Note FDIC loss-share asset and true-up payment obligation (Activity in the FDIC loss share indemnification asset) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
FDIC Indemnification Asset [Roll Forward]
Beginning Balance	$ 46,316
Amortization	934
Credit impairment losses to be covered under loss sharing agreements	104
Reimbursable expenses	537
Net payment from FDIC under loss-sharing agreements	(364)
Ending Balance	45,659
Balance due to the FDIC for recoveries on covered assets	(1,190)
FDIC loss-share asset net	$ 44,469