XML 26 R42.htm IDEA: XBRL DOCUMENT v2.4.1.9
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
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans $ 3,857,742us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 3,860,831us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 3,542,270us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Non-residential Real Estate Owner Occupied [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 486,858us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
  458,794us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
Non-residential Real Estate Other [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 957,182us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
  879,505us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
Residential Real Estate Permanent Mortgage [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 312,777us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
  273,204us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
Residential Real Estate All Other [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 639,621us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
  567,747us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
Non-consumer Non-real Estate [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 963,610us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
  828,039us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
Consumer Non-real Estate [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 242,202us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
  225,962us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
Other Loans [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 165,128us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
  148,211us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
Acquired Loans [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 90,364us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
  160,808us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
Grade 1 [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans 3,240,546us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  2,943,976us-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 403,255us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  381,290us-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 794,097us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  724,181us-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 276,186us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  240,653us-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 526,322us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  474,152us-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 811,529us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  673,757us-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 227,722us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  212,492us-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 158,895us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  144,870us-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 42,540us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeOneMember
  92,581us-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 511,088us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  520,907us-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 77,545us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  70,949us-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 127,716us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  129,390us-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 29,103us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  25,074us-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 100,008us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  86,033us-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 125,609us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  147,625us-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 12,321us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  11,388us-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 5,116us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  2,375us-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 33,670us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeTwoMember
  48,073us-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 89,764us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  59,144us-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 5,590us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  6,052us-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 30,255us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  20,155us-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 6,743us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  6,610us-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 11,216us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  6,495us-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 24,107us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  5,350us-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 1,716us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  1,655us-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 779us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  736us-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 9,358us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeThreeMember
  12,091us-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 16,051us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  18,097us-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 468us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOwnerOccupiedMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  503us-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 5,114us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonResidentialRealEstateOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  5,779us-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 745us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstatePermanentMortgageMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  867us-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 2,075us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ResidentialRealEstateAllOtherMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  1,067us-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 2,365us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_NonConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  1,307us-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 443us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  427us-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 338us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_OtherLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  230us-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 4,503us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFourMember
  7,917us-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 293us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFiveMember
  146us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFiveMember
Grade 5 [Member] | Acquired Loans [Member]      
Financing Receivable, Allowance for Credit Losses [Line Items]      
Total loans $ 293us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFiveMember
  $ 146us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancialInstrumentAxis
= banf_AcquiredLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= banf_GradeFiveMember