Other Noninterest Income and Other Noninterest Expense - Components of Other Noninterest Income and Other Noninterest Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other noninterest income:
Income from bank-owned life insurance	$ 10,881	$ 10,314	$ 11,223
Credit-related fees	11,057	11,121	8,724
Income from derivatives	2,745	1,645	4,675
Gain on sales of assets	186	1,279	1,932
Safety deposit box income	1,758	1,830	1,923
Other miscellaneous income	9,334	9,249	8,754
Total other noninterest income	35,961	35,438	37,231
Other noninterest expense:
Advertising	11,225	8,937	10,399
Ad valorem and franchise taxes	10,498	10,492	9,727
Printing and supplies	4,851	4,550	5,112
Insurance expense	3,482	3,919	4,094
Travel	5,331	4,066	4,716
Entertainment and contributions	6,723	5,762	5,265
Tax credit investment amortization	8,513	8,817	10,781
Other miscellaneous expense	21,580	30,585	45,242
Total other noninterest expense	$ 72,203	$ 77,128	$ 95,336