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Retirement Plans - Aggregate Amounts of Contributions to the 401(k) and ESOP Plans (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |
Total contributions | $ 3,558 | $ 3,393 | $ 3,163
401(k) contributions [Member] |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |
Aggregate amounts of contributions | 1,738 | 1,690 | 1,534
ESOP contributions [Member] |  |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |  |
Aggregate amounts of contributions | $ 1,820 | $ 1,703 | $ 1,629

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- Definition Aggregate Contribution By Employer + References No definition available. + Details
Name: | banf_AggregateContributionByEmployer
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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