Investment in AB Investments in and Advances to Affiliates, Schedule of Investments [Text Block] Document Type Document Type Other comprehensive (loss) income: Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Federal tax rate on partnership gross income (percent) Federal Tax on Partnership Gross Income, Percent Federal Tax on Partnership Gross Income, Percent Equity Components [Axis] Equity Components [Axis] Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Consolidated Entities [Domain] Consolidated Entities [Domain] Total amount of AB Holding Units Purchased (in units) Stock Repurchased During Period, Shares Limited Partner Limited Partner [Member] LIABILITIES AND PARTNERS’ CAPITAL Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Investments in AB with proceeds from exercise of compensatory options to buy AB Holding Units Additional investments with proceeds from exercise of compensatory options to buy AB Holding Units Payments to Acquire Interest in Subsidiaries and Affiliates Entity Interactive Data Current Entity Interactive Data Current Units Outstanding Increase (Decrease) in Partners' Capital [Roll Forward] Security Exchange Name Security Exchange Name Change in net income attributable to AllianceBernstein Unitholders (percent) Increase (decrease) in net income attributable to equity method investments The percentage change in the amount of net income (loss) reported by an equity method investments of the entity. Entity Registrant Name Entity Registrant Name Subsequent Event Type [Domain] Subsequent Event Type [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Increase (decrease) in other liabilities Increase (Decrease) in Other Operating Liabilities Unaffiliated holders Unaffiliated Holders [Member] Represents holders of ownership interest in Company that are otherwise unaffiliated with Company. Commitments and contingencies (See Note 8) Commitments and Contingencies ASSETS Assets [Abstract] Computation of income tax [Abstract] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Issuance of AB Holding Units to fund long-term incentive compensation plan awards AB Holding Units issued to fund long-term incentive compensation plans Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Entity Address, State or Province Entity Address, State or Province Units outstanding (in units) General Partners' Capital Account, Units Outstanding Computation of equity in net income attributable to AllianceBernstein Unitholders [Abstract] Equity Method Investment, Financial Statement, Reported Amounts [Abstract] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Cash Distributions Cash Distributions Disclosure [Text Block] The entire disclosure for cash distributions. Restricted AB Holding Unit awards granted to employees and Eligible Directors (in units) Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture Entity Address, Postal Zip Code Entity Address, Postal Zip Code State income taxes Current State and Local Tax Expense (Benefit) Outstanding as of December 31, 2020 (in units) Outstanding as of March 31, 2021 (in units) Shares, Outstanding Long-term Incentive Compensation Plans Compensation Related Costs, General [Text Block] Foreign currency translation adjustments, net of tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Other comprehensive (loss) Changes in accumulated other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Document Transition Report Document Transition Report Title of Individual [Axis] Title of Individual [Axis] Employees and Eligible Directors Employees and Eligible Directors [Member] Individuals employed for wages or salary. Also includes individuals serving on the board of directors (who collectively have responsibility for governing the entity). General Partner General Partner [Member] Retirement of AB Holding Units Stock Repurchased and Retired During Period, Value Change in Equity Method Investment [Roll Forward] Change in Equity Method Investment [Roll Forward] Change in Equity Method Investment [Roll Forward] Document Quarterly Report Document Quarterly Report Equity [Abstract] Equity [Abstract] Statement [Line Items] Statement [Line Items] Partners’ capital: Partners' Capital [Abstract] Summary of Ownership Structure of AllianceBernstein Schedule of Other Ownership Interests [Table Text Block] Entity File Number Entity File Number Statement [Table] Statement [Table] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities AB Holding AB Holding [Member] AB Holding [Member] Change in equity in net income attributable to AllianceBernstein Unitholders (percent) Increase (decrease) in equity in net income attributable to equity method investments The percentage change in the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. Distributions Made to Member or Limited Partner by Distribution Type [Axis] Distribution Type [Axis] Document Fiscal Year Focus Document Fiscal Year Focus Entity Small Business Entity Small Business Distribution Type [Domain] Distribution Type [Domain] Cash distributions to Unitholders Payments of Ordinary Dividends Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] EQH and its subsidiaries EQH And Its Subsidiaries [Member] EQH And Its Subsidiaries [Member] Entity Current Reporting Status Entity Current Reporting Status Basic (in dollars per unit) Basic net income per unit (in dollars per unit) Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax Amendment Flag Amendment Flag Schedule of Earnings Per