Business Combinations Rofin acquisition (Details) - Rofin-Sinar - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2016	Jul. 01, 2017
Business Acquisition [Line Items]
Cash consideration to Rofin's shareholders	$ 904,491
payment due to cancellation of options held by Rofin employees	15,290
Payments to Acquire Businesses, Gross	919,781
Fair value of previously owned Rofin shares	20,685
Post-merger stock based compensation expense for cancelled options held by Rofin employees		$ (4,152)
Total purchase price to allocate	$ 936,314