Segments (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Net Revenues [Abstract]
Total net revenues	$ 1,105,796,000		$ 1,012,407,000		$ 3,327,952,000		$ 2,903,325,000
Segment Operating Income [Abstract]
Total segment operating income	221,200,000		244,500,000		709,200,000		689,900,000
Amortization of purchased intangible assets	(6,700,000)	[1]	(2,400,000)	[1]	(20,200,000)	[1]	(5,000,000)	[1]
Share-based Compensation Expense	(60,500,000)		(44,400,000)		(169,600,000)		(129,600,000)
Share-based payroll tax expense	(200,000)		(500,000)		(9,200,000)		(3,800,000)
Restructuring	(16,813,000)		(181,000)		(15,550,000)		(8,550,000)
Acquisition-related and other charges	0	[2]	(1,500,000)	[2]	(9,300,000)	[2]	(2,100,000)	[2]
Operating income	137,026,000		195,536,000		485,339,000		540,786,000
Other (expense) income, net	(15,957,000)		205,000		(36,107,000)		5,729,000
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	121,069,000		195,741,000		449,232,000		546,515,000
Infrastructure Segment [Member]
Net Revenues [Abstract]
Total net revenues	834,500,000		744,100,000		2,573,400,000		2,143,100,000
Segment Operating Income [Abstract]
Total segment operating income	154,600,000		179,900,000		573,800,000		537,600,000
Depreciation by Segment [Abstract]
Depreciation expense	28,700,000		27,800,000		81,300,000		78,900,000
Infrastructure Routers [Member]
Net Revenues [Abstract]
Total net revenues	703,000,000		642,600,000		2,213,600,000		1,872,100,000
Infrastructure Switches [Member]
Net Revenues [Abstract]
Total net revenues	131,500,000		101,500,000		359,800,000		271,000,000
Service Layer Technologies Segment [Member]
Net Revenues [Abstract]
Total net revenues	271,300,000		268,300,000		754,600,000		760,200,000
Segment Operating Income [Abstract]
Total segment operating income	66,600,000		64,600,000		135,400,000		152,300,000
Depreciation by Segment [Abstract]
Depreciation expense	$ 8,000,000		$ 9,400,000		$ 24,500,000		$ 28,500,000

[1] Amount includes amortization expense of purchased intangible assets in operating expenses and in cost of revenues.

[2] Amount includes acquisition-related costs in operating expenses and in cost of revenues.