Inventories - Schedule of Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Raw materials	$ 36,328	$ 36,760
Finished goods	17,458	15,126
Inventories, net	53,786	51,886
Service and sales demonstration inventory, net	$ 39,614	$ 29,136
Service Inventory
Property, Plant and Equipment [Line Items]
Inventory, remaining life	3 years