Income Taxes (Deferred tax liabilities and assets) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Depreciation	$ 256.3	$ 259.6
Deferred revenue	13.9	14.7
Intangibles	16.2	22.3
Gain on debt redemption	38.5	51.3
Other	92.8	87.0
Deferred tax liabilities	417.7	434.9
Claims and insurance	(165.7)	(168.8)
Net operating loss carryforwards	(302.4)	(316.4)
Employee benefit accruals	(255.2)	(273.8)
Other	(161.4)	(169.0)
Deferred tax assets	(884.7)	(928.0)
Valuation allowance	470.5	494.5
Net deferred tax assets	(414.2)	(433.5)
Net deferred tax liability	$ 3.5	$ 1.4