Unit, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Income tax benefit (expense) Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Entity Central Index Key Entity Central Index Key Changes in employee benefit related items: Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax, after Reclassification Adjustment, Attributable to Parent [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Schedule of Unit Award Repurchase Activity Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity [Table Text Block] Change in income taxes (percent) Increase (decrease) in income tax The percentage change in the sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations. Total liabilities and partners’ capital Liabilities and Equity Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Income Taxes Income Tax Disclosure [Text Block] Entity Address, City or Town Entity Address, City or Town Options exercised (in units) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Net income – diluted Net Income (Loss) Attributable to Parent, Diluted Anti-dilutive units excluded from diluted net income (in units) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Accumulated Other Comprehensive (Loss) Income Accumulated Other Comprehensive Income (Loss) [Member] Accumulated Other Comprehensive Income (Loss) [Member] Equity Component [Domain] Equity Component [Domain] Open Market Purchases of AB Holding Units (in units) Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Liabilities: Liabilities [Abstract] Changes in employee benefit related items Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax Entity Tax Identification Number Entity Tax Identification Number Federal income taxes Current Federal Tax Expense (Benefit) Net income Net income Net income – basic Net Income (Loss) Attributable to Parent Limited partners or members ownership interest in Company (percent) Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Other liabilities Other Liabilities AB qualifying revenues Equity Method Investment, Summarized Financial Information, Qualifying Revenue The amount of qualifying revenue (primarily investment advisory fees and certain equity commissions) reported by an equity method investment of the entity. Weighted average units outstanding – diluted (in units) Weighted Average Limited Partnership Units Outstanding, Diluted Earnings Per Unit [Abstract] Earnings Per Unit [Abstract] Total assets Assets Current Fiscal Year End Date Current Fiscal Year End Date Net income per unit: Earnings Per Share [Abstract] Title of 12(b) Security Title of 12(b) Security Amortization of prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Subsequent Event Type [Axis] Subsequent Event Type [Axis] Multiplied by: weighted average equity ownership interest for calculating tax (percent) Equity Method Investment Weighted Average Ownership Percentage For Calculating Tax The weighted average percentage of ownership of common stock or equity participation in the investee for calculating tax, net of units held in the rabbi trust. Change in AllianceBernstein qualifying revenues (percent) Increase (decrease) in qualifying revenue of equity method investment The percentage change in the amount of qualifying revenue (primarily investment advisory fees and certain equity commissions) reported by an equity method investment of the entity. Document Fiscal Period Focus Document Fiscal Period Focus Ownership structure of AB Holding Distribution Made to Limited Partner [Line Items] Distribution Made to Limited Partner [Line Items] Employee benefit related items, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent Total liabilities Liabilities Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Cash Distribution Cash Distribution [Member] General partnership interest (percent) Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Changes in Holding Units Outstanding Schedule of Capital Units [Table Text Block] Entity Filer Category Entity Filer Category Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Foreign currency translation adjustments, before tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent Changes in components for calculation of income tax [Abstract] Income Tax Expense (Benefit), Continuing Operations [Abstract] Partner Type [Axis] Partner Type [Axis] Other assets Other Assets Income tax (expense) benefit Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax General Partner: units issued (in units) General Partners' Capital Account, Units Issued Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Units issued upon options exercised (in units) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Total partners’ capital Balance, beginning of period Balance, end of period Partners' Capital Limited partners: units outstanding (in units) Limited Partners' Capital Account, Units Outstanding Change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Change in AB Holding Units held by AB to fund long-term incentive compensation plans Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Summary of Changes in Investment in AB Schedule of Investments in and Advances to Affiliates, Schedule of Investments [Table Text Block] Investment in AB Investment in AB as of December 31, 2020 Investment in AB as of March 31, 2021 Equity Method Investments Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] AB AllianceBernstein L.P. [Member] AllianceBernstein L.P. [Member] Dilutive effect of compensatory options (in units) Weighted Average Number Diluted