Business Combinations- Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	May 26, 2017	Dec. 31, 2016
Summary of estimated fair values of the assets acquired and liabilities assumed
Goodwill	$ 184,302	$ 307,131		$ 114,908
Ultratech
Summary of estimated fair values of the assets acquired and liabilities assumed
Short-term investments			$ 47,161
Account receivable			45,465
Inventories			59,100
Deferred cost of sales			242
Prepaid expense and other current assets			7,217
Property, plant, and equipment			18,152
Intangible assets			346,940
Other assets			6,442
Total identifiable assets acquired			530,719
Accounts payable			24,291
Accrued expenses and other current liabilities			16,356
Customer deposits and deferred revenue			4,834
Deferred income taxes			32,478
Other liabilities			11,622
Total liabilities assumed			89,581
Net identifiable assets acquired			441,138
Goodwill			192,223
Net assets acquired			633,361
Gross contractual value of accounts receivable			$ 46,000