Segment Information (Revenues By Geographic Location) (Details) - USD ($) $ in Thousands	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
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 904,763	$ 813,270	$ 796,759	$ 760,802	$ 851,483	$ 758,994	$ 781,560	$ 750,819	$ 3,275,594	$ 3,142,856	$ 2,918,434
Enterprise and Service Provider
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									2,544,302	2,491,294	2,335,562
Enterprise and Service Provider | Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									1,394,985	1,328,851	1,263,673
Enterprise and Service Provider | EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									866,775	859,404	785,862
Enterprise and Service Provider | Asia-Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									282,542	303,039	286,027
Mobility Apps division
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									731,292	651,562	582,872
Mobility Apps division | Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									616,900	541,145	488,307
Mobility Apps division | EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									91,324	87,705	73,529
Mobility Apps division | Asia-Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 23,068	$ 22,712	$ 21,036