Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues
Commissions	$ 54,198	$ 42,690	$ 101,384	$ 87,592
Information and post-trade services	7,192	1,790	10,895	3,661
Technology products and services	3,537	3,220	6,676	6,128
Investment income	44	268	176	571
Other	588	857	1,985	1,608
Total revenues	65,559	48,825	121,116	99,560
Expenses
Employee compensation and benefits	15,927	15,305	32,280	31,146
Depreciation and amortization	4,504	1,961	7,073	3,815
Technology and communications	4,099	3,015	7,290	5,970
Professional and consulting fees	4,726	2,837	9,327	5,861
Occupancy	1,287	757	2,219	1,516
Marketing and advertising	1,432	1,732	2,417	3,179
General and administrative	2,073	2,018	4,686	4,125
Total expenses	34,048	27,625	65,292	55,612
Income before income taxes	31,511	21,200	55,824	43,948
Provision for income taxes	12,168	8,571	21,155	17,826
Net income	$ 19,343	$ 12,629	$ 34,669	$ 26,122
Net income per common share
Basic	$ 0.52	$ 0.35	$ 0.94	$ 0.72
Diluted	$ 0.51	$ 0.34	$ 0.92	$ 0.69
Cash dividends declared per common share	$ 0.13	$ 0.11	$ 0.26	$ 0.22
Weighted average common shares
Basic	36,868	36,128	36,821	36,531
Diluted	37,819	37,440	37,746	38,067