3.10.0.1 html 134 91 1 true 78 0 false 2 false false R1.htm 000001 - Document - Document and Entity Information Sheet http://sei.com/20180928/role/DocumentAndEntityInformation Document and Entity Information 1 false true R2.htm 020000 - Document - Risk/Return Summary {Unlabeled} - SIIT LARGE CAP FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLARGECAPFUND Risk/Return Summary- SIIT LARGE CAP FUND 2 false false R7.htm 020005 - Disclosure - Risk/Return Detail Data {Elements} - SIIT LARGE CAP FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPFUND Risk/Return Detail Data- SIIT LARGE CAP FUND 3 false true R8.htm 020006 - Document - Risk/Return Summary {Unlabeled} - SIIT LARGE CAP DISCIPLINED EQUITY FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLARGECAPDISCIPLINEDEQUITYFUND Risk/Return Summary- SIIT LARGE CAP DISCIPLINED EQUITY FUND 4 false false R13.htm 020011 - Disclosure - Risk/Return Detail Data {Elements} - SIIT LARGE CAP DISCIPLINED EQUITY FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPDISCIPLINEDEQUITYFUND Risk/Return Detail Data- SIIT LARGE CAP DISCIPLINED EQUITY FUND 5 false true R14.htm 020012 - Document - Risk/Return Summary {Unlabeled} - SIIT LARGE CAP INDEX FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLARGECAPINDEXFUND Risk/Return Summary- SIIT LARGE CAP INDEX FUND 6 false false R19.htm 020017 - Disclosure - Risk/Return Detail Data {Elements} - SIIT LARGE CAP INDEX FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPINDEXFUND Risk/Return Detail Data- SIIT LARGE CAP INDEX FUND 7 false true R20.htm 020018 - Document - Risk/Return Summary {Unlabeled} - SIIT S&P 500 Index Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITSP500IndexFund Risk/Return Summary- SIIT S&P 500 Index Fund 8 false false R25.htm 020023 - Disclosure - Risk/Return Detail Data {Elements} - SIIT S&P 500 Index Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITSP500IndexFund Risk/Return Detail Data- SIIT S&P 500 Index Fund 9 false true R26.htm 020024 - Document - Risk/Return Summary {Unlabeled} - SIIT Extended Market Index Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITExtendedMarketIndexFund Risk/Return Summary- SIIT Extended Market Index Fund 10 false false R31.htm 020029 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Extended Market Index Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITExtendedMarketIndexFund Risk/Return Detail Data- SIIT Extended Market Index Fund 11 false true R32.htm 020030 - Document - Risk/Return Summary {Unlabeled} - SIIT SMALL CAP FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITSMALLCAPFUND Risk/Return Summary- SIIT SMALL CAP FUND 12 false false R37.htm 020035 - Disclosure - Risk/Return Detail Data {Elements} - SIIT SMALL CAP FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITSMALLCAPFUND Risk/Return Detail Data- SIIT SMALL CAP FUND 13 false true R38.htm 020036 - Document - Risk/Return Summary {Unlabeled} - SIIT Small Cap II Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITSmallCapIIFund Risk/Return Summary- SIIT Small Cap II Fund 14 false false R43.htm 020041 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Small Cap II Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITSmallCapIIFund Risk/Return Detail Data- SIIT Small Cap II Fund 15 false true R44.htm 020042 - Document - Risk/Return Summary {Unlabeled} - SIIT SMALL MID CAP EQUITY FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITSMALLMIDCAPEQUITYFUND Risk/Return Summary- SIIT SMALL MID CAP EQUITY FUND 16 false false R49.htm 020047 - Disclosure - Risk/Return Detail Data {Elements} - SIIT SMALL MID CAP EQUITY FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITSMALLMIDCAPEQUITYFUND Risk/Return Detail Data- SIIT SMALL MID CAP EQUITY FUND 17 false true R50.htm 020048 - Document - Risk/Return Summary {Unlabeled} - SIIT U.S. Equity Factor Allocation Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITUSEquityFactorAllocationFund Risk/Return Summary- SIIT U.S. Equity Factor Allocation Fund 18 false false R53.htm 020051 - Disclosure - Risk/Return Detail Data {Elements} - SIIT U.S. Equity Factor Allocation Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITUSEquityFactorAllocationFund Risk/Return Detail Data- SIIT U.S. Equity Factor Allocation Fund 19 false true R54.htm 020052 - Document - Risk/Return Summary {Unlabeled} - SIIT U.S. Managed Volatility Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITUSManagedVolatilityFund Risk/Return Summary- SIIT U.S. Managed Volatility Fund 20 false false R59.htm 020057 - Disclosure - Risk/Return Detail Data {Elements} - SIIT U.S. Managed Volatility Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITUSManagedVolatilityFund Risk/Return Detail Data- SIIT U.S. Managed Volatility Fund 21 false true R60.htm 020058 - Document - Risk/Return Summary {Unlabeled} - SIIT Global Managed Volatility Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITGlobalManagedVolatilityFund Risk/Return Summary- SIIT Global Managed Volatility Fund 22 false false R65.htm 020063 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Global Managed Volatility Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITGlobalManagedVolatilityFund Risk/Return Detail Data- SIIT Global Managed Volatility Fund 23 false true R66.htm 020064 - Document - Risk/Return Summary {Unlabeled} - SIIT World Select Equity Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITWorldSelectEquityFund Risk/Return Summary- SIIT World Select Equity Fund 24 false false R69.htm 020067 - Disclosure - Risk/Return Detail Data {Elements} - SIIT World Select Equity Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITWorldSelectEquityFund Risk/Return Detail Data- SIIT World Select Equity Fund 25 false true R70.htm 020068 - Document - Risk/Return Summary {Unlabeled} - SIIT WORLD EQUITY EX-US FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITWORLDEQUITYEXUSFUND Risk/Return Summary- SIIT WORLD EQUITY EX-US FUND 26 false false R75.htm 020073 - Disclosure - Risk/Return Detail Data {Elements} - SIIT WORLD EQUITY EX-US FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITWORLDEQUITYEXUSFUND Risk/Return Detail Data- SIIT WORLD EQUITY EX-US FUND 27 false true R76.htm 020074 - Document - Risk/Return Summary {Unlabeled} - SIIT Screened World Equity Ex-US Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITScreenedWorldEquityExUSFund Risk/Return Summary- SIIT Screened World Equity Ex-US Fund 28 false false R81.htm 020079 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Screened World Equity Ex-US Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITScreenedWorldEquityExUSFund Risk/Return Detail Data- SIIT Screened World Equity Ex-US Fund 29 false true R82.htm 020080 - Document - Risk/Return Summary {Unlabeled} - SIIT EMERGING MARKETS EQUITY FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITEMERGINGMARKETSEQUITYFUND Risk/Return Summary- SIIT EMERGING MARKETS EQUITY FUND 30 false false R87.htm 020085 - Disclosure - Risk/Return Detail Data {Elements} - SIIT EMERGING MARKETS EQUITY FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSEQUITYFUND Risk/Return Detail Data- SIIT EMERGING MARKETS EQUITY FUND 31 false true R88.htm 020086 - Document - Risk/Return Summary {Unlabeled} - SIIT Opportunistic Income Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITOpportunisticIncomeFund Risk/Return Summary- SIIT Opportunistic Income Fund 32 false false R93.htm 020091 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Opportunistic Income Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITOpportunisticIncomeFund Risk/Return Detail Data- SIIT Opportunistic Income Fund 33 false true R94.htm 020092 - Document - Risk/Return Summary {Unlabeled} - SIIT CORE FIXED INCOME Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITCOREFIXEDINCOME Risk/Return Summary- SIIT CORE FIXED INCOME 34 false false R99.htm 020097 - Disclosure - Risk/Return Detail Data {Elements} - SIIT CORE FIXED INCOME Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITCOREFIXEDINCOME Risk/Return Detail Data- SIIT CORE FIXED INCOME 35 false true R100.htm 020098 - Document - Risk/Return Summary {Unlabeled} - SIIT HIGH YIELD BOND FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITHIGHYIELDBONDFUND Risk/Return Summary- SIIT HIGH YIELD BOND FUND 36 false false R105.htm 020103 - Disclosure - Risk/Return Detail Data {Elements} - SIIT HIGH YIELD BOND FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITHIGHYIELDBONDFUND Risk/Return Detail Data- SIIT HIGH YIELD BOND FUND 37 false true R106.htm 020104 - Document - Risk/Return Summary {Unlabeled} - SIIT LONG DURATION FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLONGDURATIONFUND Risk/Return Summary- SIIT LONG DURATION FUND 38 false false R111.htm 020109 - Disclosure - Risk/Return Detail Data {Elements} - SIIT LONG DURATION FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLONGDURATIONFUND Risk/Return Detail Data- SIIT LONG DURATION FUND 39 false true R112.htm 020110 - Document - Risk/Return Summary {Unlabeled} - SIIT Long Duration Credit Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLongDurationCreditFund