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Fair Value Measurements - Additional Information (Detail) - USD ($) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 | Dec. 31, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Days from origination after which mortgage loans are sold | 30 days |
Amount of non-financial assets (liabilities) measured at fair value on a recurring basis | $ 0 | $ 0
Non-financial assets for which no impairment was provided | $ 0 | $ 0

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- Definition Non financial assets liabilities for which no impairment provided. + References No definition available. + Details
Name: | banf_NonFinancialAssetsLiabilitiesForWhichNoImpairmentProvided
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of non-financial assets (liabilities) measured at fair value on a recurring basis. + References No definition available. + Details
Name: | banf_NonFinancialAssetsLiabilitiesValue
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Period for sale of mortgage loan from origination. + References No definition available. + Details
Name: | banf_PeriodForSaleOfMortgageLoanFromOrigination
Namespace Prefix: | banf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration