Business Segment and Geographic Region Information - Revenue by Product Line (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue by product lines
Revenue	$ 116,396	$ 104,482	$ 102,790	$ 86,893	$ 69,358	$ 65,650	$ 64,451	$ 67,521	$ 410,561	$ 266,980	$ 301,495
Ion implantation systems services
Revenue by product lines
Revenue									391,051	248,885	282,624
Other systems and services
Revenue by product lines
Revenue									$ 19,510	$ 18,095	$ 18,871