XML 122 R109.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Commitments and Contingent Liabilities - Additional Information (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2017 StorageSpaces Land_Parcel ATM ParkingSpaces Buildings
Commitments And Contingencies Disclosure [Abstract] |
Parcels of land | Land_Parcel | 2
Number of ATM locations | ATM | 20
Number of storage facilities | StorageSpaces | 2
Number of parking lots | ParkingSpaces | 4
Number of buildings | Buildings | 13
Lease expiry period maximum | 2064

X
- 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
- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration