Geographic Information - Net Sales to External Customers Based Upon Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Geographic Reporting Disclosure [Line Items]
Sales	$ 104,141	$ 90,516	$ 93,491	$ 93,617	$ 112,844	$ 99,705	$ 98,244	$ 92,834	$ 381,765	$ 403,627	$ 360,917
United States
Geographic Reporting Disclosure [Line Items]
Sales									151,646	156,242	141,595
Americas-Other
Geographic Reporting Disclosure [Line Items]
Sales									14,110	15,086	13,531
Germany
Geographic Reporting Disclosure [Line Items]
Sales									52,083	53,251	49,860
Europe-Other
Geographic Reporting Disclosure [Line Items]
Sales									70,196	74,010	65,201
Japan
Geographic Reporting Disclosure [Line Items]
Sales									33,361	37,607	35,270
China
Geographic Reporting Disclosure [Line Items]
Sales									32,934	36,130	30,405
Asia-Other
Geographic Reporting Disclosure [Line Items]
Sales									$ 27,435	$ 31,301	$ 25,055