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Loans and Allowance for Loan Losses - Internal Loan Grading by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014 | Mar. 31, 2014
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Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | $ 3,857,742 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount | $ 3,860,831 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount | $ 3,542,270 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Non-residential Real Estate Owner Occupied [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 486,858 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember |  | 458,794 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember
Non-residential Real Estate Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 957,182 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember |  | 879,505 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember
Residential Real Estate Permanent Mortgage [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 312,777 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember |  | 273,204 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember
Residential Real Estate All Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 639,621 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember |  | 567,747 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember
Non-consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 963,610 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember |  | 828,039 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember
Consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 242,202 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember |  | 225,962 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember
Other Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 165,128 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember |  | 148,211 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember
Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 90,364 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember |  | 160,808 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember
Grade 1 [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 3,240,546 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 2,943,976 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Non-residential Real Estate Owner Occupied [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 403,255 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 381,290 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Non-residential Real Estate Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 794,097 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 724,181 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Residential Real Estate Permanent Mortgage [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 276,186 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 240,653 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Residential Real Estate All Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 526,322 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 474,152 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Non-consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 811,529 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 673,757 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 227,722 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 212,492 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Other Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 158,895 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 144,870 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 1 [Member] | Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 42,540 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember |  | 92,581 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeOneMember
Grade 2 [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 511,088 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 520,907 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Non-residential Real Estate Owner Occupied [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 77,545 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 70,949 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Non-residential Real Estate Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 127,716 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 129,390 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Residential Real Estate Permanent Mortgage [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 29,103 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 25,074 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Residential Real Estate All Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 100,008 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 86,033 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Non-consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 125,609 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 147,625 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 12,321 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 11,388 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Other Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 5,116 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 2,375 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 2 [Member] | Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 33,670 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember |  | 48,073 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeTwoMember
Grade 3 [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 89,764 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 59,144 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Non-residential Real Estate Owner Occupied [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 5,590 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 6,052 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Non-residential Real Estate Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 30,255 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 20,155 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Residential Real Estate Permanent Mortgage [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 6,743 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 6,610 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Residential Real Estate All Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 11,216 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 6,495 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Non-consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 24,107 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 5,350 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 1,716 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 1,655 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Other Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 779 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 736 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 3 [Member] | Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 9,358 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember |  | 12,091 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeThreeMember
Grade 4 [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 16,051 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 18,097 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Non-residential Real Estate Owner Occupied [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 468 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 503 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOwnerOccupiedMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Non-residential Real Estate Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 5,114 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 5,779 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonResidentialRealEstateOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Residential Real Estate Permanent Mortgage [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 745 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 867 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstatePermanentMortgageMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Residential Real Estate All Other [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 2,075 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 1,067 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ResidentialRealEstateAllOtherMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Non-consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 2,365 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 1,307 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_NonConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Consumer Non-real Estate [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 443 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 427 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_ConsumerNonRealEstateMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Other Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 338 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 230 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_OtherLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 4 [Member] | Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 4,503 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember |  | 7,917 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFourMember
Grade 5 [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | 293 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeFiveMember |  | 146 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_InternalCreditAssessmentAxis = banf_GradeFiveMember
Grade 5 [Member] | Acquired Loans [Member] |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |
Total loans | $ 293 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFiveMember |  | $ 146 us-gaap_LoansAndLeasesReceivableGrossCarryingAmount / us-gaap_FinancialInstrumentAxis = banf_AcquiredLoansMember / us-gaap_InternalCreditAssessmentAxis = banf_GradeFiveMember

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- Definition Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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