Loans and Allowances for Loan Losses - Schedule of Activity in Loss Share Receivable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Receivables [Abstract]
Balance, January 1	$ 177,844	$ 231,085
Discount accretion		3,000
Charge-offs, write-downs and other losses	1,272	30,285
External expenses qualifying under loss share agreement	3,490	2,887
Payments received from the FDIC	(29,875)	(23,600)
Ending balance	$ 152,731	$ 243,656