Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash Flows from Operating Activities:
Net income	$ 25,034	$ 78,554
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation expense, intangible asset and other amortization	5,241	5,055
Stock-based compensation	9,166	7,021
Excess tax benefits from stock-based compensation	(1,515)	(25,089)
Amortization of deferred commissions	6,903	14,032
Payments of deferred commissions	(2,585)	(11,761)
Equity in earnings of equity method investments, net	(804)	(295)
Realized and unrealized losses (gains) on trading securities, net	1,490	(1,712)
Sales (purchases) of trading securities, net	9,945	24,996
Deferred taxes, net	655	4,826
Changes in operating assets and liabilities:
Accounts receivable, net and other assets	4,101	(17,776)
Accrued compensation and benefits, accounts payable, accrued liabilities and other liabilities	(8,102)	8,424
Net cash used in operating activities	(56,951)	(102,288)
Cash Flows from Investing Activities:
Capital expenditures	(3,723)	(1,814)
Asset acquisitions and purchases of other investments	(1,617)	(5,000)
Cash acquired in business combination	89	0
Purchases of available-for-sale securities	(168)	(260)
Net cash used in investing activities	(5,419)	(7,440)
Cash Flows from Financing Activities:
Dividends paid	(12,146)	(4,104)
Repurchases of common shares	(45,000)	(26,257)
Proceeds from exercise of stock options	70	660
Taxes paid related to net share settlement of restricted stock units	(5,080)	(9,512)
Excess tax benefits from stock-based compensation	1,515	25,089
Contributions of noncontrolling interests, net	38,747	24,871
Net cash (used in) provided by financing activities	(12,087)	11,947
Net decrease in cash and cash equivalents	(74,457)	(97,781)
Cash and cash equivalents, beginning of period	203,304	271,545
Cash and Cash Equivalents, End of Period	128,847	173,764
Non-Cash Investing Activities:
Change in accrual for capital expenditures	(313)	97
Investment in acquired business	4,800	0
Non-Cash Financing Activities:
Decrease to noncontrolling interest due to consolidation (deconsolidation) of consolidated sponsored investment products, net	(8,640)	(44,613)
Dividends payable	4,258	4,229
Consolidated Sponsored Investment Products [Member]
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Realized and unrealized losses (gains) on trading securities, net	21,611	(1,247)
Sales (purchases) of trading securities, net	(96,222)	(184,584)
Sales of securities sold short by consolidated sponsored investment products, net	3,534	10,461
Changes in operating assets and liabilities:
Cash pledged or on deposit of consolidated sponsored investment products	(6,912)	(12,492)
Other assets of consolidated sponsored investment products	(1,649)	(1,502)
Liabilities of consolidated sponsored investment products	1,499	801
Cash Flows from Investing Activities:
Change in cash and cash equivalents of consolidated sponsored investment products due to deconsolidation	0	(366)
Cash Flows from Financing Activities:
Borrowings of proceeds from short sales by consolidated sponsored investment products	831	1,200
Payments on borrowings by consolidated sponsored investment products	(164)	0
Cash and cash equivalents, beginning of period	8,687
Cash and Cash Equivalents, End of Period	16,732
Consolidated Investment Product [Member]
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Realized and unrealized losses (gains) on trading securities, net	764	0
Sales (purchases) of trading securities, net	(29,085)	0
Changes in operating assets and liabilities:
Liabilities and other assets of consolidated investment product, net	(20)	0
Cash Flows from Financing Activities:
Borrowings of debt of consolidated investment product	$ 9,140	$ 0