Risk/Return Summary- SIIT Long Duration Credit Fund 40 false false R117.htm 020115 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Long Duration Credit Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLongDurationCreditFund Risk/Return Detail Data- SIIT Long Duration Credit Fund 41 false true R118.htm 020116 - Document - Risk/Return Summary {Unlabeled} - SIIT Ultra Short Duration Bond Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITUltraShortDurationBondFund Risk/Return Summary- SIIT Ultra Short Duration Bond Fund 42 false false R123.htm 020121 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Ultra Short Duration Bond Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITUltraShortDurationBondFund Risk/Return Detail Data- SIIT Ultra Short Duration Bond Fund 43 false true R124.htm 020122 - Document - Risk/Return Summary {Unlabeled} - SIIT EMERGING MARKETS DEBT FUND Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITEMERGINGMARKETSDEBTFUND Risk/Return Summary- SIIT EMERGING MARKETS DEBT FUND 44 false false R129.htm 020127 - Disclosure - Risk/Return Detail Data {Elements} - SIIT EMERGING MARKETS DEBT FUND Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSDEBTFUND Risk/Return Detail Data- SIIT EMERGING MARKETS DEBT FUND 45 false true R130.htm 020128 - Document - Risk/Return Summary {Unlabeled} - SIIT Real Return Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITRealReturnFund Risk/Return Summary- SIIT Real Return Fund 46 false false R135.htm 020133 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Real Return Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITRealReturnFund Risk/Return Detail Data- SIIT Real Return Fund 47 false true R136.htm 020134 - Document - Risk/Return Summary {Unlabeled} - SIIT Limited Duration Bond Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITLimitedDurationBondFund Risk/Return Summary- SIIT Limited Duration Bond Fund 48 false false R141.htm 020139 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Limited Duration Bond Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITLimitedDurationBondFund Risk/Return Detail Data- SIIT Limited Duration Bond Fund 49 false true R142.htm 020140 - Document - Risk/Return Summary {Unlabeled} - SIIT Intermediate Duration Credit Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITIntermediateDurationCreditFund Risk/Return Summary- SIIT Intermediate Duration Credit Fund 50 false false R147.htm 020145 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Intermediate Duration Credit Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITIntermediateDurationCreditFund Risk/Return Detail Data- SIIT Intermediate Duration Credit Fund 51 false true R148.htm 020146 - Document - Risk/Return Summary {Unlabeled} - SIIT Dynamic Asset Allocation Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITDynamicAssetAllocationFund Risk/Return Summary- SIIT Dynamic Asset Allocation Fund 52 false false R153.htm 020151 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Dynamic Asset Allocation Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITDynamicAssetAllocationFund Risk/Return Detail Data- SIIT Dynamic Asset Allocation Fund 53 false true R154.htm 020152 - Document - Risk/Return Summary {Unlabeled} - SIIT Multi-Asset Real Return Fund Sheet http://sei.com/20180928/role/DocumentRiskReturnSummaryUnlabeledSIITMultiAssetRealReturnFund Risk/Return Summary- SIIT Multi-Asset Real Return Fund 54 false false R159.htm 020157 - Disclosure - Risk/Return Detail Data {Elements} - SIIT Multi-Asset Real Return Fund Sheet http://sei.com/20180928/role/DisclosureRiskReturnDetailDataElementsSIITMultiAssetRealReturnFund Risk/Return Detail Data- SIIT Multi-Asset Real Return Fund 55 false false R160.htm 040000 - Disclosure - Risk/Return Detail Data {Elements} Sheet http://xbrl.sec.gov/rr/role/RiskReturnDetailData Risk/Return Detail Data 56 false false All Reports Book All Reports ck0000939934-20180928.xml ck0000939934-20180928.xsd ck0000939934-20180928_cal.xml ck0000939934-20180928_def.xml ck0000939934-20180928_lab.xml ck0000939934-20180928_pre.xml BarChart1.png BarChart2.png BarChart3.png BarChart4.png BarChart5.png BarChart6.png BarChart7.png BarChart8.png BarChart9.png BarChart10.png BarChart11.png BarChart12.png BarChart13.png BarChart14.png BarChart15.png BarChart16.png BarChart17.png BarChart18.png BarChart19.png BarChart20.png BarChart21.png BarChart22.png BarChart23.png BarChart24.png BarChart25.png http://xbrl.sec.gov/rr/2012-01-31 http://xbrl.sec.gov/dei/2012-01-31 true true