Segment Reporting (Schedule Of Net Revenues Earned On Major Geographical Areas) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total net revenues	[1]	$ 4,391,439	$ 4,737,088	$ 3,752,061
United States [Member]
Segment Reporting Information [Line Items]
Total net revenues		4,125,563	4,332,743	3,460,930
United Kingdom [Member]
Segment Reporting Information [Line Items]
Total net revenues		192,985	239,559	197,859
Canada [Member]
Segment Reporting Information [Line Items]
Total net revenues		29,268	109,285	39,893
Other [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 43,623	$ 55,501	$ 53,379

[1] No individual client accounted for more than 10 percent of total net revenues for the years ended December 31, 2022, 2021, and 2020.