Employee Benefit Plans - Net Period Benefit Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Service cost	$ 1,953	$ 1,735	$ 1,933
Interest cost	875	714	645
Expected return on plan assets	(568)	(514)	(401)
Amortization of actuarial (gain)/loss	(159)	(153)	256
Net periodic benefit cost	$ 2,101	$ 1,782	$ 2,433