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All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross4false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse14260000001426falsefalsefalsefalsefalse2truefalsefalse15740000001574falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. 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All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross5false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9069100000090691falsefalsefalsefalsefalse2truefalsefalse8188100000081881falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. 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All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value6false0us-gaap_HeldToMaturitySecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse1225300000012253falsefalsefalsefalsefalse2truefalsefalse1224900000012249falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity; such investments are measured at amortized cost (carrying value). 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Such item represents the gross unrecognized holding gain.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Gains8false0us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingLossesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse173000000173falsefalsefalsefalsefalse2truefalsefalse214000000214falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAs of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Losses9false0us-gaap_HeldToMaturitySecuritiesFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse1265500000012655falsefalsefalsefalsefalse2truefalsefalse1257600000012576falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Fair Value10false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalseUSDtruefalse{us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsMajorTypesOfTradingSecuritiesAndAssetsAxis} : US Treasury and Federal Agencies [Member] {invest_InvestmentAxis} : Mortgage-Backed Securities [Member] 1/1/2011 - 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All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross14false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse2687700000026877falsefalsefalsefalsefalse2truefalsefalse2364000000023640falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. 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Such item represents the gross unrecognized holding gain.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Gains17false0us-gaap_HeldToMaturitySecuritiesFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse388000000388falsefalsefalsefalsefalse2truefalsefalse439000000439falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Fair Value18false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse5falsefalseUSDtruefalse{invest_InvestmentAxis} : Asset-Backed Securities [Member] {us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsMajorTypesOfTradingSecuritiesAndAssetsAxis} : Non-U.S. Debt Securities [Member] 1/1/2011 - 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Such item represents the gross unrecognized holding loss.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Losses44false0us-gaap_HeldToMaturitySecuritiesFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse75630000007563falsefalsefalsefalsefalse2truefalsefalse72050000007205falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Fair Value45false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse11falsefalseUSDtruefalse{invest_InvestmentAxis} : Direct Obligations [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_stt_DirectObligationsMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseDirect Obligations [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_DirectObligationsMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$12falsefalseUSDtruefalse{invest_InvestmentAxis} : Direct Obligations [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_stt_DirectObligationsMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseDirect Obligations [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_DirectObligationsMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseDirect Obligations [Member]46false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse74400000007440falsefalsefalsefalsefalse2truefalsefalse75050000007505falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost47false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse1900000019falsefalsefalsefalsefalse2truefalsefalse7400000074falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross48false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse20000002falsefalsefalsefalsefalse2truefalsefalse20000002falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross49false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse74570000007457falsefalsefalsefalsefalse2truefalsefalse75770000007577falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value50false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse13falsefalseUSDtruefalse{invest_InvestmentAxis} : Student Loans [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_stt_StudentLoansMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseStudent Loans [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_StudentLoansMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$14falsefalseUSDtruefalse{invest_InvestmentAxis} : Student Loans [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_stt_StudentLoansMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseStudent Loans [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_StudentLoansMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseStudent Loans [Member]51false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse1644200000016442[1]falsefalsefalsefalsefalse2truefalsefalse1497500000014975[1]falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost52false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9900000099[1]falsefalsefalsefalsefalse2truefalsefalse9300000093[1]falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross53false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse617000000617[1]falsefalsefalsefalsefalse2truefalsefalse652000000652[1]falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross54false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse1592400000015924[1]falsefalsefalsefalsefalse2truefalsefalse1441600000014416[1]falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value55false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse15falsefalseUSDtruefalse{invest_InvestmentAxis} : Credit Cards [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_stt_CreditCardsMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseCredit Cards [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_CreditCardsMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$16falsefalseUSDtruefalse{invest_InvestmentAxis} : Credit Cards [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_stt_CreditCardsMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseCredit Cards [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_CreditCardsMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseCredit Cards [Member]56false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse85000000008500falsefalsefalsefalsefalse2truefalsefalse74290000007429falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost57false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse5700000057falsefalsefalsefalsefalse2truefalsefalse5300000053falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross58false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1800000018falsefalsefalsefalsefalse2truefalsefalse3100000031falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross59false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse85390000008539falsefalsefalsefalsefalse2truefalsefalse74510000007451falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value60false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse17falsefalseUSDtruefalse{invest_InvestmentAxis} : Sub-Prime [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_stt_SubPrimeMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseSub-Prime [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_SubPrimeMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$18falsefalseUSDtruefalse{invest_InvestmentAxis} : Sub-Prime [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_stt_SubPrimeMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseSub-Prime [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_SubPrimeMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit13Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseSub-Prime [Member]61false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse20830000002083falsefalsefalsefalsefalse2truefalsefalse21610000002161falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost62false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse40000004falsefalsefalsefalsefalse2truefalsefalse30000003falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross63false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse333000000333falsefalsefalsefalsefalse2truefalsefalse346000000346falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. 