Credit Quality Assessment (Summary of Impaired Loans) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Credit Quality Assessment [Abstract]
Impaired loans with a specific allowance	$ 14,208	$ 11,411	$ 12,217
Impaired loans without a specific allowance	14,719	18,008	20,306
Total impaired loans	28,927	29,419	32,523
Allowance for loan and lease losses related to impaired loans	3,375	2,894	3,058
Allowance for loan and lease losses related to loans collectively evaluated	37,520	34,908	35,708
Total allowance for loan and lease losses	40,895	37,802	38,766
Average impaired loans for the period	29,828	34,331	38,379
Contractual interest income due on impaired loans during the period	2,527	2,339	2,612
Interest income on impaired loans recognized on a cash basis	961	773	1,374
Interest income on impaired loans recognized on an accrual basis	$ 274	$ 280	$ 473