Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 1,116,527	$ 1,134,789
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		1,055,102	1,015,895
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		43,864	61,218
Canada [Member]
Segment Reporting Information [Line Items]
Total net revenues		7,451	42,356
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 10,110	$ 15,320

[1] No individual client accounted for more than 10 percent of total net revenues for the three months ended March 31, 2022 and 2021.