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Commitments and Contingent Liabilities - Summary of Financial Instruments with Off-Balance-Sheet Risks (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Commitments And Contingencies Disclosure [Abstract] |  |
Loan commitments | $ 937,221 banf_UnfundedLoanCommitments | $ 945,270 banf_UnfundedLoanCommitments
Stand-by letters of credit | $ 63,734 banf_StandbyLettersOfCredit | $ 61,262 banf_StandbyLettersOfCredit

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- Definition Standby letters of credit. + References No definition available. + Details
Name: | banf_StandbyLettersOfCredit
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Unfunded loan commitments. + References No definition available. + Details
Name: | banf_UnfundedLoanCommitments
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration