Selected Quarterly Financial Data (Unaudited) (Details) - USD ($)							3 Months Ended								12 Months Ended
	Oct. 22, 2015	Jul. 23, 2015	Apr. 23, 2015	Jan. 27, 2015	Oct. 23, 2014	Jul. 22, 2014	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
Net revenues:
Product							$ 973,900,000	$ 925,400,000	$ 899,700,000	$ 764,100,000	$ 794,000,000	$ 809,500,000	$ 929,200,000	$ 876,000,000	$ 3,563,100,000	$ 3,408,700,000	$ 3,519,900,000
Service							345,700,000	323,200,000	322,500,000	303,300,000	307,600,000	316,400,000	300,300,000	294,100,000	1,294,700,000	1,218,400,000	1,149,200,000
Total net revenues							1,319,600,000	1,248,600,000	1,222,200,000	1,067,400,000	1,101,600,000	1,125,900,000	1,229,500,000	1,170,100,000	4,857,800,000	4,627,100,000	4,669,100,000
Cost of revenues:
Product							346,500,000	322,600,000	311,700,000	288,800,000	310,900,000	290,000,000	359,300,000	326,600,000	1,269,600,000	1,286,800,000	1,276,600,000
Service							130,700,000	128,600,000	129,000,000	121,300,000	115,600,000	121,100,000	122,000,000	123,400,000	509,600,000	482,100,000	451,100,000
Total cost of revenues							477,200,000	451,200,000	440,700,000	410,100,000	426,500,000	411,100,000	481,300,000	450,000,000	1,779,200,000	1,768,900,000	1,727,700,000
Gross margin							842,400,000	797,400,000	781,500,000	657,300,000	675,100,000	714,800,000	748,200,000	720,100,000	3,078,600,000	2,858,200,000	2,941,400,000
Operating expenses:
Research and development							247,200,000	247,000,000	251,600,000	248,700,000	233,500,000	253,200,000	255,500,000	264,000,000	994,500,000	1,006,200,000	1,043,200,000
Sales and marketing							255,900,000	235,300,000	232,400,000	220,200,000	243,000,000	249,200,000	258,000,000	273,400,000	943,800,000	1,023,600,000	1,075,900,000
General and administrative							60,300,000	57,100,000	56,300,000	55,200,000	40,600,000	55,000,000	60,600,000	74,900,000	228,900,000	231,100,000	217,300,000
Restructuring and other (benefits) charges							(100,000)	0	(1,900,000)	1,400,000	9,800,000	(15,000,000)	58,200,000	114,000,000	(600,000)	167,000,000	39,100,000
Impairment of goodwill											850,000,000	0	0	0	0	850,000,000	0
Total operating expenses							563,300,000	539,400,000	538,400,000	525,500,000	1,376,900,000	542,400,000	632,300,000	726,300,000	2,166,600,000	3,277,900,000	2,375,500,000
Operating income (loss)							279,100,000	258,000,000	243,100,000	131,800,000	(701,800,000)	172,400,000	115,900,000	(6,200,000)	912,000,000	(419,700,000)	565,900,000
Other (expense) income, net							(18,500,000)	(8,400,000)	(17,100,000)	(15,800,000)	7,400,000	(6,800,000)	178,600,000	154,200,000	(59,800,000)	333,400,000	(40,400,000)
Income (loss) before income taxes							260,600,000	249,600,000	226,000,000	116,000,000	(694,400,000)	165,600,000	294,500,000	148,000,000	852,200,000	(86,300,000)	525,500,000
Income tax provision							62,800,000	51,900,000	68,000,000	35,800,000	75,200,000	62,000,000	73,400,000	37,400,000	218,500,000	248,000,000	85,700,000
Net income (loss)							$ 197,800,000	$ 197,700,000	$ 158,000,000	$ 80,200,000	$ (769,600,000)	$ 103,600,000	$ 221,100,000	$ 110,600,000	$ 633,700,000	$ (334,300,000)	$ 439,800,000
Net income (loss) per share:
Basic (in dollars per share)							$ 0.52	$ 0.52	$ 0.41	$ 0.20	$ (1.81)	$ 0.23	$ 0.47	$ 0.23	$ 1.62	$ (0.73)	$ 0.88
Diluted (in dollars per share)							0.51	0.51	0.40	0.19	(1.81)	0.23	0.46	0.22	1.59	(0.73)	0.86
Cash dividends declared per share of common stock (in dollars per share)	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0	$ 0	$ 0.40	$ 0.20	$ 0
Interest expense, long-term debt															$ 79,800,000	$ 57,500,000	$ 45,200,000
Cost sharing adjustment															(13,200,000)	0	0
Cost-method investments, realized gains (loss)							$ 7,300,000								6,800,000		7,100,000
Restructuring charges															(4,100,000)
Publicly-traded equity and privately-held investments, net realized gain														$ 163,000,000		163,000,000
Net gain on legal settlement												$ 800,000	$ 195,300,000		0	196,100,000	0
Gain (loss) on disposition of business											$ 19,600,000				0	19,600,000	0
Security [Member]
Net revenues:
Total net revenues															435,600,000	463,600,000	$ 563,900,000
Operating expenses:
Impairment of goodwill											850,000,000					850,000,000
Asset Write-Down [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges											20,600,000	2,900,000	8,900,000	84,700,000		12,300,000
Employee Severance [Member]
Net income (loss) per share:
Restructuring charges															400,000
Employee Severance [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges											6,900,000	7,100,000	9,900,000	28,000,000		52,000,000
Contract Termination [Member]
Net income (loss) per share:
Restructuring charges															(3,500,000)
Contract Termination [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges													1,500,000	800,000		2,300,000
Acceleration of Certain End of Life Products [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges													2,300,000	$ 8,400,000		6,700,000
Facility Closing [Member]
Net income (loss) per share:
Restructuring charges															(1,000,000)
Facility Closing [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges											$ 1,600,000	$ 25,000,000	37,600,000			14,200,000
Inventory Write-down [Member] | Restructuring Plan 2014 [Member]
Net income (loss) per share:
Restructuring charges													$ 11,500,000			$ 15,500,000
Fixed rate note due 2020 [Member]
Net income (loss) per share:
Long-term debt							$ 300,000,000			$ 300,000,000					$ 300,000,000
Stated interest rate							3.30%			3.30%					3.30%
Fixed Rate Note Due 2025 [Member]
Net income (loss) per share:
Long-term debt							$ 300,000,000			$ 300,000,000					$ 300,000,000
Stated interest rate							4.35%			4.35%					4.35%
Fixed Rate Notes Due 2020 And 2025 [Member]
Net income (loss) per share:
Interest expense, long-term debt															$ 19,100,000