Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2016
Variable Interest Entity [Line Items]
Basis of Accounting	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, these financial statements contain all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the Company’s financial condition and results of operations. Operating results for the six months ended June 30, 2016 are not necessarily indicative of the results that may be expected for the year ending December 31, 2016
Consolidation	The condensed consolidated financial statements include the accounts of the Company, its subsidiaries and investment products that are consolidated. Voting interest entities ("VOEs") are consolidated when the Company is considered to have a controlling financial interest which is typically present when the Company owns a majority of the voting interest in an entity or otherwise has the power to govern the financial and operating policies of the subsidiary or investment product. The Company evaluates any variable interest entities (“VIEs”) in which the Company has a variable interest for consolidation. A VIE is an entity in which either (a) the equity investment at risk is not sufficient to permit the entity to finance its own activities without additional financial support or (b) where as a group, the holders of the equity investment at risk do not possess: (i) the power through voting or similar rights to direct the activities that most significantly impact the entity’s economic performance; (ii) the obligation to absorb expected losses or the right to receive expected residual returns of the entity; or (iii) proportionate voting and economic interests and where substantially all of the entity’s activities either involve or are conducted on behalf of an investor with disproportionately fewer voting rights. If any entity has any of these characteristics, it is considered a VIE and is required to be consolidated by its primary beneficiary. The primary beneficiary is the entity that has both the power to direct the activities that most significantly impact the VIE’s economic performance and has the obligation to absorb losses of, or the right to receive benefits from, the VIE that could potentially be significant to the VIE. The Company's investment products that are consolidated are referred to as consolidated sponsored investment products or the consolidated investment product. Consolidated sponsored investment products are investment products in which the Company generally holds a majority of the economic interests. The consolidated investment product is a collateralized loan obligation ("CLO") in which the Company has a beneficial interest. The consolidation and deconsolidation of these investment products have no impact on net income attributable to stockholders. The Company’s risk with respect to these investments is limited to its investment in these products and any investment management fees it earns. The Company has no right to the benefits from, and does not bear the risks associated with, these investment products beyond the Company’s investments in, and fees generated from, these products. The Company does not consider cash and investments held by the investment products it consolidates to be assets of the Company other than its direct investment in these products. See Note 13 for additional information related to the consolidation of sponsored investment products and the investment product. Intercompany accounts and transactions have been eliminated.
Consolidation, Variable Interest Entities	The Company evaluates any variable interest entities (“VIEs”) in which the Company has a variable interest for consolidation. A VIE is an entity in which either (a) the equity investment at risk is not sufficient to permit the entity to finance its own activities without additional financial support or (b) where as a group, the holders of the equity investment at risk do not possess: (i) the power through voting or similar rights to direct the activities that most significantly impact the entity’s economic performance; (ii) the obligation to absorb expected losses or the right to receive expected residual returns of the entity; or (iii) proportionate voting and economic interests and where substantially all of the entity’s activities either involve or are conducted on behalf of an investor with disproportionately fewer voting rights. If any entity has any of these characteristics, it is considered a VIE and is required to be consolidated by its primary beneficiary. The primary beneficiary is the entity that has both the power to direct the activities that most significantly impact the VIE’s economic performance and has the obligation to absorb losses of, or the right to receive benefits from, the VIE that could potentially be significant to the VIE. The Company's investment products that are consolidated are referred to as consolidated sponsored investment products or the consolidated investment product. Consolidated sponsored investment products are investment products in which the Company generally holds a majority of the economic interests. The consolidated investment product is a collateralized loan obligation ("CLO") in which the Company has a beneficial interest. The consolidation and deconsolidation of these investment products have no impact on net income attributable to stockholders. The Company’s risk with respect to these investments is limited to its investment in these products and any investment management fees it earns. The Company has no right to the benefits from, and does not bear the risks associated with, these investment products beyond the Company’s investments in, and fees generated from, these products. The Company does not consider cash and investments held by the investment products it consolidates to be assets of the Company other than its direct investment in these products. See Note 13 for additional information related to the consolidation of sponsored investment products and the investment product. Intercompany accounts and transactions have been eliminated.
New Accounting Standards	New Accounting Standards Implemented The Company adopted Accounting Standards Update ("ASU") No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis ("ASU 2015-02") on January 1, 2016. This standard modifies existing consolidation guidance for reporting organizations that are required to evaluate whether they should consolidate certain entities. Certain unconsolidated entities that had been classified as VOEs under previous consolidation guidance are now classified as VIEs under ASU 2015-02. As such, disclosure for VIEs is included in Note 13 to the condensed consolidated financial statements. Adoption of this standard did not have a material impact on the Company’s condensed consolidated financial statements. The Company adopted ASU No. 2014-13, Measuring the Financial Assets and Financial Liabilities of a Consolidated Collateralized Financing Entity (“CFE”) ("ASU 2014-13") on January 1, 2016. This new standard requires reporting entities to use the more observable of the fair value of the financial assets or the financial liabilities to measure the financial assets and the financial liabilities of a CFE when a CFE is initially consolidated. It permits entities to make an accounting policy election to apply this same measurement approach after initial consolidation or to apply other GAAP to account for the consolidated CFE’s financial assets and financial liabilities. It also prohibits all entities from electing to use the fair value option in ASC 825, Financial Instruments, to measure either the financial assets or financial liabilities of a consolidated CFE that is within the scope of this issue. The Company has elected the measurement alternative for its consolidated investment product. The Company's subsequent earnings from the consolidated investment product will reflect changes in value of the Company's own economic interest in the consolidated investment product. Adoption of this standard did not have a material impact on the Company's condensed consolidated financial statements. The Company adopted ASU No. 2015-16 “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments” ("ASU 2015-16") on January 1, 2016. ASU 2015-16 requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. ASU 2015-16 requires that the acquirer record, in the financial statements of the period in which adjustments to provisional amounts are determined, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. Adoption of this standard did not have a material impact on the Company's condensed consolidated financial statements. The Company adopted ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs ("ASU 2015-3") on January 1, 2016, which changes the presentation of debt issuance costs in the balance sheet. This new standard requires that debt issuance costs be presented as a deduction from the carrying amount of the related debt rather than being presented as an asset. Amortization of debt issuance costs will continue to be reported as interest expense. In August 2015, the FASB issued ASU 2015-15 to amend ASU 2015-03 to address line-of-credit agreements. ASU 2015-15 allows entities to present debt issuance costs related to line-of-credit agreements as an asset and amortize deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings. Adoption of this standard did not have a material impact on the Company's condensed consolidated financial statements. New Accounting Standards Not Yet Implemented In March 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718) ("ASU 2016-09"). This standard makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The standard is effective for interim and annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is currently evaluating the potential impact of this standard on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-08, Principal Versus Agent Considerations (Reporting Revenue Gross Versus Net), which amends the principal-versus-agent implementation guidance in ASU 2014-09. The new guidance will impact whether an entity reports revenue on a gross or net basis. The Company is currently evaluating the impact of adopting ASU 2016-08, which is effective for the Company in conjunction with the adoption of ASU 2014-09. In March 2016, the FASB issued ASU No. 2016-07, "Investments—Equity Method and Joint Ventures (Topic 232): Simplifying the Transition to the Equity Method of Accounting." This standard eliminates the requirement that when an existing cost method investment qualifies for use of the equity method, an investor must restate its historical financial statements, as if the equity method had been used during all previous periods. Under the new guidance, at the point an investment qualifies for the equity method, any unrealized gain or loss in accumulated other comprehensive income/(loss) will be recognized through earnings. The standard is effective for interim and annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is currently evaluating the potential impact of this standard on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ("ASU 2016-02"). The standard replaces current codification Topic 840 with updated guidance on accounting for leases and requires a lessee to recognize assets and liabilities arising from an operating lease on the balance sheet, whereas previous U.S. GAAP did not require lease assets and liabilities to be recognized for most leases. Furthermore, companies are permitted to make an accounting policy election to not recognize lease assets and liabilities for leases with a term of 12 months or less. For both finance leases and operating leases, the lease liability should be initially measured at the present value of the lease payments. The recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will not significantly change under this new guidance. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods therein. Early adoption is permitted. The Company is currently evaluating the potential impact of this standard on its consolidated financial statements. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-1"), which requires all equity investments (other than those accounted for under the equity method) to be measured at fair value with changes in the fair value recognized through net income. ASU 2016-01 is effective for fiscal years beginning after December 15, 2017 and interim periods therein. Early adoption is not permitted. The Company is currently evaluating the potential impact of this standard on its consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”). ASU 2014-09 provides a comprehensive new revenue recognition model requiring a company to recognize revenue to depict the transfer of goods or services to a customer at an amount reflecting the consideration it expects to receive in exchange for those goods or services. Companies may use either a full retrospective or a modified retrospective approach. In July 2015, the FASB confirmed a deferral of the effective date by one year, with early adoption on the original effective date permitted. As deferred, ASU 2014-09 is effective for the first interim period within annual reporting periods beginning after December 15, 2017 with early adoption permitted. The Company is currently evaluating the potential impact of this standard on its consolidated financial statements.
Fair Value Measurements	The following is a discussion of the valuation methodologies used for the Company’s assets measured at fair value: Cash equivalents represent investments in money market funds. Cash investments in actively traded money market funds are valued using published net asset values and are classified as Level 1. Sponsored funds represent investments in open-end mutual funds, variable insurance funds and closed-end funds for which the Company acts as the investment manager. The fair value of open-end mutual funds and variable insurance funds is determined based on their published net asset values and are categorized as Level 1. The fair value of closed-end funds is determined based on the official closing price on the exchange on which they are traded and are categorized as Level 1. Equity securities include securities traded on active markets and are valued at the official closing price (typically last sale or bid) on the exchange on which the securities are primarily traded and are categorized as Level 1. Nonqualified retirement plan assets represent mutual funds within a nonqualified retirement plan whose fair value is determined based on their published net asset value and are categorized as Level 1. Cash, accounts receivable, accounts payable and accrued liabilities equal or approximate fair value based on the short-term nature of these instruments.
Fair Value Measurements, Transfers	Transfers into and out of levels are reflected when (1) significant inputs used for the fair value measurement, including market inputs or performance attributes, become observable or unobservable, (2) when the Company determines it has the ability, or no longer has the ability, to redeem, in the near term, certain investments that the Company values using a net asset value, or (3) if the book value no longer represents fair value.
Consolidated Sponsored Investment Products [Member]
Variable Interest Entity [Line Items]
Fair Value Measurements	Investments of consolidated sponsored investment products represent the underlying debt, equity and other securities held in sponsored products which are consolidated by the Company. Equity securities are valued at the official closing price on the exchange on which the securities are traded and are categorized within Level 1. Level 2 investments include most debt securities, which are valued based on quotations received from independent pricing services or from dealers who make markets in such securities and certain equity securities, including non-US securities, for which closing prices are not readily available or are deemed to not reflect readily available market prices and are valued using an independent pricing service. Pricing services do not provide pricing for all securities, and therefore indicative bids from dealers are utilized, which are based on pricing models used by market makers in the security and are also included within Level 2. Level 3 investments include debt securities that are not widely traded, are illiquid or are priced by dealers based on pricing models used by market makers in the security.
Derivatives	The Company has certain consolidated sponsored investment products which include derivative instruments as part of their investment strategies. These derivatives may include futures contracts, options contracts and forward contracts. Derivative instruments in an asset position are classified as other assets of consolidated sponsored investment products in the Condensed Consolidated Balance Sheets. Derivative instruments in a liability position are classified as liabilities of consolidated sponsored investment products within the Condensed Consolidated Balance Sheets. The change in fair value of such derivatives is recorded in realized and unrealized gain (loss) on investments of consolidated sponsored investment products, net, in the Condensed Consolidated Statements of Operations. In connection with entering into these derivative contracts, these funds may be required to pledge to the broker an amount of cash equal to the “initial margin” requirements that varies based on the type of derivative. The cash pledged or on deposit is recorded in the Condensed Consolidated Balance Sheets of the Company as cash pledged or on deposit of consolidated sponsored investment products.
Short Sales	Some of the Company’s consolidated sponsored investment products may engage in short sales, which are transactions in which a security is sold which is not owned or is owned but there is no intention to deliver, in anticipation that the price of the security will decline. Short sales are recorded in the Condensed Consolidated Balance Sheets within other liabilities of consolidated sponsored investment products.
Consolidated Investment Product [Member]
Variable Interest Entity [Line Items]
Fair Value Measurements	Cash equivalents represent investments in money market funds. Cash investments in actively traded money market funds are valued using published net asset values and are classified as Level 1. Bank loans represent the underlying debt securities held in the sponsored product which are consolidated by the Company. Bank loan investments include debt securities, which are valued based on quotations received from an independent pricing service. Pricing services do not provide pricing for all securities, and therefore indicative bids from dealers are utilized, which are based on pricing models used by market makers in the security and are also included within Level 2.