Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues
Revenues	$ 172,284	$ 172,112	$ 555,299	$ 540,398
Expenses
Employee compensation and benefits	48,872	44,805	149,570	137,996
Depreciation and amortization	17,561	15,302	51,027	45,716
Technology and communications	15,339	14,169	45,573	38,851
Professional and consulting fees	9,181	7,560	24,331	26,101
Occupancy	3,503	3,381	10,313	10,468
Marketing and advertising	2,100	1,797	8,403	6,535
Clearing costs	3,665	4,211	12,392	13,049
General and administrative	5,154	4,576	15,698	12,479
Total expenses	105,375	95,801	317,307	291,195
Operating income	66,909	76,311	237,992	249,203
Other income (expense)
Interest income	6,590	1,433	16,151	1,746
Interest expense	(164)	(138)	(347)	(648)
Equity in earnings of unconsolidated affiliate	125	869	579	1,060
Other, net	(1,717)	388	(5,487)	7,499
Total other income (expense)	4,834	2,552	10,896	9,657
Income before income taxes	71,743	78,863	248,888	258,860
Provision for income taxes	16,802	19,556	60,460	67,862
Net income	$ 54,941	$ 59,307	$ 188,428	$ 190,998
Net income per common share
Basic	$ 1.47	$ 1.58	$ 5.03	$ 5.1
Diluted	1.46	1.58	5.01	5.07
Cash dividends declared per common share	$ 0.72	$ 0.7	$ 2.16	$ 2.1
Weighted average shares outstanding
Basic	37,491	37,479	37,485	37,464
Diluted	37,574	37,567	37,603	37,666
Commissions [Member]
Revenues
Revenues	$ 150,496	$ 153,164	$ 491,073	$ 482,740
Information Services [Member]
Revenues
Revenues	11,801	9,711	34,466	28,916
Post-trade Services [Member]
Revenues
Revenues	9,833	9,000	29,228	28,056
Other [Member]
Revenues
Revenues	$ 154	$ 237	$ 532	$ 686