Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenues
Revenues	$ 179,846	$ 182,229	$ 383,015	$ 368,286
Expenses
Employee compensation and benefits	48,383	45,435	100,698	93,191
Depreciation and amortization	17,005	15,240	33,466	30,414
Technology and communications	15,235	12,490	30,234	24,682
Professional and consulting fees	8,023	8,920	15,150	18,541
Occupancy	3,199	3,700	6,810	7,087
Marketing and advertising	3,308	2,949	6,303	4,738
Clearing costs	4,182	4,263	8,727	8,838
General and administrative	4,784	4,444	10,544	7,903
Total expenses	104,119	97,441	211,932	195,394
Operating income	75,727	84,788	171,083	172,892
Other income (expense)
Interest income	5,312	254	9,561	313
Interest expense	(53)	(337)	(183)	(510)
Equity in earnings of unconsolidated affiliate	250	191	454	191
Other, net	(2,286)	4,682	(3,770)	7,111
Total other income (expense)	3,223	4,790	6,062	7,105
Income before income taxes	78,950	89,578	177,145	179,997
Provision for income taxes	19,091	22,656	43,658	48,306
Net income	$ 59,859	$ 66,922	$ 133,487	$ 131,691
Net income per common share
Basic	$ 1.6	$ 1.78	$ 3.56	$ 3.52
Diluted	1.59	1.78	3.55	3.49
Cash dividends declared per common share	$ 0.72	$ 0.7	$ 1.44	$ 1.4
Weighted average shares outstanding
Basic	37,485	37,529	37,482	37,456
Diluted	37,588	37,608	37,617	37,716
Commissions [Member]
Revenues
Revenues	$ 158,586	$ 163,463	$ 340,577	$ 329,576
Information Services [Member]
Revenues
Revenues	11,655	9,396	22,665	19,205
Post-trade Services [Member]
Revenues
Revenues	9,415	9,144	19,395	19,056
Other [Member]
Revenues
Revenues	$ 190	$ 226	$ 378	$ 449