Income Taxes Uncertain tax positions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 12	$ 1
Unrecognized Tax Benefits	23.5	11.3	13.0	14.4
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	12.7	0.7	1.3
Unrecognized Tax Benefits, Decreases Resulting from Current Period Tax Positions	(0.3)	(0.7)	(1.6)
Unrecognized Tax Benefits, Decreases Resulting from Settlements with Taxing Authorities	(0.2)	(1.7)	(1.1)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	1.0	1.0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 3.7	$ 2.5