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