturn2005	6.14%
Annual Return 2006	rr_AnnualReturn2006	16.84%
Annual Return 2007	rr_AnnualReturn2007	(1.02%)
Annual Return 2008	rr_AnnualReturn2008	(40.66%)
Annual Return 2009	rr_AnnualReturn2009	37.36%
Annual Return 2010	rr_AnnualReturn2010	24.04%
Annual Return 2011	rr_AnnualReturn2011	(5.39%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	7.28%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	24.27%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(28.10%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(5.39%)
5 Years	rr_AverageAnnualReturnYear05	(1.09%)
10 Years	rr_AverageAnnualReturnYear10	4.86%
Since Inception	rr_AverageAnnualReturnSinceInception	6.69%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(5.53%)
5 Years	rr_AverageAnnualReturnYear05	(1.83%)
10 Years	rr_AverageAnnualReturnYear10	3.60%
Since Inception	rr_AverageAnnualReturnSinceInception	5.21%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(3.40%)
5 Years	rr_AverageAnnualReturnYear05	(1.14%)
10 Years	rr_AverageAnnualReturnYear10	3.79%
Since Inception	rr_AverageAnnualReturnSinceInception	5.20%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996

[1] Index returns are shown from June 30, 1996.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT EMERGING MARKETS EQUITY FUND (Prospectus Summary) | SIIT EMERGING MARKETS EQUITY FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	EMERGING MARKETS EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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 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.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other Expenses are based on estimated amounts for the current fiscal year.
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 Emerging Markets Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of emerging market issuers. The Fund will invest primarily in common stocks and other equity securities of foreign companies located in emerging market countries. The Fund normally maintains investments in at least six emerging market countries and does not invest more than 35% of its total assets in any one emerging market country. Emerging market countries are countries that the World Bank classifies as low, low-middle and upper-middle income countries. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund is diversified as to issuers, market capitalization, industry and country. The Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time.    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. Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investment Style Risk - The risk that emerging market equity securities may underperform other segments of the equity markets or the equity markets as a whole.    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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	As of September 30, 2012, the Fund had not yet commenced operations and did not have a performance history.
SIIT EMERGING MARKETS EQUITY FUND (Prospectus Summary) | SIIT EMERGING MARKETS EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	1.05%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.45%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.50%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	153
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	474

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SIIT Small Cap II Fund (Prospectus Summary) | SIIT Small Cap II Fund

SMALL CAP II FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Small Cap II Fund Class A
Management Fees		0.65%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.13%
Total Annual Fund Operating Expenses		0.78%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT Small Cap II Fund Class A	80	249

PORTFOLIO TURNOVER

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, for the period April 10, 2012 through May 31, 2012,
the Fund's annualized portfolio turnover rate was 9% of the average value of its
portfolio.

Principal Investment Strategies

Under normal circumstances, the Small Cap II Fund will invest at least 80% of
its net assets (plus the amount of any borrowings for investment purposes) in
equity securities of small companies. For purposes of this Fund, a small company
is a company with a market capitalization in the range of companies in the
Russell 2000 Index (between $30.7 million and $3.67 billion as of July 31, 2012)
at the time of purchase. The market capitalization range and the composition
of the Russell 2000 Index are subject to change. The Fund's investments in equity
securities may include common and preferred stocks and, to a lesser extent,
securities of real estate investment trusts (REITs) and securities of large
capitalization companies.

The Fund uses a multi-manager approach, relying upon one or more sub-advisers
(each, a Sub-Adviser and collectively, the Sub-Advisers) with differing
investment philosophies to manage portions of the Fund's portfolio under the
general supervision of SIMC. Each Sub-Adviser, in managing its portion of the
Fund's assets, generally applies a growth-oriented, a value-oriented or a
blended approach to selecting investments. Growth-oriented managers generally
select stocks they believe have attractive growth and appreciation potential in
light of such characteristics as revenue and earnings growth, expectations from
sell-side analysts and relative valuation, while value-oriented managers
generally select stocks they believe are attractively valued in light of
fundamental characteristics such as earnings, capital structure and/or return on
invested capital.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

Investment Style Risk - The risk that the securities in which the Fund principally
invests may underperform other segments of the equity markets or the equity markets
as a whole.

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 equity market as a whole.

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.

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 include fluctuations in the
value of underlying properties, defaults by borrowers or tenants, changes in
interest rates and risks related to general or local economic conditions. Some
REITs may have limited diversification and may be subject to risks inherent in
financing a limited number of properties.

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

Loss of money is a risk of investing in the Fund.

Performance Information

The Fund commenced operations on April 10, 2012. Because the Fund did not have a
full calendar year of performance as of September 30, 2012, performance results
have not been provided.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

SIIT Ultra Short Duration Bond Fund (Prospectus Summary) | SIIT Ultra Short Duration Bond Fund

ULTRA SHORT DURATION BOND FUND

Investment Goal

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.

Fees and Expenses

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

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

Annual Fund Operating Expenses	SIIT Ultra Short Duration Bond Fund Class A
Management Fees	0.15%
Distribution (12b-1) Fees	none
Other Expenses	0.06%
Total Annual Fund Operating Expenses	0.21%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Ultra Short Duration Bond Fund Class A	22	68	118	268

PORTFOLIO TURNOVER

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 222% of the average value of its portfolio.

Principal Investment Strategies

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.

Principal Risks

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 risk, liquidity risk and market
risk are described below. 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 swap agreements is also subject to credit risk and
valuation risk. Valuation risk is the risk that the derivative may be difficult
to value and/or may be 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.

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.

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.

Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in values of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in values of such securities.

Leverage Risk - 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.

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.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

The Fund commenced operations on February 28, 2011. Because the Fund did not
have a full calendar year of performance as of September 30, 2012, performance
results have not been provided.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Multi-Asset Real Return Fund (Prospectus Summary) | SIIT Multi-Asset Real Return Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	MULTI-ASSET REAL RETURN FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Total return exceeding the rate of inflation.
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 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, for the period July 29, 2011 through May 31, 2012, the Fund's annualized portfolio turnover rate was 58% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	58.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the current fiscal year.
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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	The Fund uses a multi-manager approach under the general supervision of SIMC, allocating its assets among one or more Sub-Advisers using different investment strategies designed to produce a total return that exceeds the rate of inflation in the U.S. SIMC may also directly manage a portion of the Fund's portfolio. 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) TIPS and other inflation-linked debt securities; (iv) U.S. and foreign 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 mortgage-backed securities, asset-backed securities, commercial mortgage-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 affiliated and unaffiliated funds, including open-end funds, closed-end funds and ETFs (collectively, Underlying Funds). The Fund may also invest in 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 indices. The Fund may also invest in equity and debt securities of issuers in commodity-related industries. The Fund may also purchase or sell futures contracts, options, forward contracts and swaps 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 indices 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-Advisers 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-Advisers 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. Due to its investment strategy, the Fund may buy and sell securities frequently.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The success of the Fund's investment strategy depends both on SIMC's selection of the Underlying Funds and Sub-Advisers and allocating assets to such Underlying Funds and Sub-Advisers. SIMC, an Underlying Fund or Sub-Advisers 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 Underlying Funds and Sub-Advisers may not achieve desired results and may cause the Fund to lose money or underperform other comparable mutual funds. The Fund, Underlying Funds and Sub-Advisers 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 their designated 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. Asset-Backed Securities Risk - Payment of principal and interest on asset-backed securities is dependent largely on 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. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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.    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. 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. 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. Derivatives Risk - The Fund's use of futures contracts, forward contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk, liquidity risk and market risk are described below. 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 forward contracts and swap agreements is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or may be 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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 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. Inflation Protected Securities Risk - The value of inflation protected securities, including TIPS, will generally fluctuate in response to changes in "real" interest rates, 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.    Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in the value of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in the value of such securities. 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. Leverage Risk - 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 otherwise be advantageous to do so in order to satisfy its obligations. Liquidity Risk - The risk that certain securities may be difficult or impossible to sell at the time and price that the Fund would like. The Fund 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. 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. 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. 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. 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. Small and Medium Capitalization Risk - The small and medium capitalization companies in which the Fund invests 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 stocks may be traded over the counter or listed on an exchange. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	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.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund commenced operations on July 29, 2011. Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
SIIT Multi-Asset Real Return Fund (Prospectus Summary) | SIIT Multi-Asset Real Return Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.55%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.11%	[1]
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.11%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.77%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	79
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	246
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	428
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	954

[1] Other Expenses are based on estimated amounts for the current fiscal year.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund

REAL RETURN FUND

Investment Goal

Total return exceeding the rate of inflation.

Fees and Expenses

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

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

Annual Fund Operating Expenses	SIIT Real Return Fund Class A
Management Fees	0.22%
Distribution (12b-1) Fees	none
Other Expenses	0.06%
Total Annual Fund Operating Expenses	0.28%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Real Return Fund Class A	29	90	157	356

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 96%
of the average value of its portfolio.

Principal Investment Strategies

The Fund uses a multi-manager approach under the general supervision of SIMC,
allocating the assets among multiple Sub-Advisers using different investment
strategies designed to produce a total return that exceeds the rate of inflation
in the U.S. To a limited extent, SIMC may also directly manage a portion of the
Fund's portfolio.

Under normal circumstances, the Fund will invest a significant portion of
its assets in investment grade fixed income securities, including
inflation-indexed bonds of varying maturities issued by the U.S. Treasury, other
U.S. Government agencies and instrumentalities, and non-government entities such
as corporations. An inflation-indexed bond is a bond that is structured so that
its principal value will change with inflation. Treasury Inflation-Protected
Securities (TIPS) are a type of inflation-indexed bond in which the Fund may
invest. The Fund's exposure to fixed income securities is not restricted by
maturity requirements.

The Fund may also invest in futures contracts, forward contracts and swaps for
speculative or hedging purposes. Futures, forwards 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. Interest
rate swaps are further used to manage the Fund's yield spread sensitivity.
Securities index swaps are used to manage the inflation adjusted return of the
Fund.

The Fund may also invest in other financial instruments or use other investment
techniques, such as reverse repurchase agreements, to seek to obtain market
exposure to the securities in which the Fund primarily invests.

The Fund may also invest in: (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) U.S. and foreign corporate debt securities, including commercial paper,
and fully-collateralized repurchase agreements with highly rated counterparties
(those rated A or better); and (iv) securitized issues, such as mortgage-backed
securities issued by U.S. Government agencies.

Principal Risks

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.

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.

Currency Risk - As a result of the Fund's investments in securities 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.

Derivatives Risk - The Fund's use of futures, forwards and swaps is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 forwards 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.
  
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 risks due to, among other things, political, social and economic
developments abroad, currency movements, and different legal, regulatory and tax
environments.

Foreign Sovereign Debt Securities Risk - The risk 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, due to 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.

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.

Interest Rate Risk - The risk that the value of fixed income securities,
including U.S. Government securities, will fall due to rising interest rates.

Investment Style Risk - The Fund is also subject to the risk that the Fund's
securities may underperform other segments of the markets or the markets as a
whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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 interests 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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 5.47% (03/31/08)

Worst Quarter: -4.42% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 0.97%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT Real Return Fund	Label	1 Year	5 Years	Since Inception		Inception Date
Class A	Return Before Taxes	5.06%	5.68%	5.59%	[1]	Dec. 14, 2006
Class A After Taxes on Distributions	Return After Taxes on Distributions	3.06%	3.92%	3.84%	[1]	Dec. 14, 2006
Class A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	3.59%	3.87%	3.80%	[1]	Dec. 14, 2006
Barclays Capital U.S. Treasury Inflation Notes 1-5 Year Index	Barclays Capital U.S. Treasury Inflation Notes 1-5 Year Index	4.88%	5.48%	5.48%	[1]	Dec. 14, 2006
Barclays Capital U.S. Treasury Inflation Notes 1-10 Year Index Return	Barclays Capital U.S. Treasury Inflation Notes 1-10 Year Index Return (reflects no deduction for fees, expenses or taxes)	8.93%	6.90%	6.90%	[1]	Dec. 14, 2006

[1] Index returns are shown from December 31, 2006.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LARGE CAP FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Long-term growth of capital and income.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy 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, 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 83% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	83.00%
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 Large Cap Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of large companies. For purposes of this Fund, a large company is a company with a market capitalization in the range of companies in the Russell 1000 Index (between $212.3 million and $572.4 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the Russell 1000 Index are subject to change. These securities may include common stocks, preferred stocks, warrants and exchange-traded funds (ETFs). The Fund may also, to a lesser extent, invest in common and preferred stocks of small capitalization companies. The Fund uses a multi-manager approach, relying on a number of sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) with differing investment philosophies and strategies to manage portions of the Fund's portfolio under the general supervision of SEI Investments Management Corporation (SIMC). The Sub-Advisers may engage in short sales in an amount up to 20% of the Fund's value (measured at the time of investment) in an attempt to capitalize on equity securities that they believe will underperform the market or their peers. When the Sub-Advisers sell securities short, they may use the proceeds from the sales to purchase long positions in additional equity securities that they believe will outperform the market or their peers. This strategy may effectively result in the Fund having a leveraged investment portfolio, which increases the potential for loss.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Investment Style Risk - The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Short Sales Risk - 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. Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund's share price. Small Capitalization Risk - Smaller capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past ten years and by showing how the Fund's average annual returns for 1, 5 and 10 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 17.27% (06/30/09) Worst Quarter: -21.67% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 9.09%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND | Russell 1000 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	1.50%
5 Years	rr_AverageAnnualReturnYear05	(0.02%)
10 Years	rr_AverageAnnualReturnYear10	3.34%
Since Inception	rr_AverageAnnualReturnSinceInception	6.23%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.47%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	48
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	151
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	263
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	591
Annual Return 2002	rr_AnnualReturn2002	(22.82%)
Annual Return 2003	rr_AnnualReturn2003	28.05%
Annual Return 2004	rr_AnnualReturn2004	11.98%
Annual Return 2005	rr_AnnualReturn2005	7.68%
Annual Return 2006	rr_AnnualReturn2006	14.41%
Annual Return 2007	rr_AnnualReturn2007	6.59%
Annual Return 2008	rr_AnnualReturn2008	(37.97%)
Annual Return 2009	rr_AnnualReturn2009	29.62%
Annual Return 2010	rr_AnnualReturn2010	14.02%
Annual Return 2011	rr_AnnualReturn2011	0.74%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	9.09%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	17.27%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.67%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	0.74%
5 Years	rr_AverageAnnualReturnYear05	(0.31%)
10 Years	rr_AverageAnnualReturnYear10	2.99%
Since Inception	rr_AverageAnnualReturnSinceInception	5.86%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(0.14%)
5 Years	rr_AverageAnnualReturnYear05	(0.71%)
10 Years	rr_AverageAnnualReturnYear10	2.64%
Since Inception	rr_AverageAnnualReturnSinceInception	5.21%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	1.61%
5 Years	rr_AverageAnnualReturnYear05	(0.30%)
10 Years	rr_AverageAnnualReturnYear10	2.52%
Since Inception	rr_AverageAnnualReturnSinceInception	4.92%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 14, 1996

[1] Index returns are shown from June 30, 1996.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LONG DURATION FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Return characteristics similar to those of high quality corporate bonds, with a duration range of between nine and fourteen years.
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, 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 121% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	121.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Long Duration Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in long duration fixed income securities and synthetic instruments or derivatives having economic characteristics similar to fixed income securities. The Fund invests in a broad array of investment grade fixed income instruments, including securities issued or guaranteed by the U.S. Government and its agencies and instrumentalities and corporate bonds. The Fund will invest primarily in long duration government and corporate fixed income securities and may also invest in futures contracts, forward contracts and swaps for speculative or hedging purposes. Futures, forwards 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, currencies or market segments. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities. The Fund will invest primarily in fixed income securities rated in one of the three highest rating categories by a major rating agency and may also invest, to a lesser extent, in fixed income securities rated in the fourth highest rating category by a major rating agency. The Fund may also invest in unrated fixed income securities that are determined by the Sub-Advisers to be of equivalent quality to those securities rated in one of the four highest rating categories. The Fund is expected to maintain an effective average duration of between nine and fourteen years. The Fund's effective average duration was 13.68 years as of July 31, 2012. Duration is a measure that is used to determine the sensitivity of a security's price to changes in interest rates. For each year of duration of a fixed income security, a 1% change in interest rates will result in a 1% change in the value of the security. For example, a duration of ten years means that the fixed income security's price will change by 10% if interest rates change by 1%. The Fund uses Sub-Advisers to manage the Fund's portfolio under the general supervision of SIMC. The Sub-Advisers are selected for their expertise in managing various kinds of fixed income securities, and the Sub-Advisers make investment decisions based on an analysis of yield trends, credit ratings and other factors in accordance with their particular discipline. To a lesser extent, the Fund may also invest in ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. 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, forward contracts and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 forwards and swap agreements 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. 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. 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. 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. Investment Style Risk - The risk that longer-term U.S. fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past seven years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past seven years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 13.85% (09/30/11) Worst Quarter: -5.85% (06/30/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 5.81%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 Narrative	rr_PerformanceTableNarrativeTextBlock	This table compares the Fund's average annual total returns to those of a broad-based index and the Fund's 60/40 Blended Benchmark, which consists of the Barclays Capital U.S. Long Credit Index and the Barclays Capital U.S. Long Government Index. The Fund's Blended Benchmark is designed to provide a useful comparison to the Fund's overall performance and more accurately reflects the Fund's investment strategy than the broad-based index. 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.
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | Barclays Capital Long U.S. Government/Credit Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Barclays Capital Long U.S. Government/Credit Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	22.49%
5 Years	rr_AverageAnnualReturnYear05	9.71%
Since Inception	rr_AverageAnnualReturnSinceInception	8.56%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 21, 2004
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | The Fund's Blended Benchmark Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	The Fund's Blended Benchmark Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	22.02%
5 Years	rr_AverageAnnualReturnYear05	9.62%
Since Inception	rr_AverageAnnualReturnSinceInception	8.51%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 21, 2004
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.30%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.38%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	39
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	122
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	213
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	480
Annual Return 2005	rr_AnnualReturn2005	3.77%
Annual Return 2006	rr_AnnualReturn2006	3.39%
Annual Return 2007	rr_AnnualReturn2007	3.06%
Annual Return 2008	rr_AnnualReturn2008	(5.52%)
Annual Return 2009	rr_AnnualReturn2009	3.38%
Annual Return 2010	rr_AnnualReturn2010	12.68%
Annual Return 2011	rr_AnnualReturn2011	20.50%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	5.81%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	13.85%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.85%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	20.50%
5 Years	rr_AverageAnnualReturnYear05	6.45%
Since Inception	rr_AverageAnnualReturnSinceInception	6.10%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 21, 2004
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	16.49%
5 Years	rr_AverageAnnualReturnYear05	3.89%
Since Inception	rr_AverageAnnualReturnSinceInception	3.67%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 21, 2004
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	13.68%
5 Years	rr_AverageAnnualReturnYear05	4.00%
Since Inception	rr_AverageAnnualReturnSinceInception	3.78%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Apr. 21, 2004

[1] Index returns are shown from April 30, 2004.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT GLOBAL EQUITY FUND (Prospectus Summary) | SIIT GLOBAL EQUITY FUND

GLOBAL EQUITY FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT GLOBAL EQUITY FUND CLASS A
Management Fees		0.60%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.25%
Total Annual Fund Operating Expenses		0.85%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT GLOBAL EQUITY FUND CLASS A	87	271

PORTFOLIO TURNOVER

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.

Principal Investment Strategies

Under normal circumstances, the Global Equity Fund will invest at least 80% of
its net assets (plus the amount of any borrowings for investment purposes) in
equity securities. The Fund also may invest in futures contracts, foreign
currency forward contracts, swaps and options, either for hedging and risk
management purposes, including to seek to manage the Fund's currency exposure
to foreign securities and mitigate the Fund's overall risk, or as part of its
investment strategies.

The Fund will invest primarily in common stocks and other equity securities of
issuers located in developed market countries, including the U.S. Under normal
circumstances, the Fund will invest in at least four countries outside of the
U.S., but will typically invest much more broadly. At least 30% of the Fund's
assets will be invested in non-U.S. issuers at any time and it is generally
expected that approximately 50% of the Fund's assets will be invested in
non-U.S. issuers consistent with the Fund's benchmark. However, the Fund's
investments in non-U.S. issuers will vary depending on market conditions and
implementation of the Fund's investment strategy at a particular point in time.

The Fund may also invest, to a limited extent, in securities of issuers located
in emerging market countries. The Fund will not invest more than 15% of its
assets in the common stock or other equity securities of issuers located in
emerging market countries. Emerging market countries are countries that the
World Bank classifies as low, low-middle and upper-middle income countries.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment philosophies to manage portions of the Fund's
portfolio under the general supervision of SIMC. The Fund is diversified as to
issuers, market capitalization, industry and country. The Fund may also invest
in ETFs to gain exposure to a particular portion of the market while awaiting an
opportunity to purchase securities directly.

Principal Risks

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, forward contracts,
options and swaps is subject to market risk, leverage risk, correlation risk and
liquidity risk. Leverage risk, liquidity risk and market risk are described
below. 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 forward contracts and swap agreements is also subject to credit risk and
valuation risk. Valuation risk is the risk that the derivative may be difficult
to value and/or may be 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes in
economic conditions are more likely to occur in these countries.
  
Investment Style Risk - The risk that investments in securities pursuant to a
global strategy may underperform other segments of the equity markets or the
equity markets as a whole.

Leverage Risk - 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.

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, 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.

Small and Medium Capitalization Risk - The risk that small and medium
capitalization companies in which the Fund invests may be more vulnerable to
adverse business or economic events than larger, more established companies. In
particular, small and medium capitalization 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.

Loss of money is a risk of investing in the Fund.

Performance Information

As of September 30, 2012, the Fund had not yet commenced operations and did not
have a performance history.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	DYNAMIC ASSET ALLOCATION FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Long-term total return.
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, 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 140% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	140.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 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	The Fund employs a dynamic asset allocation investment strategy, seeking to achieve its investment objective through a risk-controlled, disciplined process that is designed to attempt to capture returns from short- and intermediate-term market anomalies that may arise in particular asset classes within a broad range of possible asset classes. The Fund seeks to generate total return over time by selecting investments from among a broad range of asset classes based upon SEI Investments Management Corporation's (SIMC or the Adviser) expectations of risk and return. The asset classes used and the Fund's allocations among those asset classes are determined based on SIMC's views of fundamental, technical or valuation measures. The Fund's allocations among asset classes may be adjusted over short periods of time and at any particular point in time the Fund may be diversified across many asset classes or concentrated in a limited number of asset classes, including possibly a single asset class. The Fund uses a multi-manager approach under the general supervision of SIMC, allocating its assets among one or more sub-advisers (each, a Sub-Adviser and collectively, the Sub-Advisers) that will implement different investment strategies. SIMC allocates Fund assets among one or more Sub-Advisers based on SIMC's expectations of risk and return as informed by SIMC's views of fundamental, technical or valuation measures. The Fund is also managed, in part, by SIMC. The Fund may obtain its exposures to a particular asset class by investing directly (e.g., in equity and fixed income securities and other instruments) or indirectly (e.g., through the use of other pooled investment vehicles and derivative instruments, principally futures contracts, forward contracts, options and swaps). The particular types of securities and other instruments that the Fund may invest in within a particular asset class are further described below. The Fund may invest in particular securities or instruments that are not specifically listed below, but which have similar characteristics or represent similar exposures as those described below. Equity Securities. The Fund may invest in equity securities, including common stocks, preferred stocks, convertible securities, warrants and depositary receipts of U.S. and non-U.S. issuers (including emerging markets) of various market capitalizations and industries. Fixed Income Securities. The Fund may invest in fixed income securities that are investment or non-investment grade (also known as "junk bonds"), U.S.- or foreign-issued (including emerging markets), and corporate- or government-issued. The Fund's fixed income investments may include asset-backed securities, mortgage-backed securities, collateralized debt obligations (CDOs) and collateralized loan obligations (CLOs), corporate bonds and debentures, commercial paper, exchange traded notes (ETNs), money market instruments, mortgage dollar rolls, repurchase and reverse repurchase agreements, when issued/delayed delivery securities, zero coupon bonds, obligations of foreign governments, and obligations of either supranational entities issued or guaranteed by certain banks and entities organized to restructure the outstanding debt of such issuers. The Fund's fixed income investments may also include U.S. Treasury obligations, obligations issued by agencies or instrumentalities of the U.S. Government (including obligations not guaranteed by the U.S. Treasury), such as obligations issued by U.S. Government sponsored entities, and Treasury Inflation Protected Securities (TIPS) and other inflation-linked debt securities of both U.S. and non-U.S. governments and corporations.    The Fund may also invest a portion of its assets in bank loans, which are, generally, non-investment grade floating rate instruments, in the form of participations in the loans (participations) and assignments of all or a portion of the loans from third parties (assignments). The Fund may invest in fixed, variable and floating rate fixed income instruments. The Fund's portfolio and the Fund's investments in particular fixed income securities are not subject to any maturity or duration restrictions. Other Instruments. The Fund may also invest in real estate investment trusts (REITs) and securities issued by U.S. and non-U.S. real estate companies. Pooled Investment Vehicles. In addition to direct investment in securities and other instruments, the Fund may invest in affiliated and unaffiliated funds, including open-end funds, money market funds, closed-end funds and exchange-traded funds (ETFs), to obtain the Fund's desired exposure to a particular asset class. Derivative Instruments. The Fund may also purchase or sell futures contracts, forward contracts, options and swaps (including swaptions, caps, floors or collars) for return enhancement or hedging purposes or to obtain the Fund's desired exposure to a particular asset class. Futures contracts, forward contracts, options and swaps may be 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 may also be used to mitigate the Fund's overall level of risk and/or the Fund's exposure to the risk of particular types of securities or market segments. The Fund may purchase or sell futures contracts on U.S. Government securities for return enhancement and hedging purposes. The Fund may purchase and sell forward contracts on currencies or securities for return enhancement and hedging purposes. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. Currency swaps may be used for return enhancement or hedging purposes. Securities index and single-security swaps may be used to manage the inflation-adjusted return of the Fund or to more efficiently gain exposure to a particular security or basket of securities. 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. 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 marketable securities issued by companies that own or invest in commodities or commodities contracts, equity and debt securities of issuers in commodity-related industries, 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 indices. The Fund may invest in U.S. dollar and non-U.S. dollar denominated securities. SIMC or the Sub-Advisers may also seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, SIMC or the Sub-Advisers may buy and sell currencies (i.e., take long or short positions) using futures and foreign currency forward contracts. 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 its exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another. In managing the Fund's currency exposure for foreign securities, SIMC or the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes. The Sub-Advisers may engage in short sales in an attempt to capitalize on equity securities that they believe will underperform the market or their peers. When the Sub-Advisers sell securities short, they 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. Due to its investment strategy, the Fund may buy and sell securities and other instruments frequently. The goal of the Fund is to serve as a dynamic overlay to broader strategic allocations. This Fund is intended to be used by shareholders seeking to add a dynamic component to their broader overall investment strategy. An investment in the Fund should not constitute a shareholder's complete investment program.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	American Depositary Receipts (ADRs) Risk - ADRs are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. ADRs 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. 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. Bank Loans Risk - With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. CDOs and 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 of 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 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. 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. Convertible and Preferred Securities Risk - Convertible and preferred securities have many of the same characteristics as stocks, including many of the same risks. In addition, convertible securities may be more sensitive to changes in interest rates than stocks. Convertible securities may also have credit ratings below investment grade, meaning that they carry a higher risk of failure by the issuer to pay principal and/or interest when due. 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. 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. Currency Risk - 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. 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 risk, liquidity risk and market risk are described below. 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 forwards and swap agreements 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. 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. 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. 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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in values of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in values of such securities. Investment Company Risk - When the Fund invests in an investment company, including closed-end funds and ETFs, 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. Further, 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. Closed-end investment companies issue a fixed number of shares that trade on a stock exchange or over-the-counter at a premium or a discount to their net asset value. As a result, a closed-end fund's share price fluctuates based on what another investor is willing to pay rather than on the market value of the securities in the fund. Leverage Risk - 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. 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 equity or 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. Private Placements Risk - Investment in privately placed securities may be less liquid than in publicly traded securities. Although these securities may be resold in privately negotiated transactions, the prices realized from these sales could be less than those originally paid by the Fund or less than what may be considered the fair value of such securities. Further, companies whose securities are not publicly traded may not be subject to the disclosure and other investor protection requirements that might be applicable if their securities were publicly traded. 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. Risks commonly associated with the direst ownership of real estate include fluctuations in the value of underlying properties, 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 are subject to the risks associated with the direct ownership of real estate, which are discussed above. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties. 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. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance for each calendar year since its inception and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared 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]	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 for each calendar year since its inception and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 5.36% (12/31/11) Worst Quarter: -5.05% (09/30/11) The Fund's total return from January 1, 2012 to June 30, 2012 was 9.72%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deduction for frees, 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 Narrative	rr_PerformanceTableNarrativeTextBlock	This table compares the Fund's average annual total returns to those of a broad-based index and the Fund's 80/10/10 Blended Benchmark, which consists of the S&P 500 Index (80%), the iBoxx $ Liquid High Yield Index (10%) and the J.P. Morgan EMBI Global Core Index (10%). The Fund's Blended Benchmark is designed to provide a useful comparison to the Fund's overall performance and more accurately reflects the Fund's investment strategy than the broad-based index. 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.
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | The Fund's Blended Benchmark Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	The Fund's Blended Benchmark Return (reflects no deduction for frees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	7.71%
Since Inception	rr_AverageAnnualReturnSinceInception	10.45%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 30, 2010
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | S&P 500 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	2.11%
Since Inception	rr_AverageAnnualReturnSinceInception	12.14%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 30, 2010
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.15%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.82%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	84
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	262
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	455
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,014
Annual Return 2011	rr_AnnualReturn2011	2.58%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	9.72%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.36%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.05%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.58%
Since Inception	rr_AverageAnnualReturnSinceInception	7.58%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 30, 2010
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | Class A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	1.50%
Since Inception	rr_AverageAnnualReturnSinceInception	6.48%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 30, 2010
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | Class A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	2.26%
Since Inception	rr_AverageAnnualReturnSinceInception	6.08%
Inception Date	rr_AverageAnnualReturnInceptionDate	Jul. 30, 2010

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	May 31, 2012
Registrant Name	dei_EntityRegistrantName	SEI INSTITUTIONAL INVESTMENTS TRUST
Central Index Key	dei_EntityCentralIndexKey	0000939934
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Sep. 28, 2012
Document Effective Date	dei_DocumentEffectiveDate	Sep. 30, 2012
SIIT LARGE CAP FUND (Prospectus Summary) | SIIT LARGE CAP FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SLCAX
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SCDAX
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SCPAX
SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LCIAX
SIIT SMALL CAP FUND (Prospectus Summary) | SIIT SMALL CAP FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SLPAX
SIIT SMALL MID CAP EQUITY FUND (Prospectus Summary) | SIIT SMALL MID CAP EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SSMAX
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SVYAX
SIIT INTERNATIONAL EQUITY FUND (Prospectus Summary) | SIIT INTERNATIONAL EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SNTAX
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	WEUSX
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SSEAX
SIIT Enhanced LIBOR Opportunities Fund (Prospectus Summary) | SIIT Enhanced LIBOR Opportunities Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	ENIAX
SIIT CORE FIXED INCOME (Prospectus Summary) | SIIT CORE FIXED INCOME | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SCOAX
SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SGYAX
SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LDRAX
SIIT Ultra Short Duration Bond Fund (Prospectus Summary) | SIIT Ultra Short Duration Bond Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SUSAX
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SEDAX
SIIT Real Return Fund (Prospectus Summary) | SIIT Real Return Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	RRPAX
SIIT Dynamic Asset Allocation Fund (Prospectus Summary) | SIIT Dynamic Asset Allocation Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SDLAX
SIIT Multi-Asset Real Return Fund (Prospectus Summary) | SIIT Multi-Asset Real Return Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	SEIAX

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LARGE CAP DISCIPLINED EQUITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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, 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 93% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	93.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Large Cap Disciplined Equity Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of large companies. These securities may include common stocks, preferred stocks, warrants and ETFs based on a large capitalization equity index. The Fund will invest primarily in common stocks of U.S. companies with market capitalizations in the range of companies in the S&P 500 Composite Stock Price Index (S&P 500 Index) (between $1.22 billion and $572.4 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the S&P 500 Index are subject to change. The Fund may also, to a lesser extent, invest in common and preferred stocks of small capitalization companies. The Fund seeks to exceed the total return of the S&P 500 Index, with a similar level of volatility, by investing primarily in a portfolio of common stocks included in the S&P 500 Index, as well as other equity investments and derivative instruments whose value is derived from the performance of the S&P 500 Index. The Fund uses a multi-manager approach, relying on Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund may employ Sub-Advisers that use a variety of different methods to seek to outperform the Fund's benchmark, including purchasing stocks with strong anticipated future earnings growth, selecting stocks that the Sub-Adviser believes are undervalued relative to their fundamentals, capturing returns from the natural volatility of the market and employing strategies that rotate among various sectors of the market. The Fund may also utilize one or more additional Sub-Advisers who manage in a complementary style with the objective to seek to add value over the S&P 500 Index while maintaining a similar level of volatility to the S&P 500 Index. Certain Sub-Advisers use portfolio strategies that are designed to correlate with a portfolio of large capitalization equity securities, but which are composed of futures contracts or swaps backed by other types of securities. These portfolio strategies are included in the Fund's principal investment strategy described above. The Sub-Advisers may purchase these instruments, generally using only a fraction of the assets that would be needed to purchase the equity securities directly, so that the remainder of the assets in a portfolio may be invested in other types of securities. Therefore, a Sub-Adviser would seek to outperform a large capitalization benchmark by purchasing futures contracts and swaps correlated to a broad large capitalization index and investing the remaining assets in other types of securities to add excess return. This portion of the Fund's assets may be invested in a wide range of asset classes other than large capitalization equities. Pursuant to a derivatives strategy, the other types of securities backing the derivative instruments may include investments in U.S. and foreign corporate and government fixed income securities of different types and maturities, including mortgage-backed or other asset-backed securities, securities rated below the fourth highest rating category by an NRSRO (junk bonds) and repurchase or reverse repurchase agreements. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes. The amount of the Fund's portfolio that may be allocated to derivative strategies is expected to vary over time. The Fund may also invest in futures contracts and swaps for speculative or hedging purposes. Futures and swaps are used to synthetically obtain exposure to securities or baskets of securities. 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. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities. To achieve its investment goal, the Fund may invest in the SEI LIBOR Plus Portfolio (Portfolio), which is a portfolio of SEI Alpha Strategy Portfolios, LP, a registered open-end investment company that was established to permit certain Funds to pursue their respective investment strategies in an efficient manner. The Fund will invest in the Portfolio only if the Portfolio invests in securities and pursues investment strategies that are consistent with the Fund's investment strategy. The Portfolio has expenses associated with its operations, including advisory and administration fees. When the Fund invests in the Portfolio, it will bear a pro rata portion of the Portfolio's expenses, which will be reflected in the Fund's fee table as "Acquired Fund Fees and Expenses."
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. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - 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. Derivatives Risk - The Fund's use of futures and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 swap agreements 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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.    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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investment Style Risk - The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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. Short Sales Risk - 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. Small Capitalization Risk - Smaller capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past eight years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past eight years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 15.99% (06/30/09) Worst Quarter: -25.66% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 9.70%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND | S&P 500 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	2.11%
5 Years	rr_AverageAnnualReturnYear05	(0.25%)
Since Inception	rr_AverageAnnualReturnSinceInception	4.79%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 28, 2003
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.49%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	50
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	157
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	274
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	616
Annual Return 2004	rr_AnnualReturn2004	11.35%
Annual Return 2005	rr_AnnualReturn2005	6.97%
Annual Return 2006	rr_AnnualReturn2006	15.52%
Annual Return 2007	rr_AnnualReturn2007	3.85%
Annual Return 2008	rr_AnnualReturn2008	(41.98%)
Annual Return 2009	rr_AnnualReturn2009	25.25%
Annual Return 2010	rr_AnnualReturn2010	14.97%
Annual Return 2011	rr_AnnualReturn2011	1.18%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	9.70%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	15.99%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.66%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	1.18%
5 Years	rr_AverageAnnualReturnYear05	(2.57%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.65%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 28, 2003
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	0.81%
5 Years	rr_AverageAnnualReturnYear05	(3.17%)
Since Inception	rr_AverageAnnualReturnSinceInception	2.85%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 28, 2003
SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	1.06%
5 Years	rr_AverageAnnualReturnYear05	(2.34%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.11%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 28, 2003

[1] Index returns are shown from August 31, 2003.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	LARGE CAP DIVERSIFIED ALPHA FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Long-term growth of capital and income.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy 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, 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 101% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	101.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Large Cap Diversified Alpha Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of large companies or in portfolio strategies designed to correlate to a portfolio composed of large capitalization equity securities. For purposes of this Fund, a large company is a company with a market capitalization in the range of companies in the Russell 1000 Index (between $212.3 million and $572.4 billion as of July 31, 2012) at the time of purchase. The market capitalization range and the composition of the Russell 1000 Index are subject to change. The Fund may also, to a lesser extent, invest in common and preferred stocks of small capitalization companies. The Fund may also invest in ETFs based on a large capitalization index. The Fund uses a multi-manager approach under the general supervision of SIMC, allocating the assets among multiple Sub-Advisers that use different investment strategies to seek to achieve returns in excess of the performance of the Russell 1000 Index. This allocation among investment strategies aims to diversify the sources from which Sub-Advisers seek to achieve excess returns (i.e., returns in excess of a benchmark index or "alpha"), thereby diversifying the relative risk of the Fund. While the Fund is expected to have an absolute return and risk profile similar to the broad U.S. large capitalization equity market, returns may be derived in part from investing up to 20% of the Fund in securities outside of the large capitalization market. Certain Sub-Advisers use portfolio strategies that are designed to correlate with a portfolio of large capitalization equity securities, but which are composed of futures contracts (also called "futures") and swaps backed by other types of securities. The Fund may invest in futures and swaps either for risk management purposes or as part of its investment strategies. These portfolio strategies are included in the Fund's principal investment strategy described above. The managers may purchase futures contracts or swaps, generally using only a fraction of the assets that would be needed to purchase the equity securities directly, so that the remainder of the assets in a portfolio may be invested in other types of securities. Therefore, a Sub-Adviser would seek to outperform a large capitalization benchmark by purchasing futures contracts or swaps correlated to a broad large capitalization index and investing the remaining assets in other types of securities to add excess return. This portion of the Fund's assets may be invested in a wide range of asset classes other than large capitalization equities. Pursuant to a derivatives strategy, the other types of securities backing the futures and swaps held by the Fund may include investments in U.S. and foreign corporate and government fixed income securities of different types and maturities, including mortgage-backed or other asset-backed securities, securities rated below the fourth highest rating category by a Nationally Recognized Statistical Rating Organization (NRSRO) (junk bonds) and repurchase or reverse repurchase agreements. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes. The amount of the Fund's portfolio that may be allocated to derivative strategies is expected to vary over time. The Fund may also invest in futures contracts and swaps for speculative or hedging purposes. Futures and swaps are used to synthetically obtain exposure to securities or baskets of securities. 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. Interest rate swaps are further used to manage the Fund's yield spread sensitivity. When the Fund seeks to take an active long or short position with respect to the likelihood of an event of default of a security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities.
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. Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - 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. Derivatives Risk - The Fund's use of futures and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 swap agreements 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. 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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Foreign Sovereign Debt Securities Risk - The risk 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, due to 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. Investment Style Risk - The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. The Fund uses portfolio strategies that are designed to correlate with a portfolio of large capitalization equity securities, but which are composed of derivative instruments backed by other types of securities in order to seek to generate excess return. The financial performance of the Fund will be affected, positively or negatively, by the financial performance of the securities backing such derivative instruments. These factors, among others, may cause the Fund to perform differently than a fund that is invested solely in large capitalization equity securities or other funds with similar investment objectives or cause the Fund to underperform its benchmark. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. 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.    Short Sales Risk - 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. Small Capitalization Risk - Smaller capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years, and by showing how the Fund's average annual returns for 1 year and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past five years, and by showing how the Fund's average annual returns for 1 year and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 17.00% (06/30/09) Worst Quarter: -25.55% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 8.84%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND | Russell 1000 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	1.50%
5 Years	rr_AverageAnnualReturnYear05	(0.02%)
Since Inception	rr_AverageAnnualReturnSinceInception	1.95%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2006
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.48%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	49
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	154
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	269
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	604
Annual Return 2007	rr_AnnualReturn2007	5.35%
Annual Return 2008	rr_AnnualReturn2008	(42.67%)
Annual Return 2009	rr_AnnualReturn2009	29.39%
Annual Return 2010	rr_AnnualReturn2010	14.72%
Annual Return 2011	rr_AnnualReturn2011	2.27%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	8.84%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	17.00%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.55%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	2.27%
5 Years	rr_AverageAnnualReturnYear05	(1.72%)
Since Inception	rr_AverageAnnualReturnSinceInception	0.30%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2006
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	2.08%
5 Years	rr_AverageAnnualReturnYear05	(2.18%)
Since Inception	rr_AverageAnnualReturnSinceInception	(0.17%)
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2006
SIIT LARGE CAP DIVERSIFIED ALPHA FUND (Prospectus Summary) | SIIT LARGE CAP DIVERSIFIED ALPHA FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	1.73%
5 Years	rr_AverageAnnualReturnYear05	(1.58%)
Since Inception	rr_AverageAnnualReturnSinceInception	0.12%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2006

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT LARGE CAP DISCIPLINED EQUITY FUND (Prospectus Summary) | SIIT LARGE CAP DISCIPLINED EQUITY FUND

LARGE CAP DISCIPLINED EQUITY FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT LARGE CAP DISCIPLINED EQUITY FUND CLASS A
Management Fees		0.40%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.02%
Total Annual Fund Operating Expenses	[1]	0.49%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT LARGE CAP DISCIPLINED EQUITY FUND CLASS A	50	157	274	616

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 93%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Large Cap Disciplined Equity Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of large companies. These securities may include
common stocks, preferred stocks, warrants and ETFs based on a large
capitalization equity index. The Fund will invest primarily in common stocks of
U.S. companies with market capitalizations in the range of companies in the S&P
500 Composite Stock Price Index (S&P 500 Index) (between $1.22 billion and
$572.4 billion as of July 31, 2012) at the time of purchase. The market
capitalization range and the composition of the S&P 500 Index are subject to
change. The Fund may also, to a lesser extent, invest in common and preferred
stocks of small capitalization companies.

The Fund seeks to exceed the total return of the S&P 500 Index, with a similar
level of volatility, by investing primarily in a portfolio of common stocks
included in the S&P 500 Index, as well as other equity investments and
derivative instruments whose value is derived from the performance of the S&P
500 Index. The Fund uses a multi-manager approach, relying on Sub-Advisers with
differing investment philosophies to manage portions of the Fund's portfolio
under the general supervision of SIMC. The Fund may employ Sub-Advisers that use
a variety of different methods to seek to outperform the Fund's benchmark,
including purchasing stocks with strong anticipated future earnings growth,
selecting stocks that the Sub-Adviser believes are undervalued relative to their
fundamentals, capturing returns from the natural volatility of the market and
employing strategies that rotate among various sectors of the market. The Fund
may also utilize one or more additional Sub-Advisers who manage in a
complementary style with the objective to seek to add value over the S&P 500
Index while maintaining a similar level of volatility to the S&P 500 Index.

Certain Sub-Advisers use portfolio strategies that are designed to correlate
with a portfolio of large capitalization equity securities, but which are
composed of futures contracts or swaps backed by other types of securities.
These portfolio strategies are included in the Fund's principal investment
strategy described above. The Sub-Advisers may purchase these instruments,
generally using only a fraction of the assets that would be needed to purchase
the equity securities directly, so that the remainder of the assets in a
portfolio may be invested in other types of securities. Therefore, a Sub-Adviser
would seek to outperform a large capitalization benchmark by purchasing futures
contracts and swaps correlated to a broad large capitalization index and
investing the remaining assets in other types of securities to add excess
return. This portion of the Fund's assets may be invested in a wide range of
asset classes other than large capitalization equities. Pursuant to a
derivatives strategy, the other types of securities backing the derivative
instruments may include investments in U.S. and foreign corporate and government
fixed income securities of different types and maturities, including
mortgage-backed or other asset-backed securities, securities rated below the
fourth highest rating category by an NRSRO (junk bonds) and repurchase or
reverse repurchase agreements. In managing the Fund's currency exposure for
foreign securities, the Sub-Advisers may buy and sell currencies for hedging or
for speculative purposes. The amount of the Fund's portfolio that may be
allocated to derivative strategies is expected to vary over time.

The Fund may also invest in futures contracts and swaps for speculative or
hedging purposes. Futures and swaps are used to synthetically obtain exposure to
securities or baskets of securities. 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. When the Fund seeks to take an active long or
short position with respect to the likelihood of an event of default of a
security or basket of securities, the Fund may use credit default swaps. 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 such security or basket of securities.

To achieve its investment goal, the Fund may invest in the SEI LIBOR Plus
Portfolio (Portfolio), which is a portfolio of SEI Alpha Strategy Portfolios,
LP, a registered open-end investment company that was established to permit
certain Funds to pursue their respective investment strategies in an efficient
manner. The Fund will invest in the Portfolio only if the Portfolio invests in
securities and pursues investment strategies that are consistent with the Fund's
investment strategy. The Portfolio has expenses associated with its operations,
including advisory and administration fees. When the Fund invests in the
Portfolio, it will bear a pro rata portion of the Portfolio's expenses, which
will be reflected in the Fund's fee table as "Acquired Fund Fees and Expenses."

Principal Risks

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.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.

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.

Currency Risk - 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.

Derivatives Risk - The Fund's use of futures and swaps is subject to market
risk, leverage risk, correlation risk and liquidity risk. Leverage risk and
liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 swap agreements 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.
  
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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Investment Style Risk - The risk that large capitalization securities may
underperform other segments of the equity markets or the equity markets as a
whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

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.

Short Sales Risk - 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.

Small Capitalization Risk - Smaller capitalization companies in which the Fund
invests may be more vulnerable to adverse business or economic events than
larger, more established companies. In particular, small capitalization
companies may have limited product lines, markets and financial resources and
may depend upon a relatively small management group. Therefore, small
capitalization stocks may be more volatile than those of larger companies.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 15.99% (06/30/09)

Worst Quarter: -25.66% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 9.70%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT LARGE CAP DISCIPLINED EQUITY FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	1.18%	(2.57%)	3.65%	[1]	Aug. 28, 2003
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	0.81%	(3.17%)	2.85%	[1]	Aug. 28, 2003
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	1.06%	(2.34%)	3.11%	[1]	Aug. 28, 2003
S&P 500 Index Return	S&P 500 Index Return (reflects no deduction for fees, expenses or taxes)	2.11%	(0.25%)	4.79%	[1]	Aug. 28, 2003

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from August 31, 2003.

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SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund

SCREENED WORLD EQUITY EX-US FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Screened World Equity Ex-US Fund Class A
Management Fees		0.65%
Distribution (12b-1) Fees		none
Other Expenses		0.28%
Acquired Fund Fees and Expenses (AFFE)		0.02%
Total Annual Fund Operating Expenses	[1]	0.95%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Screened World Equity Ex-US Fund Class A	97	303	525	1,166

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate
may indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 76%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Screened World Equity Ex-US Fund will invest at
least 80% of its net assets (plus the amount of any borrowings for investment
purposes) in equity securities of foreign companies. These securities may
include common stocks, preferred stocks, warrants, ETFs based on an international
equity index, derivative instruments (principally futures and forward contracts)
whose value is based on an international equity index or an underlying equity
security or basket of equity securities and investment companies whose portfolios
are designed to correlate with a portfolio of international equity securities.
The Fund will invest in securities of foreign issuers located in developed and
emerging market countries, but will seek to avoid investing in companies whose
activities directly or indirectly benefit the governments of countries that
support terrorism, genocide or human rights abuses. However, the Fund will not
invest more than 35% of its assets in the common stocks or other equity securities
of issuers located in emerging market countries. The Fund's benchmark is the MSCI
All Country World Ex-U.S. Index (net of dividends). The Fund is expected to have
an absolute return and risk profile similar to the international equity market.
The Fund is diversified as to issuers, market capitalization, industry and country.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment strategies to manage portions of the Fund's portfolio
under the general supervision of SIMC.

The Sub-Advisers may seek to enhance the Fund's return by actively managing the
Fund's foreign currency exposure. In managing the Fund's currency exposure, the
Sub-Advisers may buy and sell currencies (i.e., take long or short positions)
using derivatives, principally foreign currency forward contracts and futures.
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 Fund may also invest in futures contracts and forward contracts for hedging
purposes, including to seek to manage the Fund's currency exposure to foreign
securities and mitigate the Fund's overall risk.

Potential investments for the Fund are first selected for financial soundness
and then evaluated according to the Fund's social criteria. The Fund seeks to
avoid investing in companies whose activities directly or indirectly benefit the
governments of countries that support terrorism, genocide or human rights abuses.
This includes companies that pay royalties, such as those on oil or mining, to
these governments and companies that help provide a stable economic environment
that supports the government in its oppressive policies by having substantial
operations or customers in the country. The Sub-Advisers will rely on a list of
issuers that have been identified by an independent compliance support organization
when determining whether a company's activities directly or indirectly benefit
the governments of countries that support terrorism, genocide or human rights
abuses. The list is developed using information gathered from a variety of
sources, such as government agencies, trade journals, direct company contacts
and industry and regional publications. The Adviser reserves the right to modify
the Fund's social criteria from time to time in response to world events. All
social criteria may be changed without shareholder approval.

Principal Risks

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.

Currency Risk - 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.

Derivatives Risk - The Fund's use of futures and forward contracts is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and unpredictably.
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
over-the-counter forward contracts 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 the above
risks could cause the Fund to lose more than the principal amount invested in a
derivative instrument.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal, regulatory
and tax environments. These additional risks may be heightened with respect to
emerging market countries since political turmoil and rapid changes in economic
conditions are more likely to occur in these countries.

Investment Style Risk - The risk that equity securities of developed and emerging
market countries may underperform other segments of the equity markets or the
equity markets as a whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment opportunity,
any of which could have a negative effect on Fund management or performance.

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.

Social Investment Criteria Risk - The Fund's portfolio is subject to certain
social investment criteria. As a result, the Sub-Advisers may avoid purchasing
certain securities for social reasons when it is otherwise economically
advantageous to purchase those securities or may sell certain securities for
social reasons when it is otherwise economically advantageous to hold those
securities. In general, the application of the Fund's social investment criteria
may affect the Fund's exposure to certain industries, sectors and geographic
areas, which may affect the financial performance of the Fund, positively or
negatively, depending on whether these industries or sectors are in or out of
favor.

Loss of money is a risk of investing in the Fund.

Performance Information

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 calendar years and by showing how the Fund's
average annual returns for 1 year, and since the Fund's inception, compared with
those of a broad measure of market performance. The performance information
shown is based on a full calendar year. 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.

Best Quarter: 24.07% (06/30/09)

Worst Quarter: -21.65% (09/30/11)

The Fund's total return from January 1, 2012 to June 30, 2012 was 3.09%.

Average Annual Total Returns (for the period ended December 31, 2011)

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.

Average Annual Total Returns SIIT Screened World Equity Ex-US Fund	Label	1 Year	Since Inception	Inception Date
Class A	Return Before Taxes	(14.31%)	(7.70%)	Jun. 30, 2008
Class A After Taxes on Distributions	Return After Taxes on Distributions	(14.33%)	(7.74%)	Jun. 30, 2008
Class A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(8.69%)	(6.25%)	Jun. 30, 2008
MSCI All Country World Ex-US Index Return (net of dividends)	MSCI All Country World Ex-US Index Return (net of dividends) (reflects no deduction for fees, expenses or taxes)	(13.71%)	(5.42%)	Jun. 30, 2008

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT Multi-Asset Real Return Fund (Prospectus Summary) | SIIT Multi-Asset Real Return Fund

MULTI-ASSET REAL RETURN FUND

Investment Goal

Total return exceeding the rate of inflation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Multi-Asset Real Return Fund Class A
Management Fees		0.55%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.11%
Acquired Fund Fees and Expenses (AFFE)	[1]	0.11%
Total Annual Fund Operating Expenses	[2]	0.77%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT Multi-Asset Real Return Fund Class A	79	246	428	954

PORTFOLIO TURNOVER

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, for the period July 29, 2011 through May 31, 2012,
the Fund's annualized portfolio turnover rate was 58% of the average value of its
portfolio.

Principal Investment Strategies

The Fund uses a multi-manager approach under the general supervision of SIMC,
allocating its assets among one or more Sub-Advisers using different investment
strategies designed to produce a total return that exceeds the rate of inflation
in the U.S. SIMC may also directly manage a portion of the Fund's portfolio.

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) TIPS and other inflation-linked debt securities; (iv) U.S. and foreign
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 mortgage-backed
securities, asset-backed securities, commercial mortgage-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
affiliated and unaffiliated funds, including open-end funds, closed-end funds
and ETFs (collectively, Underlying Funds). The Fund may also invest in 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 indices. The Fund may also invest in equity and debt
securities of issuers in commodity-related industries.

The Fund may also purchase or sell futures contracts, options, forward contracts
and swaps 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 indices 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-Advisers 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-Advisers 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.

Due to its investment strategy, the Fund may buy and sell securities frequently.

Principal Risks

The success of the Fund's investment strategy depends both on SIMC's selection
of the Underlying Funds and Sub-Advisers and allocating assets to such Underlying
Funds and Sub-Advisers. SIMC, an Underlying Fund or Sub-Advisers 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 Underlying Funds and Sub-Advisers may not achieve desired
results and may cause the Fund to lose money or underperform other comparable
mutual funds.

The Fund, Underlying Funds and Sub-Advisers 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 their designated 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.

Asset-Backed Securities Risk - Payment of principal and interest on asset-backed
securities is dependent largely on 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.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.
  
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.

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.

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.

Derivatives Risk - The Fund's use of futures contracts, forward contracts,
options and swaps is subject to market risk, leverage risk, correlation risk and
liquidity risk. Leverage risk, liquidity risk and market risk are described
below. 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 forward contracts and swap agreements is also subject to credit risk and
valuation risk. Valuation risk is the risk that the derivative may be difficult
to value and/or may be 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.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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 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.

Inflation Protected Securities Risk - The value of inflation protected securities,
including TIPS, will generally fluctuate in response to changes in "real" interest
rates, 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.
  
Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in the value of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in the value of such securities.

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.

Leverage Risk - 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 otherwise be advantageous to do so in order to
satisfy its obligations.

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

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.

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.

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.

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.

Small and Medium Capitalization Risk - The small and medium capitalization
companies in which the Fund invests 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 stocks may be traded over the
counter or listed on an exchange.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

The Fund commenced operations on July 29, 2011. Because the Fund did not have a
full calendar year of performance as of September 30, 2012, performance results
have not been provided.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND

EMERGING MARKETS DEBT FUND

Investment Goal

Maximize total return.

Fees and Expenses

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

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

Annual Fund Operating Expenses	SIIT EMERGING MARKETS DEBT FUND CLASS A
Management Fees	0.85%
Distribution (12b-1) Fees	none
Other Expenses	0.08%
Total Annual Fund Operating Expenses	0.93%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT EMERGING MARKETS DEBT FUND CLASS A	95	296	515	1,143

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 55%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Emerging Markets Debt Fund will invest at least
80% of its net assets (plus the amount of any borrowings for investment
purposes) in fixed income securities of emerging market issuers. The Fund will
invest in debt securities of government, government-related and corporate
issuers in emerging market countries, as well as entities organized to
restructure the outstanding debt of such issuers. The Fund may obtain its
exposures by investing directly (e.g., in fixed income securities and other
instruments) or indirectly/synthetically (e.g., through the use of derivative
instruments, principally futures contracts, forward contracts, swaps, including
fully funded total return swaps, and structured securities, such as credit-linked
notes). Emerging market countries are those countries that are: (i) characterized
as developing or emerging by any of the World Bank, the United Nations, the
International Finance Corporation, or the European Bank for Reconstruction and
Development; (ii) included in an emerging markets index by a recognized index
provider; or (iii) countries with similar developing or emerging characteristics
as countries classified as emerging market countries pursuant to sub-paragraph
(i) and (ii) above, in each case determined at the time of purchase.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment philosophies to manage portions of the Fund's
portfolio under the general supervision of SIMC. The Sub-Advisers will spread
the Fund's holdings across a number of countries and industries to limit its
exposure to a single emerging market economy and may not invest more than 25% of
its assets in any single country. There are no restrictions on the Fund's
average portfolio maturity or on the maturity of any specific security. There is
no minimum rating standard for the Fund's securities and the Fund's securities
will generally be in the lower or lowest rating categories (including those
below the fourth highest rating category by an NRSRO, commonly referred to as
junk bonds).

The Sub-Advisers seek to enhance the Fund's return by actively managing the
Fund's foreign currency exposure. In managing the Fund's currency exposure, the
Sub-Advisers buy and sell currencies (i.e., take long or short positions) using
derivatives, principally futures and foreign currency forward contracts. 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 its exposure to a foreign currency
or to shift exposure to foreign currency fluctuations from one currency to
another. In managing the Fund's currency exposure for foreign securities, the
Sub-Advisers may buy and sell currencies for hedging or for speculative
purposes.

Principal Risks

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

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.

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.

Currency Risk - 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 U.S. or abroad.

Derivatives Risk - The Fund's use of futures contracts, forward contracts, swaps
and credit-linked notes is subject to market risk, leverage risk, correlation
risk and liquidity risk. Leverage risk and liquidity risk are described below.
Market risk is the risk that the market value of an investment may move up and down,
sometimes rapidly and unpredictably. 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 over-the-counter forward contracts, credit linked
notes and swap agreements 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 the above risks could
cause the Fund to lose more than the principal amount invested in a derivative
instrument.

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/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Foreign Sovereign Debt Securities Risk - The risk 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, due to 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.

Investment Style Risk - The risk that emerging market debt securities may
underperform other segments of the fixed income markets or the fixed income
markets as a whole.

Leverage Risk - 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.

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, 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.
  
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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 15.09% (06/30/09)

Worst Quarter: -11.06% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 7.59%.

Average Annual Total Returns (for the periods ended December 31, 2011)

This table compares the Fund's average annual total returns to those of a
broad-based index and the Fund's 50/50 Blended Benchmark, which consists of the
J.P. Morgan EMBI Global Diversified Index (50%) and the J.P. Morgan GBI-EM
Global Diversified Index (50%). The Fund's Blended Benchmark is designed to
provide a useful comparison to the Fund's overall performance and more
accurately reflects the Fund's investment strategy than the broad-based index.

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.

