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
	Mar. 31, 2016	Mar. 31, 2015
Allowance for Covered Loan Losses [Roll Forward]
Balance at beginning of period	$ 3,026	$ 2,131
Provision for covered loan losses before benefit attributable to FDIC loss share agreements	(1,946)	(529)
Benefit attributable to FDIC loss share agreements	1,557	423
Net provision for covered loan losses	(389)	(106)
Decrease in FDIC indemnification asset	(1,557)	(423)
Loans charged-off	(230)	(237)
Recoveries of loans charged-off	1,657	513
Net recoveries (charge-offs)	1,427	276
Balance at end of period	$ 2,507	$ 1,878