FDIC loss share (expense) income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
F D I C Loss Share Expense Income [Line Items]
(Amortization) accretion of indemnification asset	$ (29,184)		$ (21,072)		$ (95,972)		$ 13,361
80% mirror accounting on credit impairment losses	18,095	[1]	20,458	[1]	60,943	[1]	71,787	[1]
80% mirror accounting on reimbursable expenses	7,378	[2]	(447)	[2]	19,846	[2]	570	[2]
80% mirror accounting on discount accretion on loans and unfunded commitments accounted for under ASC 310-20	(248)		(2,916)		(744)		(32,919)
Change in true-up payment obligation	(2,991)		(1,640)		(4,849)		(4,684)
Other	243		256		1,389		1,229
FDIC loss share (expense) income	$ (6,707)		$ (5,361)		$ (19,387)		$ 49,344

[1] Reductions in expected cash flows for ASC 310-30 loans, which may impact the provision for loan losses, may consider reductions in both principal and interest cash flow expectations. The amount covered under the FDIC loss sharing agreements for interest not collected from borrowers is limited under the agreements (approximately 90 days); accordingly, these amounts are not subject fully to the 80% mirror accounting.

[2] Amounts presented are net of the mirror accounting on gains on sales of foreclosed assets.