Income Taxes - Components of Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Depreciation	$ (104.5)	$ (83.8)
Operating lease right-of-use assets	(42.1)	(65.3)
Deferred revenue	0.0	(3.3)
Intangibles	(1.4)	(2.9)
State taxes	(17.9)	(19.6)
Other, including debt and interest	(13.7)	(22.3)
Deferred tax liabilities	(179.6)	(197.2)
Claims and insurance	88.6	84.4
Net operating loss carryforwards	219.1	216.7
Employee benefit accruals	55.6	23.9
Sale/leaseback transactions	50.8	53.0
Operating lease liabilities	46.3	68.7
Employer payroll taxes	9.7	20.0
Other, including debt and interest	39.0	37.0
Deferred tax assets	509.1	503.7
Valuation allowance	(328.1)	(305.6)
Net deferred tax assets	181.0	198.1
Net deferred tax asset	$ 1.4	$ 0.9