Fair Value Measurements Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	$ 17,152
Defined Benefit Plan, Benefit Obligation	5,259	$ 4,881	$ 5,033
Assets, Fair Value Disclosure	43
Financial and Nonfinancial Liabilities, Fair Value Disclosure	112	333
Restructuring Reserve	4,850	5,335
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	17,200	19,700
Assets, Fair Value Disclosure	43
Financial and Nonfinancial Liabilities, Fair Value Disclosure	112	333
French Voluntary Departure Plan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restructuring Reserve	806	2,409
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0	$ 0
Convertible Note due 2020 [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Debt, Fair Value Disclosures	66,800	$ 136,500
Convertible Note due 2024 [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Debt, Fair Value Disclosures	$ 131,900