Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 210,085	$ 167,014
Investments, at fair value	236,101	239,521
Accounts receivable, net of allowance of $91 and $178 as of September 30, 2018 and December 31, 2017, respectively	62,004	52,636
Goodwill and intangible assets, net of accumulated amortization	62,771	63,059
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	54,320	38,548
Prepaid expenses and other assets	18,594	18,717
Deferred tax assets, net	2,256	1,737
Total assets	646,131	581,232
Liabilities
Accrued employee compensation	31,468	36,502
Income and other tax liabilities	12,921	13,061
Deferred revenue	3,785	2,660
Accounts payable, accrued expenses and other liabilities	19,339	14,241
Total liabilities	67,513	66,464
Commitments and Contingencies (Note 10)
Stockholders' equity
Additional paid-in capital	336,079	331,081
Treasury stock - Common stock voting, at cost, 2,870,326 and 2,781,323 shares as of September 30, 2018 and December 31, 2017, respectively	(178,776)	(159,791)
Retained earnings	433,227	353,583
Accumulated other comprehensive (loss)	(12,033)	(10,226)
Total stockholders' equity	578,618	514,768
Total liabilities and stockholders' equity	646,131	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