Average Annual Total Returns SIIT EMERGING MARKETS DEBT FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	5.42%	8.72%	9.42%	[1]	Dec. 05, 2005
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	2.67%	5.82%	6.62%	[1]	Dec. 05, 2005
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	3.70%	5.73%	6.42%	[1]	Dec. 05, 2005
The Fund's Blended Benchmark Return	The Fund's Blended Benchmark Return (reflects no deducation for fees, expenses or taxes)	2.79%	8.62%	9.39%	[1]	Dec. 05, 2005
J.P. Morgan EMBI Global Diversified Index Return	J.P. Morgan EMBI Global Diversified Index Return (reflects no deduction for fees, expenses or taxes)	7.35%	7.87%	8.37%	[1]	Dec. 05, 2005

[1] Index returns are shown from December 31, 2005.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	WORLD EQUITY EX-US FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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, 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 56% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	56.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 World Equity Ex-US Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of foreign companies. These securities may include common stocks, preferred stocks, warrants, ETFs based on an international equity index and derivative instruments, principally futures and forward contracts, whose value is based on an international equity index or an underlying equity security or basket of equity securities. The Fund will invest in securities of foreign issuers located in developed and emerging market countries. However, the Fund will not invest more than 35% of its assets in the common stocks or other equity securities of issuers located in emerging market countries. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment strategies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund's benchmark is the MSCI All Country World Ex-U.S. Index (net of dividends). The Fund is expected to have an absolute return and risk profile similar to the international equity market. The Fund is diversified as to issuers, market capitalization, industry and country. The Sub-Advisers may seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers may buy and sell currencies (i.e., take long or short positions) using futures and foreign currency forward contracts. 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 Fund may also invest in futures contracts and forward contracts for hedging purposes, including to seek to manage the Fund's currency exposure to foreign securities and mitigate the Fund's overall risk.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. Currency Risk - 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 U.S. or abroad. Derivatives Risk - The Fund's use of futures and forward contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 over-the-counter forward contracts 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 the above risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time.    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. Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investment Style Risk - The risk that equity securities of developed and emerging market countries may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 25.15% (06/30/09) Worst Quarter: -25.87% (09/30/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 3.63%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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. Your actual after-tax returns will depend on your tax situation and may differ from those shown.
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 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.
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND | MSCI All Country World Ex-US Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	MSCI All Country World Ex-US Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(13.71%)
5 Years	rr_AverageAnnualReturnYear05	(2.92%)
Since Inception	rr_AverageAnnualReturnSinceInception	3.61%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 28, 2005
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.55%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.64%	[2]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	65
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	205
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	357
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	798
Annual Return 2006	rr_AnnualReturn2006	27.54%
Annual Return 2007	rr_AnnualReturn2007	13.16%
Annual Return 2008	rr_AnnualReturn2008	(49.36%)
Annual Return 2009	rr_AnnualReturn2009	34.79%
Annual Return 2010	rr_AnnualReturn2010	12.95%
Annual Return 2011	rr_AnnualReturn2011	(13.11%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.63%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	25.15%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(25.87%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.11%)
5 Years	rr_AverageAnnualReturnYear05	(5.39%)
Since Inception	rr_AverageAnnualReturnSinceInception	2.14%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 28, 2005
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(13.33%)
5 Years	rr_AverageAnnualReturnYear05	(5.96%)
Since Inception	rr_AverageAnnualReturnSinceInception	1.43%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 28, 2005
SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(8.09%)
5 Years	rr_AverageAnnualReturnYear05	(4.58%)
Since Inception	rr_AverageAnnualReturnSinceInception	1.69%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 28, 2005

[1] Index returns are shown from March 31, 2005.

[2] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	U.S. MANAGED VOLATILITY FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation with less volatility than the broad U.S. equity markets.
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, 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 44% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	44.00%
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 U.S. Managed Volatility Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of U.S. companies of all capitalization ranges. These securities may include common stocks, preferred stocks, ETFs and warrants. The Fund may also, to a lesser extent, invest in ADRs and securities of non-U.S. companies. The Fund uses a multi-manager approach, relying on a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Fund is expected to achieve an absolute return of the broad U.S. equity markets, but with a lower absolute volatility. Over the long term, the Fund is expected to achieve a return similar to that of the Russell 3000 Index, but with a lower level of volatility. However, given that the Fund's investment strategy focuses on absolute return and risk, the Fund's sector and market capitalization exposures will typically vary from the index and may cause significant performance deviations relative to the index over shorter-term periods. The Fund seeks to achieve lower volatility by constructing a portfolio of securities that effectively weighs securities based on their total expected risk and return, without regard to market capitalization and industry.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	American Depositary Receipts (ADRs) Risk - ADRs are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. ADRs 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. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Foreign Investment Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments. Hedged Strategies Risk - The Fund may employ investment strategies that involve greater risks than the strategies used by typical mutual funds. Although some of the Sub-Advisers use hedged strategies, there is no assurance that hedged strategies will protect against losses or perform better than non-hedged strategies, and some Sub-Advisers may use long-only strategies. Investment Style Risk - The risk that equity securities of U.S. companies of all capitalization ranges may underperform other segments of the equity markets or the equity markets as a whole. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Small and Medium Capitalization Risk - The risk that small and medium capitalization companies in which the Fund invests may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past three calendar years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on a full calendar year. 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 calendar years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on a full calendar year.
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: 11.39% (09/30/09) Worst Quarter: -11.59% (03/31/09) The Fund's total return from January 1, 2012 to June 30, 2012 was 8.68%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
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 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.
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund | Russell 3000 Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 3000 Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	1.03%
Since Inception	rr_AverageAnnualReturnSinceInception	14.88%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 30, 2008
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.65%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.73%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	75
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	233
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	406
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	906
Annual Return 2009	rr_AnnualReturn2009	15.27%
Annual Return 2010	rr_AnnualReturn2010	15.72%
Annual Return 2011	rr_AnnualReturn2011	10.43%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	8.68%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	11.39%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(11.59%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	10.43%
Since Inception	rr_AverageAnnualReturnSinceInception	13.78%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 30, 2008
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund | Class A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	8.64%
Since Inception	rr_AverageAnnualReturnSinceInception	11.23%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 30, 2008
SIIT U.S. Managed Volatility Fund (Prospectus Summary) | SIIT U.S. Managed Volatility Fund | Class A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	8.32%
Since Inception	rr_AverageAnnualReturnSinceInception	10.81%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 30, 2008

[1] Index returns are shown from December 31, 2008.

XML

SIIT Extended Market Index Fund (Prospectus Summary) | SIIT Extended Market Index Fund

EXTENDED MARKET INDEX FUND

Investment Goal

Seeks investment results that approximate, as closely as practicable and before
expenses, the performance of the Russell Small Cap Completeness® Index.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT Extended Market Index Fund Class A
Management Fees		0.12%
Distribution (12b-1) Fees		none
Other Expenses	[1]	0.15%
Total Annual Fund Operating Expenses		0.27%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
SIIT Extended Market Index Fund Class A	28	87

PORTFOLIO TURNOVER

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.

Principal Investment Strategies

The Fund is managed using a passive/indexing investment approach and invests
substantially all of its assets in securities (mostly common stocks) of companies
that are included (at the time of purchase) in the Russell Small Cap Completeness®
Index (the Index). As of July 31, 2012, the market capitalization of the companies
included in the Index ranged from $30.7 million to $30.9 billion. The Index is
composed of securities of the companies included in the Russell 3000® Index (which
includes the largest 3,000 U.S. companies), excluding the securities of companies
that are constituents of the S&P 500 Index (which includes 500 leading U.S.
companies). The Index is constructed to attempt to provide a comprehensive and
unbiased barometer of the extended broad market of U.S. equity securities beyond
that of the 500 leading U.S. companies included in the S&P 500 Index. The market
capitalization range and the composition of the Index are subject to change.

The Fund generally will attempt to invest in securities (including interests of
real estate investment trusts (REITs)) composing the Index in approximately the
same proportions as they are represented in the Index. The Fund's ability to
fully replicate the performance of the Index will depend to some extent on the
size and timing of cash flows into and out of the Fund, as well as on the level
of the Fund's expenses. In some cases, it may not be possible or practicable to
purchase all of the securities composing the Index or to hold them in the same
weightings as they are represented in the Index. In those cases, the Fund's
sub-adviser (the Sub-Adviser) may employ a sampling or optimization technique to
construct the Fund's portfolio. In seeking to replicate the performance of the
Index, the Fund may also invest in exchange-traded funds (ETFs) and REITs that
are not constituents of the Index.

The Sub-Adviser selects the Fund's securities under the general supervision of
SEI Investments Management Corporation, the Fund's adviser (SIMC), but the
Sub-Adviser makes no attempt to "manage" the Fund in the traditional sense
(i.e., by using economic, market or financial analyses). Instead, the
Sub-Adviser purchases a basket of securities that includes most of the companies
in the Index. However, the Sub-Adviser may sell an investment if the merit of
the investment has been substantially impaired by extraordinary events or
adverse financial conditions.

The Fund may, at times, purchase or sell index futures contracts, or options on
those futures, or engage in forward or swap transactions in lieu of investing
directly in the securities making up the Index or to enhance the Fund's replication
of the Index's return. In addition, for liquidity purposes, the Fund may invest in
securities that are not included in the Index, cash and cash equivalents or money
market instruments, such as reverse repurchase agreements and money market funds.
The Fund's return may not match the return of the Index.

Russell Investment Group is the source and owner of the trademarks, service marks
and copyrights related to Russell Indexes. Russell Small Cap Completeness® Index
and Russell 3000® Index are trademarks of Russell Investment Group.

Principal Risks

Derivatives Risk - The Fund's use of futures, forwards, options and swaps is
subject to market risk, leverage risk, correlation risk and liquidity risk.
Market risk, leverage risk and liquidity risk are described below. 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 forwards
and swap agreements 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 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. Each of these risks could cause the Fund to lose more than
the principal amount invested in a derivative instrument.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that the Fund's investment approach, which
attempts to replicate the performance of the Index, may underperform other
segments of the equity markets or the equity markets as a whole. The Fund is
also subject to the risk that the securities in which it invests may
underperform other segments of the equity markets or the equity markets as a
whole.

Leverage Risk - 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.

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 equity market as a whole.

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.

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 include fluctuations in the
value of underlying properties, defaults by borrowers or tenants, changes in
interest rates and risks related to general or local economic conditions. Some
REITs may have limited diversification and may be subject to risks inherent in
financing a limited number of properties.

Sampling Risk - The Fund may not fully replicate the Index and may hold securities
not included in the Index. As a result, the Fund may not track the return of the
Index as well as it would have if the Fund purchased all of the securities in the
Index.

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

Tracking Error Risk - The risk that the Fund's performance may vary substantially
from the performance of the Index as a result of cash flows, Fund expenses,
imperfect correlation between the Fund's and Index's investments and other factors.

Loss of money is a risk of investing in the Fund.

Performance Information

As of September 30, 2012, the Fund had not yet commenced operations and did not
have a performance history.

