Leases - Supplemental information related to leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Leases
Operating cash flows from operating leases	$ 3,087	$ 2,702
Cost of goods sold	1,004	668
Selling, general and administrative expenses	1,977	1,970
Total lease costs	2,981	2,638
Rent expense	$ 3,500	$ 3,200