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Stockholders' Equity - Additional Information (Detail) (USD $) | 3 Months Ended
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Mar. 31, 2015
Stockholders Equity [Line Items] |
Minimum Tier 1 Ratio to be well capitalized | 8.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Minimum Common Equity Tier 1 Ratio to be well capitalized | 6.50%banf_CommonEquityTierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Minimum Total Capital Ratio to be well capitalized | 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
Minimum Leverage Ratio to be well capitalized | 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
2015 [Member] |
Stockholders Equity [Line Items] |
Implementation of the deductions and other adjustments to CET1 | 4 years
Implementation of the deductions and other adjustments to CET1, Percentage | 40.00%banf_ImplementationOfDeductionsAndOtherAdjustmentsToCETOnePercentage / us-gaap_CreationDateAxis = banf_TwoThousandAndFifteenMember
After 2015 [Member] |
Stockholders Equity [Line Items] |
Implementation of the deductions and other adjustments to CET1, Additional Percentage | 20.00%banf_ImplementationOfDeductionsAndOtherAdjustmentsToCETOneAdditionalPercentage / us-gaap_CreationDateAxis = banf_AfterJanuaryOneTwoThousandFifteenMember
2016 [Member] |
Stockholders Equity [Line Items] |
Implementation of the capital conservation buffer, Percentage | 0.625%banf_TierOneCapitalConservationBufferToRiskWeightedAssetsRequiredUnderRegulatory / us-gaap_CreationDateAxis = banf_TwoThousandAndSixteenMember
Capital conservation buffer implementation phase-out period | 4 years
2019 [Member] |
Stockholders Equity [Line Items] |
Capital Conservation Buffer Maximum Level | 2.50%banf_TierOneCapitalConservationBufferMaximumLevel / us-gaap_CreationDateAxis = banf_TwoThousandAndNineteenMember
Maximum [Member] |
Stockholders Equity [Line Items] |
Quantitative limit for trust preferred securities to be included in tier 1 capital | 15,000,000,000 banf_QuantitativeLimitForTrustPreferredSecuritiesToBeIncludedInTierOneCapital / us-gaap_RangeAxis = us-gaap_MaximumMember

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- Definition Common equity tier one risk based capital required to be well capitalized to risk weighted assets. + References No definition available. + Details
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- Definition Implementation of deductions and other adjustments to CET one. + References No definition available. + Details
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- Definition Implementation of deductions and other adjustments to CET one additional Percentage. + References No definition available. + Details
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- Definition Implementation of deductions and other adjustments to CET one percentage. + References No definition available. + Details
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- Definition Quantitative limit for trust preferred securities to be included in tier one capital. + References No definition available. + Details
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- Definition Tier one capital conservation buffer maximum level. + References No definition available. + Details
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- Definition Tier one capital conservation buffer to risk weighted assets required under regulatory. + References No definition available. + Details
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- Definition The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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- Definition The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826 + Details
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