Pension and Postretirement Benefits (Change in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Postretirement Medical Benefits
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Balance — January 1	$ 2,425	$ 880
Amortization of net loss	(164)	(584)
Amortization of prior service cost	94	93
Net gain (loss) arising during the year	(1,699)	2,036
Prior service cost arising during the year	(122)	(122)	$ (122)
Balance — December 31	656	2,425	880
United States | Pension Plan
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Balance — January 1	(62,018)	(49,790)
Amortization of net loss	2,809	4,216
Amortization of prior service cost	125	125
Net gain (loss) arising during the year	9,785	(16,216)
Settlement gain	0	(353)
Prior service cost arising during the year	(211)	0
Balance — December 31	(49,510)	(62,018)	(49,790)
Foreign Plan | Pension Plan
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Balance — January 1	(62,088)	(67,872)
Amortization of net loss	2,946	3,260
Net gain (loss) arising during the year	(29,910)	2,458
Prior service cost arising during the year	(265)	(33)	4
Settlement loss (gain)	746	(386)
Prior service cost arising during the year	0	(3,080)
Currency translation impact and other	(1,031)	3,532
Balance — December 31	$ (89,337)	$ (62,088)	$ (67,872)