2.2.0.25truefalse41708 - Disclosure - Derivative Financial Instruments (Schedule of Differences Between the Gains (Losses) on the Derivative and the Gains (Losses) on the Hedged Item) (Details)truefalseIn Millionsfalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $Duration_1_1_2010_To_12_31_2010http://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00Unit15Standardhttp://xbrl.us/us-types/2009-01-31sqftxbrlus0Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit1Standardhttp://www.xbrl.org/2003/instancesharesxbrli0Unit14Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDfalsefalse1/1/2009 - 12/31/2009 USD ($) USD ($) / shares $Duration_1_1_2009_To_12_31_2009http://www.sec.gov/CIK0000093751duration2009-01-01T00:00:002009-12-31T00:00:00Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit14Divide http://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0Unit1Standardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2false0us-gaap_DerivativeInstrumentsGainLossRec ognizedInIncomeNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1400000014< IsIndependantCurrency>falsetruefalsefalsefalse2truefalsefalse148000000148falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of net gains and losses recognized in income during the period on derivative instruments design ated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b falsefalse3false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosurederivativefinancialinstrumentsscheduleofdifferencesbetweengainslossesonderiva tiveandgainslossesonhedgeditemdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalseUSDtruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Interest Rate Contracts [Member] {us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxis} : Derivatives Designated as Cash Flow Value Hedges [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_201052422http://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseInterest Rate Contracts [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_InterestRateContractMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberfalsefalseDerivatives Designated as Cash Flow Value Hedges [Member]us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisxbrldihttp://xbrl.org/2006/xbrldistt_DerivativesDesignedAsCashFlowValueHedgesMemberus-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4falsefalseUSDtruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Interest Rate Contracts [Member] {us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxis} : Derivatives Designated as Cash Flow Value Hedges [Member] 1/1/2009 - 12/31/2009 USD ($) $Duration_1_1_2009_To_12_31_2009810http://www.sec.gov/CIK0000093751duration2009-01-01T00:00:002009-12-31T00:00:00falsefalseInterest Rate Contracts [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_InterestRateContractMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberfalsefalseDerivatives Designated as Cash Flow Value Hedges [Member]us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisxbrldihttp://xbrl.org/2006/xbrldistt_DerivativesDesignedAsCashFlowValueHedgesMemberus-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalse4false0us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse70000007falsefalsefalsefalsefalse2truefalsefalse14000000 14falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b -Clause 2 falsefalse5false0us-gaap_CashFlowHedgeGainLossReclassifiedToRevenueNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse-7000000-7falsefalsefalsefalsefalse2falsefalsefalse00&nbsp;falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of net gains (losses) on a cash flow hedge reclassified to revenues from accumulated other comprehensive income.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph b(1) falsefalse6false0us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse50000005falsefalsefalsefalsefalse2falsefalsefalse00&nbsp;falsefalsefalsefalse< hasScenarios>falseMonetaryxbrli:monetaryItemTypemonetaryThe amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b falsefalse7false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosurederivativefinancialinstrumentsscheduleofdifferencesbetweengainslossesonderiva tiveandgainslossesonhedgeditemdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse5falsefalseUSDtruefalse{us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxis} : Derivatives Designated as Cash Flow Value Hedges [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_20105242http://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseDerivatives Designated as Cash Flow Value Hedges [Member]us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisxbrldihttp://xbrl.org/2006/xbrldistt_DerivativesDesignedAsCashFlowValueHedgesMemberus-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisexplicitMemberU nit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$6falsefalseUSDtruefalse{us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxis} : Derivatives Designated as Cash Flow Value Hedges [Member] 1/1/2009 - 12/31/2009 USD ($) $Duration_1_1_2009_To_12_31_200989http://www.sec.gov/CIK0000093751duration2009-01-01T00:00:002009-12-31T00:00:00falsefalseDerivatives Designated as Cash Flow Value Hedges [Member]us-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisxbrldihttp://xbrl.org/2006/xbrldistt_DerivativesDesignedAsCashFlowValueHedgesMemberus-gaap_TradingActivityGainsAndLossesByIncomeStatementLocationAxisexplicitMemberUni t12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalse8false0us-gaap_DerivativeInstrumen tsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse70000007falsefalsefalsefalsefalse2truefalsefalse1400000014falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe effective portion of gains and losses (net) on derivative i nstruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b -Clause 2 falsefalse9false0us-gaap_CashFlowHedgeGainLossReclassifiedToRevenueNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse-7000000-7falsefalsefalsefalsefalse2falsefalsefalse00&nbsp;falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of net gains (losses) on a cash flow hedge reclassified to revenues from accumulated other comprehensive income.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -Subparagraph b(1) falsefalse10false0us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse50000005falsetruefalsefalsefalse2falsefalsefalse00&nbsp;falsefalsefalsefalse< hasScenarios>falseMonetaryxbrli:monetaryItemTypemonetaryThe amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 205G Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44C -Subparagraph b falsefalse29Derivative Financial Instruments (Schedule of Differences Between the Gains (Losses) on the Derivative and the Gains (Losses) on the Hedged Item) (Details) (USD $)MillionsUnKnownUnKnownUnKnownfalsetrue