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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2023 | Dec. 31, 2022
Derivative [Line Items] |  |
Percentage share of total profit | 35.00% |
Other Assets [Member] | Oil and Gas Reserves [Member] |  |
Derivative [Line Items] |  |
Derivative instrument margin amount |  | $ 6.6
Other Liabilities [Member] | Oil and Gas Reserves [Member] |  |
Derivative [Line Items] |  |
Derivative instrument margin amount | $ 4.6 |

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- Definition Derivative instrument margin amount. + References No definition available. + Details
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Namespace Prefix: | banf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Derivative instrument, percentage of share profit. + References No definition available. + Details
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Namespace Prefix: | banf_
Data Type: | dtr-types:percentItemType
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
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=banf_OilAndGasReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |