Employee Benefits - Benefit Obligation and Plan Assets Deriving Funded Status, in Other Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Actuarial Gain (Loss)	$ (4,257)	$ 16,020
Change in Projected Benefit Obligation
Projected benefit obligation at beginning of year	113,124	95,969
Service cost	2,601	2,369	$ 2,767
Interest cost	4,425	4,470	3,985
Benefits paid	(6,146)	(5,704)
Projected Benefit Obligation at End of Year	109,747	113,124	95,969
Change in Plan Assets
Fair value of plan assets at beginning of year	93,486	89,556
Actual return on plan assets	(2,755)	9,634
Benefits paid	(6,146)	(5,704)
Fair Value of Plan Assets at End of Year	84,585	93,486	$ 89,556
Funded Status	$ (25,162)	$ (19,638)