Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Income Taxes
Effective income tax rate (as a percent)	18.10%	24.70%
Unrecognized tax benefits including interest and penalties	$ 44.2
Portion of UTB, expected to be recognized upon settlement of tax examinations and the expiration of various statutes of limitations within next twelve months	$ 5.2