FDIC loss share (expense) income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
F D I C Loss Share Expense Income [Line Items]
(Amortization) accretion of indemnification asset	$ (37,413)		$ 8,637		$ (66,788)		$ 34,433
80% mirror accounting on credit impairment losses	29,426	[1]	38,884	[1]	42,848	[1]	51,329	[1]
80% mirror accounting on reimbursable expenses	10,663		1,017		12,468		1,017
80% mirror accounting on discount accretion on loans and unfunded commitments accounted for under ASC 310-20	(248)		(8,538)		(496)		(30,003)
Change in true-up payment obligation	(236)		1,555		1,858		3,044
Other	383		225		1,146		973
FDIC loss share (expense) income	$ 2,575		$ 38,670		$ (12,680)		$ 54,705

[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.