Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 770,420	$ 750,358
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		741,230	706,068
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		26,390	41,558
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 2,800	$ 2,732

[1] No individual client accounted for more than 10 percent of total net revenues for the three months ended March 31, 2019 or 2018.