Recent Developments Including Mergers and Acquisitions - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Community	Dec. 31, 2015 USD ($)	Oct. 08, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 24, 2014 USD ($)
Business Combination Separately Recognized Transactions [Line Items]
Goodwill	$ 54,042,000	$ 54,042,000		$ 44,962,000
Number of additional banking communities | Community	2
Bank of Commerce [Member]
Business Combination Separately Recognized Transactions [Line Items]
Total assets acquired			$ 196,000,000
Loans			147,000,000
Deposits			175,000,000
Equity capital			$ 22,000,000
Percentage of voting interests acquired			100.00%
Intangibles assets, net			$ 7,100,000
Goodwill			$ 9,400,000
The Bank of Union [Member] | BancFirst [Member]
Business Combination Separately Recognized Transactions [Line Items]
Loans					$ 121,000,000
Deposits					302,000,000
Equity capital					4,800,000
Intangibles assets, net					2,200,000
Goodwill					417,000
Other real estate					$ 10,000