Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues
Revenues	$ 182,229	$ 176,334	$ 368,286	$ 371,798
Expenses
Employee compensation and benefits	45,435	40,732	93,191	88,820
Depreciation and amortization	15,240	13,097	30,414	24,876
Technology and communications	12,490	10,544	24,682	20,580
Professional and consulting fees	8,920	10,704	18,541	20,344
Occupancy	3,700	3,300	7,087	6,617
Marketing and advertising	2,949	3,128	4,738	4,332
Clearing costs	4,263	4,372	8,838	9,066
General and administrative	4,444	3,280	7,903	6,512
Total expenses	97,441	89,157	195,394	181,147
Operating income	84,788	87,177	172,892	190,651
Other income (expense)
Investment income	254	107	313	214
Interest expense	(337)	(171)	(510)	(362)
Equity in earnings of unconsolidated affiliate	191	0	191	0
Other, net	4,682	(1,060)	7,111	(2,649)
Total other income (expense)	4,790	(1,124)	7,105	(2,797)
Income before income taxes	89,578	86,053	179,997	187,854
Provision for income taxes	22,656	18,765	48,306	40,109
Net income	$ 66,922	$ 67,288	$ 131,691	$ 147,745
Net income per common share
Basic	$ 1.78	$ 1.79	$ 3.52	$ 3.94
Diluted	1.78	1.77	3.49	3.87
Cash dividends declared per common share	$ 0.70	$ 0.66	$ 1.40	$ 1.32
Weighted average shares outstanding
Basic	37,529	37,508	37,456	37,489
Diluted	37,608	38,104	37,716	38,129
Commissions [Member]
Revenues
Revenues	$ 163,463	$ 156,431	$ 329,576	$ 332,269
Information Services [Member]
Revenues
Revenues	9,396	9,844	19,205	19,006
Post-trade Services [Member]
Revenues
Revenues	9,144	9,848	19,056	20,109
Other [Member]
Revenues
Revenues	$ 226	$ 211	$ 449	$ 414