Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Effective tax rates	38.00%	40.00%
Gross unrecognized tax benefits	$ 38.2		$ 34.8
Reduction in provision for income taxes due to impact of effective tax rate	31.8
Gross interest and penalties accrued	0.5
Deferred tax assets classified as other current assets	14.0		13.4
Deferred tax assets classified as other non-current assets	143.3		106.9
Income tax benefits attributable to the exercise of employee stock options recorded directly to Additional paid-in-capital	$ 28.8	$ 32.5