Depreciation and Amortization by Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Depreciation and Amortization
Depreciation and amortization	$ 9,067	$ 6,482
Photonics
Depreciation and Amortization
Depreciation and amortization	3,067	3,244
Vision
Depreciation and Amortization
Depreciation and amortization	5,174	2,437
Precision Motion
Depreciation and Amortization
Depreciation and amortization	503	566
Unallocated Corporate and Shared Services
Depreciation and Amortization
Depreciation and amortization	$ 323	$ 235