Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 591,575	$ 523,455	$ 1,750,308	$ 1,630,348
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		567,153	491,860	1,654,500	1,532,196
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		22,174	29,073	88,022	89,665
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 2,248	$ 2,522	$ 7,786	$ 8,487

[1] No individual client accounted for more than 10 percent of total net revenues for the three and nine months ended September 30, 2015 or 2014.