Consolidated Statements of Cash Flow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities:
Net income	$ 30,671	$ 96,965	$ 77,130
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation expense, intangible asset and other amortization	6,967	6,759	7,046
Stock-based compensation	11,863	9,778	7,960
Excess tax benefit from stock-based compensation	(1,586)	(24,805)	(478)
Amortization of deferred commissions	7,924	17,907	14,453
Payments of deferred commissions	(3,322)	(13,796)	(18,912)
Equity in earnings of equity method investments	(879)	(488)	(161)
Realized and unrealized losses (gains) on trading securities, net	1,158	(914)	(2,350)
Sales (purchases) of trading securities, net	8,962	26,742	(2,701)
Deferred taxes, net	6,356	4,394	32,596
Changes in operating assets and liabilities:
Accounts receivable, net and other assets	10,620	(4,157)	(13,416)
Accrued compensation and benefits, accounts payable, accrued liabilities and other liabilities	(14,795)	17,754	31,051
Net cash (used in) provided by operating activities	(209,430)	(58,871)	28,837
Cash Flows from Investing Activities:
Capital expenditures	(4,683)	(2,432)	(2,009)
Asset acquisitions and purchases of other investments	(1,617)	(5,000)	(3,364)
Cash acquired in business combination	89	0	0
Purchases of available-for-sale securities	(227)	(313)	(196)
Net cash used in investing activities	(6,438)	(8,181)	(6,231)
Cash Flows from Financing Activities:
Contingent consideration paid for acquired investment management contracts	0	0	(630)
Repurchase of common shares	(80,000)	(40,261)	(19,704)
Dividends paid	(16,047)	(8,182)	0
Proceeds from exercise of stock options	116	753	570
Taxes paid related to net share settlement of restricted stock units	(5,080)	(9,512)	(7,513)
Proceeds from issuance of common stock, net of issuance costs	0	0	191,771
Excess tax benefits from stock-based compensation	1,586	24,805	478
Payment of debt and deferred financing costs	(47)	0	(15,026)
Contributions of noncontrolling interests, net	55,700	28,653	35,547
Net cash provided by (used in) financing activities	109,948	(1,189)	185,493
Net (decrease) increase in cash and cash equivalents	(105,920)	(68,241)	208,099
Cash and cash equivalents, beginning of year	203,304	271,545	63,446
Cash and Cash Equivalents, end of year	97,384	203,304	271,545
Supplemental Disclosure of Cash Flow Information
Interest paid	266	266	393
Income taxes paid, net	31,850	23,274	1,697
Supplemental Disclosure of Non-Cash Activities
Activity related to rabbi trust	(247)	(843)	(1,250)
Capital expenditures	(692)	(311)	52
Dividends payable	4,233	4,270	0
(Decrease) increase to noncontrolling interest due to (deconsolidation) consolidation of sponsored investment products, net	(648)	(47,165)	1,477
Consolidated Investment Product [Member]
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Realized and unrealized losses (gains) on trading securities, net	3,505	0	0
Sales (purchases) of trading securities, net	(186,028)	0	0
Changes in operating assets and liabilities:
Other assets	(426)	0	0
Liabilities of consolidated investment product, net	484	0	0
Cash Flows from Financing Activities:
Borrowings of debt of consolidated investment product	152,597	0	0
Consolidated Sponsored Investment Products [Member]
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Realized and unrealized losses (gains) on trading securities, net	26,532	4,671	(3,515)
Sales (purchases) of trading securities, net	(113,190)	(195,850)	(100,526)
(Purchases) sales of securities sold short by consolidated sponsored investment products, net	(1,747)	8,071	0
Changes in operating assets and liabilities:
Cash pledged or on deposit of consolidated sponsored investment products	(2,604)	(10,785)	0
Other assets	(2,002)	(1,468)	508
Liabilities of consolidated sponsored investment products	2,107	351	152
Cash Flows from Investing Activities:
Change in cash and cash equivalents of consolidated sponsored investment products due to deconsolidation	0	(436)	(662)
Cash Flows from Financing Activities:
Borrowings of proceeds from short sales by consolidated sponsored investment products	1,473	2,555	0
Payments on borrowings by consolidated sponsored investment products	(350)	0	$ 0
Cash and cash equivalents, beginning of year	8,687
Cash and Cash Equivalents, end of year	$ 11,866	$ 8,687