Income Taxes (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	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense (Benefit) [Abstract]
Net unrecognized tax benefit	$ 37.6		$ 37.6		$ 79.2
Income tax interest and penalties accrued	0.5		0.5
Income tax examination, RAR asserted income tax deficiencies						13.1
Net recognized tax benefit	(24.2)
Deferred tax assets	$ 71.8		$ 71.8
Effective tax rate	(7.60%)	19.10%	5.80%	18.20%
U.S. federal statutory rate			35.00%