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The held-to-maturity category is for those securities that the Entity has the positive intent and ability to hold until maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 3 -Section A -Paragraph 4, 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 17 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 7, 8, 9, 10, 11 falsefalseHeld to maturity, Amortized Cost107false0us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse359000000359falsefalsefalsefalsefalse2truefalsefalse328000000328falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAs of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Gains108false0us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingLossesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1800000018falsefalsefalsefalsefalse2truefalsefalse4400000044falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAs of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Gross Unrealized Losses109false0us-gaap_HeldToMaturitySecuritiesFairValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse45270000004527falsefalsefalsefalsefalse2truefalsefalse47360000004736falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 137 falsefalseHeld to maturity, Fair Value110false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse31falsefalseUSDtruefalse{invest_InvestmentAxis} : Other U.S. Debt Securities [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_us-gaap_OtherDebtSecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseOther U.S. Debt Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OtherDebtSecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$32falsefalseUSDtruefalse{invest_InvestmentAxis} : Other U.S. Debt Securities [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_us-gaap_OtherDebtSecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseOther U.S. Debt Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OtherDebtSecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseOther U.S. Debt Securities [Member]111false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse26200000002620falsefalsefalsefalsefalse2truefalsefalse25410000002541falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost112false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse114000000114falsefalsefalsefalsefalse2truefalsefalse117000000117falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross113false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1700000017falsefalsefalsefalsefalse2truefalsefalse1800000018falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross114false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse27170000002717falsefalsefalsefalsefalse2truefalsefalse26400000002640falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value115false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse33falsefalseUSDtruefalse{invest_InvestmentAxis} : U.S. Equity Securities [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_us-gaap_EquitySecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseU.S. Equity Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EquitySecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$34falsefalseUSDtruefalse{invest_InvestmentAxis} : U.S. Equity Securities [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_us-gaap_EquitySecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseU.S. Equity Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_EquitySecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseU.S. Equity Securities [Member]116false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse631000000631falsefalsefalsefalsefalse2truefalsefalse11150000001115falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost117false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse30000003falsefalsefalsefalsefalse2falsefalsefalse00 falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross118false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00 falsefalsefalsefalsefalse2falsefalsefalse00 falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross119false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse634000000634falsefalsefalsefalsefalse2truefalsefalse11150000001115falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value120false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.statestreet.com/taxonomy/role/disclosureinvestmentsecuritiesscheduleofmarketablesecuritiesdetails1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse35falsefalseUSDtruefalse{invest_InvestmentAxis} : Non-U.S. Equity Securities [Member] 1/1/2011 - 3/31/2011 USD ($) $Duration_1_1_2011_To_3_31_2011_invest_InvestmentAxis_stt_NonUsEquitySecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseNon-U.S. Equity Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_NonUsEquitySecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$36falsefalseUSDtruefalse{invest_InvestmentAxis} : Non-U.S. Equity Securities [Member] 1/1/2010 - 12/31/2010 USD ($) $Duration_1_1_2010_To_12_31_2010_invest_InvestmentAxis_stt_NonUsEquitySecuritiesMemberhttp://www.sec.gov/CIK0000093751duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseNon-U.S. Equity Securities [Member]invest_InvestmentAxisxbrldihttp://xbrl.org/2006/xbrldistt_NonUsEquitySecuritiesMemberinvest_InvestmentAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseNon-U.S. Equity Securities [Member]121false0us-gaap_AvailableForSaleSecuritiesAmortizedCostus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse150000000150falsefalsefalsefalsefalse2truefalsefalse122000000122falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 7 -Footnote 2 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 19 falsefalseAvailable for sale, Amortized Cost122false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse30000003falsefalsefalsefalsefalse2truefalsefalse50000005falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized gains for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized gains are the excess of the fair value of the Available-for-sale Securities over their carrying value as of the reporting date. Such gross unrealized gains are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge. All or a portion of the unrealized holding gain of an available-for-sale security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized Gains Gross123false0us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLossus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00 falsefalsefalsefalsefalse2truefalsefalse10000001falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents the gross unrealized losses for securities which are categorized neither as held-to-maturity nor trading securities. Such gross unrealized losses are the excess of the carrying value of the Available-for-sale Securities over their fair value as of the reporting date. Such gross unrealized losses are included in other comprehensive income in the statement of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13, 19 falsefalseAvailable for sale, Unrealized losses Gross124false0us-gaap_AvailableForSaleSecuritiesus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse153000000153falsetruefalsefalsefalse2truefalsefalse126000000126falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFor an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading. Such securities are reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 22 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14 falsefalseAvailable for sale, Fair Value1 Substantially composed of securities guaranteed by the federal government with respect to the payment of principal and interest. 2123Investment Securities (Schedule of Marketable Securities) (Details) (USD $)MillionsUnKnownUnKnownUnKnownfalsetrue