Stockholders' Equity - Required Capital Amounts and Company's Respective Ratios (Detail) $ in Thousands	Sep. 30, 2015 USD ($)
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital Amount	$ 662,299
Total Capital To Risk Weighted Assets Actual Ratio	15.27%
Capital Required For Capital Adequacy Amount	$ 346,902
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Common Equity Tier 1 Risk Based Capital Amount	$ 595,329
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	13.73%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 195,133
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	4.50%
Tier 1 Risk Based Capital Amount	$ 621,329
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	14.33%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 260,177
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Capital Amount	$ 621,329
Tier 1 Capital To Average Assets Ratio	9.77%
Tier 1 Capital Required For Capital Adequacy Amount	$ 256,245
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	$ 606,989
Total Capital To Risk Weighted Assets Actual Ratio	14.08%
Capital Required For Capital Adequacy Amount	$ 344,890
Capital Required For Capital Adequacy to Risk Weighted Assets Ratio	8.00%
Capital Required To Be Well Capitalized Amount	$ 431,113
Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	10.00%
Common Equity Tier 1 Risk Based Capital Amount	$ 546,019
Common Equity Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	12.67%
Common Equity Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 194,001
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 Required To Be well Capitalized Amount	$ 280,223
Common Equity Tier 1 Risk Based Capital Required To Be well Capitalized Amount	6.50%
Tier 1 Risk Based Capital Amount	$ 566,019
Tier 1 Risk Based Capital To Risk Weighted Assets Ratio	13.13%
Tier 1 Risk Based Capital Required For Capital Adequacy Amount	$ 258,668
Tier 1 Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets Ratio	6.00%
Tier 1 Risk Based Capital Required To Be well Capitalized Amount	$ 344,890
Tier 1 Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets Ratio	8.00%
Tier 1 Capital Amount	$ 566,019
Tier 1 Capital To Average Assets Ratio	8.91%
Tier 1 Capital Required For Capital Adequacy Amount	$ 255,669
Tier 1 Capital Required For Capital Adequacy To Average Assets Ratio	4.00%
Tier 1 Capital Required To Be Well Capitalized Amount	$ 319,586
Tier 1 Capital Required To Be Well Capitalized To Average assets Ratio	5.00%