Segments (Details) (USD $)	3 Months Ended														12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Net Revenues [Abstract]
Total net revenues	$ 1,120,800,000		$ 1,105,800,000		$ 1,120,500,000	$ 1,101,600,000	$ 1,190,000,000		$ 1,012,400,000		$ 978,300,000		$ 912,600,000		$ 4,448,709,000		$ 4,093,266,000		$ 3,315,912,000
Segment Operating Income [Abstract]
Total segment operating income															917,300,000		981,700,000		668,400,000
Amortization of purchased intangible assets															(27,100,000)	[1]	(8,600,000)	[1]	(15,400,000)	[1]
Share-based Compensation Expense															(222,200,000)		(182,000,000)		(139,700,000)
Share-based payroll tax expense															(9,300,000)		(6,400,000)		(800,000)
Restructuring	(15,000,000)	[2]	(16,800,000)	[2]	900,000	300,000	(2,300,000)	[3]	(200,000)	[3]	(200,000)	[3]	(8,100,000)	[3]	(30,564,000)		(10,805,000)		(19,463,000)
Acquisition-related and other charges															(9,600,000)	[4]	(6,300,000)	[4]	(182,300,000)	[4]
Operating income	133,200,000		137,000,000		170,900,000	177,400,000	226,800,000		195,500,000		185,000,000		160,300,000		618,524,000		767,584,000		310,695,000
Other (expense) income, net	(10,700,000)		(15,900,000)		(13,700,000)	(6,500,000)	4,800,000		200,000		4,000,000		1,400,000		(46,808,000)		10,570,000		1,366,000
Income before income taxes and noncontrolling interest	122,500,000		121,100,000		157,200,000	170,900,000	231,600,000		195,700,000		189,000,000		161,700,000		571,716,000		778,154,000		312,061,000
Depreciation by Segment [Abstract]
Depreciation															142,160,000		146,757,000		132,946,000
Infrastructure Segment [Member]
Net Revenues [Abstract]
Total net revenues															3,422,600,000		3,050,300,000		2,441,600,000
Segment Operating Income [Abstract]
Total segment operating income															718,300,000		773,700,000		541,400,000
Depreciation by Segment [Abstract]
Depreciation															110,000,000		108,900,000		94,000,000
Infrastructure Routers [Member]
Net Revenues [Abstract]
Total net revenues															2,894,400,000		2,655,700,000		2,244,200,000
Infrastructure Switches [Member]
Net Revenues [Abstract]
Total net revenues															528,200,000		394,600,000		197,400,000
Service Layer Technologies Segment [Member]
Net Revenues [Abstract]
Total net revenues															1,026,100,000		1,043,000,000		874,300,000
Segment Operating Income [Abstract]
Total segment operating income															199,000,000		208,000,000		127,000,000
Depreciation by Segment [Abstract]
Depreciation															$ 32,200,000		$ 37,900,000		$ 39,000,000

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

[2] Restructuring and other charges consisted of restructuring charges and asset impairment charges. In the third quarter of 2011, the Company implemented the 2011 Restructuring Plan for workforce reduction and recorded restructuring charges of $16.8 million. In the fourth quarter of 2011, the Company recorded a charge of $13.5 million associated with an abandoned in-process internal used software project.

[3] Restructuring costs are typically comprised of employee severance costs, costs of consolidating duplicate facilities and contract termination costs. In the first quarter of 2010, the Company implemented a plan that resulted in reduction in workforce and facilities in certain business operations.

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