Note FDIC loss share (expense) income (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure F D I C Loss Share Expense Income [Abstract]
Accretion of loss share indemnification asset, net		$ 567	$ (1,259)	$ (62)	$ (9,337)
80% mirror accounting on credit impairment losses (reversal)	[1]	(329)	659	1,945	(959)
80% mirror accounting on reimbursable expenses		588	853	2,232	7,038
80% mirror accounting on recoveries on covered assets, including rental income on OREOs, subject to reimbursement to the FDIC		(1,601)	(522)	2,832	(5,123)
Change in true-up payment obligation		(3,208)	(6,611)	(13,718)	(14,742)
Arbitration decision charge		0	(54,924)	0	(54,924)
Other		35	81	(5,909)	602
FDIC loss share (expense) income		$ (3,948)	$ (61,723)	$ (12,680)	$ (77,445)

[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.