Summary Information on Allowance for Loan and Lease Loss Activity (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year	$ 49,426	$ 62,135	$ 64,559
Provision for loan and lease losses	3,649	1,428	25,908
Loan and lease charge-offs	(12,804)	(16,505)	(32,616)
Loan and lease recoveries	2,686	2,368	4,284
Net charge-offs	(10,118)	(14,137)	(28,332)
Balance at period end	$ 42,957	$ 49,426	$ 62,135