Geographic Information - Net Sales to External Customers Based Upon Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Geographic Reporting Disclosure [Line Items]
Sales	$ 92,953	$ 70,736	$ 60,564	$ 79,515	$ 104,141	$ 90,516	$ 93,491	$ 93,617	$ 303,768	$ 381,765	$ 403,627
United States and Canada
Geographic Reporting Disclosure [Line Items]
Sales									119,769	151,646	156,242
Americas-Other
Geographic Reporting Disclosure [Line Items]
Sales									9,057	14,110	15,086
Germany
Geographic Reporting Disclosure [Line Items]
Sales									46,166	52,083	53,251
Europe-Other
Geographic Reporting Disclosure [Line Items]
Sales									45,224	70,196	74,010
Japan
Geographic Reporting Disclosure [Line Items]
Sales									4,998	33,361	37,607
China
Geographic Reporting Disclosure [Line Items]
Sales									31,748	32,934	36,130
Asia-Other
Geographic Reporting Disclosure [Line Items]
Sales									$ 46,806	$ 27,435	$ 31,301