Note FDIC loss share (expense) income (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Disclosure F D I C Loss Share Expense Income [Abstract]
Accretion (amortization)	$ 0		$ 147	$ (934)		$ (629)
80% mirror accounting on credit impairment losses (reversal)	0		2,126	104		2,274
80% mirror accounting on reimbursable expenses	0		723	537		1,644
80% mirror accounting on recoveries on covered assets, including rental income on OREOs, subject to reimbursement to the FDIC	0		(400)	(1,658)		4,433
Change in true-up payment obligation	0		(3,125)	(6,112)		(10,510)
Gain on FDIC LSA termination agreement	102,752	[1]	0	102,752	[1]	0
Other	0		54	36		(5,944)
FDIC loss share (expense) income	$ 102,752		$ (475)	$ 94,725		$ (8,732)

[1] Refer to Note 9 for additional information of the Termination Agreement with the FDIC.