Other Noninterest Income and Other Noninterest Expense - Components of Other Noninterest Income and Other Noninterest Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other noninterest income:
Income from bank-owned life insurance	$ 11,163	$ 9,311	$ 5,219
Credit-related fees	6,681	5,752	1,451
Income from derivatives	3,600	760
Gain on sales of assets	4,366	1,083	618
Safety deposit box income	2,006	1,591	841
Other miscellaneous income	9,072	7,081	3,896
Total other noninterest income	36,888	25,578	12,025
Other noninterest expense:
Advertising	13,515	17,687	7,713
Ad valorem and franchise taxes	8,321	5,330	3,568
Printing and supplies	7,491	5,608	2,380
Insurance expense	5,494	7,490	2,010
Travel	5,758	3,590	2,137
Entertainment and contributions	6,049	3,954	1,651
Tax credit investment amortization	5,974	3,515
Other expense	26,053	31,539	13,671
Total other noninterest expense	$ 78,655	$ 78,713	$ 33,130