Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Activity in the Allowance for Covered Loan Losses) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Allowance for Covered Loan Losses [Roll Forward]
Balance at beginning of period	$ 1,319	$ 1,322
Provision for covered loan losses before benefit attributable to FDIC loss share agreements	(303)	(838)
Benefit attributable to FDIC loss share agreements	242	670
Net provision for covered loan losses	(61)	(168)
Increase in FDIC indemnification liability	(242)	(670)
Loans charged-off	(120)	(336)
Recoveries of loans charged-off	178	926
Net (charge-offs) recoveries	58	590
Balance at end of period	$ 1,074	$ 1,074