Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent		31.30%	41.00%	32.70%
Deferred Tax Liabilities
Book/tax basis difference due to depreciation	$ 1,119.1	$ 1,119.1	$ 1,058.1
Investments in affiliated companies	69.5	69.5	72.9
Lease accounting (other than leveraged)	11.1	11.1	7.3
Other	1.0	1.0	0.0
Total deferred tax liabilities	1,200.7	1,200.7	1,138.3
Deferred Tax Assets
Alternative minimum tax credit	8.0	8.0	14.8
Federal net operating loss	0.0	0.0	13.2
Foreign tax credit	0.0	0.0	5.8
Valuation on foreign tax credit	0.0	0.0	(5.8)
State net operating loss	25.4	25.4	27.7
Valuation on state net operating loss	(12.9)	(12.9)	(12.6)
Foreign net operating loss	2.9	2.9	3.6
Deferred Tax Assets, Valuation Allowance	(0.3)	(0.3)	(0.3)
Accruals not currently deductible for tax purposes	26.7	26.7	22.2
Allowance for losses	1.5	1.5	3.2
Pension and post-retirement benefits	30.9	30.9	35.8
Other	29.1	29.1	12.4
Total deferred tax assets	111.3	111.3	120.0
Net deferred tax liabilities	1,089.4	1,089.4	1,018.3
Gross liability for unrecognized tax benefits
Beginning balance		5.7	5.6
Additions to tax positions of prior years		0.0	0.1
Reductions due to expiration of the applicable statute of limitations		(1.4)	0.0
Ending balance	4.3	4.3	5.7	$ 5.6
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	$ 7.1	$ 7.8	$ 0.0	$ 0.0