Loans and Allowance for Loan Losses - Allowance for Loan Losses Outstanding by Impairment Methodology (Detail) (USD $) In Thousands, unless otherwise specified
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Mar. 31, 2015
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Mar. 31, 2014
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
$ 8,898us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |
$ 5,375us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 |
Collectively evaluated for impairment |
32,659us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |
34,549us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment |
Non-residential Real Estate Owner Occupied [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
227us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
361us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
Collectively evaluated for impairment |
4,234us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
4,651us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
Non-residential Real Estate Other [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
1,885us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
1,929us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
Collectively evaluated for impairment |
8,013us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
8,756us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
Residential Real Estate Permanent Mortgage [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
396us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
588us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
Collectively evaluated for impairment |
2,588us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
2,649us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
Residential Real Estate All Other [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
1,067us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
733us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
Collectively evaluated for impairment |
5,511us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
5,752us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
Non-consumer Non-real Estate [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
4,935us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
1,133us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
Collectively evaluated for impairment |
8,133us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
8,570us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
Consumer Non-real Estate [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
346us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
389us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Collectively evaluated for impairment |
1,981us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
2,184us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Other Loans [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Individually evaluated for impairment |
42us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
242us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1 / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Collectively evaluated for impairment |
2,199us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
1,830us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Acquired Loans [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Collectively evaluated for impairment |
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$ 157us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |