Segment Information (Revenues By Geographic Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	[1]	Dec. 31, 2017	[1]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues	$ 809,823	$ 732,901	$ 748,697	$ 719,143	$ 801,870	$ 732,476	$ 742,365	$ 697,192	$ 3,010,564	$ 2,973,903	[2]	$ 2,824,686	[2]
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									1,704,763	1,716,876		1,644,008
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									991,216	956,365		888,072
APJ
Revenues from External Customers and Long-Lived Assets [Line Items]
Net revenues									$ 314,585	$ 300,662		$ 292,606

[1] As noted above, prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard.

[2] Prior period amounts have not been adjusted under the modified retrospective method of adoption of the revenue recognition standard.