Depreciation and Amortization Expenses by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 27, 2019	Sep. 28, 2018
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 9,840	$ 9,199	$ 27,954	$ 27,386
Unallocated Corporate and Shared Services
Depreciation and Amortization Expenses
Depreciation and amortization expenses	71	82	197	621
Photonics | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	3,276	2,997	8,486	9,030
Vision | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	5,432	5,100	15,658	15,371
Precision Motion | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 1,061	$ 1,020	$ 3,613	$ 2,364