Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 2,331,594	$ 2,208,424	$ 1,973,446
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		2,195,538	2,082,876	1,894,300
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		125,552	113,943	67,394
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 10,504	$ 11,605	$ 11,752

[1] No individual client accounted for more than 10 percent of total net revenues for the years ended December 31, 2015, 2014, and 2013.