Depreciation and Amortization by Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation and Amortization
Depreciation and amortization	$ 30,758	$ 20,973	$ 20,196
Photonics
Depreciation and Amortization
Depreciation and amortization	13,806	6,738	6,083
Vision
Depreciation and Amortization
Depreciation and amortization	13,590	10,402	8,599
Precision Motion
Depreciation and Amortization
Depreciation and amortization	2,308	2,439	2,533
Unallocated Corporate and Shared Services
Depreciation and Amortization
Depreciation and amortization	$ 1,054	$ 1,394	$ 2,981