Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 170,686	$ 167,014
Investments, at fair value	249,591	239,521
Accounts receivable, net of allowance of $74 and $178 as of June 30, 2018 and December 31, 2017, respectively	61,883	52,636
Goodwill and intangible assets, net of accumulated amortization	62,867	63,059
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	50,088	38,548
Prepaid expenses and other assets	21,030	18,717
Deferred tax assets, net	1,453	1,737
Total assets	617,598	581,232
Liabilities
Accrued employee compensation	23,612	36,502
Income and other tax liabilities	12,972	13,061
Deferred revenue	3,595	2,660
Accounts payable, accrued expenses and other liabilities	20,041	14,241
Total liabilities	60,220	66,464
Commitments and Contingencies (Note 10)
Stockholders' equity
Additional paid-in capital	331,056	331,081
Treasury stock - Common stock voting, at cost, 2,841,245 and 2,781,323 shares as of June 30, 2018 and December 31, 2017, respectively	(172,695)	(159,791)
Retained earnings	410,419	353,583
Accumulated other comprehensive loss	(11,523)	(10,226)
Total stockholders' equity	557,378	514,768
Total liabilities and stockholders' equity	617,598	581,232
Undefined Preferred Stock [Member]
Stockholders' equity
Preferred stock
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock
Voting Common Stock [Member]
Stockholders' equity
Common stock	$ 121	$ 121