Other Noninterest Expense - Components of Other Noninterest Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Advertising	$ 2,457	$ 2,858	$ 6,395	$ 7,216
Ad valorem and franchise taxes	3,098	2,809	8,397	7,193
Printing and supplies	1,189	1,143	3,467	3,963
Insurance expense	944	887	3,002	3,018
Travel expense	1,009	1,074	2,966	3,475
Entertainment and contributions	1,396	969	4,337	3,960
Tax credit investment amortization	2,220	4,880	6,590	7,553
Other miscellaneous	6,821	19,851	25,105	32,504
Total other noninterest expense	$ 19,134	$ 34,471	$ 60,259	$ 68,882