Derivative Instruments (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Effect of mark to market valuation [Member]
Other Derivatives
Other Derivatives	$ 0	$ 0	$ (0.3)
Settlements [Member]
Other Derivatives
Other Derivatives	0.4	(0.1)	(1.2)
Commodity Contract [Member]
Other Derivatives
Other Derivatives	0.4	(0.1)	(1.5)
Foreign exchange hedges [Member]
Other Derivatives
Other Derivatives	$ 0.1	$ (0.9)	$ (1.9)