Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012 Mg	Dec. 31, 2011
Environmental and Safety Matters [Abstract]
Accrual for Environmental Loss Contingencies	$ 8.1	$ 8.1	$ 8.8
Number of years the related expenditures are expected to cover assessment and remediation costs (in years)		9
Accrued Environmental Loss Contingencies, Current	2.2	2.2	2.2
Accrued Environmental Loss Contingencies, Noncurrent	5.9	5.9	6.6
Number of facilities operated affected by non-attainment requirements	2	2
Current ozone standard (in hours)		8-hour
Site Contingency, Name of Site	1
Minimum volume of annual greenhouse gas emissions to be reported (in metric tons)		25,000
Commitments for Construction [Abstract]
Purchase Commitment, Remaining Minimum Amount Committed	$ 94.6	$ 94.6