Employee Benefits (Detail) - Components of Net Periodic Pension Expense - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 2,780	$ 2,620	$ 2,630
Interest cost	850	790	1,190
Expected return on plan assets	(375)	(345)	(540)
Recognition of actuarial loss	200	300	75
Recognition of termination benefits	0	85	30
Total defined benefit pension expense	$ 3,455	$ 3,450	$ 3,385