Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 597,751	$ 560,105	$ 1,158,733	$ 1,106,862
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		564,731	528,787	1,087,347	1,046,271
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		30,562	28,742	65,848	54,626
Other European [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 2,458	$ 2,576	$ 5,538	$ 5,965

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