Income Taxes Reconciliation of unrecognized tax benefit (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, Beginning of Period	$ 12.8	$ 11.0
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions		7.7
Unrecognized Tax Benefit, Change as a Result of Current Year Tax Positions	0	0
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(3.3)
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(0.8)	(5.6)
Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations	(0.5)	(0.3)
Unrecognized Tax Benefits, End of Period	$ 8.2	$ 12.8