Geographic And Customer Information (Comparison Of Geographic Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,142,167	$ 1,059,366	$ 1,010,117
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	667,301	639,170	616,125
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	207,474	193,623	182,897
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	127,298	83,456	65,525
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 140,094	$ 143,117	$ 145,570