Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective tax rates	40.00%	(189.00%)
2012 Federal R&D credit recognized		$ 3.1
Unrecognized tax benefits	73.4		68.2
Reduction in provision for income taxes due to impact of effective tax rate	61.1
Gross interest and penalties accrued	4.1
Deferred tax assets, other current assets	19.9		21.5
Deferred tax assets, other non-current assets	83.5		69.1
Income tax benefits attributable to the exercise of employee stock options recorded directly to Additional paid-in-capital	$ 32.5	$ 11.3