Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 167,014	$ 168,243
Investments, at fair value	239,521	194,404
Accounts receivable, net of allowance of $178 and $82 as of December 31, 2017 and 2016, respectively	52,636	50,668
Goodwill and intangible assets, net of accumulated amortization	63,059	63,443
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	38,548	31,104
Prepaid expenses and other assets	18,717	11,618
Deferred tax assets, net	1,737	8,562
Total assets	581,232	528,042
Liabilities
Accrued employee compensation	36,502	34,783
Income and other tax liabilities	13,061	7,582
Deferred revenue	2,660	2,515
Accounts payable, accrued expenses and other liabilities	14,241	15,149
Total liabilities	66,464	60,029
Commitments and Contingencies (Note 12)
Stockholders' equity
Additional paid-in capital	331,081	342,311
Treasury stock - Common stock voting, at cost, 2,781,323 and 2,562,585 shares as of December 31, 2017 and 2016, respectively	(159,791)	(117,330)
Retained earnings	353,583	255,140
Accumulated other comprehensive loss	(10,226)	(12,228)
Total stockholders' equity	514,768	468,013
Total liabilities and stockholders' equity	581,232	528,042
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	$ 120