Pension and Other Postretirement Benefit Plans Projected Benefit Obligation and Fair Value of Plan Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Projected Benefit Obligation:
Projected benefit obligation at beginning of year	$ 60,671	$ 63,398
Service cost	755	1,453	$ 1,494
Prior service cost		(157)
Interest cost	1,027	1,244	1,121
Amendments/curtailments	(2,621)	(1,219)
Benefits paid and administrative expenses	(1,229)	(1,349)
Actuarial (gain) loss, net	7,979	(383)
Unrealized (gain) loss on foreign exchange	(1,336)	(2,316)
Projected benefit obligation at end of year	65,246	60,671	63,398
Fair Value of Plan Assets:
Fair value of plan assets at beginning of year	53,273	53,145
Increase in plan asset value	6,905	2,251
Employer contributions	1,558	1,282
Benefits paid and administrative expenses	(1,246)	(1,386)
Unrealized gain (loss) on foreign exchange	(1,172)	(2,019)
Fair value of plan assets at end of year	59,318	53,273	$ 53,145
Under-funded status of the plan at end of the year	(5,928)	(7,398)
Accumulated Benefit Obligation	$ 65,246	$ 55,863