Leases - Schedule of supplemental cash flow information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Supplemental Cash Flow Information
Operating cash flows from operating leases	$ 3,419	$ 2,671	$ 6,939	$ 4,951
Financing cash flows from finance leases	268	162	535	325
Right-of-use assets obtained in exchange for lease obligations
Operating leases	$ 2,995	$ 5,174	$ 7,985	$ 6,236