Other Financial Information, Other Income (Expense), Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Other Financial Information [Abstract]
Interest income	$ 5.7	$ 2.7	$ 16.3	$ 6.9
Interest expense	(21.6)	(16.9)	(61.9)	(50.2)
Net gain on legal settlement	0.0	0.8	0.0	196.1
Gain (loss) on investments	6.0	(1.9)	6.8	165.1
Other	1.5	8.5	(2.5)	8.1
Other (expense) income, net	(8.4)	(6.8)	(41.3)	326.0
Gain Contingencies [Line Items]
Publicly-traded equity and privately-held investments, net realized gain				163.0
Net gain on legal settlement	0.0	0.8	0.0	196.1
Gain (loss) on sale of securities		$ 0.8
Cost-method investments, realized gain (loss)	$ 6.0		$ 6.0
Palo Alto Networks [Member]
Other Financial Information [Abstract]
Net gain on legal settlement				196.1
Gain Contingencies [Line Items]
Net gain on legal settlement				196.1
Proceeds from legal settlements				$ 75.0