Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues
Revenues	$ 131,597	$ 101,443	$ 381,578	$ 323,121
Expenses
Employee compensation and benefits	32,681	26,282	97,962	81,315
Depreciation and amortization	6,700	6,173	19,127	17,232
Technology and communications	7,381	5,879	19,637	17,451
Professional and consulting fees	7,018	5,685	19,145	16,168
Occupancy	2,802	3,528	8,549	10,332
Marketing and advertising	2,506	2,980	8,472	8,580
Clearing costs	2,782	1,760	7,969	5,497
General and administrative	3,762	2,744	10,686	7,927
Total expenses	65,632	55,031	191,547	164,502
Operating income	65,965	46,412	190,031	158,619
Other income (expense)
Investment income	2,211	1,635	6,296	4,186
Other, net	(838)	(250)	(860)	(785)
Total other income	1,373	1,385	5,436	3,401
Income before income taxes	67,338	47,797	195,467	162,020
Provision for income taxes	13,336	9,203	40,838	34,999
Net income	$ 54,002	$ 38,594	$ 154,629	$ 127,021
Net income per common share
Basic	$ 1.46	$ 1.04	$ 4.17	$ 3.44
Diluted	1.42	1.02	4.08	3.36
Cash dividends declared per common share	$ 0.51	$ 0.42	$ 1.53	$ 1.26
Weighted average shares outstanding
Basic	37,066	36,951	37,053	36,952
Diluted	37,995	37,828	37,913	37,859
Commissions [Member]
Revenues
Revenues	$ 119,869	$ 90,513	$ 346,753	$ 289,398
Information Services [Member]
Revenues
Revenues	7,693	7,174	22,215	21,170
Post-trade Services [Member]
Revenues
Revenues	3,784	3,475	11,840	11,671
Other [Member]
Revenues
Revenues	$ 251	$ 281	$ 770	$ 882