Income Taxes - Deferred Taxes (Details) - USD ($) $ in Millions	Dec. 27, 2020	Dec. 29, 2019
Deferred tax assets:
Stock-based compensation	$ 7.9	$ 5.3
Payroll related accruals	11.7	9.2
Lease accruals	21.7	22.1
Net operating loss carryforwards	66.0	75.1
Tax credit carryforwards	11.7	11.2
Other	18.5	20.2
Gross deferred tax assets	137.5	143.1
Valuation allowance	(7.4)	(88.6)
Total deferred tax assets, net of valuation allowance	130.1	54.5
Deferred tax liabilities:
Unearned revenue	(10.7)	(19.0)
Operating lease right-of-use assets	(19.7)	(20.2)
Other intangibles	(24.6)	(21.0)
Property and equipment, principally due to differences in depreciation	(7.0)	(2.0)
Other	(1.5)	(1.3)
Total deferred tax liabilities	(63.5)	(63.5)
Net deferred tax asset (liability)		$ (9.0)
Net deferred tax asset (liability)	$ 66.6