CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS UNAUDITED - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities
Net income	$ 31,582				$ 22,894		$ 58,843	$ 47,714
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization							289	294
Stock based compensation expense	351	$ 187	$ 1,488	$ 369	4,381	$ 699	541	5,078	$ 6,937
Deferred income taxes							(3,896)	(5,698)
Foreign currency translation loss							29	47
Cost basis of donated securities							85	16
(Increase) decrease in assets:
Investments in trading securities							2,750	27
Receivable from affiliates							1,257	1,069
Receivable from brokers							(1,416)	(390)
Investment advisory fees receivable							10,176	16,241
Income tax receivable and deferred tax assets							(1,562)	(10,013)
Other assets							299	(357)
Increase (decrease) in liabilities:
Payable to affiliates							123	974
Payable to brokers							(117)	4,604
Income taxes payable and deferred tax liabilities							4,011	6,134
Compensation payable							14,720	11,254
Accrued expenses and other liabilities							(300)	(458)
Total adjustments							26,989	28,822
Net cash provided by operating activities							85,832	76,536
Investing activities
Purchases of available for sale securities							0	(50)
Proceeds from sales of available for sale securities					0			0
Net cash used in investing activities							0	(50)
Financing activities
Dividends paid							(1,756)	(1,156)
Purchase of treasury stock							(6,852)	(4,757)
Amortization of debt issuance costs							12	30
Net cash used in financing activities							(62,075)	(25,883)
Effect of exchange rates on cash and cash equivalents							(90)	(10)
Net increase in cash and cash equivalents							23,667	50,593
Cash and cash equivalents at beginning of period		$ 17,821		$ 90,405		$ 39,812	17,821	39,812	39,812
Cash and cash equivalents at end of period	$ 41,488		$ 17,821		$ 90,405		41,488	90,405	$ 17,821
Supplemental disclosures of cash flow information:
Cash paid for interest							1,386	3,824
Cash paid for taxes							19,447	38,905
AC 4% PIK Note [Member]
Financing activities
Repayment of debt							(30,000)	(20,000)
AC 1.6% Note [Member]
Financing activities
Repayment of debt							(15,000)	0
Margin Loan [Member]
Financing activities
Repayment of debt							(19,479)	0
Issuance of debt							$ 11,000	$ 0