Entity Central Index Key Represents deposits with banks and investments with a maturity of less than 90 days. Deposits and other customer payables principally related to customer-related interest-bearing time and demand deposits, short-term inter-bank borrowing with registered banks, amounts due on collateralized borrowing activities and other related party payables. Occupancy and equipment expense. Technology and information services expense. Fund administration and outsourced services expense. Amount of amortization and other acquisition related costs (benefits). Amortization of deferred expenses and share- based compensation. Amount of gain (loss) on acquisition of portion of business already owned. Dividends Received From Subsidiaries The aggregate increase (decrease) during the reporting period in the amount due to and from subsidiaries. Capital Contributions To Subsidiaries Proceeds relating to customer deposits. The cash inflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. The cash outflow from the settlement of share-based incentive compensation. The cash outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Document and entity information abstract. Document And Entity Information [Abstract] Document Information [Table] Document Information [Table] Consolidated Entities Consolidated Entities [Axis] Consolidated Entities Consolidated Entities [Domain] Subsidiaries of Lazard Ltd [Member] Subsidiaries [Member] Document Information [Line Items] Document Information [Line Items] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well Known Seasoned Issuer Entity Current Reporting Status Entity Current Reporting Status Entity Voluntary Filers Entity Voluntary Filers Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity Public Float Entity Public Float Managing Membership Interests Outstanding Common Unit Outstanding Receivables from customers related to collateralized lending activities, loans granted by bank to third party clients, managing directors, employees in the ordinary course of business, receivables from brokers-dealers and clearing organizations relating to unsettled securities transactions and receivables from related parties. Statement Of Financial Position [Abstract] ASSETS Assets [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Deposits with banks and short-term investments Deposits With Banks And Short Term Investments Cash deposited with clearing organizations and other segregated cash Cash And Securities Segregated Under Federal And Other Regulations Receivables (net of allowance for doubtful accounts of $40,115 and $23,692 at December 31, 2018 and 2017, respectively): Accounts Receivable Net [Abstract] Fees Accrued Fees And Other Revenue Receivable Customers and other Receivables From Customers And Other Lazard Ltd subsidiaries Due From Related Parties Total receivables, net Accounts Receivable Net Investments Investments Property (net of accumulated amortization and depreciation of $339,448 and $317,816 at December 31, 2018 and 2017, respectively) Property Plant And Equipment Net Goodwill and other intangible assets (net of accumulated amortization of $63,591 and $61,202 at December 31, 2018 and 2017, respectively) Intangible Assets Net Including Goodwill Deferred tax assets Deferred Income Tax Assets Net Other assets Other Assets Total Assets Assets Allowance for doubtful accounts receivables Allowance For Doubtful Accounts Receivable Property, accumulated amortization and depreciation Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Other intangible assets, accumulated amortization Finite Lived Intangible Assets Accumulated Amortization Liabilities: Liabilities [Abstract] Deposits and other customer payables Deposits And Other Customer Payables Accrued compensation and benefits Employee Related Liabilities Current And Noncurrent Senior debt Long Term Debt Payable to Lazard Ltd subsidiaries Due To Related Parties Current And Noncurrent Deferred tax liabilities Deferred Income Tax Liabilities Net Other liabilities Other Liabilities Total Liabilities Liabilities Commitments and contingencies Commitments And Contingencies MEMBERS’ EQUITY Members Equity [Abstract] Members' equity (net of 16,737,000 and 9,907,479 shares of Lazard Ltd Class A common stock, at a cost of $729,910 and $411,560 at December 31, 2018 and 2017, respectively) Members Capital Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income Loss Net Of Tax Total Lazard Group LLC Members' Equity Members Equity Noncontrolling interests Members Equity Attributable To Noncontrolling Interest Total Members’ Equity Limited Liability Company Llc Members Equity Including Portion Attributable To Noncontrolling Interest Total Liabilities and Members’ Equity Liabilities And Stockholders Equity Number of shares of common stock held in the parent company, which are purchased for the purpose of granting the shares to senior employees as part of an employee stock option plan at the parent company. Value of common stock held in the Parent Company, which are purchased for the purpose of granting the shares to senior employees as part of an employee stock option