Derivative Contracts Schedule of Derivatives Financial Statement Presentation (Details) (Fair Value, Inputs, Level 2 [Member], Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative instruments - assets	$ 349.2	$ 6.5
Derivative instruments - liabilities	0.3	32.0
Interest Rate Swap [Member] | Short term [Member]
Derivative [Line Items]
Derivative instruments - assets	0	0
Derivative instruments - liabilities	0	2.6
Interest Rate Swap [Member] | Long term [Member]
Derivative [Line Items]
Derivative instruments - assets	0	0.6
Derivative instruments - liabilities	0	0
Commodity Contract [Member] | Short term [Member]
Derivative [Line Items]
Derivative instruments - assets	339.3	5.5
Derivative instruments - liabilities	0.3	29.4
Commodity Contract [Member] | Long term [Member]
Derivative [Line Items]
Derivative instruments - assets	9.9	0.4
Derivative instruments - liabilities	$ 0	$ 0