Geographic And Customer Information (Comparison Of Geographic Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,059,366	$ 1,010,117	$ 965,087
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	639,170	616,125	585,201
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	193,623	182,897	169,767
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	151,461	133,748	129,664
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 75,112	$ 77,347	$ 80,455