Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Segment Reporting Information [Line Items]
Total net revenues	$ 523,455	[1]	$ 478,639	[1]	$ 1,630,348	[1]	$ 1,410,921	[1]
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues	491,860		453,381		1,532,196		1,357,938
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues	29,073		22,697		89,665		45,120
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues	$ 2,522		$ 2,561		$ 8,487		$ 7,863

[1] No individual client accounted for more than 10 percent of total net revenues for the three and nine months ended September 30, 2014 or 2013.