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(B) If the Fund is a Money Market Fund that is a government Money Market Fund, as defined in \u00a7 270.2a\u20137(a)(16), or a retail Money Market Fund, as defined in \u00a7 270.2a\u20137(a)(25), and that is subject to the requirements of \u00a7\u00a7 270.2a\u20137(c)(2)(i) and/or (ii) of this chapter (or is not subject to the requirements of \u00a7\u00a7 270.2a\u20137(c)(2)(i) and/or (ii) of this chapter pursuant to \u00a7 270.2a\u20137(c)(2)(iii) of this chapter, but has chosen to rely on the ability to impose liquidity fees and suspend redemptions consistent with the requirements of \u00a7\u00a7 270.2a\u20137(c)(2)(i) and/or (ii)), include the following statement: You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund's liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund's sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.  (C) If the Fund is a Money Market Fund that is a government Money Market Fund, as defined in \u00a7 270.2a\u20137(a)(16), that is not subject to the requirements of \u00a7\u00a7 270.2a\u20137(c)(2)(i) and/or (ii) of this chapter pursuant to \u00a7 270.2a\u20137(c)(2)(iii) of this chapter, and that has not chosen to rely on the ability to impose liquidity fees and suspend redemptions consistent with the requirements of \u00a7\u00a7 270.2a\u20137(c)(2)(i) and/or (ii), include the following statement: You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund's sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time. Instruction. If an affiliated person, promoter, or principal underwriter of the Fund, or an affiliated person of such a person, has contractually committed to provide financial support to the Fund, and the term of the agreement will extend for at least one year following the effective date of the Fund's registration statement, the statement specified in Item 4(b)(1)(ii)(A), Item 4(b)(1)(ii)(B), or Item 4(b)(1)(ii)(C) may omit the last sentence (\"The Fund's sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.\"). For purposes of this Instruction, the term \"financial support\" includes any capital contribution, purchase of a security from the Fund in reliance on \u00a7 270.17a\u20139, purchase of any defaulted or devalued security at par, execution of letter of credit or letter of indemnity, capital support agreement (whether or not the Fund ultimately received support), performance guarantee, or any other similar action reasonably intended to increase or stabilize the value or liquidity of the fund's portfolio; however, the term \"financial support\" excludes any routine waiver of fees or reimbursement of fund expenses, routine inter-fund lending, routine inter-fund purchases of fund shares, or any action that would qualify as financial support as defined above, that the board of directors has otherwise determined not to be reasonably intended to increase or stabilize the value or liquidity of the fund's portfolio.  (iii) If the Fund is advised by or sold through an insured depository institution, state that:  An investment in the Fund is not a deposit of the bank and is not insured or guaranteed by the Federal Deposit Insurance corporation or any other government agency.  Instruction. A Money Market Fund that is advised by or sold through an insured depository institution should combine the disclosure required by Items 4(b)(1)(ii) and (iii) in a single statement.",
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      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITSMALLCAPFUND",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITSMALLMIDCAPEQUITYFUND",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITSP500IndexFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITScreenedWorldEquityExUSFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITSmallCapIIFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITUSEquityFactorAllocationFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITUSManagedVolatilityFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITUltraShortDurationBondFund",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITWORLDEQUITYEXUSFUND",
      "http://www.sei.com/20200928/role/DocumentRiskReturnSummaryUnlabeledSIITWorldSelectEquityFund"
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    "rr_RiskLoseMoney": {
     "auth_ref": [
      "r47",
      "r50",
      "r51",
      "r52"
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     "lang": {
      "en-US": {
       "role": {
        "documentation": "Summarize the principal risks of investing in the Fund, including the risks to which the Fund's portfolio as a whole is subject and the circumstances reasonably likely to affect adversely the Fund's net asset value, yield, and total return. Unless the Fund is a Money Market Fund, disclose that loss of money is a risk of investing in the Fund. If the Fund is a Money Market Fund, include the following statement: \"You could lose money by investing in the Fund.\"",
        "label": "Risk Lose Money [Text]",
        "terseLabel": "Risk Lose Money [Text]"
       }
      }
     },
     "localname": "RiskLoseMoney",
     "nsuri": "http://xbrl.sec.gov/rr/2018-01-31",
     "presentation": [
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITCOREFIXEDINCOME",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITDynamicAssetAllocationFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSDEBTFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSEQUITYFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITExtendedMarketIndexFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITGlobalManagedVolatilityFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITHIGHYIELDBONDFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITIntermediateDurationCreditFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPDISCIPLINEDEQUITYFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPINDEXFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLONGDURATIONFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLimitedDurationBondFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLongDurationCreditFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITMultiAssetRealReturnFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITOpportunisticIncomeFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITRealReturnFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSMALLCAPFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSMALLMIDCAPEQUITYFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSP500IndexFund",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSmallCapIIFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUSEquityFactorAllocationFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUSManagedVolatilityFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUltraShortDurationBondFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITWORLDEQUITYEXUSFUND",
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     },
     "localname": "RiskMoneyMarketFund",
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     "presentation": [
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITCOREFIXEDINCOME",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITDynamicAssetAllocationFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSDEBTFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITEMERGINGMARKETSEQUITYFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITExtendedMarketIndexFund",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITHIGHYIELDBONDFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITIntermediateDurationCreditFund",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLARGECAPINDEXFUND",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLONGDURATIONFUND",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITMultiAssetRealReturnFund",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITScreenedWorldEquityExUSFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSmallCapIIFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUSEquityFactorAllocationFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUSManagedVolatilityFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUltraShortDurationBondFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITWORLDEQUITYEXUSFUND",
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        "label": "Risk Money Market Fund May Impose Fees or Suspend Sales [Text]",
        "terseLabel": "Risk Money Market Fund May Impose Fees or Suspend Sales [Text]"
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      }
     },
     "localname": "RiskMoneyMarketFundMayImposeFeesOrSuspendSales",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITLongDurationCreditFund",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITSMALLMIDCAPEQUITYFUND",
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      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUSManagedVolatilityFund",
      "http://www.sei.com/20200928/role/DisclosureRiskReturnDetailDataElementsSIITUltraShortDurationBondFund",
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        "label": "Risk Money Market Fund May Not Preserve Dollar [Text]",
        "terseLabel": "Risk Money Market Fund May Not Preserve Dollar [Text]"
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     },
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        "label": "Risk Money Market Fund Price Fluctuates [Text]",
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     "lang": {
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        "documentation": "Narrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.",
        "label": "Risk Narrative [Text Block]",
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     "localname": "RiskNarrativeTextBlock",
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