Revenues - Disaggregation of Revenue (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
Disaggregation of Revenue [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
Disaggregation of Revenue [Line Items]
Sales									151,646	156,242	141,595
EMEA
Disaggregation of Revenue [Line Items]
Sales									122,279	127,261	115,061
Other APAC
Disaggregation of Revenue [Line Items]
Sales									60,796	68,908	60,325
China
Disaggregation of Revenue [Line Items]
Sales									32,934	36,130	30,405
Other Americas
Disaggregation of Revenue [Line Items]
Sales									14,110	15,086	13,531
Product
Disaggregation of Revenue [Line Items]
Sales									289,679	320,584	287,248
Product | Product or service transferred to customers at a point in time
Disaggregation of Revenue [Line Items]
Sales									277,841	311,102	277,922
Product | Product or service transferred to customers over time
Disaggregation of Revenue [Line Items]
Sales									11,838	9,482	9,326
Service
Disaggregation of Revenue [Line Items]
Sales									92,086	83,043	73,669
Service | Product or service transferred to customers at a point in time
Disaggregation of Revenue [Line Items]
Sales									48,593	42,932	36,164
Service | Product or service transferred to customers over time
Disaggregation of Revenue [Line Items]
Sales									$ 43,493	$ 40,111	$ 37,505