[1] Other Expenses are based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	EMERGING MARKETS DEBT FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Maximize total return.
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, 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 55% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	55.00%
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 Emerging Markets Debt Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in fixed income securities of emerging market issuers. The Fund will invest in debt securities of government, government-related and corporate issuers in emerging market countries, as well as entities organized to restructure the outstanding debt of such issuers. The Fund may obtain its exposures by investing directly (e.g., in fixed income securities and other instruments) or indirectly/synthetically (e.g., through the use of derivative instruments, principally futures contracts, forward contracts, swaps, including fully funded total return swaps, and structured securities, such as credit-linked notes). Emerging market countries are those countries that are: (i) characterized as developing or emerging by any of the World Bank, the United Nations, the International Finance Corporation, or the European Bank for Reconstruction and Development; (ii) included in an emerging markets index by a recognized index provider; or (iii) countries with similar developing or emerging characteristics as countries classified as emerging market countries pursuant to sub-paragraph (i) and (ii) above, in each case determined at the time of purchase. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Sub-Advisers will spread the Fund's holdings across a number of countries and industries to limit its exposure to a single emerging market economy and may not invest more than 25% of its assets in any single country. There are no restrictions on the Fund's average portfolio maturity or on the maturity of any specific security. There is no minimum rating standard for the Fund's securities and the Fund's securities will generally be in the lower or lowest rating categories (including those below the fourth highest rating category by an NRSRO, commonly referred to as junk bonds). The Sub-Advisers seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers buy and sell currencies (i.e., take long or short positions) using derivatives, principally futures and foreign currency forward contracts. 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 its exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Below Investment Grade Securities Risk - Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. 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. 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. Currency Risk - 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 U.S. or abroad. Derivatives Risk - The Fund's use of futures contracts, forward contracts, swaps and credit-linked notes is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 over-the-counter forward contracts, credit linked notes and swap agreements 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 the above risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. 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/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Foreign Sovereign Debt Securities Risk - The risk 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, due to 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. Investment Style Risk - The risk that emerging market debt securities may underperform other segments of the fixed income markets or the fixed income markets as a whole. Leverage Risk - 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. 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, 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.    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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	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.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on full calendar years. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1-800-DIAL-SEI.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past six years and by showing how the Fund's average annual returns for 1 and 5 years, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 15.09% (06/30/09) Worst Quarter: -11.06% (12/31/08) The Fund's total return from January 1, 2012 to June 30, 2012 was 7.59%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the periods ended December 31, 2011)
Index No Deduction for Fees, Expenses, Taxes [Text]	rr_IndexNoDeductionForFeesExpensesTaxes	reflects no deducation 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 Narrative	rr_PerformanceTableNarrativeTextBlock	This table compares the Fund's average annual total returns to those of a broad-based index and the Fund's 50/50 Blended Benchmark, which consists of the J.P. Morgan EMBI Global Diversified Index (50%) and the J.P. Morgan GBI-EM Global Diversified Index (50%). The Fund's Blended Benchmark is designed to provide a useful comparison to the Fund's overall performance and more accurately reflects the Fund's investment strategy than the broad-based index. 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.
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | The Fund's Blended Benchmark Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	The Fund's Blended Benchmark Return (reflects no deducation for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	2.79%
5 Years	rr_AverageAnnualReturnYear05	8.62%
Since Inception	rr_AverageAnnualReturnSinceInception	9.39%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | J.P. Morgan EMBI Global Diversified Index Return
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	J.P. Morgan EMBI Global Diversified Index Return (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	7.35%
5 Years	rr_AverageAnnualReturnYear05	7.87%
Since Inception	rr_AverageAnnualReturnSinceInception	8.37%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | CLASS A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.93%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	95
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	296
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	515
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,143
Annual Return 2006	rr_AnnualReturn2006	11.94%
Annual Return 2007	rr_AnnualReturn2007	6.42%
Annual Return 2008	rr_AnnualReturn2008	(17.46%)
Annual Return 2009	rr_AnnualReturn2009	42.36%
Annual Return 2010	rr_AnnualReturn2010	15.23%
Annual Return 2011	rr_AnnualReturn2011	5.42%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	7.59%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	15.09%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(11.06%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	5.42%
5 Years	rr_AverageAnnualReturnYear05	8.72%
Since Inception	rr_AverageAnnualReturnSinceInception	9.42%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | CLASS A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	2.67%
5 Years	rr_AverageAnnualReturnYear05	5.82%
Since Inception	rr_AverageAnnualReturnSinceInception	6.62%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005
SIIT EMERGING MARKETS DEBT FUND (Prospectus Summary) | SIIT EMERGING MARKETS DEBT FUND | CLASS A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	3.70%
5 Years	rr_AverageAnnualReturnYear05	5.73%
Since Inception	rr_AverageAnnualReturnSinceInception	6.42%	[1]
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 05, 2005

[1] Index returns are shown from December 31, 2005.

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SIIT LONG DURATION FUND (Prospectus Summary) | SIIT LONG DURATION FUND

LONG DURATION FUND

Investment Goal

Return characteristics similar to those of high quality corporate bonds, with a
duration range of between nine and fourteen years.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT LONG DURATION FUND CLASS A
Management Fees		0.30%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.38%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT LONG DURATION FUND CLASS A	39	122	213	480

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 121%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Long Duration Fund will invest at least 80% of
its net assets (plus the amount of any borrowings for investment purposes) in
long duration fixed income securities and synthetic instruments or derivatives
having economic characteristics similar to fixed income securities. The Fund
invests in a broad array of investment grade fixed income instruments, including
securities issued or guaranteed by the U.S. Government and its agencies and
instrumentalities and corporate bonds.

The Fund will invest primarily in long duration government and corporate fixed
income securities and may also invest in futures contracts, forward contracts
and swaps for speculative or hedging purposes. Futures, forwards 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, currencies or market
segments. Interest rate swaps are further used to manage the Fund's yield spread
sensitivity. When the Fund seeks to take an active long or short position with
respect to the likelihood of an event of default of a security or basket of
securities, the Fund may use credit default swaps. 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 such security or basket of securities.

The Fund will invest primarily in fixed income securities rated in one of the
three highest rating categories by a major rating agency and may also invest, to
a lesser extent, in fixed income securities rated in the fourth highest rating
category by a major rating agency. The Fund may also invest in unrated fixed
income securities that are determined by the Sub-Advisers to be of equivalent
quality to those securities rated in one of the four highest rating categories.
The Fund is expected to maintain an effective average duration of between nine
and fourteen years. The Fund's effective average duration was 13.68 years as of
July 31, 2012. Duration is a measure that is used to determine the sensitivity
of a security's price to changes in interest rates. For each year of duration of
a fixed income security, a 1% change in interest rates will result in a 1%
change in the value of the security. For example, a duration of ten years means
that the fixed income security's price will change by 10% if interest rates
change by 1%.

The Fund uses Sub-Advisers to manage the Fund's portfolio under the general
supervision of SIMC. The Sub-Advisers are selected for their expertise in
managing various kinds of fixed income securities, and the Sub-Advisers make
investment decisions based on an analysis of yield trends, credit ratings and
other factors in accordance with their particular discipline. To a lesser
extent, the Fund may also invest in ETFs to gain exposure to a particular
portion of the market while awaiting an opportunity to purchase securities
directly.

Principal Risks

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.

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, forward contracts and
swaps is subject to market risk, leverage risk, correlation risk and liquidity
risk. Leverage risk and liquidity risk are described below. Market risk is the
risk that the market value of an investment may move up and down, sometimes
rapidly and unpredictably. 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 forwards and swap agreements 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.

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.

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.

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.

Investment Style Risk - The risk that longer-term U.S. fixed income securities
may underperform other segments of the fixed income markets or the fixed income
markets as a whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 13.85% (09/30/11)

Worst Quarter: -5.85% (06/30/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 5.81%.

Average Annual Total Returns (for the periods ended December 31, 2011)

This table compares the Fund's average annual total returns to those of a
broad-based index and the Fund's 60/40 Blended Benchmark, which consists of the
Barclays Capital U.S. Long Credit Index and the Barclays Capital U.S. Long
Government Index. The Fund's Blended Benchmark is designed to provide a useful
comparison to the Fund's overall performance and more accurately reflects the
Fund's investment strategy than the broad-based index.

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.

Average Annual Total Returns SIIT LONG DURATION FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	20.50%	6.45%	6.10%	[1]	Apr. 21, 2004
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	16.49%	3.89%	3.67%	[1]	Apr. 21, 2004
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	13.68%	4.00%	3.78%	[1]	Apr. 21, 2004
Barclays Capital Long U.S. Government/Credit Index	Barclays Capital Long U.S. Government/Credit Index (reflects no deduction for fees, expenses or taxes)	22.49%	9.71%	8.56%	[1]	Apr. 21, 2004
The Fund's Blended Benchmark Return	The Fund's Blended Benchmark Return (reflects no deduction for fees, expenses or taxes)	22.02%	9.62%	8.51%	[1]	Apr. 21, 2004

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from April 30, 2004.

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SIIT WORLD EQUITY EX-US FUND (Prospectus Summary) | SIIT WORLD EQUITY EX-US FUND

WORLD EQUITY EX-US FUND

Investment Goal

Capital appreciation.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT WORLD EQUITY EX-US FUND CLASS A
Management Fees		0.55%
Distribution (12b-1) Fees		none
Other Expenses		0.08%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.64%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT WORLD EQUITY EX-US FUND CLASS A	65	205	357	798

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 56%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the World Equity Ex-US Fund will invest at least 80%
of its net assets (plus the amount of any borrowings for investment purposes) in
equity securities of foreign companies. These securities may include common
stocks, preferred stocks, warrants, ETFs based on an international equity index
and derivative instruments, principally futures and forward contracts, whose
value is based on an international equity index or an underlying equity security
or basket of equity securities. The Fund will invest in securities of foreign
issuers located in developed and emerging market countries. However, the Fund
will not invest more than 35% of its assets in the common stocks or other equity
securities of issuers located in emerging market countries. The Fund uses a
multi-manager approach, relying upon a number of Sub-Advisers with differing
investment strategies to manage portions of the Fund's portfolio under the
general supervision of SIMC. The Fund's benchmark is the MSCI All Country World
Ex-U.S. Index (net of dividends). The Fund is expected to have an absolute
return and risk profile similar to the international equity market. The Fund is
diversified as to issuers, market capitalization, industry and country.

The Sub-Advisers may seek to enhance the Fund's return by actively managing the
Fund's foreign currency exposure. In managing the Fund's currency exposure, the
Sub-Advisers may buy and sell currencies (i.e., take long or short positions)
using futures and foreign currency forward contracts. 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 Fund may also invest in futures contracts and forward contracts for hedging
purposes, including to seek to manage the Fund's currency exposure to foreign
securities and mitigate the Fund's overall risk.

Principal Risks

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.

Currency Risk - 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 U.S. or abroad.

Derivatives Risk - The Fund's use of futures and forward contracts is subject to
market risk, leverage risk, correlation risk and liquidity risk. Leverage risk
and liquidity risk are described below. Market risk is the risk that the market
value of an investment may move up and down, sometimes rapidly and
unpredictably. 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 over-the-counter forward contracts 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 the above risks could cause the Fund to lose more than the principal
amount invested in a derivative instrument.

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.
  
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.

Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may
be subject to additional risks due to, among other things, political, social and
economic developments abroad, currency movements, and different legal,
regulatory and tax environments. These additional risks may be heightened with
respect to emerging market countries since political turmoil and rapid changes
in economic conditions are more likely to occur in these countries.

Investment Style Risk - The risk that equity securities of developed and
emerging market countries may underperform other segments of the equity markets
or the equity markets as a whole.

Leverage Risk - 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.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 25.15% (06/30/09)

Worst Quarter: -25.87% (09/30/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 3.63%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT WORLD EQUITY EX-US FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	(13.11%)	(5.39%)	2.14%	[1]	Mar. 28, 2005
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	(13.33%)	(5.96%)	1.43%	[1]	Mar. 28, 2005
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	(8.09%)	(4.58%)	1.69%	[1]	Mar. 28, 2005
MSCI All Country World Ex-US Index Return	MSCI All Country World Ex-US Index Return (reflects no deduction for fees, expenses or taxes)	(13.71%)	(2.92%)	3.61%	[1]	Mar. 28, 2005

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from March 31, 2005.

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SIIT HIGH YIELD BOND FUND (Prospectus Summary) | SIIT HIGH YIELD BOND FUND

HIGH YIELD BOND FUND

Investment Goal

Total return.

Fund Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT HIGH YIELD BOND FUND CLASS A
Management Fees		0.49%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.57%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT HIGH YIELD BOND FUND CLASS A	58	183	318	714

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 50%
of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the High Yield Bond Fund will invest at least 80% of
its net assets (plus the amount of any borrowings for investment purposes) in
high yield fixed income securities. The Fund will invest primarily in fixed
income securities rated below investment grade (junk bonds), including corporate
bonds and debentures, convertible and preferred securities and zero coupon
obligations.

The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers
with differing investment philosophies to manage portions of the Fund's
portfolio under the general supervision of SIMC. To a limited extent, SIMC may
also directly manage a portion of the Fund's portfolio. In managing the Fund's
assets, the Sub-Advisers and, to the extent applicable, SIMC, select securities
that offer a high current yield as well as total return potential. The Fund's
securities are diversified as to issuers and industries. The Fund's average
weighted maturity may vary and will generally not exceed ten years. There is no
limit on the maturity or on the credit quality of any security.

As noted above, the Fund will invest primarily in securities rated BB, B, CCC,
CC, C and D. However, it may also invest in non-rated securities or securities
rated investment grade (AAA, AA, A and BBB). The Fund may also invest in ETFs to
gain exposure to a particular portion of the market while awaiting an
opportunity to purchase securities directly. The Fund may also invest a portion
of its assets in bank loans, which are generally non-investment grade (junk
bond) floating rate instruments. The Fund may invest in bank loans in the form
of participations in the loans (participations) and assignments of all or a
portion of the loans from third parties (assignments).

Principal Risks

Bank Loans Risk - With respect to bank loans, the Fund will assume the credit
risk of both the borrower of the loan and the lender that is selling the
participation in the loan. The Fund may also have difficulty disposing of bank
loans because, in certain cases, the market for such instruments is not highly
liquid.

