Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	$ 90,516	$ 99,705	$ 277,624	$ 290,783
United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	37,166	38,090	108,174	115,670
EMEA
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	26,424	29,577	87,554	88,858
Other APAC
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	16,120	16,602	46,550	48,502
China
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	7,751	11,340	25,007	26,973
Other Americas
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	3,055	4,096	10,339	10,780
Product sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	63,641	75,817	200,434	222,118
Product sales | Product transferred to customers at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	63,641	75,817	200,434	222,118
Product sales | Product transferred to customers over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	0	0	0	0
Service sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	26,875	23,888	77,190	68,665
Service sales | Product transferred to customers at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	12,526	11,580	36,960	30,939
Service sales | Product transferred to customers over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Sales	$ 14,349	$ 12,308	$ 40,230	$ 37,726