Derivative Contracts - Schedule of Derivatives Financial Statement Presentation (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	$ 49.7	$ 6.5
Derivative Liability, Fair Value, Gross Liability	9.1	32.0
Interest Rate Swap [Member] | Short-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	0	0
Derivative Liability, Fair Value, Gross Liability		2.6
Interest Rate Swap [Member] | Long-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross		0.6
Derivative Liability, Fair Value, Gross Liability	0	0
Commodity Contract [Member] | Short-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross		5.5
Derivative Liability, Fair Value, Gross Liability		29.4
Commodity Contract [Member] | Long-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross		0.4
Derivative Liability, Fair Value, Gross Liability		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	49.7	6.5
Derivative Liability, Fair Value, Gross Liability	9.1	32.0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member] | Short-term [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	4.3	2.6
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member] | Long-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	3.5	0.6
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member] | Short-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	36.6	5.5
Derivative Liability, Fair Value, Gross Liability	4.2	29.4
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Contract [Member] | Long-term [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross	9.6	0.4
Derivative Liability, Fair Value, Gross Liability	$ 0.6