Schedule of Valuation and Qualifying Accounts (Details) (Allowance for bad debts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for bad debts [Member]
Valuation and qualifying accounts [Roll Forward]
Beginning Balance	$ 2.3	$ 3.0	$ 2.7
Amounts charged to expense	0.2	(0.3)	0.4
Deductions for accounts written off and other	(0.9)	(0.4)	(0.1)
Ending Balance	$ 1.6	$ 2.3	$ 3.0