Stockholders' Equity - Required Capital Amounts and Company's Respective Ratios (Detail) $ in Thousands	Jun. 30, 2016 USD ($)
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital Amount	$ 689,071
Total Capital To Risk Weighted Assets Actual Ratio	14.46%
Capital Required For Capital Adequacy Amount	$ 381,153
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Capital With Capital Conservation Buffer Amount	$ 410,931
Capital With Capital Conservation To Risk Based Weighted Assets Buffer Ratio	8.625%
Common Equity Tier 1 Risk Based Capital Amount	$ 611,505
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	12.83%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 214,399
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	4.50%
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 244,176
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	5.125%
Tier 1 Risk Based Capital Amount	$ 642,505
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	13.49%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 285,865
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 315,642
Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	6.625%
Tier 1 Capital Amount	$ 642,505
Tier 1 Capital To Average Assets Ratio	9.65%
Tier 1 Capital Required For Capital Adequacy Amount	$ 266,346
Tier 1 Capital Required For Capital Adequacy To Average Assets Ratio	4.00%
BancFirst [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital Amount	$ 629,830
Total Capital To Risk Weighted Assets Actual Ratio	13.23%
Capital Required For Capital Adequacy Amount	$ 380,759
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Capital With Capital Conservation Buffer Amount	$ 410,505
Capital With Capital Conservation To Risk Based Weighted Assets Buffer Ratio	8.625%
Capital Required To Be Well Capitalized Amount	$ 475,948
Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	10.00%
Common Equity Tier 1 Risk Based Capital Amount	$ 563,264
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	11.83%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 214,177
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	4.50%
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 243,924
Common Equity Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	5.125%
Common Equity Tier 1 Risk Based Capital Required To Be well Capitalized Amount	$ 309,366
Common Equity Tier 1 Risk Based Capital Required To Be well Capitalized Amount	6.50%
Tier 1 Risk Based Capital Amount	$ 583,264
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	12.25%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 285,569
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Risk Based Capital With Capital Conservation Buffer Amount	$ 315,316
Tier 1 Risk Based Capital With Capital Conservation Buffer To Risk Weighted Assets Ratio	6.625%
Tier 1 Risk Based Capital Required To Be well Capitalized Amount	$ 380,759
Tier 1 Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	8.00%
Tier 1 Capital Amount	$ 583,264
Tier 1 Capital To Average Assets Ratio	8.77%
Tier 1 Capital Required For Capital Adequacy Amount	$ 265,942
Tier 1 Capital Required For Capital Adequacy To Average Assets Ratio	4.00%
Tier 1 Capital Required To Be Well Capitalized Amount	$ 332,427
Tier 1 Capital Required To Be Well Capitalized To Average assets Ratio	5.00%