Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 619,974	$ 560,982
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		581,737	522,616
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		35,748	35,286
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 2,489	$ 3,080

[1] No individual client accounted for more than 10 percent of total net revenues for the three months ended March 31, 2016 or 2015.