Pension plan and 401(k) Program - Change in Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Benefit obligation, beginning of year	$ 30,185	$ 32,594
Service cost	2,166	1,982	$ 2,087
Interest cost	197	253	238
Actuarial losses (gains)	771	(1,129)
Benefits paid	(2,446)	(4,767)
Translation adjustments and other	(101)	1,252
Benefit obligation, end of year	$ 30,772	$ 30,185	$ 32,594