Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 188,010,000	$ 30,731,000
Additions - Cascade Microtech acquisition		158,141,000
Foreign currency translation	1,694,000	(862,000)
Goodwill, ending balance	189,704,000	188,010,000
Goodwill impairment	0
Probe Cards
Goodwill [Roll Forward]
Goodwill, beginning balance	172,482,000	30,731,000
Additions - Cascade Microtech acquisition		141,751,000
Foreign currency translation	0	0
Goodwill, ending balance	172,482,000	172,482,000
Systems
Goodwill [Roll Forward]
Goodwill, beginning balance	15,528,000	0
Additions - Cascade Microtech acquisition		16,390,000
Foreign currency translation	1,694,000	(862,000)
Goodwill, ending balance	$ 17,222,000	$ 15,528,000