Revenue - Sales by product line (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Sales, net	$ 338,268	$ 175,127	$ 134,810	$ 140,743	$ 154,161	$ 173,082	$ 196,032	$ 195,617	$ 788,948	$ 718,892	$ 671,012
Semiconductor Equipment [Member]
Revenue from External Customer [Line Items]
Sales, net									403,018	533,770	554,063
Industrial And Medical [Member]
Revenue from External Customer [Line Items]
Sales, net									245,992	$ 185,122	$ 116,949
Data Center Computing [Member]
Revenue from External Customer [Line Items]
Sales, net									91,438
Telecom And Networking [Member]
Revenue from External Customer [Line Items]
Sales, net									$ 48,500