Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 57,277	$ 39,822
Work-in-process	14,847	8,012
Finished goods	16,443	9,511
Demo and consigned inventory	2,711	2,400
Total inventories	$ 91,278	$ 59,745	$ 59,566