Segment Information (Net Revenues And Profit By Segment) (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment				2
Net revenues		$ 841,251	$ 813,270	$ 2,509,909	$ 2,370,831
Segment profit		153,827	63,798	417,868	237,679
Stock-based compensation		(48,282)	(38,671)	(136,202)	(103,674)
Restructuring		(12,061)	(13,766)	(62,142)	(62,251)
Separation costs		(17,580)	0	(46,190)	0
Consolidated income before income taxes		147,260	53,358	395,590	199,682
Operating Segments [Member] | Enterprise and Service Provider Division [Member]
Segment Reporting Information [Line Items]
Net revenues		668,736	649,185	2,001,496	1,906,223
Segment profit		209,991	175,488	621,930	454,088
Operating Segments [Member] | GoTo Business Division [Member]
Segment Reporting Information [Line Items]
Net revenues		172,515	164,085	508,413	464,608
Segment profit		45,233	37,785	109,412	103,465
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Amortization and impairment of intangible assets	[1]	(23,474)	(97,038)	(68,939)	(154,931)
Stock-based compensation	[1]	(48,282)	(38,671)	(136,202)	(103,674)
Restructuring	[1]	(12,061)	(13,766)	(62,142)	(62,251)
Separation costs	[1]	(17,580)	0	(46,190)	0
Other	[1]	0	0	0	982
Net interest and other expense, net	[1]	$ (6,567)	$ (10,440)	$ (22,279)	$ (37,997)

[1] Represents expenses presented to management on a consolidated basis only and not allocated to the operating segments.