Income Taxes - Net deferred tax assets (liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Lease liabilities	$ 112.9	$ 119.6
Employee compensation	12.1	7.5
Revenue recognition	35.4	36.6
Other	8.4	10.2
Deferred tax assets	168.8	173.9
Valuation allowance	(4.2)	(3.0)
Total deferred tax assets after valuation allowance	164.6	170.9
Recognition of franchise and equipment sales	(8.2)	(10.7)
Capitalization and depreciation	(122.7)	(123.2)
Lease assets	(108.6)	(114.2)
Other	(1.3)	(1.1)
Deferred tax liabilities	(240.8)	(249.2)
Net deferred tax liabilities	$ (76.2)	$ (78.3)