Below Investment Grade Securities Risk - Fixed income securities rated below
investment grade (junk bonds) involve greater risks of default or downgrade and
are more volatile than investment grade securities because the prospect for
repayment of principal and interest of many of these securities is speculative.

Convertible and Preferred Securities - Convertible and preferred securities have
many of the same characteristics as stocks, including many of the same risks. In
addition, convertible bonds may be more sensitive to changes in interest rates
than stocks. Convertible bonds may also have credit ratings below investment
grade, meaning that they carry a higher risk of failure by the issuer to pay
principal and/or interest when due.

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.

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.
  
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.

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.

Interest Rate Risk - The risk that the Fund's yield will decline due to falling
interest rates. A rise in interest rates typically causes a fall in values of
fixed income securities in which the Fund invests, while a fall in interest
rates typically causes a rise in values of such securities.

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

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

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.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 22.79% (06/30/09)

Worst Quarter: -20.84% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 7.91%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT HIGH YIELD BOND FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	5.24%	7.49%	8.07%	[1]	Dec. 05, 2005
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	2.36%	3.96%	4.58%	[1]	Dec. 05, 2005
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	3.39%	4.21%	4.75%	[1]	Dec. 05, 2005
BofA Merrill Lynch U.S. High Yield Constrained Index Return	BofA Merrill Lynch U.S. High Yield Constrained Index Return (reflects no deduction for fees, expenses or taxes)	4.37%	7.54%	8.13%	[1]	Dec. 05, 2005

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from December 31, 2005.

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SCREENED WORLD EQUITY EX-US FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Goal
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Capital appreciation.
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, 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 76% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	76.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.
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 Screened World Equity Ex-US Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity securities of foreign companies. These securities may include common stocks, preferred stocks, warrants, ETFs based on an international equity index, derivative instruments (principally futures and forward contracts) whose value is based on an international equity index or an underlying equity security or basket of equity securities and investment companies whose portfolios are designed to correlate with a portfolio of international equity securities. The Fund will invest in securities of foreign issuers located in developed and emerging market countries, but will seek to avoid investing in companies whose activities directly or indirectly benefit the governments of countries that support terrorism, genocide or human rights abuses. However, the Fund will not invest more than 35% of its assets in the common stocks or other equity securities of issuers located in emerging market countries. The Fund's benchmark is the MSCI All Country World Ex-U.S. Index (net of dividends). The Fund is expected to have an absolute return and risk profile similar to the international equity market. The Fund is diversified as to issuers, market capitalization, industry and country. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment strategies to manage portions of the Fund's portfolio under the general supervision of SIMC. The Sub-Advisers may seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers may buy and sell currencies (i.e., take long or short positions) using derivatives, principally foreign currency forward contracts and futures. 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 Fund may also invest in futures contracts and forward contracts for hedging purposes, including to seek to manage the Fund's currency exposure to foreign securities and mitigate the Fund's overall risk. Potential investments for the Fund are first selected for financial soundness and then evaluated according to the Fund's social criteria. The Fund seeks to avoid investing in companies whose activities directly or indirectly benefit the governments of countries that support terrorism, genocide or human rights abuses. This includes companies that pay royalties, such as those on oil or mining, to these governments and companies that help provide a stable economic environment that supports the government in its oppressive policies by having substantial operations or customers in the country. The Sub-Advisers will rely on a list of issuers that have been identified by an independent compliance support organization when determining whether a company's activities directly or indirectly benefit the governments of countries that support terrorism, genocide or human rights abuses. The list is developed using information gathered from a variety of sources, such as government agencies, trade journals, direct company contacts and industry and regional publications. The Adviser reserves the right to modify the Fund's social criteria from time to time in response to world events. All social criteria may be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. Currency Risk - 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. Derivatives Risk - The Fund's use of futures and forward contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below. Market risk is the risk that the market value of an investment may move up and down, sometimes rapidly and unpredictably. 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 over-the-counter forward contracts 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 the above risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Equity Market Risk - The risk that stock prices will fall over short or extended periods of time. 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. Foreign Investment/Emerging Markets Risk - The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax environments. These additional risks may be heightened with respect to emerging market countries since political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investment Style Risk - The risk that equity securities of developed and emerging market countries may underperform other segments of the equity markets or the equity markets as a whole. Leverage Risk - 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. 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, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance. 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. Social Investment Criteria Risk - The Fund's portfolio is subject to certain social investment criteria. As a result, the Sub-Advisers may avoid purchasing certain securities for social reasons when it is otherwise economically advantageous to purchase those securities or may sell certain securities for social reasons when it is otherwise economically advantageous to hold those securities. In general, the application of the Fund's social investment criteria may affect the Fund's exposure to certain industries, sectors and geographic areas, which may affect the financial performance of the Fund, positively or negatively, depending on whether these industries or sectors are in or out of favor. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year for the past three calendar years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance. The performance information shown is based on a full calendar year. 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 calendar years and by showing how the Fund's average annual returns for 1 year, and since the Fund's inception, compared with those of a broad measure of market performance.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-DIAL-SEI
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter: 24.07% (06/30/09) Worst Quarter: -21.65% (09/30/11) The Fund's total return from January 1, 2012 to June 30, 2012 was 3.09%.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (for the period ended December 31, 2011)
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 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.
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund | MSCI All Country World Ex-US Index Return (net of dividends)
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	MSCI All Country World Ex-US Index Return (net of dividends) (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(13.71%)
Since Inception	rr_AverageAnnualReturnSinceInception	(5.42%)
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 30, 2008
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.65%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.28%
Acquired Fund Fees and Expenses (AFFE)	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.95%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	97
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	303
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	525
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	1,166
Annual Return 2009	rr_AnnualReturn2009	34.05%
Annual Return 2010	rr_AnnualReturn2010	11.64%
Annual Return 2011	rr_AnnualReturn2011	(14.31%)
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.09%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter:
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	24.07%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter:
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.65%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(14.31%)
Since Inception	rr_AverageAnnualReturnSinceInception	(7.70%)
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 30, 2008
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund | Class A | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(14.33%)
Since Inception	rr_AverageAnnualReturnSinceInception	(7.74%)
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 30, 2008
SIIT Screened World Equity Ex-US Fund (Prospectus Summary) | SIIT Screened World Equity Ex-US Fund | Class A | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(8.69%)
Since Inception	rr_AverageAnnualReturnSinceInception	(6.25%)
Inception Date	rr_AverageAnnualReturnInceptionDate	Jun. 30, 2008

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

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SIIT LARGE CAP INDEX FUND (Prospectus Summary) | SIIT LARGE CAP INDEX FUND

LARGE CAP INDEX FUND

Investment Goal

Investment results that correspond to the aggregate price and dividend
performance of the securities in the Russell 1000 Index.

Fees and Expenses

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

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

Annual Fund Operating Expenses		SIIT LARGE CAP INDEX FUND CLASS A
Management Fees		0.17%
Distribution (12b-1) Fees		none
Other Expenses		0.07%
Acquired Fund Fees and Expenses (AFFE)		0.01%
Total Annual Fund Operating Expenses	[1]	0.25%

EXAMPLE

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.

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

Expense Example (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
SIIT LARGE CAP INDEX FUND CLASS A	26	80	141	318

PORTFOLIO TURNOVER

The Fund pays transaction costs, such as commissions, when it buys and sells
securities (or "turns over" its portfolio). A higher portfolio turnover rate may
indicate higher transaction costs and may result in higher taxes when Fund
shares are held in a taxable account. These costs, which are not reflected in
annual Fund operating expenses or in the Example, affect the Fund's performance.
During the most recent fiscal year, the Fund's portfolio turnover rate was 12%
of the average value of its portfolio.

Principal Investment Strategies

The Large Cap Index Fund invests substantially all of its assets in securities
(mostly common stocks) of U.S. companies that are included at the time of
purchase in the Russell 1000 Index, which is composed of the 1,000 largest U.S.
companies with market capitalizations between $212.3 million and $572.4 billion
as of July 31, 2012. The market capitalization range and the composition of the
Russell 1000 Index are subject to change. The Fund's ability to replicate the
performance of the Russell 1000 Index will depend to some extent on the size and
timing of cash flows into and out of the Fund, as well as on the level of the
Fund's expenses. The Sub-Adviser selects the Fund's securities under the general
supervision of SIMC, but the Sub-Adviser makes no attempt to "manage" the Fund
in the traditional sense (i.e., by using economic, market or financial
analyses). Instead, the Sub-Adviser purchases a basket of securities that
includes a representative sample of the companies in the Russell 1000 Index.
However, the Fund's Sub-Adviser may, but is not required to, sell an investment
if the merit of the investment has been substantially impaired by extraordinary
events, such as fraud or a material adverse change in an issuer, or adverse
financial conditions. In addition, for liquidity purposes, the Fund may invest
in securities that are not included in the Russell 1000 Index, cash and cash
equivalents or money market instruments, such as reverse repurchase agreements
and money market funds. The Fund may also invest in ETFs based on a large
capitalization index.

Principal Risks

Equity Market Risk - The risk that stock prices will fall over short or extended
periods of time.

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.

Investment Style Risk - The risk that its investment approach, which attempts to
replicate the performance of the Russell 1000 Index, may underperform other
segments of the equity markets or the equity markets as a whole. The Fund is
also subject to the risk that large capitalization securities may underperform
other segments of the equity markets or the equity markets as a whole.

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, sell other securities instead or forego an investment
opportunity, any of which could have a negative effect on Fund management or
performance.

Sampling Risk - The Fund may not fully replicate the benchmark index and may
hold securities not included in the index. As a result, the Fund may not track
the return of its benchmark index as well as it would have if the Fund purchased
all of the securities in its benchmark index.

Tracking Error Risk - The risk that the Fund's performance may vary
substantially from the performance of the benchmark index it tracks as a result
of cash flows, Fund expenses, imperfect correlation between the Fund's and
benchmark's investments and other factors.

Loss of money is a risk of investing in the Fund.

Performance Information

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

Best Quarter: 16.46% (06/30/09)

Worst Quarter: -22.51% (12/31/08)

The Fund's total return from January 1, 2012 to June 30, 2012 was 9.31%.

Average Annual Total Returns (for the periods ended December 31, 2011)

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.

Average Annual Total Returns SIIT LARGE CAP INDEX FUND	Label	1 Year	5 Years	Since Inception		Inception Date
CLASS A	Return Before Taxes	1.47%	(0.04%)	3.29%	[1]	Apr. 01, 2002
CLASS A After Taxes on Distributions	Return After Taxes on Distributions	1.15%	(0.53%)	2.83%	[1]	Apr. 01, 2002
CLASS A After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	1.30%	(0.15%)	2.70%	[1]	Apr. 01, 2002
Russell 1000 Index Return	Russell 1000 Index Return (reflects no deduction for fees, expenses or taxes)	1.50%	(0.02%)	4.02%	[1]	Apr. 01, 2002

[1] Because the Fund incurred AFFE during the most recent fiscal year, the operating expenses in this fee table will not correlate to the expense ratio in the Fund's financial statements (or the "Financial Highlights" section in the prospectus) because the financial statements include only the direct operating expenses incurred by the Fund, not the indirect costs of investing in other investment companies.

[1] Index returns are shown from April 30, 2002.

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Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Sep. 30, 2012
SIIT Ultra Short Duration Bond Fund (Prospectus Summary) | SIIT Ultra Short Duration Bond Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	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 222% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	222.00%
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 risk, liquidity risk and market risk are described below. 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 swap agreements is also subject to credit risk and valuation risk. Valuation risk is the risk that the derivative may be difficult to value and/or may be 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. 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. 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. Interest Rate Risk - The risk that the Fund's yield will decline due to falling interest rates. A rise in interest rates typically causes a fall in values of fixed income securities in which the Fund invests, while a fall in interest rates typically causes a rise in values of such securities. Leverage Risk - 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. 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. 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. Loss of money is a risk of investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	Loss of money is a risk of investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund commenced operations on February 28, 2011. Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Because the Fund did not have a full calendar year of performance as of September 30, 2012, performance results have not been provided.
SIIT Ultra Short Duration Bond Fund (Prospectus Summary) | SIIT Ultra Short Duration Bond Fund | Class A
Risk Return [Abstract]	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.15%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.06%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.21%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	22
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	68
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	118
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	268