Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash Flows from Operating Activities:
Net income	$ 11,870	$ 19,725
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation expense, intangible asset and other amortization	1,573	1,671
Stock-based compensation	3,270	3,063
Excess tax benefits from stock-based compensation	(130)	(1,314)
Amortization of deferred commissions	763	3,064
Payments of deferred commissions	(500)	(1,168)
Equity in earnings of equity method investments	(218)	(425)
Realized and unrealized losses (gains) on trading securities, net	658	(545)
Sales (purchases) of trading securities, net	11,197	8,710
Deferred taxes, net	4,900	2,368
Changes in operating assets and liabilities:
Accounts receivable, net and other assets	(4,944)	(6,054)
Accrued compensation and benefits, accounts payable, accrued liabilities and other liabilities	(35,710)	(35,020)
Net cash used in operating activities	(38,375)	(24,852)
Cash Flows from Investing Activities:
Capital expenditures	(591)	(1,397)
Purchases of other investments	(759)	0
Purchases of available-for-sale securities	(60)	(43)
Net cash used in investing activities	(1,307)	(1,440)
Cash Flows from Financing Activities:
Dividends paid	(3,911)	(4,129)
Repurchases of common shares	(15,000)	(14,000)
Proceeds from exercise of stock options	375	54
Taxes paid related to net share settlement of restricted stock units	(1,001)	(4,122)
Excess tax benefits from stock-based compensation	130	1,314
Contributions of noncontrolling interests, net	19,928	11,039
Net cash provided by (used in) financing activities	1,549	(8,923)
Net decrease in cash and cash equivalents	(38,133)	(35,215)
Cash and cash equivalents, beginning of period	97,384	203,304
Cash and Cash Equivalents, End of Period	59,251	168,089
Non-Cash Investing Activities:
Change in accrual for capital expenditures	(153)	458
Non-Cash Financing Activities:
(Decrease) increase to noncontrolling interest due to (deconsolidation) consolidation of consolidated sponsored investment products, net	(52,874)	450
Dividends payable	4,173	4,095
Consolidated Sponsored Investment Products [Member]
Adjustments to reconcile net income to net cash used in operating activities:
Realized and unrealized losses (gains) on trading securities, net	(683)	(1,659)
Sales (purchases) of trading securities, net	(21,545)	(16,583)
(Purchases) sales of securities sold short by consolidated sponsored investment products, net	(3,655)	1,533
Changes in operating assets and liabilities:
Cash pledged or on deposit of consolidated sponsored investment products	1,682	(2,245)
Other assets of consolidated sponsored investment products	(1,292)	(81)
Liabilities of consolidated sponsored investment products	618	108
Cash Flows from Investing Activities:
Change in cash and cash equivalents of consolidated sponsored investment products due to deconsolidation	103	0
Cash Flows from Financing Activities:
Borrowings of proceeds from short sales by consolidated sponsored investment products	0	921
Payments on borrowings by consolidated sponsored investment products	(1,839)	0
Consolidated Investment Product [Member]
Adjustments to reconcile net income to net cash used in operating activities:
Realized and unrealized losses (gains) on trading securities, net	(2,235)	0
Sales (purchases) of trading securities, net	(4,079)	0
Changes in operating assets and liabilities:
Other assets of consolidated sponsored investment products	(163)	0
Liabilities of consolidated investment product, net	248	0
Cash Flows from Financing Activities:
Borrowings of debt of consolidated investment product	$ 2,867	$ 0