Other Income (Expense) - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Income And Expenses [Abstract]
Income From Third Party License Fees	$ 189	$ 202	$ 439	$ 471
Foreign Exchange (Losses) Gains, Net	(493)	249	(722)	35
Gain (loss) on Fixed Asset Disposals, Net	547	13	599	28
Non-Income Tax Refunds and Other Related Credits	505	324	541	618
Pension and Post Retirement Benefit Costs Non-service Components	(569)	(2,436)	(1,145)	(3,002)
Other Nonoperating Income	102	110	259	241
Other Nonoperating Expense	(20)	(33)	(79)	(67)
Total Other (Expense) Income, Net	$ 261	$ (1,571)	$ (108)	$ (1,676)
Property Plant And Equipment Additional Disclosures			Gain on fixed asset disposals, net, during the three and six months ended June 30, 2018 includes a $0.6 million gain on the sale of an available-for-sale asset.