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Line of Credit - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2019 USD ($)
Debt Instrument [Line Items] |
Maximum drawing capacity | $ 632,000,000.0
FHLB stock holdings | 554,000
Advances outstanding | 0
Residential Mortgage [Member] |
Debt Instrument [Line Items] |
Line of credit assets pledged as collateral | 814,200,000
Revolving Line of Credit Member] |
Debt Instrument [Line Items] |
Maximum drawing capacity | 10,000,000.0
Advances outstanding | $ 0
Description of variable interest rate | prime rate minus 25 basis points
Line of credit maturity year | 2020

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- Definition Line of credit maturity year. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Line of credit residential first mortgages pledged as collateral. + 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 The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
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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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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | debit
Period Type: | instant

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- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | credit
Period Type: | instant

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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Balance Type: | credit
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- Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |