Depreciation and Amortization Expenses by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2019	Mar. 30, 2018
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 9,074	$ 9,067
Unallocated Corporate and Shared Services
Depreciation and Amortization Expenses
Depreciation and amortization expenses	55	323
Photonics | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	2,621	3,067
Vision | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	5,029	5,174
Precision Motion | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 1,369	$ 503