Derivative Instruments and Hedging Activities, Derivative Instruments and Hedging Activities, Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative Assets [Abstract]
Current assets	$ 1.6	$ 2.0
Long-term assets	2.9	3.1
Total derivative assets	4.5	5.1
Derivative Liabilities [Abstract]
Current liabilities	(12.9)	(8.0)
Long-term liabilities	(1.2)	(1.4)
Total derivative liabilities	(14.1)	(9.4)
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Fair value, net	9.6
Asset Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	2.6	2.6
Counterparties without offsetting position - assets	1.9	2.5
Counterparties without offsetting position - liabilities	0	0
Fair value, net	4.5	5.1
Asset Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	0.7	0
Counterparties without offsetting position - assets	1.9	2.5
Counterparties without offsetting position - liabilities	0	0
Fair value, net	2.6	2.5
Liability Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	(3.7)	(5.6)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(10.4)	(3.8)
Fair value, net	(14.1)	(9.4)
Liability Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	(1.8)	(3.0)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(10.4)	(3.8)
Fair value, net	(12.2)	(6.8)
Current Position [Member] | Asset Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	1.6	1.9
Counterparties without offsetting position - assets	0	0.1
Counterparties without offsetting position - liabilities	0	0
Fair value, net	1.6	2.0
Current Position [Member] | Asset Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	0	0
Counterparties without offsetting position - assets	0	0.1
Counterparties without offsetting position - liabilities	0	0
Fair value, net	0	0.1
Current Position [Member] | Liability Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	(3.4)	(4.4)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(9.5)	(3.6)
Fair value, net	(12.9)	(8.0)
Current Position [Member] | Liability Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	(1.8)	(2.5)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(9.5)	(3.6)
Fair value, net	(11.3)	(6.1)
Long-term Position [Member] | Asset Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	1.0	0.7
Counterparties without offsetting position - assets	1.9	2.4
Counterparties without offsetting position - liabilities	0	0
Fair value, net	2.9	3.1
Long-term Position [Member] | Asset Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	0.7	0
Counterparties without offsetting position - assets	1.9	2.4
Counterparties without offsetting position - liabilities	0	0
Fair value, net	2.6	2.4
Long-term Position [Member] | Liability Position [Member] | Gross Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	(0.3)	(1.2)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(0.9)	(0.2)
Fair value, net	(1.2)	(1.4)
Long-term Position [Member] | Liability Position [Member] | Pro-forma Net Presentation [Member]
Pro forma impact of reporting derivatives in the Consolidated Balance Sheet [Abstract]
Counterparties with offsetting position	0	(0.5)
Counterparties without offsetting position - assets	0	0
Counterparties without offsetting position - liabilities	(0.9)	(0.2)
Fair value, net	(0.9)	(0.7)
Designated as Hedging Instrument [Member]
Derivative Assets [Abstract]
Total derivative assets	4.5	5.1
Derivative Liabilities [Abstract]
Total derivative liabilities	(14.0)	(9.1)
Designated as Hedging Instrument [Member] | Commodity Contracts [Member]
Derivative Assets [Abstract]
Current assets	1.6	2.0
Long-term assets	2.9	3.1
Derivative Liabilities [Abstract]
Current liabilities	(12.8)	(7.7)
Long-term liabilities	(1.2)	(1.4)
Not Designated as Hedging Instrument [Member]
Derivative Assets [Abstract]
Total derivative assets	0	0
Derivative Liabilities [Abstract]
Total derivative liabilities	(0.1)	(0.3)
Not Designated as Hedging Instrument [Member] | Commodity Contracts [Member]
Derivative Assets [Abstract]
Current assets	0	0
Derivative Liabilities [Abstract]
Current liabilities	$ (0.1)	$ (0.3)