Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Revenues	$ 101,443	$ 95,584	$ 323,121	$ 294,862
Expenses
Employee compensation and benefits	26,282	25,485	81,315	78,088
Depreciation and amortization	6,173	4,583	17,232	14,066
Technology and communications	5,879	5,035	17,451	14,442
Professional and consulting fees	5,685	5,547	16,168	13,912
Occupancy	3,528	1,795	10,332	4,621
Marketing and advertising	2,980	2,089	8,580	6,757
Clearing costs	1,760	1,476	5,497	4,320
General and administrative	2,744	2,939	7,927	7,878
Total expenses	55,031	48,949	164,502	144,084
Operating income	46,412	46,635	158,619	150,778
Other income (expense)
Investment income	1,635	964	4,186	2,551
Other, net	(250)	(382)	(785)	(932)
Total other income	1,385	582	3,401	1,619
Income before income taxes	47,797	47,217	162,020	152,397
Provision for income taxes	9,203	13,087	34,999	37,781
Net income	$ 38,594	$ 34,130	$ 127,021	$ 114,616
Net income per common share
Basic	$ 1.04	$ 0.93	$ 3.44	$ 3.11
Diluted	1.02	0.90	3.36	3.01
Cash dividends declared per common share	$ 0.42	$ 0.33	$ 1.26	$ 0.99
Weighted average shares outstanding
Basic	36,951	36,865	36,952	36,856
Diluted	37,828	38,019	37,859	38,069
Commissions [Member]
Revenues
Revenues	$ 90,513	$ 86,270	$ 289,398	$ 267,307
Information Services [Member]
Revenues
Revenues	7,174	6,331	21,170	19,013
Post-trade Services [Member]
Revenues
Revenues	3,475	2,678	11,671	7,623
Other [Member]
Revenues
Revenues	$ 281	$ 305	$ 882	$ 919