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Stock-Based Compensation - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2014
May 31, 2013
May 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of options granted for non-employee director 10,000banf_NumberOfOptionsGrantedForEachNonEmployeeDirector    
Deferred board fees percentage for stock units accumulation 100.00%banf_BoardFeesDeferredPercentageForCreditToStockUnits    
Nonqualified Incentive Stock Option Plan [Member] | Stock Option [ Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of shares to be issued under incentive stock option plan   3,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= banf_BankFirstISOPMember		  
Shares for future grants 114,985us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= banf_BankFirstISOPMember		    
Stock option plan termination date Dec. 31, 2019    
Option exercisable rate 25.00%banf_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionExercisableRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= banf_BankFirstISOPMember		    
Option exercisable period 4 years    
Options expire period 15 years    
Share based compensation options exercisable period 2021    
Vesting period in years, start 4 years    
Options vest and exercisable Description The options vest and are exercisable beginning four years from the date of grant at the rate of 25% per year for four years. Options expire at the end of fifteen years from the date of grant    
Vesting period in years 7 years    
Nonqualified Incentive Stock Option Plan [Member] | Stock Option [ Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Stock price percentage to fair value at grant date 100.00%banf_ShareBasedCompensationByShareBasedPaymentAwardPercentageOfStockPriceToFairValueAtGrantDate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= banf_BankFirstISOPMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		    
Non-Employee Directors Stock Option Plan [ Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of shares to be issued under incentive stock option plan     230,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= banf_NonEmployeeDirectorsStockOptionPlanMember
Shares for future grants 20,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= banf_NonEmployeeDirectorsStockOptionPlanMember		    
Option exercisable rate 25.00%banf_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionExercisableRate
/ us-gaap_PlanNameAxis
= banf_NonEmployeeDirectorsStockOptionPlanMember		    
Option exercisable period 1 year    
Options expire period 15 years    
Share based compensation options exercisable period 2018    
Options vest and exercisable Description The options vest and are exercisable beginning one year from the date of grant at the rate of 25% per year for four years    
Vesting period in years 4 years    
Non-Employee Directors Stock Option Plan [ Member] | Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Stock price percentage to fair value at grant date 100.00%banf_ShareBasedCompensationByShareBasedPaymentAwardPercentageOfStockPriceToFairValueAtGrantDate
/ us-gaap_PlanNameAxis
= banf_NonEmployeeDirectorsStockOptionPlanMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		    
Banc First Deferred Stock Compensation Plan [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of shares authorized for issuance under deferred compensation plan     91,110us-gaap_DeferredCompensationArrangementWithIndividualSharesAuthorizedForIssuance
/ us-gaap_PlanNameAxis
= banf_BancFirstDeferredStockCompensationPlanMember