Segment Information (Revenues By Geographic Location) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 802,420	$ 712,731	$ 730,384	$ 672,899	$ 739,996	$ 641,422	$ 615,210	$ 589,495	$ 2,918,434	$ 2,586,123	$ 2,206,392
Enterprise and Service Provider division
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									2,335,562	2,074,800	1,778,646
Enterprise and Service Provider division | Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									1,263,673	1,106,801	993,062
Enterprise and Service Provider division | EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									785,862	691,111	576,953
Enterprise and Service Provider division | Asia-Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									286,027	276,888	208,631
SaaS division
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									582,872	511,323	427,746
SaaS division | Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									488,307	433,263	367,260
SaaS division | EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									73,529	63,484	50,711
SaaS division | Asia-Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 21,036	$ 14,576	$ 9,775