Derivative Instruments and Hedging Activities, Pro Forma Impact - Offsetting Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Derivative Liability [Abstract]
Gross liability	$ 2.4		$ 5.2
Pro forma net presentation, liability, total	0	[1]	0.8
Counterparties without Offsetting Position [Member]
Derivative Liability [Abstract]
Gross liability	0		0.8
Current Position [Member]
Derivative Liability [Abstract]
Gross liability	0.6		5.2
Pro forma net presentation, liability, current	0		0.8
Current Position [Member] | Counterparties without Offsetting Position [Member]
Derivative Liability [Abstract]
Gross liability	0		0.8
Long-term Position [Member]
Derivative Liability [Abstract]
Gross liability	1.8		0
Pro forma net presentation, liability, noncurrent	0		0
Long-term Position [Member] | Counterparties without Offsetting Position [Member]
Derivative Liability [Abstract]
Gross liability	$ 0		$ 0

[1] The fair value of the derivative contracts in this table is presented on a different basis than the Consolidated Balance Sheets presentation as disclosed in Note 14. The above fair values reflect the total value of each derivative contract taken as a whole, whereas the Consolidated Balance Sheets presentation is based on the individual maturity dates of estimated future settlements. As such, an individual contract could have both an asset and liability position when segregated into its current and long-term portions for Consolidated Balance Sheets classification purposes.