Income Taxes (Details of Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income before income taxes	$ 245.2	$ 192.2	$ 385.8	$ 318.7
Income tax provision	$ 65.4	$ 52.2	$ 97.2	$ 87.3
Effective tax rate	26.70%	27.20%	25.20%	27.40%
Unrecognized tax benefits	$ 235.0		$ 235.0
Unrecognized tax benefits that would impact effective tax rate	$ 202.7		$ 202.7