Trading Securities (Details) (USD $)
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Dec. 31, 2014
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Dec. 31, 2013
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Schedule of Trading Securities [Line Items] |
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Trading Securities, Fair Value |
$ 188,700,000us-gaap_TradingSecurities |
$ 91,616,000us-gaap_TradingSecurities |
Trading Securities, Net Unrealized Gain (Loss) |
187,000bokf_TradingSecuritiesNetUnrealizedGainsLosses |
11,000bokf_TradingSecuritiesNetUnrealizedGainsLosses |
Trading Securities Pledged as Collateral |
0us-gaap_TradingSecuritiesPledgedAsCollateral |
0us-gaap_TradingSecuritiesPledgedAsCollateral |
U.S. government agency debentures [Member] |
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Schedule of Trading Securities [Line Items] |
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Trading Securities, Fair Value |
85,092,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
34,120,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
Trading Securities, Net Unrealized Gain (Loss) |
(62,000)bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
77,000bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember |
U.S. government agency residential mortgage-backed securities [Member] |
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Schedule of Trading Securities [Line Items] |
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Trading Securities, Fair Value |
31,199,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember |
21,011,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember |
Trading Securities, Net Unrealized Gain (Loss) |
269,000bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember |
123,000bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember |
Municipal and other tax-exempt securities [Member] |
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Schedule of Trading Securities [Line Items] |
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Trading Securities, Fair Value |
38,951,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember |
27,350,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember |
Trading Securities, Net Unrealized Gain (Loss) |
18,000bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember |
(182,000)bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember |
Other trading securities [Member] |
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Schedule of Trading Securities [Line Items] |
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Trading Securities, Fair Value |
33,458,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = bokf_OtherTradingSecuritiesMember |
9,135,000us-gaap_TradingSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = bokf_OtherTradingSecuritiesMember |
Trading Securities, Net Unrealized Gain (Loss) |
$ (38,000)bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = bokf_OtherTradingSecuritiesMember |
$ (7,000)bokf_TradingSecuritiesNetUnrealizedGainsLosses / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = bokf_OtherTradingSecuritiesMember |