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Commitments and Contingent Liabilities - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2014 Buildings ParkingSpaces ATM Land_Parcel StorageSpaces
Commitments And Contingencies Disclosure [Abstract] |
Number of buildings | 13 banf_NumberOfLeasedBuildings
Parcels of land | 2 banf_NumberOfLeasedParcelsOfLand
Number of ATM locations | 19 banf_NumberOfLeasedATMLocations
Number of storage facilities | 2 banf_NumberOfStorageFacilities
Number of parking lots | 3 banf_NumberOfParkingLots
Lease expiry period maximum | 2064

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- Definition Lease expiry period maximum. + References No definition available. + Details
Name: | banf_LeaseExpiryPeriodMaximum
Namespace Prefix: | banf_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of leased ATM locations. + References No definition available. + Details
Name: | banf_NumberOfLeasedATMLocations
Namespace Prefix: | banf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of leased buildings. + References No definition available. + Details
Name: | banf_NumberOfLeasedBuildings
Namespace Prefix: | banf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of leased parcels of land. + References No definition available. + Details
Name: | banf_NumberOfLeasedParcelsOfLand
Namespace Prefix: | banf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of parking lots. + References No definition available. + Details
Name: | banf_NumberOfParkingLots
Namespace Prefix: | banf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of storage facilities. + References No definition available. + Details
Name: | banf_NumberOfStorageFacilities
Namespace Prefix: | banf_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration