Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Foreign operating loss carryforwards	$ 35,394	$ 41,611
Pension and other benefit programs	39,633	37,397
Foreign tax credit carryforwards	11,423	17,356
Accrued liabilities	10,726	11,114
Other credit carryforwards	6,707	5,815
Other	11,161	9,035
State and local operating loss carryforwards	2,058	2,272
Inventories	2,366	2,153
Allowance for doubtful accounts	746	704
Currency differences	1,407
Total deferred tax assets	121,621	127,457
Deferred tax liabilities:
Property, plant and equipment and intangibles -- depreciation and amortization	23,617	28,601
Unremitted earnings of foreign subsidiaries	1,594	1,575
Other	2,115	2,784
Total deferred tax liabilities	27,326	32,960
Net deferred tax assets before valuation allowance	94,295	94,497
Valuation allowance	(10,447)	(24,577)
Net deferred tax assets	$ 83,848	$ 69,920