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Cash Due from Banks Interest-Bearing Deposits and Federal Funds Sold - Summary of Average Amount of Required Reserves (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Average Amount Of Required Reserves [Abstract] |  |
Vault cash and funds on deposit with the Federal Reserve Bank | $ 1,804,028 banf_VaultCashAndFundsInBank | $ 1,758,908 banf_VaultCashAndFundsInBank
Average required reserves | $ 44,711 banf_VaultCashEquivalentsReserves | $ 37,456 banf_VaultCashEquivalentsReserves

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- Details
Name: | banf_AverageAmountOfRequiredReservesAbstract
Namespace Prefix: | banf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Vault cash and funds in bank. + References No definition available. + Details
Name: | banf_VaultCashAndFundsInBank
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Vault cash equivalents reserves. + References No definition available. + Details
Name: | banf_VaultCashEquivalentsReserves
Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant