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Fair Value Measurements - Additional Information (Detail) (USD $) | 6 Months Ended
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Jun. 30, 2013
Fair Value Disclosures [Abstract] |
Loan held for sale selling period | 30 days
Amount of non-financial assets (liabilities) | $ 0
Non-financial assets or liabilities for which no impairment was provided | $ 0

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- Definition Mortgage Loans Selling Period + References No definition available. + Details
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Namespace Prefix: | banf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Non Financial Assets Liabilities For Which No Impairment Provided + References No definition available. + Details
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Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Non Financial Assets Liabilities Value + 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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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration