Accounting Changes Accounting Changes (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Depreciation, Nonproduction	$ 273.5	$ 255.0	$ 237.4
Service Life [Member]
Property, Plant and Equipment [Line Items]
Depreciation, Nonproduction	21.9
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ 14.0
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Diluted Earnings Per Share	$ 0.31
Railcars [Member]
Property, Plant and Equipment [Line Items]
Average Increase (Decrease) in Estimated Railcar Useful Life	2 years 2 months 12 days
Railcars [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	27 years	30 years
Railcars [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	42 years	38 years