Loans and Allowance for Loan Losses - Impaired Loans Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified
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12 Months Ended |
Dec. 31, 2014
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Dec. 31, 2013
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Unpaid Principal Balance |
$ 42,843us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance |
$ 43,130us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance |
Recorded Investment with Allowance |
36,357us-gaap_ImpairedFinancingReceivableRecordedInvestment |
38,326us-gaap_ImpairedFinancingReceivableRecordedInvestment |
Related Allowance |
2,560us-gaap_ImpairedFinancingReceivableRelatedAllowance |
3,478us-gaap_ImpairedFinancingReceivableRelatedAllowance |
Average Recorded Investment |
37,132us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment |
39,262us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment |
Non-residential Real Estate Owner Occupied [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Unpaid Principal Balance |
521us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
877us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
Recorded Investment with Allowance |
448us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
752us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
Related Allowance |
15us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
28us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
Average Recorded Investment |
453us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |
881us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / 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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Unpaid Principal Balance |
23,154us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
24,964us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
Recorded Investment with Allowance |
21,164us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
23,351us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
Related Allowance |
1,364us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
2,161us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
Average Recorded Investment |
21,522us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |
23,816us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / 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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Unpaid Principal Balance |
1,095us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
1,253us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
Recorded Investment with Allowance |
880us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
1,025us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
Related Allowance |
85us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
58us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
Average Recorded Investment |
1,042us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |
1,170us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / 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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Unpaid Principal Balance |
2,480us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
2,214us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
Recorded Investment with Allowance |
2,270us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
1,803us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
Related Allowance |
299us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
361us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
Average Recorded Investment |
2,273us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |
1,857us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / 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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Unpaid Principal Balance |
1,895us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
1,801us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
Recorded Investment with Allowance |
1,580us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
1,459us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
Related Allowance |
431us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
388us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
Average Recorded Investment |
1,646us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |
1,553us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / 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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Unpaid Principal Balance |
664us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
628us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Recorded Investment with Allowance |
648us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
611us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Related Allowance |
138us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
139us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Average Recorded Investment |
602us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
455us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |
Other Loans [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Unpaid Principal Balance |
2,101us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
1,545us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Recorded Investment with Allowance |
1,659us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
1,464us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Related Allowance |
228us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
219us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Average Recorded Investment |
1,512us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
1,602us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |
Acquired Loans [Member] |
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Accounts, Notes, Loans and Financing Receivable [Line Items] |
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Unpaid Principal Balance |
10,933us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
9,848us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
Recorded Investment with Allowance |
7,708us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
7,861us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
Related Allowance |
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124us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
Average Recorded Investment |
$ 8,082us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |
$ 7,928us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |