Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred Tax Assets [Abstract]
Retirement benefits other than pensions	$ 60.7	$ 127.2
Pension liabilities	70.0	136.4
Workers' compensation and other claims	35.1	38.3
Other assets and liabilities	138.6	115.3
Net operating loss carryforwards	26.8	63.5
Alternative minimum and other tax credits	44.7	37.9
Subtotal	375.9	518.6
Valuation Allowance	(32.4)	(47.4)	(43.9)	(45.9)
Net Deferred Tax Asset	343.5	471.2
Deferred Tax Liabilities [Abstract]
Property and equipment, net	9.9	11.2
Other assets and miscellaneous	31.0	37.4
Deferred tax liabilities	40.9	48.6
Net deferred tax asset	302.6	422.6
Deferred Tax Assets (Liabilities), Net [Abstract]
Current assets	72.0	59.4
Noncurrent assets	251.7	385.3
Current liabilities, included in accrued liabilities	(3.1)	(3.4)
Deferred Tax Liabilities, Noncurrent	(18.0)	(18.7)
Net deferred tax asset	302.6	422.6
Alternative minimum and other tax credits - unlimited carryforward period	43.8
Alternative minimum and other tax credits - various carryforward periods	$ 0.9