Limited Partnership Units Outstanding Adjustment Cash distribution declared (in dollars per unit) Distribution Made to Limited Partner, Distributions Declared, Per Unit EQH EQH [Member] EQH [Member] Ownership [Axis] Ownership [Axis] Foreign currency translation adjustment, net of tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Subsequent Event Subsequent Event [Member] Weighted average units outstanding – basic (in units) Weighted Average Limited Partnership Units Outstanding, Basic Total Cash Paid for Open Market Purchases of AB Holding Units Payments for Repurchase of Equity Multiplied by: weighted average equity ownership interest (percent) Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions Ownership [Domain] Ownership [Domain] Change in AB Holding Units held by AB for long-term incentive compensation plans Partners' Capital Account, Treasury Units, Purchased Proceeds from exercise of compensatory options to buy AB Holding Units Proceeds from stock options exercised Proceeds from Stock Options Exercised Limited partners: 100,389,849 and 98,092,098 limited partnership units issued and outstanding Limited Partners' Capital Account Additional allocation of equity in net income attributable to AB resulting from assumed dilutive effect of compensatory options Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Business Description, Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Partner Type of Partners' Capital Account, Name [Domain] Partner Type of Partners' Capital Account, Name [Domain] Recognized actuarial (loss) gain Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax AB Holding Units retired Treasury Stock, Retired, Par Value Method, Amount Income taxes Total income taxes Income Tax Expense (Benefit) Income Statement [Abstract] Income Statement [Abstract] Cash and cash equivalents as of beginning of period Cash and cash equivalents as of end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Units Outstanding Capital Units [Text Block] Entire disclosure of an entity's capital units or capital shares. Title of Individual with Relationship to Entity [Domain] Title of Individual [Domain] Local Phone Number Local Phone Number Changes in employee benefit related items, net of tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Entity Address, Address Line One Entity Address, Address Line One Decrease in other assets Increase (Decrease) in Other Operating Assets Entity Emerging Growth Company Entity Emerging Growth Company Consolidated Entities [Axis] Consolidated Entities [Axis] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Cash distributions received from AB Cash distributions received from AB Proceeds from Dividends Received Computation of Effective Income Tax Rate and Changes in Components of Income Tax Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Legal Entity [Axis] Legal Entity [Axis] City Area Code City Area Code Limited partners: units issued (in units) Limited Partners' Capital Account, Units Issued Exercise of compensatory options to buy AB Holding Units Partners' Capital Account, Option Exercise Document Period End Date Document Period End Date Distributions Made to Limited Partner [Table] Distributions Made to Limited Partner [Table] Cash distributions to Unitholders Partners' Capital Account, Distributions Capital contributions (to) from AB Capital contributions (to) from AB Payments of Distributions to Affiliates Effective tax rate (percent) Effective Income Tax Rate Reconciliation, Percent Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Equity in net income attributable to AB Unitholders Equity in net income attributable to AB Unitholders Income (Loss) from Equity Method Investments Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net Income (Loss), Including Portion Attributable to Noncontrolling Interest New York City unincorporated business tax (percent) New York City unincorporated business tax rate Tax rate attributable to operating income for unincorporated business entities operating in New York City, before credits paid for unincorporated business entities by a subsidiary. Trading Symbol Trading Symbol Diluted (in dollars per unit) Diluted net income per unit (in dollars per unit) Net Income (Loss), Net of Tax, Per Outstanding Limited Partnership Unit, Diluted General Partner: 100,000 general partnership units issued and outstanding General Partners' Capital Account Total Cash Paid for AB Holding Units Purchased Stock Repurchased During Period, Value AB Holding Units held by AB to fund long-term incentive compensation plans Deferred Compensation Equity AllianceBernstein Corporation AllianceBernstein Corporation [Member] AllianceBernstein Corporation [Member] Entity [Domain] Entity [Domain] Capital contributions (to) from AB Proceeds from Contributions from Affiliates Units issued (in units) Stock Issued During Period, Shares, Restricted Stock Award, Gross Net Income per Unit Earnings Per Share [Text Block] Cover [Abstract] Cover [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Multiplied by: federal tax (percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] AB Holding Units held by AB to fund long-term incentive compensation plans Deferred Compensation, Share-based Payments [Member] Entity Shell Company Entity Shell Company Units retired (in units) Stock Repurchased and Retired During Period, Shares Income Tax Contingency [Table] Income Tax Contingency [Table] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract]