Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
New Accounting Pronouncements Adopted	New Accounting Pronouncements Adopted—In February 2015, the Financial Accounting Standards Board (FASB) revised the guidance applicable to consolidation of legal entities. The revised rules include guidance for evaluating (a) limited partnerships and similar entities, (b) the impact of decision maker or service provider fees on the consolidation analysis, (c) the impact of interests held by related parties on the consolidation analysis and (d) consolidation of certain investment funds. The Company adopted this guidance effective January 1, 2016, using a full retrospective method. In connection with the adoption of this guidance, the Company reevaluated all of its sponsored funds and management fees under the new guidance. The Company concluded that certain entities that were not previously considered Variable Interest Entities (VIEs) would be considered VIEs under the revised guidance. See Note 4 for further discussion of the Company's seed investments. In May 2015, the FASB issued new guidance related to the disclosure of certain investments that calculate net asset value per share (NAV) as a practical expedient. This guidance removes the requirement to categorize such investments within the fair value hierarchy table. The Company adopted this guidance on January 1, 2016 on a retrospective basis to all periods presented. As a result of adoption, $7.2 million and $6.5 million of NAV investments at December 31, 2016 and December 31, 2015, respectively, are no longer classified within Level 2 and Level 3 within the fair value hierarchy. The fair value amounts presented in Note 5 are intended to permit reconciliation of the investments included in the fair value hierarchy to the amounts presented on the consolidated statement of financial position. In August 2014, the FASB issued new guidance regarding disclosure of going concern uncertainties in the financial statements. The guidance requires management to evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the entity's ability to continue as a going concern within one year after the date that the financial statements are issued at each annual and interim reporting period. This new guidance was effective for the Company's first quarter of 2016. The adoption of this new guidance did not have a material impact on its consolidated financial statements and related disclosures.
Accounting Estimates	Accounting Estimates—The preparation of the consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosures of contingent assets and liabilities at the dates of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. Management believes the estimates used in preparing the consolidated financial statements are reasonable and prudent. Actual results could differ from those estimates.
Consolidation of Company-sponsored Funds	Consolidation of Company-sponsored Funds—The Company consolidates entities, including sponsored funds, that are deemed to be voting interest entities (VOE) when it has financial control over the entity which is generally when the Company owns a majority of the outstanding voting interest. Investments in Company-sponsored funds and management fees are evaluated at inception and subsequently if there is a reconsideration event to determine if the fund is a VIE or VOE and which consolidation model to apply. All of the Company's management fees are presumed to be commensurate and at market and are therefore not considered variable interests. VIEs for which the Company is deemed to be the primary beneficiary are consolidated. Investments in Company-sponsored funds that are determined to be VOEs are consolidated when the Company’s ownership interest is greater than 50% of the outstanding voting interests of the fund or when the Company is the general partner of the fund and the limited partners do not have substantive kick-out or participating rights in the fund. The Company records noncontrolling interests in consolidated subsidiaries for which the Company’s ownership is less than 100 percent.
VIE	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) the group of holders of the equity investment at risk lack certain characteristics of a controlling financial interest. The primary beneficiary is the entity that has (a) the power to direct the activities of the VIE that most significantly affect its performance and (b) the obligation to absorb losses of the entity or the right to receive benefits from the entity that could potentially be significant to the VIE. Investments and redemptions or amendments to the governing documents of the respective entities could affect an entity's status as a VIE or the determination of the primary beneficiary. The Company assesses whether it is the primary beneficiary of any VIEs identified by evaluating its economic interests in the entity held either directly by the Company and its affiliates or indirectly through employees. See Note 4 for further discussion about the Company’s seed investments.
Cash and Cash Equivalents	Cash and Cash Equivalents—Cash equivalents consist of short-term, highly liquid investments, which are readily convertible into cash and have original maturities of three months or less.
Due from/to Brokers	Due from/to Brokers—The Company conducts business, primarily with respect to its consolidated seed investments, with brokers for certain of its investment activities. The clearing and custody operations for these investment activities are performed pursuant to contractual agreements. The due from/to brokers balance represents cash and cash equivalents balances at brokers/custodians and/or receivables and payables for unsettled securities transactions.
Investments	Investments—Management of the Company determines the appropriate classification of its investments at the time of purchase and re-evaluates such determination at each statement of financial condition date. Investments classified as trading represent securities held within the affiliated funds that the Company consolidates and are measured at fair value based on quoted market prices, market prices obtained from independent pricing services engaged by management or as determined by management and approved by the Company’s valuation committee. Unrealized gains and losses are recorded as gain (loss) from trading investments—net in the Company’s consolidated statements of operations. Investments classified as equity method investments represent seed investments in which the Company owns between 20-50% of the outstanding voting interests in the affiliated fund or when it is determined that the Company is able to exercise significant influence but not control over the investments. When using the equity method, the Company recognizes its respective share of the affiliated investee fund net income or loss for the period which is recorded as equity in earnings (losses) of affiliates in the Company’s consolidated statements of operations. As of December 31, 2016, the Company's equity method investments consisted of interests in affiliated funds which measure their underlying investments at fair value based on quoted market prices or NAV (or its equivalent) as a practical expedient and report a net asset value on a recurring basis. The carrying amounts of these investments approximate their fair value. Investments classified as available-for-sale are comprised of equity securities, investment-grade preferred instruments and investments in Company-sponsored open-end funds where the Company has neither control nor the ability to exercise significant influence. These investments are carried at fair value based on quoted market prices or market prices obtained from independent pricing services engaged by management, with unrealized gains and losses, net of tax, reported in accumulated other comprehensive income. The Company periodically reviews each individual security position that has an unrealized loss, or impairment, to determine if that impairment is other than temporary. If the Company believes an impairment of a security position is other than temporary, based on available quantitative and qualitative information as of the report date, the loss will be recognized as gain (loss) from available-for-sale investments—net in the Company’s consolidated statements of operations. From time to time, the affiliated funds consolidated by the Company enter into derivative contracts to gain exposure to the underlying commodities markets or to hedge market and credit risks of the underlying portfolios utilizing options, total return swaps, credit default swaps and futures contracts. These instruments are measured at fair value based on their settlement price at the close of trading on the associated commodities exchange or board of trade with gains and losses recorded as gain (loss) from trading investments—net in the Company's consolidated statements of operations. The fair values of these instruments are recorded in other assets or other liabilities and accrued expenses in the Company's consolidated statements of financial condition. As of December 31, 2016, none of the outstanding derivative contracts were subject to a master netting agreement or other similar arrangement. Additionally, from time to time, the Company enters into foreign exchange contracts to hedge its currency exposure related to certain client receivables. These instruments are measured at fair value with gains and losses recorded in other non-operating income in the Company's consolidated statements of operations. The fair values of these contracts are recorded in other assets or other liabilities and accrued expenses in the Company's consolidated statements of financial condition.
Goodwill and Intangible Assets	Goodwill and Intangible Assets—Goodwill represents the excess of the cost of the Company’s investment in the net assets of an acquired company over the fair value of the underlying identifiable net assets at the date of acquisition. Goodwill and indefinite lived intangible assets are not amortized but are tested at least annually for impairment by comparing the fair value to their carrying amounts. Finite lived intangible assets are amortized over their useful lives and are tested for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest—Redeemable noncontrolling interest represents third-party interests in the Company's consolidated entities. This interest is redeemable at the option of the investors and therefore is not treated as permanent equity. Redeemable noncontrolling interest is remeasured at redemption value which approximates the fair value at each reporting period.
Investment Advisory and Administration Fees	Investment Advisory and Administration Fees—The Company earns revenue by providing asset management services to institutional accounts and to Company-sponsored open-end and closed-end funds. Investment advisory fees are earned pursuant to the terms of investment management agreements, and are based on a contractual fee rate applied to the assets in the portfolio. The Company also earns administration fees from certain Company-sponsored open-end and closed-end funds pursuant to the terms of underlying administration contracts. Administration fees are based on the average assets under management of such funds. Investment advisory and administration fee revenue is recognized as such fees are earned.
Distribution and Service Fee Revenue	Distribution and Service Fee Revenue—CSS acts as the principal distributor of the Company’s sponsored open-end funds which may offer the following classes: Class A (initial sales load), Class C (back-end sales load), Class R (load retirement) and Class Z (no load retirement). Effective May 2007, the Company suspended sales of Class B shares and all remaining Class B shares converted to Class A shares in 2015. Distribution and service fee revenue is based on the average daily net assets of the funds as detailed below. Distribution and service fee revenue is earned daily and is recorded gross of any third-party distribution and service fee expense for applicable share classes. Pursuant to distribution plans with the Company's sponsored open-end funds, CSS receives distribution fees of up to 25bps for Class A shares and 75bps for Class C shares. CSS also receives shareholder servicing fees of up to 10bps on Class A shares, 25bps on Class C shares and 15bps on Class Z shares, pursuant to shareholder servicing plans with the funds. Effective October 1, 2014, the Company no longer receives shareholder servicing fees on Class Z shares. CSS receives combined distribution and shareholder servicing fees of up to 50bps for Class R shares.
Distribution and Service Fee Expense	Distribution and Service Fee Expense—Distribution and service fee expense includes distribution fees, service fees and intermediary assistance payments. Distribution and service fee expense is recorded as incurred. Distribution fee expense represents payments made to qualified intermediaries for (i) assistance in connection with the distribution of the Company's sponsored open-end funds' shares and (ii) for other expenses such as advertising costs and printing and distribution of prospectuses to investors. Such amounts may also be used to pay financial intermediaries for services as specified in the terms of written agreements complying with Rule 12b-1 of the Investment Company Act of 1940 (Rule 12b-1). CSS pays distribution fee expense based on the average daily net assets under management of up to 25bps on Class A shares and 75bps on Class C shares. Shareholder servicing fee expense represents payments made to qualified intermediaries for shareholder account service and maintenance. These services are provided pursuant to written agreements with such qualified institutions. CSS pays service fee expenses based on the average daily net assets under management of up to 10bps on Class A shares, 25bps on Class C shares and 15bps on Class Z shares. Effective October 1, 2014, the Company no longer pays shareholder service fees on Class Z shares. CSS pays combined distribution and service fee expenses based on the average daily net assets under management of up to 50bps on Class R shares. Intermediary assistance payments represent payments to qualified intermediaries for activities related to distribution, shareholder servicing and marketing and support of Company-sponsored open-end funds and are incremental to those described above. Intermediary assistance payments are generally based on the average assets under management or the number of accounts being serviced.
Portfolio Consulting and Other	Portfolio Consulting and Other—The Company earns portfolio consulting and other fees by: (i) providing portfolio consulting services in connection with model-based strategy accounts; (ii) earning a licensing fee for the use of the Company's proprietary indexes; and (iii) providing portfolio monitoring services related to a number of unit investment trusts. This revenue is earned pursuant to the terms of the underlying contract, and the fee schedules for these relationships vary based on the type of services the Company provides for each relationship. This revenue is recognized as such fees are earned.
Stock-based Compensation	Stock-based Compensation—The Company recognizes compensation expense for the grant-date fair value of awards of equity instruments to employees. This expense is recognized over the period during which employees are required to provide service. The Company also estimates forfeitures.
Income Taxes	Income Taxes—The Company records the current and deferred tax consequences of all transactions that have been recognized in the consolidated financial statements in accordance with the provisions of the enacted tax laws. Deferred tax assets are recognized for temporary differences that will result in deductible amounts in future years at tax rates that are expected to apply in those years. Deferred tax liabilities are recognized for temporary differences that will result in taxable income in future years at tax rates that are expected to apply in those years. The Company records a valuation allowance, when necessary, to reduce deferred tax assets to an amount that more likely than not will be realized. The calculation of the tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations in a multitude of jurisdictions across our global operations. A tax benefit from an uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits.
Currency Translation and Transactions	Currency Translation and Transactions—Assets and liabilities of subsidiaries having non-U.S. dollar functional currencies are translated at exchange rates at the applicable consolidated statement of financial condition date. Revenue and expenses of such subsidiaries are translated at average exchange rates during the period. The gains or losses resulting from translating non-U.S. dollar functional currency into U.S. dollars are included in the Company's consolidated statements of comprehensive income.
Comprehensive Income	Comprehensive Income—The Company reports all changes in comprehensive income in the consolidated statements of comprehensive income. Comprehensive income includes net income or loss attributable to common stockholders, foreign currency translation gain and loss (net of tax), unrealized gain and loss from available-for-sale investments (net of tax) and reclassification to statements of operations of realized gain and loss from available-for-sale investments (net of tax).
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements—In January 2017, the FASB issued guidance to simplify the impairment test by removing the requirement to perform a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. This new guidance will be effective for the Company’s first quarter of 2020. The Company is currently evaluating the potential effect of this new guidance on its consolidated financial statements and related disclosures. In August 2016, the FASB issued new guidance amending the current guidance on the classification of certain cash receipts and payments in the statement of cash flows. This guidance is intended to unify the currently diverse presentations and classifications, which address eight classification issues related to the statement of cash flows, including debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies, distributions received from equity method investees, beneficial interests in securitization transactions, and separately identifiable cash flows and application of the predominance principle. This new guidance will be effective for the Company’s first quarter of 2018 and requires a retrospective approach to adoption. The Company is currently evaluating the potential effect of this new guidance on its consolidated financial statements and the related disclosures. In March 2016, the FASB issued new guidance amending the current accounting for an investment that becomes qualified for the equity method of accounting. The guidance requires that the cost of acquiring an additional interest in the investment, if any, that resulted in it qualifying for the equity method be added to the carrying value of the investment. The equity method will then be applied from that point forward without any retroactive application or adjustment. This new guidance will be effective for the Company’s first quarter of 2017. The Company does not expect the adoption of the new standard to have a material effect on its consolidated financial statements and related disclosures. In March 2016, the FASB issued new guidance which simplifies several aspects of the accounting for share-based payment transactions, including the accounting for income taxes, excess tax benefits, forfeitures and statutory tax withholding requirements, as well as classification in the statement of cash flows. This new guidance will be effective for the Company’s first quarter of 2017. The Company has evaluated the impact that adoption of this standard will have on its financial statements and related disclosures and has concluded that adoption will result in the tax effect associated with differences between the grant date price and delivery date price of restricted stock units being recorded on the income statement rather than in additional paid-in capital and reclassification of such amounts on the statement of cash flows from financing activities to operating activities. In February 2016, the FASB issued guidance introducing a new lease model which requires all operating leases to be recorded on the balance sheet as right of use assets and offsetting lease liability obligations. The guidance requires disclosures by lessees and lessors to enable users of financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. This new guidance will be effective for the Company’s first quarter of 2019. The Company is currently evaluating the potential effect of this new guidance on its consolidated financial statements and related disclosures. In January 2016, the FASB issued new guidance amending the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. In addition, the FASB clarified guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities. This new guidance will be effective for the Company’s first quarter of 2018. Upon adoption of this guidance, changes in the fair value of the Company's available-for-sale investments will be reported through earnings rather than through other comprehensive income. In May 2014, the FASB issued new guidance which outlined a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In March 2016, the FASB issued revised guidance which clarifies the guidance related to (a) determining the appropriate unit of account under the revenue standard’s principal versus agent guidance and (b) applying the indicators of whether an entity is a principal or an agent in accordance with the revenue standard’s control principle. In April 2016, the FASB issued an amendment to provide more detailed guidance including additional implementation guidance and examples related to a) identifying performance obligations and b) licenses of intellectual property. In May 2016, the FASB amended the standard to clarify the guidance on assessing collectibility, presenting sales taxes, measuring noncash consideration, and certain transition matters. This new guidance will be effective for the Company's first quarter of 2018 and requires either a retrospective or a modified retrospective approach to adoption. The Company's implementation analysis is ongoing, however, it does not expect the adoption of the guidance to have a significant effect on the timing of the recognition of revenue. The Company is currently evaluating performance obligations and the related transaction costs. The overall effect upon adoption may change based on further analysis and implementation efforts. The Company has not yet determined which transition method will be employed.
Valuation Techniques	Valuation Techniques In certain instances, debt and equity securities are valued on the basis of prices from an orderly transaction between market participants provided by reputable brokers/dealers or independent pricing services. In determining the value of a particular investment, independent pricing services may use information with respect to transactions in such investments, broker quotes, pricing matrices, market transactions in comparable investments and various relationships between investments. As part of its independent price verification process, the Company generally performs reviews of valuations provided by broker-dealers or independent pricing services. Investments in Company-sponsored funds are valued at their closing price or NAV (or its equivalent) as a practical expedient. Foreign exchange contracts are valued by interpolating a value using the spot foreign exchange rate and forward points (based on the spot rate and currency rate differentials), which are all inputs that are observable in active markets (level 2). In the absence of observable market prices, the Company values its investments using valuation methodologies applied on a consistent basis. For some investments, little market activity may exist; management's determination of fair value is then based on the best information available in the circumstances, and may incorporate management's own assumptions and involves a significant degree of judgment, taking into consideration a combination of internal and external factors. Such investments are valued on a quarterly basis, taking into consideration any changes in key inputs and changes in economic and other relevant conditions, and valuation models are updated accordingly. The valuation process also includes a review by the Company's valuation committee which is comprised of senior members from various departments within the Company, including investment management. The valuation committee provides independent oversight of the valuation policies and procedures.