Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 675,531	$ 619,974
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		648,331	581,737
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		24,519	35,748
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 2,681	$ 2,489

[1] No individual client accounted for more than 10 percent of total net revenues for the three months ended March 31, 2017 or 2016.