FDIC loss share (expense) income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
F D I C Loss Share Expense Income [Line Items]
(Amortization) accretion of indemnification asset	$ (38,557)		$ (37,413)		$ (78,761)		$ (66,788)
80% mirror accounting on credit impairment losses	25,338	[1]	29,426	[1]	39,383	[1]	42,848
80% mirror accounting on reimbursable expenses	12,131		10,775		19,914		13,042
80% mirror accounting on discount accretion on loans and unfunded commitments accounted for under ASC 310-20	(193)		(248)		(386)		(496)
Change in true-up payment obligation	(476)		(236)		(7,251)		(1,858)
Other	(1,998)		271		(2,920)		572
FDIC loss share (expense) income	$ (3,755)		$ 2,575		$ (30,021)		$ (12,680)

[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.