Assets Acquired In FDIC-Assisted Acquisitions (Rollforward Of Acquired Loans Deterioration Of Credit Quality) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended				6 Months Ended		12 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2012 Loans with Deterioration of Credit Quality	Jun. 30, 2011 Loans with Deterioration of Credit Quality	Dec. 31, 2011 Loans with Deterioration of Credit Quality	Jun. 30, 2012 Loans without Deterioration of Credit Quality	Jun. 30, 2011 Loans without Deterioration of Credit Quality	Dec. 31, 2011 Loans without Deterioration of Credit Quality
Balance, January 1	$ 29,537	$ 37,383	$ 22,423	$ 20,132		$ 307,790	$ 252,535	$ 252,535	$ 266,966	$ 302,456	$ 302,456
Change in estimate of cash flows, net of charge-offs or recoveries						(3,702)	(6,681)	(25,787)	1,152		(11,604)
Additions due to acquisitions	9,863	24,094				73,414		124,136	51,367		35,439
Other (loan payments, transfers, etc.)						(44,164)	(2,648)	(43,094)	(42,627)	(59,173)	(59,325)
Ending balance	$ 203,801	$ 242,394		$ 160,927	$ 177,187	$ 333,338	$ 243,206	$ 307,790	$ 276,858	$ 243,283	$ 266,966