Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective tax rates	39.00%	37.00%		40.00%	32.00%
2012 Federal R&D credit recognized			$ 3.1
Unrecognized tax benefits	78.6			78.6		68.2
Reduction in provision for income taxes due to impact of effective tax rate	65.4			65.4
Gross interest and penalties accrued	4.4			4.4
Deferred tax assets, other current assets	19.0			19.0		21.5
Deferred tax assets, other non-current assets	100.9			100.9		69.1
Income tax benefits attributable to the exercise of employee stock options recorded directly to Additional paid-in-capital	$ 14.6	$ 20.2		$ 47.1	$ 31.5