Pension and Other Postretirement Benefit Plans Projected Benefit Obligation and Fair Value of Plan Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Projected Benefit Obligation:
Projected benefit obligation at beginning of year	$ 63,398	$ 56,082
Service cost	1,453	1,494	$ 1,456
Prior service cost	(157)	0	0
Interest cost	1,244	1,121	1,329
Amendments/curtailments	1,219	0
Benefits paid	(1,349)	(1,212)
Administrative expenses	0	(35)
Actuarial (gain) loss, net	(383)	(1,005)
Unrealized (gain) loss on foreign exchange	(2,316)	6,953
Projected benefit obligation at end of year	60,671	63,398	56,082
Fair Value of Plan Assets:
Fair value of plan assets at beginning of year	53,145	46,134
Increase in plan asset value	2,251	919
Employer contributions	1,282	1,595
Benefits paid	(1,349)	(1,212)
Administrative expenses	(37)	(35)
Unrealized gain (loss) on foreign exchange	(2,019)	5,744
Fair value of plan assets at end of year	53,273	53,145	$ 46,134
Under-funded status of the plan at end of the year	(7,398)	(10,253)
Accumulated Benefit Obligation	$ 55,863	$ 56,035