Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2018
Description of Business and Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. Amounts in the accompanying financial statements and notes are rounded to the nearest thousand unless otherwise stated. Certain amounts in the prior years’ financial statements have been reclassified for consistent presentation. The Company operates in one business segment as the Company’s management utilizes a consolidated approach to assess performance and allocate resources. Effective January 1, 2018, the Company changed the presentation of certain line items in the consolidated statements of income that are intended to improve the transparency of the Company’s financial statements through clearer alignment of operating expenses with financial statement captions. Specifically, the Company revised its accounting policy related to the reporting of indirect underwriting and distribution expenses in the former underwriting and distribution caption and certain expenses historically reported as general and administrative. Expenses previously recorded as underwriting and distribution expenses were retrospectively reclassified into (a) the following existing operating expense captions: Compensation and benefits and General and administrative, and (b) the following newly created operating expense captions: Distribution, Technology, Occupancy, and Marketing and advertising. Certain expenses historically reported as general and administrative were retrospectively reclassified into the following newly created operating expense captions: Technology, Occupancy, and Marketing and advertising. The Company considers the change in policy to be preferable and does not consider the change to be material to its consolidated financial statements. These changes were applied retrospectively to all periods presented and do not affect net income attributable to the Company. The Company also adopted Accounting Standards Update (“ASU”) 2017-07, “Compensation — Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost”. As a result, the Company retrospectively reclassified all net periodic pension costs, other than the historical service cost, from Compensation and benefits to Investment and other income (loss) within the consolidated statements of income. The reclassification of expenses as a result of the adoption of ASU 2017-07 does not affect net income attributable to the Company.
Consolidation	Consolidation In the normal course of our business, we sponsor and manage various types of investment products. These investment products include open-end mutual funds, a closed-end mutual fund, privately offered funds, exchange-traded managed funds, and a Luxembourg SICAV. When creating and launching a new investment product, we typically fund the initial cash investment, commonly referred to as “seeding,” to allow the investment product the ability to generate an investment performance track record so that it is able to attract third party investors. Our initial investment in a new product typically represents 100% of the ownership in that product. We generally redeem our investment in seeded products when the related product establishes a sufficient track record, when third party investments in the related product are sufficient to sustain the strategy, or when a decision is made to no longer pursue the strategy. The length of time we hold a majority interest in a product varies based on a number of factors, including market demand, market conditions and investment performance. Our exposure to risk in these investment products is generally limited to any equity investment we have in the product and any earned but uncollected management or other fund-related service fees. In accordance with financial accounting standards, we consolidate certain sponsored investment products in which we have a controlling interest or the investment product meets the criteria of a variable interest entity (“VIE”) and we are deemed to be the primary beneficiary. In order to make this determination, an analysis is performed to determine if the investment product is a VIE or a voting interest entity (“VOE”). Assessing if an entity is a VIE or VOE involves judgment and analysis on an entity by entity basis. Factors included in this assessment include the legal organization of the entity, the Company’s contractual involvement with the entity and any implications resulting from or associated with related parties’ involvement with the entity. A VIE is an entity which does not have adequate equity to finance its activities without subordinated financial support, the equity investors do not have the normal characteristics of equity investors for a potential controlling financial interest as a group, or the voting rights are not proportional to their obligations to absorb the expected losses or their rights to receive the expected residual returns of the entity. The Company is deemed to be the primary beneficiary if it absorbs a majority of the VIE’s expected losses, expected residual returns, or both. If the Company is the primary beneficiary of a VIE, we are required to consolidate the assets, liabilities, results of operations and cash flows of the VIE into our consolidated financial statements. If an entity does not meet the criteria and is not considered a VIE, it is treated as a VOE, which is subject to traditional consolidation concepts based on ownership rights. Sponsored investment products that are considered VOEs are consolidated if we have a controlling financial interest in the entity absent substantive investor rights to replace the investment manager of the entity (kick-out rights).
Use of Estimates	Use of Estimates GAAP requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses in the consolidated financial statements and accompanying notes, and related disclosures of commitments and contingencies. Estimates are used for, but are not limited to, depreciation and amortization, income taxes, valuation of assets, pension and postretirement obligations, and contingencies. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment. Actual results could differ from our estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand and short‑term investments. We consider all highly liquid investments with maturities upon acquisition of 90 days or less to be cash equivalents. Cash and cash equivalents – restricted represents cash held for the benefit of customers and non-customers segregated in compliance with federal and other regulations.
Disclosures About Fair Value of Financial Instruments	Disclosures About Fair Value of Financial Instruments Fair value of cash and cash equivalents, receivables and payables approximates carrying value. Fair values for investment securities are based on quoted market prices, where available. Otherwise, fair values for investment securities are based on Level 2 or Level 3 inputs detailed in Note 4. Fair value of long‑term debt is disclosed in Note 8.
Investment Securities and Investments in Sponsored Funds	Investment Securities and Investments in Sponsored Funds Our investments are comprised of debt and equity securities, investments in sponsored funds and sponsored privately offered funds. Sponsored funds, which include the Funds and the IGI Funds, are investments we have made to provide seed capital for new investment products. The Company has classified its investments in certain sponsored funds as either equity method investments (when the Company owns between 20% and 50% of the fund) or as equity securities measured at fair value through net income (when the Company owns less than 20% of the fund). Unrealized gains and losses on debt securities classified as available for sale, net of related tax effects, are excluded from earnings until realized and are reported as a separate component of comprehensive income. For debt securities classified as trading and equity securities, unrealized gains and losses are included in earnings. Realized gains and losses are computed using the specific identification method for all investment securities, other than sponsored funds. For sponsored funds, realized gains and losses are computed using the average cost method. Substantially all of the Company’s equity method investees are investment companies that record their underlying investments at fair value. Therefore, under the equity method of accounting, our share of the investee's underlying net income or loss is predominantly representative of fair value adjustments in the investments held by the equity method investee. Our share of the investee's net income or loss is based on the most current information available and is recorded as a net gain or loss on investments within investment and other income (loss). Our available for sale debt securities are reviewed each quarter and adjusted for other than temporary declines in value. We consider factors affecting the issuer and the industry in which the issuer operates, general market trends including interest rates, and our ability and intent to hold an investment until it has recovered. Consideration is given to the length of time an investment’s market value has been below its amortized cost basis as well as prospects for recovery to the amortized cost basis. When a decline in the fair value of debt securities is determined to be other than temporary, the amount of the impairment recognized in earnings depends on whether the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current‑period credit loss. If so, the other than temporary impairment recognized in earnings is equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date. If not, the portion of the impairment related to the credit loss is recognized in earnings while the portion of the impairment related to other factors is recognized in other comprehensive income, net of tax.
Property and Equipment	Property and Equipment Property and equipment are carried at cost. The costs of improvements that extend the life of a fixed asset are capitalized, while the costs of repairs and maintenance are expensed as incurred. Depreciation and amortization are calculated and recorded using the straight‑line method over the estimated useful life of the related asset (or lease term if shorter), generally three to 10 years for furniture and fixtures; one to 10 years for computer software; one to five years for data processing equipment; one to 30 years for buildings; two to 26 years for other equipment; and up to 15 years for leasehold improvements, determined by the lesser of the lease term or expected life.
Software Developed for Internal Use	Software Developed for Internal Use Certain internal costs incurred in connection with developing or obtaining software for internal use are capitalized in accordance with ASC 350, “Intangibles – Goodwill and Other Topic.” Internal costs capitalized are included in property and equipment, net in the consolidated balance sheets, and were $6.4 million and $10.5 million as of December 31, 2018 and 2017, respectively. Amortization begins when the software project is complete and ready for its intended use and continues over the estimated useful life, generally one to 10 years.
Goodwill and Identifiable Intangible Assets	Goodwill and Identifiable Intangible Assets Goodwill represents the excess of cost over fair value of the identifiable net assets of acquired companies. Indefinite-lived intangible assets represent advisory and subadvisory management contracts for managed assets obtained in acquisitions. The Company considers these contracts to be indefinite-lived intangible assets as they are expected to be renewed without significant cost or modification of terms. Goodwill and indefinite-lived intangible assets are tested for impairment annually or more frequently if events or circumstances indicate that the carrying value may not be recoverable. Goodwill and intangible assets require significant management estimates and judgment, including the valuation determination in connection with the initial purchase price allocation and the ongoing evaluation for impairment. Additional information related to the indefinite-lived intangible assets is included in Note 7.
Revenue Recognition	Revenue Recognition As of January 1, 2018, the Company adopted ASU 2014-09, “Revenue from Contracts with Customers” and all subsequent ASUs that modified Accounting Standards Codification (“ASC”) 606, “Revenue from Contracts with Customers.” The Company elected to apply the standard utilizing the cumulative effect approach. The implementation of the new standard did not have a material impact on the measurement or recognition of revenue. Investment Management and Advisory Fees We recognize investment management and advisory fees as earned over the period in which investment management and advisory services are provided. While our investment management and advisory contracts are long-term in nature, the performance obligations are generally satisfied daily or monthly based on AUM. We calculate investment management fees from the Funds daily based upon average daily net AUM in accordance with investment management agreements between the Funds and the Company. The majority of investment and/or advisory fees earned from institutional accounts are calculated either monthly or quarterly based upon an average of net AUM in accordance with such investment management agreements. The Company may waive certain fees for investment management services at its discretion, or in accordance with contractual expense limitations, and these waivers are reflected as a reduction to investment management fees on the consolidated statements of income. Our investment advisory business receives research products and services from broker-dealers through “soft dollar” arrangements. Consistent with the “soft dollar” safe harbor established by Section 28(e) of the Securities Exchange Act of 1934, as amended, the investment advisory business does not have any contractual obligation requiring it to pay for research products and services obtained through soft dollar arrangements with brokers. As a result, we present “soft dollar” arrangements on a net basis. The Company has contractual arrangements with third parties to provide subadvisory services. Investment advisory fees are recorded gross of any subadvisory payments and are included in investment management fees based on management’s determination that the Company is acting in the capacity of principal service provider with respect to its relationship with the Funds. Any corresponding fees paid to subadvisors are included in operating expenses. Underwriting, Distribution and Shareholder Service Fees Fee‑based asset allocation products offer clients a selection of traditional asset allocation models, as well as features such as systematic rebalancing and client and Advisor participation in determining asset allocation across asset classes. Underwriting and distribution fee-based asset allocation revenues are calculated monthly based upon beginning of month client assets and are earned over the period in which services are provided. Performance obligations are generally satisfied daily or monthly based on client assets. Under a Rule 12b-1 service plan, the Funds may charge a maximum fee of 0.25% of the average daily net AUM for Ivy Funds Class B, C, E and Y shares for expenses paid to broker-dealers and other sales professionals in connection with providing ongoing services to the Funds’ shareholders and/or maintaining the Funds’ shareholder accounts, with the exception of the Funds’ Class R shares, for which the maximum fee is 0.50%. The Funds’ Class B and C shares may charge a maximum of 0.75% of the average daily net AUM under a Rule 12b-1 distribution plan to broker-dealers and other sales professionals for their services in connection with distributing shares of that class. The Funds’ Class A shares may charge a maximum fee of 0.25% of the average daily net AUM under a Rule 12b-1 service and distribution plan for expenses detailed previously. The Rule 12b-1 plans are subject to annual approval by the Funds’ board of trustees, including a majority of the disinterested members, by votes cast in person at a meeting called for the purpose of voting on such approval. All Funds may terminate the service and distribution plans at any time with approval of fund trustees or portfolio shareholders (a majority of either) without penalty. Underwriting and distribution commission revenues resulting from the sale of investment products are recorded upon satisfaction of performance obligations, which occurs on the trade date. For certain types of investment products, primarily variable annuities, distribution revenues are generally calculated based upon average daily net assets. When a client purchases Class A or Class E shares (front-end load), the client pays an initial sales charge of up to 5.75% of the amount invested. The sales charge for Class A or Class E shares typically declines as the investment amount increases. In addition, investors may combine their purchases of all fund shares to qualify for a reduced sales charge. When a client invests in a fee-based asset allocation product, Class I or Y shares are purchased at net asset value, and we do not charge an initial sales charge. Underwriting and distribution revenues resulting from payments from Advisors for office space, compliance oversight and affiliation fees are earned over the period in which the service is provided, which is generally monthly and is based on a fee schedule. Fees collected from Advisors for various services are recorded in underwriting and distribution fees on a gross basis, as the Company is the principal in these arrangements. Shareholder service fee revenue primarily includes transfer agency fees, custodian fees from retirement plan accounts, and portfolio accounting and administration fees. Transfer agency fees and portfolio accounting and administration fees are asset‑based revenues or account‑based revenues, while custodian fees from retirement plan accounts are based on the number of client accounts. Custodian fees, transfer agency fees and portfolio accounting and administration fees are earned upon completion of the service when all performance obligations have been satisfied.
Advertising and Promotion	Advertising and Promotion We expense all advertising and promotion costs as the advertising or event takes place. Advertising expense was $8.1 million, $9.7 million and $9.4 million for the years ended December 31, 2018, 2017 and 2016, respectively, and is classified in marketing and advertising expense in the consolidated statements of income.
Leases	Leases The Company leases office space under various leasing arrangements. Certain lease agreements contain renewal options, rent escalation clauses and/or other inducements provided by the landlord. Rent expense is recorded on a straight-line basis, including escalations and inducements, over the term of the lease.
Share-Based Compensation	Share‑Based Compensation We account for share‑based compensation expense using the fair value method. Under the fair value method, share‑based compensation expense reflects the fair value of share‑based awards measured at grant date, and is recognized over the service period. The Company also issues share‑based awards to our Board of Directors. Changes in the Company’s share price result in variable compensation expense over the vesting period of awards granted to our Board of Directors. The Company’s Cash Settled RSU Plan (the “RSU Plan”) allows the Company to grant cash-settled restricted stock units (“RSUs”). Unvested RSUs have no purchase price and vest in 25% increments over four years, beginning on the first anniversary of the grant date. On the vesting date, RSU holders receive a lump sum cash payment equal to the fair market value of one share of the Company’s common stock, par value $0.01, for each RSU that has vested, subject to applicable tax withholdings. We treat RSUs as liability-classified awards and, therefore, account for them at fair value based on the closing price of our common stock on the reporting date, which results in variable compensation expense over the vesting period.
Accounting for Income Taxes	Accounting for Income Taxes Income tax expense is based on pre-tax income, including adjustments made for the recognition or derecognition related to uncertain tax positions. The recognition or derecognition of income tax expense related to uncertain tax positions is determined under the guidance as prescribed by ASC 740, “Income Taxes Topic.” Deferred tax assets and liabilities are recognized for the future tax attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. A valuation allowance is recognized to reduce deferred tax assets if, based on available evidence, it is more likely than not that all or some portion of the asset will not be realized. Deferred tax assets and liabilities are measured using enacted tax rates that will be in effect when they are expected to be realized or settled. The effect on the measurement of deferred tax assets and liabilities of a change in income tax law is recognized in earnings in the period that includes the enactment date. On December 22, 2017, the Tax Cuts and Jobs Act (the “Tax Reform Act”) was enacted, which significantly revised the U.S. corporate income tax system by, among other things, permanently reducing the federal statutory tax rate from 35% to 21% effective January 1, 2018. The Company recorded a one-time charge of $5.4 million in the fourth quarter of 2017 to measure net deferred tax assets at the reduced federal statutory rate. According to guidance from SEC Staff Accounting Bulletin 118, the Company recognized a provisional tax impact related to the revaluation of deferred tax assets and liabilities and included those amounts in its consolidated financial statements for the year ended December 31, 2017. In the third quarter of 2018, we finalized our 2017 U.S. corporate income tax return and revised provisional adjustments made to our net deferred tax asset. Accordingly, we recorded a discrete tax benefit of $1.0 million. The Company now considers its accounting for the income tax effects of the Tax Reform Act to be complete.