Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 432,715	$ 460,858
Cash segregated under federal regulations	50,134	50,059
Investments, at fair value	35,767	28,111
Accounts receivable, net of allowance of $82 and $163 as of September 30, 2021 and December 31, 2020, respectively	67,766	79,577
Receivables from broker-dealers, clearing organizations and customers	551,841	279,915
Goodwill	154,789	147,388
Intangible assets, net of accumulated amortization	119,797	95,354
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	95,575	85,204
Operating lease right-of-use assets	72,586	75,924
Prepaid expenses and other assets	30,948	29,039
Total assets	1,611,918	1,331,429
Liabilities
Accrued employee compensation	49,046	62,326
Payables to broker-dealers, clearing organizations and customers	303,439	133,326
Income and other tax liabilities	44,871	42,750
Accounts payable, accrued expenses and other liabilities	69,300	44,354
Operating lease liabilities	89,963	93,612
Total liabilities	556,619	376,368
Commitments and Contingencies (Note 13)
Stockholders' equity
Preferred stock
Common stock	123	123
Additional paid-in capital	323,631	329,742
Treasury stock - Common stock voting, at cost, 2,880,856 and 2,845,770 shares as of September 30, 2021 and December 31, 2020, respectively	(187,715)	(169,523)
Retained earnings	929,853	799,369
Accumulated other comprehensive loss	(10,593)	(4,650)
Total stockholders' equity	1,055,299	955,061
Total liabilities and stockholders' equity	1,611,918	1,331,429
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock