Assets Acquired In FDIC-Assisted Acquisitions - Rollforward of Acquired Loans Deterioration of Credit Quality (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2010
Balance, beginning of year	$ 29,537	$ 37,383	$ 16,698
Additions due to acquisitions	9,863	24,094
Balance, end of year	159,724	242,394		177,187
Loans With Deterioration Of Credit Quality [Member]
Balance, beginning of year	307,790	252,535
Change in estimate of cash flows, net of charge-offs or recoveries	(17,712)	(25,787)
Additions due to acquisitions	73,414	124,136
Other (loan payments, transfers, etc.)	(80,755)	(43,094)
Balance, end of year	282,737	307,790
Loans without Deterioration of Credit Quality [Member]
Balance, beginning of year	266,966	302,456
Change in estimate of cash flows, net of charge-offs or recoveries	1,376	(11,604)
Additions due to acquisitions	51,368	35,439
Other (loan payments, transfers, etc.)	(91,108)	(59,325)
Balance, end of year	$ 228,602	$ 266,966