Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Effective tax rates	37.00%		42.00%	32.00%	56.00%
2012 Federal R&D credit recognized		$ 3.1
Unrecognized tax benefits						43.3
Increase in gross unrecognized tax benefits				11.6
Reduction in provision for income taxes due to impact of effective tax rate	46.1			46.1
Gross interest and penalties accrued	3.5			3.5
Deferred tax assets, other current assets	11.6			11.6		11.0
Deferred tax assets, other non-current assets	66.5			66.5		56.9
Income tax benefits attributable to the exercise of employee stock options recorded directly to Additional paid-in-capital	$ 20.2		$ 0.3	$ 31.5	$ 4.1