Stockholders' Equity - Additional Information (Detail)	Jun. 30, 2019 USD ($)
Maximum [Member]
Stockholders Equity [Line Items]
Quantitative limit for trust preferred securities to be included in tier 1 capital	$ 15,000,000,000

Quantitative limit for trust preferred securities to be included in tier one capital.

No definition available.

Name:	banf_QuantitativeLimitForTrustPreferredSecuritiesToBeIncludedInTierOneCapital
Namespace Prefix:	banf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant