Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of income before provision for income taxes and noncontrolling interest
Domestic									$ 456.3	$ (509.7)	$ 248.7
Foreign									395.9	423.4	276.8
Income (loss) before income taxes	$ 260.6	$ 249.6	$ 226.0	$ 116.0	$ (694.4)	$ 165.6	$ 294.5	$ 148.0	852.2	(86.3)	525.5
Current provision (benefit):
Federal									181.4	180.1	(12.9)
States									15.9	15.2	(5.0)
Foreign									43.3	33.7	32.5
Total current provision (benefit)									240.6	229.0	14.6
Deferred provision (benefit):
Federal									(16.7)	17.3	51.2
States									(0.4)	1.2	(2.7)
Foreign									(5.0)	0.5	22.6
Total deferred provision (benefit)									(22.1)	19.0	71.1
Income tax benefits attributable to employee stock plan activity									0.0	0.0	0.0
Total provision for income taxes	62.8	51.9	68.0	35.8	75.2	62.0	73.4	37.4	218.5	248.0	85.7
Income tax reconciliation
Expected provision at 35% rate									298.3	(30.2)	184.0
State taxes (benefit), net of federal benefit									8.9	9.5	(3.6)
Foreign income at different tax rates									(68.9)	(90.2)	(37.7)
R&D tax credits									(12.7)	(17.1)	(32.5)
Share-based compensation									13.2	25.3	25.6
Non-deductible goodwill impairment									0.0	297.5	0.0
Gain on sale of Junos Pulse									0.0	75.6	0.0
Release of valuation allowance									0.0	(22.8)	0.0
Settlement with tax authorities									0.0	0.0	(28.3)
Domestic production activities									(15.1)	(6.8)	(26.3)
Non-deductible compensation									3.7	3.2	1.5
Cost sharing adjustment									(13.2)	0.0	0.0
Other									4.3	4.0	3.0
Total provision for income taxes	$ 62.8	51.9	$ 68.0	$ 35.8	$ 75.2	$ 62.0	$ 73.4	$ 37.4	$ 218.5	$ 248.0	85.7
Tax benefit related to cost sharing agreement		$ 70.3
Net income tax benefit related to items unique during current year											64.2
Income tax benefit for a multi-year claim related to the U.S. production activities deduction											19.7
U.S. federal R&D tax credit resulting from the American Taxpayer Relief Act of 2012											$ 16.2