Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Decrease in Income Tax Expenses Unrecognized Tax Benefits if Recognized Net of Federal Tax	$ 315.9	$ 315.9
Effective Income Tax Rate Reconciliation, Percent		(113.70%)	31.30%	41.00%
Deferred Tax Liabilities
Book/tax basis difference due to depreciation	872.8	$ 872.8	$ 1,119.1
Investments in affiliated companies	43.6	43.6	69.5
Lease accounting (other than leveraged)	9.0	9.0	11.1
Other	6.3	6.3	1.0
Total deferred tax liabilities	931.7	931.7	1,200.7
Deferred Tax Assets
Alternative minimum tax credit	8.0	8.0	8.0
Federal net operating loss	4.1	4.1	0.0
State net operating loss	29.5	29.5	25.4
Valuation on state net operating loss	(10.3)	(10.3)	(12.9)
Foreign net operating loss	2.1	2.1	2.9
Deferred Tax Assets, Valuation Allowance	(0.4)	(0.4)	(0.3)
Accruals not currently deductible for tax purposes	21.7	21.7	26.7
Allowance for losses	1.1	1.1	1.5
Pension and post-retirement benefits	19.6	19.6	30.9
Other	2.6	2.6	29.1
Total deferred tax assets	78.0	78.0	111.3
Net deferred tax liabilities	853.7	853.7	1,089.4
Gross liability for unrecognized tax benefits
Ending balance	4.3	4.3
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	$ 7.1	$ 0.0	$ 7.8	$ 0.0