Depreciation and Amortization Expenses by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Oct. 02, 2020	Sep. 27, 2019
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 9,596	$ 9,840	$ 28,363	$ 27,954
Unallocated Corporate and Shared Services
Depreciation and Amortization Expenses
Depreciation and amortization expenses	67	71	160	197
Photonics | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	2,864	3,276	8,303	8,486
Vision | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	5,296	5,432	15,845	15,658
Precision Motion | Operating Segments
Depreciation and Amortization Expenses
Depreciation and amortization expenses	$ 1,369	$ 1,061	$ 4,055	$ 3,613