Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 460,858	$ 270,124
Cash segregated under federal regulations	50,059
Investments, at fair value	28,111	230,477
Accounts receivable, net of allowance of $163 and $57 as of December 31, 2020 and 2019, respectively	79,577	62,017
Receivables from broker-dealers, clearing organizations and customers	279,915
Goodwill	147,388	146,861
Intangible assets, net of accumulated amortization	95,354	60,986
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	85,204	71,795
Operating lease right-of-use assets	75,924	81,399
Prepaid expenses and other assets	29,039	31,271
Total assets	1,331,429	954,930
Liabilities
Accrued employee compensation	62,326	47,365
Payables to broker-dealers, clearing organizations and customers	133,326
Income and other tax liabilities	42,750	16,690
Accounts payable, accrued expenses and other liabilities	44,354	22,793
Operating lease liabilities	93,612	97,991
Total liabilities	376,368	184,839
Commitments and Contingencies (Note 15)
Stockholders' equity
Preferred stock
Common stock	123	122
Additional paid-in capital	329,742	342,541
Treasury stock - Common stock voting, at cost, 2,845,770 and 2,810,609 shares as of December 31, 2020 and 2019, respectively	(169,523)	(153,388)
Retained earnings	799,369	591,086
Accumulated other comprehensive loss	(4,650)	(10,270)
Total stockholders' equity	955,061	770,091
Total liabilities and stockholders' equity	1,331,429	954,930
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock