Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues
Revenues	$ 168,978	$ 124,491
Expenses
Employee compensation and benefits	41,194	32,658
Depreciation and amortization	8,067	6,082
Technology and communications	8,161	5,782
Professional and consulting fees	5,675	5,831
Occupancy	3,474	2,949
Marketing and advertising	2,675	2,299
Clearing costs	5,510	2,577
General and administrative	3,133	3,124
Total expenses	77,889	61,302
Operating income	91,089	63,189
Other income (expense)
Investment income	1,269	1,989
Other, net	(656)	42
Total other income	613	2,031
Income before income taxes	91,702	65,220
Provision for income taxes	16,886	12,698
Net income	$ 74,816	$ 52,522
Net income per common share
Basic	$ 2.01	$ 1.42
Diluted	1.96	1.39
Cash dividends declared per common share	$ 0.60	$ 0.51
Weighted average shares outstanding
Basic	37,303	37,043
Diluted	38,075	37,832
Commissions [Member]
Revenues
Revenues	$ 155,954	$ 112,760
Information Services [Member]
Revenues
Revenues	8,642	7,366
Post-trade Services [Member]
Revenues
Revenues	4,153	4,100
Other [Member]
Revenues
Revenues	$ 229	$ 265