Segment Information (Revenues By Geographic Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	[1]	Dec. 31, 2016	[1]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 801,870	$ 732,476	$ 742,365	$ 697,192	$ 777,857	$ 690,925	$ 693,227	$ 662,677	$ 2,973,903	$ 2,824,686	[2]	$ 2,736,080	[2]
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									1,716,876	1,644,008		1,598,896
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									956,365	888,072		863,517
APJ
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 300,662	$ 292,606		$ 273,667

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of therevenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenuerecognition standard.

[2] Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard. See Note 2 for further information regarding the Company’s adoption of the revenue recognition standard.