Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Lease expenses included in income statement
Operating lease cost	$ 15,731
Short-term lease cost	511
Variable lease cost	4,461
Total lease cost	$ 20,703
Base rent expense		$ 13,200	$ 12,100
Weighted average remaining lease term - operating leases	9 years 7 months 6 days
Weighted average discount rate - operating leases	3.70%