Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Taxes [Abstract]
Effective income tax rate (in hundredths)	38.80%	42.10%	39.50%	42.70%
U.S. Federal statutory rate (in hundredths)	35.00%		35.00%
Gross unrecognized tax benefits, including interest and penalties	$ 33.3		$ 33.3		$ 32.3
Related tax benefits	(1.9)		(1.9)		(1.9)
Net unrecognized tax benefits	$ 31.4		$ 31.4		$ 30.4