Change in Valuation Allowance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation Allowance [Abstract]
Balance at beginning of period	$ 508.1	$ 425.5	$ 379.5
(Reversed) charged to costs and expenses	(25.1)	92.3	24.7
Charged (reversed) to gross tax assets and other accounts	6.9	(9.7)	21.3
Balance at end of period	$ 489.9	$ 508.1	$ 425.5