Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Income Taxes [Abstract]
Effective income tax rate (in hundredths)	39.70%	41.90%	41.20%	47.30%
U.S. Federal statutory rate (in hundredths)	35.00%
Expected annual effective income tax rate	approximately 40%		approximately 40%
Gross unrecognized tax benefits, including interest and penalties	$ 29.0		$ 29.0		$ 28.5
Related tax benefits	2.5		2.5		2.5
Net unrecognized tax benefits	$ 26.5		$ 26.5		$ 26.0