2.2.0.25truefalse40201 - Disclosure - Acquisitions (Narrative) (Details)truefalseIn Millionsfalse1falsefalseUSDfalsefalse1/1/2011 - 3/31/2011
USD ($)
USD ($) / shares
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EUR (€)
€Duration_10_1_2010_To_12_31_2010http://www.sec.gov/CIK0000093751duration2010-10-01T00:00:002010-12-31T00:00:00Unit16Standardhttp://www.xbrl.org/2003/iso4217EURiso42170EUREUR€3falsefalseUSDfalsefalse1/1/2010 - 12/31/2010
USD ($)
$Duration_1_1_2010_To_12_31_2010http://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit1Standardhttp://www.xbrl.org/2003/instancesharesxbrli0Unit15Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$4falsefalseUSDfalsefalse3/31/2010
USD ($)
$As_Of_3_31_2010http://www.sec.gov/CIK0000093751instant2010-03-31T00:00:000001-01-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$5falsefalseUSDfalsefalse12/31/2009
USD ($)
$As_Of_12_31_2009http://www.sec.gov/CIK0000093751instant2009-12-31T00:00:000001-01-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$6falsefalseUSDtruefalse{us-gaap_BusinessAcquisitionAxis} : Bank of Ireland Asset Management [Member]
3/31/2011
USD ($)
$As_Of_3_31_2011_us-gaap_BusinessAcquisitionAxis_stt_BankOfIrelandAssetManagementMemberhttp://www.sec.gov/CIK0000093751instant2011-03-31T00:00:000001-01-01T00:00:00falsefalseBank of Ireland Asset Management [Member]us-gaap_BusinessAcquisitionAxisxbrldihttp://xbrl.org/2006/xbrldistt_BankOfIrelandAssetManagementMemberus-gaap_BusinessAcquisitionAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$7falsefalseUSDtruefalse{us-gaap_BusinessAcquisitionAxis} : Intesa Sanpaolo's Securities Services [Member]
3/31/2011
USD ($)
$As_Of_3_31_2011_us-gaap_BusinessAcquisitionAxis_stt_IntesaSanpaoloSSecuritiesServicesMemberhttp://www.sec.gov/CIK0000093751instant2011-03-31T00:00:000001-01-01T00:00:00falsefalseIntesa Sanpaolo's Securities Services [Member]us-gaap_BusinessAcquisitionAxisxbrldihttp://xbrl.org/2006/xbrldistt_IntesaSanpaoloSSecuritiesServicesMemberus-gaap_BusinessAcquisitionAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$5false0us-gaap_IncomeTaxExaminationPenaltiesAndInterestExpenseus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse130000000130falsetruefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse5falsefalsefalse00falsefalsefalsefalsefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryThe sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.No authoritative reference available.falsefalse6false0us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillAmountus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse5falsefalsefalse00falsefalsefalsefalsefalse6truefalsefalse3100000031falsefalsefalsetruefalse7truefalsefalse932000000932falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryAmount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 52
-Subparagraph c
Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 53
-Subparagraph d
falsefalse7false0us-gaap_IntangibleAssetsNetExcludingGoodwillus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse26440000002644falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse25930000002593falsefalsefalsefalsefalse4truefalsefalse17680000001768falsefalsefalsefalsefalse5truefalsefalse18100000001810falsefalsefalsefalsefalse6truefalsefalse2700000027falsefalsefalsetruefalse7truefalsefalse848000000848falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetarySum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 42, 45
falsefalse8false0us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationAssetus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse5800000058falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse7200000072falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse5falsefalsefalse00falsefalsefalsefalsefalse6falsefalsefalse00falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents the amount of any change, including any differences arising upon settlement, recognized during the reporting period in the value of an asset or assets, arising from an item of contingent consideration, recognized in a business combination.Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 23, 24, 25
Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 72
-Subparagraph b(1)
falsefalse9false0stt_AssetsUnderMangementsttfalsedebitinstantAssets under custody and administration business acquired.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse5falsefalsefalse00falsefalsefalsefalsefalse6truefalsefalse2300000023falsetruefalsetruefalse7falsefalsefalse00falsefalsefalsetruefalseMonetaryxbrli:monetaryItemTypemonetaryAssets under custody and administration business acquired.No authoritative reference available.falsefalse75Acquisitions (Narrative) (Details)MillionsUnKnownUnKnownUnKnownfalsetrue