Financing Receivables - Schedule Of Allowance For Credit Losses (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 25, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 41.3	$ 43.8
Provision for doubtful accounts	27.1	30.9
Write-offs	(31.0)	(35.4)
Recoveries of amounts previously charged off	2.2	2.0
Balances at end of period	58.1	41.3
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	18.5	0.0
Balances at end of period		18.5
PSAs
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	29.4	29.6
Provision for doubtful accounts	22.1	26.4
Write-offs	(25.7)	(28.2)
Recoveries of amounts previously charged off	2.1	1.6
Balances at end of period	45.4	29.4
PSAs | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	17.5	0.0
Balances at end of period		17.5
Franchisee Notes
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	11.9	14.2
Provision for doubtful accounts	5.0	4.5
Write-offs	(5.3)	(7.2)
Recoveries of amounts previously charged off	0.1	0.4
Balances at end of period	12.7	11.9
Franchisee Notes | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 1.0	0.0
Balances at end of period		$ 1.0