Other Noninterest Expense - Components of Other Noninterest Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Statement [Abstract]
Insurance expense	$ 1,066	$ 1,597
Ad valorem and franchise taxes	2,202	2,207
Printing and supplies	1,309	2,471
Public relations and contributions	1,722	2,179
Travel expense	1,113	1,584
Other real estate owned expense, net	708	2,433
Tax credit investment amortization	1,426	1,513
Other miscellaneous	7,616	10,583
Total other noninterest expense	$ 17,162	$ 24,567