Other Noninterest Expense - Components of Other Noninterest Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Other Noninterest Expense [Line Items]
Insurance expense	$ 1,207	$ 1,724	$ 4,428	$ 2,878
Ad valorem and franchise taxes	2,185	1,768	6,608	4,362
Printing and supplies	1,488	1,846	6,162	3,931
Public relations and contributions	1,065	1,067	4,827	2,291
Travel expense	1,282	1,183	4,464	2,248
Other real estate owned expense, net	4,590	3,528	11,630	6,829
Tax credit investment amortization	1,513	1,513	4,538	1,728
Other miscellaneous	4,488	11,829	19,311	18,466
Total other noninterest expense	$ 17,818	$ 24,458	$ 61,968	$ 42,733