Note FDIC loss share asset (Activity in the FDIC loss share indemnification asset) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018
Disclosure Activity In The F D I C Loss Share Indemnification Asset [Abstract]
Beginning Balance	$ 45,659	$ 64,077	$ 46,316	$ 69,334
FDIC loss-sharing termination agreement	(45,659)	0	(45,659)	0
Accretion (amortization)	0	147	(934)	(629)
Credit impairment losses (reversal) to be covered under loss sharing agreements	0	2,126	104	2,274
Reimbursable expenses	0	723	537	1,644
Net payment from FDIC under loss-sharing agreements	0	(14,003)	(364)	(14,003)
Other adjustments attributable to FDIC loss sharing agreements	0	0	0	(5,550)
Ending Balance	0	53,070	0	53,070
Balance due to the FDIC for recoveries on covered assets	0	(487)	0	(487)	$ 1,100
FDIC loss-share asset net	$ 0	$ 52,583	$ 0	$ 52,583	$ 45,600