Junior Subordinated Debentures - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended
	Oct. 08, 2015	Mar. 31, 2004	Feb. 29, 2004	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Junior Subordinated Debentures [Line Items]
Junior subordinated notes assumed				$ 31,959,000	$ 26,804,000
Issuance of common securities				$ 4,428,000	$ 6,532,000	$ 5,200,000
BancFirst Capital Trust Two [Member] | Subordinated Debentures Subject to Mandatory Redemption [Member]
Junior Subordinated Debentures [Line Items]
Interest rate of securities				7.20%
Frequency of payment				Payable January 15, April 15, July 15 and October 15 of each year
Junior subordinated notes assumed				$ 26,800,000
Debt instrument maturity date				Mar. 31, 2034
BancFirst Capital Trust Two [Member] | Cumulative Preferred Stock [Member]
Junior Subordinated Debentures [Line Items]
Issue of securities		$ 1,000,000	$ 25,000,000
Cumulative trust preferred securities interest rate				7.20%
CSB Bancshares Statutory Trust I [Member]
Junior Subordinated Debentures [Line Items]
Issuance of capital securities	$ 5,000,000
Issuance of common securities	155,000
CSB Bancshares Statutory Trust I [Member] | Subordinated Deferrable Interest Debentures [Member]
Junior Subordinated Debentures [Line Items]
Frequency of payment				Payable March 15, June 15, September 15 and December 15 of each year
Junior subordinated notes assumed	$ 5,200,000
Debt instrument maturity date	Sep. 15, 2036
CSB Bancshares Statutory Trust I [Member] | Subordinated Deferrable Interest Debentures [Member] | LIBOR [Member]
Junior Subordinated Debentures [Line Items]
Debt instrument, Basis point rate	1.82%