Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective tax rates	35.00%	30.00%	30.00%	34.00%
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 16.5		$ 16.5		$ 17.1
Reduction in provision for income taxes due to impact of effective tax rate	13.7		13.7
Deferred tax assets classified as other non-current assets	200.0		200.0		$ 180.6
Income tax benefits attributable to the exercise of employee stock options recorded directly to Additional paid-in-capital	12.6	$ 37.7	37.2	$ 105.6
Other Noncurrent Liabilities
Income Tax Contingency [Line Items]
Increase in unrecognized tax benefits is reasonably possible	1.6		1.6
Other Noncurrent Assets
Income Tax Contingency [Line Items]
Deferred tax assets	$ 14.9		$ 14.9