XML 116 R103.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Commitments and Contingent Liabilities - Summary of Financial Instruments with Off-Balance-Sheet Risks (Detail) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Commitments And Contingencies Disclosure [Abstract] |  |
Loan commitments | $ 1,232,996 | $ 1,050,686
Stand-by letters of credit | $ 56,096 | $ 57,074

X
- 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

X
- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant