Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows from Operating Activities:
Net Income	$ 96,965	$ 77,130	$ 37,773
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation expense, intangible asset and other amortization	6,759	7,046	6,198
Stock-based compensation	9,778	7,960	6,927
Excess tax benefit from stock-based compensation	(24,805)	(478)	(89)
Amortization of deferred commissions	17,907	14,453	10,715
Payments of deferred commissions	(13,796)	(18,912)	(10,868)
Equity in earnings of equity method investments	(488)	(161)
Realized and unrealized gains on trading securities	(914)	(2,350)	(1,891)
Realized and unrealized losses (gains) on investments of consolidated sponsored investment products	4,671	(3,515)	(2,072)
Sales (purchases) of trading securities, net	26,742	(2,701)	2,025
Purchases of investments by consolidated sponsored investment products, net	(195,683)	(100,499)	(41,155)
Sales of securities sold short by consolidated sponsored investment products, net	8,071
Deferred taxes, net	4,394	32,596	26,689
Changes in operating assets and liabilities:
Cash pledged or on deposit of consolidated sponsored investment products	(10,785)
Accounts receivable, net and other assets	(4,157)	(13,416)	(10,047)
Other assets of consolidated sponsored investment products	1,082	(6,043)	(683)
Accrued compensation and benefits, accounts payable, accrued liabilities and other liabilities	17,754	37,575	15,919
Liabilities of consolidated sponsored investment products	(2,366)	152	377
Net cash (used in) provided by operating activities	(58,871)	28,837	39,818
Cash Flows from Investing Activities:
Capital expenditures	(2,432)	(2,009)	(3,782)
Change in cash and cash equivalents of consolidated sponsored investment products due to deconsolidation	(436)	(662)
Asset acquisitions and purchases of other investments	(5,000)	(3,364)	(1,006)
Purchase of available-for-sale securities	(313)	(196)	(379)
Net cash used in investing activities	(8,181)	(6,231)	(5,167)
Cash Flows from Financing Activities:
Contingent consideration paid for acquired investment management contracts	0	(630)	(665)
Borrowings of proceeds from short sales by consolidated sponsored investment products	2,555
Repurchase of common shares	(40,261)	(19,704)	(8,940)
Dividends paid	(8,182)
Proceeds from exercise of stock options	753	570	2,636
Taxes paid related to net share settlement of restricted stock units	(9,512)	(7,513)	(11,951)
Proceeds from issuance of common stock, net of issuance costs	0	191,771
Excess tax benefits from stock-based compensation	24,805	478	89
Payment of debt and deferred financing costs	0	(15,026)	(700)
Contributions of noncontrolling interests, net	28,653	35,547	3,059
Net cash (used in) provided by financing activities	(1,189)	185,493	(16,472)
Net (decrease) increase in cash and cash equivalents	(68,241)	208,099	18,179
Cash and cash equivalents, beginning of year	271,545	63,446	45,267
Cash and Cash Equivalents, end of year	203,304	271,545	63,446
Supplemental Cash Flow Information:
Interest paid	266	393	415
Income taxes paid, net	23,274	1,697	74
Non-Cash Investing Activities:
Purchase of investment management contracts	0		435
Non-cash activity related to rabbi trust	(843)	(1,250)	(144)
Non-Cash Financing Activities:
Dividends payable	4,270
(Decrease) increase to noncontrolling interest due to (deconsolidation) consolidation of sponsored investment products, net	(47,165)	1,477
Preferred stock conversion	$ 0		$ 35,217