Pension Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 203	$ 189	$ 118
Interest cost	1,465	1,436	1,362
Expected return on plan assets	(1,824)	(1,849)	(1,792)
Recognized net actuarial loss	522	583	16
Net periodic pension cost (income)	$ 366	$ 359	$ (296)