Leases - Minimum Future Lease Obligations (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 24, 2020	Dec. 25, 2019	Dec. 27, 2018
Lessee, Lease, Description [Line Items]
Finance Lease, Liability, Payments, Remainder of Fiscal Year	$ 27	$ 54
Operating Leases, Future Minimum Payments Due, Remainder of Fiscal Year	14,838	26,808
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Remainder Of Fiscal Year	1,393	2,754
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, Next Twelve Months	2,887	2,887
Finance Lease, Liability, Payments Due Year One	54	54
Finance Lease, Liability, Payments, Due Year Two	45	45
Lessee, Operating Lease, Liability, to be Paid, Year One	28,909	25,978
Operating Leases, Future Minimum Payments, Due in Two Years	25,975	24,871
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, within Two Years	3,284	3,284
Finance Lease, Liability, Payments, Due Year Three	0	0
Operating Leases, Future Minimum Payments, Due in Three Years	23,627	22,309
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, within Three Years	3,318	3,318
Finance Lease, Liability, Payments, Due Year Four	0	0
Operating Leases, Future Minimum Payments, Due in Four Years	21,333	19,751
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals, within Four Years	3,203	3,203
Thereafter	0	0
Thereafter	141,408	139,454
Thereafter	27,265	27,265
Total	126	153
Total	256,090	259,171
Total	41,350	42,711
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(49,051)	(45,273)
Present value of lease obligations	100	117
Finance Lease, Liability, Undiscounted Excess Amount	(26)	(36)
Less: current maturities	(37)	(34)
Obligations under finance leases, net of current portion	63	83
Finance Lease, Liability, Current	(37)	(34)
Present value of lease obligations	207,039	213,898	$ 222,300
Obligations under operating leases, net of current portion	189,060	197,492
Less: current maturities	(17,979)	(16,406)
Finance Lease, Liability, Noncurrent	$ 63	$ 83
Minimum
Lessee, Lease, Description [Line Items]
Imputed interest rate	2.33%	3.96%
Maximum
Lessee, Lease, Description [Line Items]
Imputed interest rate	11.10%	11.10%