Write-downs, Reserves, and Project Opening Costs, net of Recoveries (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Write-downs and reserves, net of recoveries:
Remediation costs	$ 3.6	$ 4.3	$ 6.0	$ 7.8
Efficiency projects	1.7	14.0	7.8	25.5
Flood insurance deductibles	0.1	4.4	0.5	4.4
Litigation reserves, awards and settlements	(0.2)	5.3	(0.2)	6.1
Divestitures and abandonments	1.9	(2.6)	14.6	(0.4)
Other	0.8	(0.3)	0.1
Total write-downs and reserves, net of recoveries	7.9	25.1	28.8	43.4
Project opening costs	0.1	4.1	1.8	4.3
Total write-downs, reserves, and project opening costs, net of recoveries	$ 8.0	$ 29.2	$ 30.6	$ 47.7