Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Revenue from contracts with customers		$ 880,472	$ 636,899	$ 2,604,651	$ 1,875,321
Principal transactions		118,977	140,883	436,580	445,566
Interest		141,844	114,411	402,975	403,956
Other income		18,760	20,258	57,629	50,979
Total revenues		1,154,961	897,122	3,471,504	2,743,414
Interest expense		10,023	13,822	38,641	51,263
Net revenues	[1]	1,144,938	883,300	3,432,863	2,692,151
Non-interest expenses:
Compensation and benefits		672,385	533,638	2,062,353	1,657,991
Occupancy and equipment rental		72,160	68,598	215,163	200,935
Communications and office supplies		40,432	40,123	123,565	124,293
Commissions and floor brokerage		14,744	13,254	44,424	43,273
Provision for credit losses		(660)	(1,353)	(15,564)	33,925
Other operating expenses		89,375	70,647	254,503	215,275
Total non-interest expenses		888,436	724,907	2,684,444	2,275,692
Income from operations before income tax expense		256,502	158,393	748,419	416,459
Provision for income taxes		64,126	37,866	184,951	101,456
Net income		192,376	120,527	563,468	315,003
Preferred dividends		9,689	9,897	26,267	19,584
Net income available to common shareholders		$ 182,687	$ 110,630	$ 537,201	$ 295,419
Earnings per common share:
Basic		$ 1.70	$ 1.04	$ 4.99	$ 2.78
Diluted		1.54	0.97	4.54	2.60
Cash dividends declared per common share		$ 0.15	$ 0.11	$ 0.45	$ 0.33
Weighted-average number of common shares outstanding:
Basic		107,379	105,941	107,655	106,221
Diluted		118,475	113,775	118,355	113,568
Commissions [Member]
Revenues:
Revenue from contracts with customers		$ 189,239	$ 172,654	$ 598,432	$ 560,780
Investment Banking [Member]
Revenues:
Revenue from contracts with customers		372,279	218,134	1,088,010	614,637
Asset Management and Service Fees [Member]
Revenues:
Revenue from contracts with customers		$ 313,862	$ 230,782	$ 887,878	$ 667,496

[1] No individual client accounted for more than 10 percent of total net revenues for the three and nine months ended September 30, 2021 or 2020.