Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Commissions	$ 221,138	$ 203,652	$ 174,199
Information and post-trade services	31,510	25,377	7,435
Technology products and services	6,874	6,331	4,988
Investment income	543	420	1,057
Other	2,709	2,953	3,161
Total revenues	262,774	238,733	190,840
Expenses
Employee compensation and benefits	74,995	64,406	54,678
Depreciation and amortization	17,379	14,123	6,758
Technology and communications	17,685	16,037	12,523
Professional and consulting fees	14,375	18,220	12,150
Occupancy	4,381	5,173	2,446
Marketing and advertising	5,769	4,632	5,169
General and administrative	9,654	8,862	7,746
Total expenses	144,238	131,453	101,470
Income before income taxes from continuing operations	118,536	107,280	89,370
Provision for income taxes	43,730	38,717	27,586
Net income from continuing operations	74,806	68,563	61,784
Loss from discontinued operations, net of income taxes		(189)	(1,715)
Gain on the sale of discontinued operations, net of tax benefit		7,642
Net income	$ 74,806	$ 76,016	$ 60,069
Basic earnings per common share
Income from continuing operations	$ 2.03	$ 1.86	$ 1.69
Income (loss) from discontinued operations		$ 0.20	$ (0.04)
Net income per common share	$ 2.03	$ 2.06	$ 1.65
Diluted earnings per common share
Income from continuing operations	$ 1.97	$ 1.81	$ 1.64
Income (loss) from discontinued operations		$ 0.20	$ (0.05)
Net income per common share	$ 1.97	$ 2.01	$ 1.59
Cash dividends declared per common share	$ 0.64	$ 0.52	$ 1.74
Weighted average shares outstanding
Basic	36,930	36,886	36,516
Diluted	37,889	37,888	37,816