Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit) [Abstract]
Net unrecognized tax benefit	$ 37.7		$ 37.7		$ 79.2
Income tax interest and penalties accrued	0		0
Income tax examination, RAR asserted income tax deficiencies						13.1
Net recognized tax benefit	24.2
Deferred tax assets	$ 17.8		$ 17.8
Effective tax rate	13.90%	10.40%	8.60%	15.40%
U.S. federal statutory rate			35.00%