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Loans and Allowance for Credit Losses, Loans by Portfolio Type (Details) (USD $)
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Loan receivables disclosure [Abstract]      
Loans, fixed rate of interest $ 4,291,278,000us-gaap_LoansReceivableWithFixedRatesOfInterest1 $ 4,259,974,000us-gaap_LoansReceivableWithFixedRatesOfInterest1 $ 4,289,302,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
Loans, variable rate of interest 10,312,125,000us-gaap_LoansReceivableWithVariableRatesOfInterest1 9,867,292,000us-gaap_LoansReceivableWithVariableRatesOfInterest1 8,683,846,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
Loans, non-accrual 80,733,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest 80,771,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest 104,706,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
Total 14,684,136,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount 14,208,037,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount 13,077,854,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Accruing loans past due (90 days) 523,000us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing [1] 125,000us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing [1] 1,991,000us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing [1]
Credit Commitments [Abstract]      
Outstanding commitments to extend credit 8,100,000,000us-gaap_UnusedCommitmentsToExtendCredit    
Outstanding standby letters of credit 394,000,000bokf_OutstandingStandbyLettersOfCredit    
Outstanding commercial letters of credit 6,600,000us-gaap_LettersOfCreditOutstandingAmount    
Texas [Member] | Geographic Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 5,100,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= stpr_TX		    
Loans receivable, other information [Abstract]      
Percentage of loan portfolio attributed to Texas (in hundredths) 35.00%bokf_PercentageofLoanPortfolioAttributedtoTexas
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= stpr_TX		    
Oklahoma [Member] | Geographic Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 3,400,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= stpr_OK		    
Loans receivable, other information [Abstract]      
Percentage of loan portfolio attributed to Oklahoma (in hundredths) 23.00%bokf_PercentageofLoanPortfolioAttributedtoOklahoma
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_StatementGeographicalAxis
= stpr_OK		    
Commercial [Member]      
Loan receivables disclosure [Abstract]      
Loans, fixed rate of interest 1,807,837,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 1,736,976,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 1,649,164,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans, variable rate of interest 7,569,446,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 7,345,167,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 6,383,495,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans, non-accrual 13,880,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 13,527,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 19,047,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Total 9,391,163,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 9,095,670,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		 8,051,706,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Commercial [Member] | Texas [Member] | Geographic Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 3,400,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_TX		    
Loans receivable, other information [Abstract]      
Percentage of loan portfolio attributed to Texas (in hundredths) 36.00%bokf_PercentageofLoanPortfolioAttributedtoTexas
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_TX		    
Commercial [Member] | Oklahoma [Member] | Geographic Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 2,000,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_OK		    
Loans receivable, other information [Abstract]      
Percentage of loan portfolio attributed to Oklahoma (in hundredths) 21.00%bokf_PercentageofLoanPortfolioAttributedtoOklahoma
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_OK		    
Energy [Member]      
Loan receivables disclosure [Abstract]      
Total 2,902,994,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyMember		 2,860,428,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyMember		 2,344,072,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyMember
Energy [Member] | Credit Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 2,900,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyMember		    
Loans receivable, other information [Abstract]      
Percentage of energy loans in loan portfolio 20.00%bokf_PercentageOfEnergyLoansInLoanPortfolio
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyMember		    
Energy Producers [Member] | Credit Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 2,500,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyProducersMember		    
Loans receivable, other information [Abstract]      
Percentage of committed energy production loans secured by oil 61.00%bokf_PercentageOfCommittedEnergyProductionLoansSecuredByOil
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyProducersMember		    
Percentage of committed energy production loans secured by natural gas 39.00%bokf_PercentageOfCommittedEnergyProductionLoansSecuredByNaturalGas
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_EnergyProducersMember		    
Services [Member]      
Loan receivables disclosure [Abstract]      
Total 2,728,354,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember		 2,518,229,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember		 2,232,471,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember
Services [Member] | Credit Concentration Risk [Member]      
Loan receivables disclosure [Abstract]      
Total 2,700,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember		    
Loans receivable, other information [Abstract]      
Amount of loans with individual balances less than $10 million 1,200,000,000bokf_MaximumAmountOfLoansWithBalancesBelowThreshold
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember		    
Maximum loan amount for certain individual loans in category 10,000,000bokf_MaximumLoanAmountForCertainIndividualLoansInCategory
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CreditConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_ServicesMember		    
Commercial Real Estate [Member]      
Loan receivables disclosure [Abstract]      
Loans, fixed rate of interest 703,511,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 721,513,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 764,688,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Loans, variable rate of interest 2,212,051,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 1,988,080,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 1,827,414,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Loans, non-accrual 19,902,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 18,557,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 39,305,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Total 2,935,464,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 2,728,150,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember		 2,631,407,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial Real Estate [Member] | Texas [Member] | Geographic Concentration Risk [Member]      
Loans receivable, other information [Abstract]      
Percentage of loan portfolio secured by property in Texas (in hundredths) 34.00%bokf_PercentageOfLoanPortfolioSecuredByPropertyInTexas
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_TX		    
Commercial Real Estate [Member] | Oklahoma [Member] | Geographic Concentration Risk [Member]      
Loans receivable, other information [Abstract]      
Percentage of loan portfolio secured by property in Oklahoma (in hundredths) 15.00%bokf_PercentageOfLoanPortfolioSecuredByPropertyInOklahoma
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_GeographicConcentrationRiskMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
/ us-gaap_StatementGeographicalAxis
= stpr_OK		    
Residential Mortgage [Member]      
Loan receivables disclosure [Abstract]      
Loans, fixed rate of interest 1,679,211,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 1,698,620,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 1,749,693,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Loans, variable rate of interest 201,301,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 202,771,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 223,602,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Loans, non-accrual 46,487,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 48,121,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 45,380,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Total 1,926,999,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 1,949,512,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember		 2,018,675,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Permanent mortage [Member]      
Loan receivables disclosure [Abstract]      
Total 964,264,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		 969,951,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		 1,033,572,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember
Loans receivable, other information [Abstract]      
Minimum FICO required for jumbo loan approval 720bokf_MinimumFicoRequiredForLoanApproval
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		    
Maximum debt-to-income ratio on jumbo loans (in hundredths) 38.00%bokf_MaximumDebtToIncomeRatioOnLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		    
Minimum loan-to-value ratio on jumbo loans (in hundredths) 60.00%bokf_MinimumLoanToValueRatioOnLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		    
Maximum loan-to-value ratio on jumbo loans (in hundredths) 100.00%bokf_MaximumLoanToValueRatioOnLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentResidentialMortgageMember		    
Minimum period for fixed rate on variable rate jumbo loans (in years) 3 years    
Maximum period for fixed rate on variable rate jumbo loans (in years) 10 years    
Permanent mortgages guaranteed by US govenment agencies [Member]      
Loan receivables disclosure [Abstract]      
Total 200,179,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentMortgagesGuaranteedByUsGovernmentAgenciesMember		 205,950,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentMortgagesGuaranteedByUsGovernmentAgenciesMember		 184,822,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentMortgagesGuaranteedByUsGovernmentAgenciesMember
Loans receivable, other information [Abstract]      
Amount of loans guaranteed by US government and previously sold into GNMA mortgage pools 200,000,000bokf_AmountOfLoanPortfolioGuaranteedByUsGovernmentPreviouslySoldIntoGnmaMortgagePool
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bokf_PermanentMortgagesGuaranteedByUsGovernmentAgenciesMember		    
Home equity {Member]      
Loan receivables disclosure [Abstract]      
Total 762,556,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 773,611,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 800,281,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
Loans receivable, other information [Abstract]      
Percentage of home equity portfolio comprised of first lien loans 70.00%bokf_PercentageOfHomeEquityPortfolioComprisedOfFirstLienLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		    
Percentage of home equity portfolio comprised of junior lien loans 30.00%bokf_PercentageOfHomeEquityPortfolioComprisedOfJuniorLienLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		    
Percentage of junior lien home equity loans that are amortizing term loans 71.00%bokf_PercentageOfJuniorLienHomeEquityLoansThatAreAmortizingTermLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		    
Percentage of junior lien home equity loans that are revolving lines of credit 29.00%bokf_PercentageOfJuniorLienHomeEquityLoansThatAreRevolvingLinesOfCredit
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		    
Home equity loans, description Home equity loans generally require a minimum FICO score of 700 and a maximum DTI of 40%.    
Home equity loans, maximum 400,000bokf_HomeEquityLoansMaximum
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		    
Home equity loans, revolving period 5 years    
Home equity loans, amortization period following revolving period 15 years    
Home equity loans, discretionary additional revolving period 5 years    
Consumer [Member]      
Loan receivables disclosure [Abstract]      
Loans, fixed rate of interest 100,719,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 102,865,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 125,757,000us-gaap_LoansReceivableWithFixedRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Loans, variable rate of interest 329,327,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 331,274,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 249,335,000us-gaap_LoansReceivableWithVariableRatesOfInterest1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Loans, non-accrual 464,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 566,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 974,000us-gaap_LoansAndLeasesReceivableImpairedNonperformingNonaccrualOfInterest
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Total $ 430,510,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 $ 434,705,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 $ 376,066,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
[1] Excludes residential mortgage loans guaranteed by agencies of the U.S. government