2.2.0.25truefalse41201 - Disclosure - Derivative Financial Instruments (Narrative) (Details)truefalseIn Millions, unless otherwise specifiedfalse1falsefalseUSDfalsefalse3/31/2011
USD ($)
USD ($) / shares
$As_Of_3_31_2011http://www.sec.gov/CIK0000093751instant2011-03-31T00:00:000001-01-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0Unit1Standardhttp://www.xbrl.org/2003/instancesharesxbrli0Unit15Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalsetruefalse{us-gaap_InvestmentTypeAxis} : 4.956% Subordinated Note [Member]
{us-gaap_DerivativeInstrumentsGainLossByDerivativeInstrumentRiskAxis} : Fair Value Hedges [Member]
3/31/2011
As_Of_3_31_2011_us-gaap_DerivativeInstrumentsGainLossByDerivativeInstrumentRiskAxis_us-gaap_FairValueHedgingMember_us-gaap_InvestmentTypeAxis_stt_FourPointNineFiveSixPercentSubordinatedNoteMemberhttp://www.sec.gov/CIK0000093751instant2011-03-31T00:00:000001-01-01T00:00:00falsefalse4.956% Subordinated Note [Member]us-gaap_InvestmentTypeAxisxbrldihttp://xbrl.org/2006/xbrldistt_FourPointNineFiveSixPercentSubordinatedNoteMemberus-gaap_InvestmentTypeAxisexplicitMemberfalsefalseFair Value Hedges [Member]us-gaap_DerivativeInstrumentsGainLossByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueHedgingMemberus-gaap_DerivativeInstrumentsGainLossByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli03falsefalsetruefalse{us-gaap_InvestmentTypeAxis} : 5.25% Subordinated Note [Member]
{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Fair Value Hedges [Member]
3/31/2011
As_Of_3_31_2011_us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis_us-gaap_FairValueHedgingMember_us-gaap_InvestmentTypeAxis_stt_FivePointTwentyFivePercentSubordinatedNoteMemberhttp://www.sec.gov/CIK0000093751instant2011-03-31T00:00:000001-01-01T00:00:00falsefalse5.25% Subordinated Note [Member]us-gaap_InvestmentTypeAxisxbrldihttp://xbrl.org/2006/xbrldistt_FivePointTwentyFivePercentSubordinatedNoteMemberus-gaap_InvestmentTypeAxisexplicitMemberfalsefalseFair Value Hedges [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueHedgingMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli04falsefalsetruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Fair Value Hedges [Member]
1/1/2011 - 3/31/2011
Duration_1_1_2011_To_3_31_2011_us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis_us-gaap_FairValueHedgingMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseFair Value Hedges [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueHedgingMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli05falsefalsetruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Fair Value Hedges [Member]
1/1/2010 - 12/31/2010
Duration_1_1_2010_To_12_31_2010_us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis_us-gaap_FairValueHedgingMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseFair Value Hedges [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueHedgingMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli06falsefalsetruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Cash Flow Hedge [Member]
1/1/2011 - 3/31/2011
Duration_1_1_2011_To_3_31_2011_us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis_us-gaap_CashFlowHedgingMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseCash Flow Hedge [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CashFlowHedgingMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli07falsefalsetruefalse{us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis} : Cash Flow Hedge [Member]
1/1/2010 - 12/31/2010
Duration_1_1_2010_To_12_31_2010_us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxis_us-gaap_CashFlowHedgingMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseCash Flow Hedge [Member]us-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_CashFlowHedgingMemberus-gaap_DerivativesFairValueByDerivativeInstrumentRiskAxisexplicitMemberUnit13Standardhttp://www.xbrl.org/2003/instancepurexbrli02false0us-gaap_DerivativeFairValueOfDerivativeLiabilityus-gaaptruecreditinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse226000000226falsetruefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryFair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.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 a
-Clause 1
falsefalse3false0us-gaap_CollateralAlreadyPostedAggregateFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse1500000015falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44D
-Subparagraph c
falsefalse4false0us-gaap_AdditionalCollateralAggregateFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse211000000211falsetruefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44D
-Subparagraph c
falsefalse5false0stt_SecuritiesWeightedAverageLifeYearssttfalsenadurationSecurities Weighted Average Life, Yearsfalsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4truefalsefalse7.67.6falsefalsefalsetruefalse5truefalsefalse7.77.7falsefalsefalsetruefalse6truefalsefalse3.63.6falsefalsefalsetruefalse7truefalsefalse3.83.8falsefalsefalsetruefalseOtherxbrli:decimalItemTypedecimalSecurities Weighted Average Life, YearsNo authoritative reference available.falsefalse6false0stt_SubordinatedNoteMaturesOfFloatingRatesttfalsenainstantSubordinated Note Matures of Floating Ratefalsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse002018falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseOtherus-types:dateStringItemTypenormalizedstringSubordinated Note Matures of Floating RateNo authoritative reference available.falsefalse7false0us-gaap_DerivativeFixedInterestRateus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsetruefalse00falsefalsefalsefalsefalse2truetruefalse0.049560.04956falsefalsefalsetruefalse3truetruefalse0.05250.0525falsefalsefalsetruefalse4falsetruefalse00falsefalsefalsetruefalse5falsetruefalse00falsefalsefalsetruefalse6falsetruefalse00falsefalsefalsetruefalse7falsetruefalse00falsefalsefalsetruefalseOtherus-types:percentItemTypepureFixed interest rate related to the interest rate derivative.No authoritative reference available.falsefalse76Derivative Financial Instruments (Narrative) (Details) (USD $)MillionsUnKnownUnKnownUnKnowntruetrue