Leases Maturity of Operating Lease LIability (Details) - USD ($) $ in Thousands	Sep. 26, 2020	Dec. 28, 2019	Dec. 30, 2018
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 1,613
Lessee, Operating Lease, Liability, Payments, Due Year Two	8,845
Lessee, Operating Lease, Liability, Payments, Due Year Three	8,564
Lessee, Operating Lease, Liability, Payments, Due Year Four	7,592
Lessee, Operating Lease, Liability, Payments, Due Year Five	6,535
Lessee, Operating Lease, Liability, Payments, Due after Year Five	35,017
Lessee, Operating Lease, Liability, Payments, Due	68,166
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	9,926
Operating Lease, Liability	58,240		$ 67,300
Current portion of operating lease liabilities	6,343	$ 6,843
Operating Lease, Liability, Noncurrent	$ 51,897	$ 54,928