plan at the Parent Company. Lazard Ltd common stock, shares Common Stock Held In Parent Company Shares Lazard Ltd common stock, cost Common Stock Held In Parent Company Value Income Statement [Abstract] Statement [Table] Statement [Table] Product and Service Product Or Service [Axis] Product and Service Products And Services [Domain] Firm providing financial advisory services regarding mergers and acquisitions, capital advisory, restructurings etc. Investment Banking and Other Advisory Fees [Member] Financial Advisory Fees [Member] Asset Management Fees [Member] Asset Management1 [Member] Other income from commission, investments, misc, fx revaluation. Other [Member] Other Types Of Revenue [Member] Statement [Line Items] Statement [Line Items] REVENUE Revenues Net Of Interest Expense [Abstract] Revenue Revenue From Contract With Customer Excluding Assessed Tax Interest income Interest Income Operating Total revenue Revenues Interest expense Interest Expense Net revenue Revenues Net Of Interest Expense OPERATING EXPENSES Costs And Expenses [Abstract] Compensation and benefits Labor And Related Expense Occupancy and equipment Occupancy And Equipment Expense Marketing and business development Marketing And Advertising Expense Technology and information services Technology And Information Services Expense Professional services Professional Fees Fund administration and outsourced services Fund Administration And Outsourced Services Expense Amortization and other acquisition-related (benefits) costs Amortization And Other Acquisition Related Costs Benefits Other Other Expenses Total operating expenses Costs And Expenses OPERATING INCOME Operating Income Loss Provision for income taxes Income Tax Expense Benefit NET INCOME Profit Loss LESS - NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS Net Income Loss Attributable To Noncontrolling Interest NET INCOME ATTRIBUTABLE TO LAZARD GROUP LLC Net Income Loss Statement Of Income And Comprehensive Income [Abstract] NET INCOME OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX: Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Currency translation adjustments Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax Employee benefit plans: Other Comprehensive Income Defined Benefit Plans Adjustment Net Of Tax Period Increase Decrease [Abstract] Prior service costs (net of tax benefit of $543 for the year ended December 31, 2018) Other Comprehensive Income Defined Benefit Plan Net Prior Service Costs Credit Arising During Period Net Of Tax Actuarial gain (loss) (net of tax benefit of $203, $3,475 and $2,754 for the years ended December 31, 2018, 2017 and 2016, respectively) Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax Adjustment for items reclassified to earnings (net of tax expense of $2,335, $2,220 and $1,757 for the years ended December 31, 2018, 2017 and 2016, respectively) Other Comprehensive Income Loss Reclassification Adjustment From A O C I Pension And Other Postretirement Benefit Plans Net Of Tax OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX Other Comprehensive Income Loss Net Of Tax COMPREHENSIVE INCOME Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest LESS - COMPREHENSIVE INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD GROUP LLC Comprehensive Income Net Of Tax Tax benefit on prior service costs, employee benefit plans Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Benefit Plan Improvement Tax Effect Tax expense (benefit) on actuarial gain (loss), employee benefit plans Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax Tax expense, adjustment for items reclassified to earnings, employee benefit plans Other Comprehensive Income Loss Reclassification Adjustment From A O C I Pension And Other Postretirement Benefit Plans Tax Proceeds from financing activities. Payments for financing activities. Statement Of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by (used in) operating activities: Adjustments Noncash Items To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization of property Depreciation Depletion And Amortization Amortization of deferred expenses and share-based incentive compensation Amortization Of Deferred Expenses And Sharebased Incentive Compensation Deferred tax provision (benefit) Deferred Income Tax Expense Benefit Loss on extinguishment of debt Gains Losses On Extinguishment Of Debt Gain on acquisition of portion of business already owned Gain Or Loss On Acquisition Of Portion Of Business Already Owned (Increase) decrease in operating assets and increase (decrease) in operating liabilities: Increase Decrease In Operating Capital [Abstract] Receivables-net Increase Decrease In Receivables Investments Increase Decrease In Financial Instruments Used In Operating Activities Other assets Increase Decrease In Other Operating Assets Accrued compensation and benefits and other liabilities Increase Decrease In Accrued Liabilities And Other Operating Liabilities Net cash provided by operating activities Net Cash Provided By Used In Operating Activities CASH FLOWS FROM INVESTING ACTIVITIES: Net Cash Provided By Used In Investing Activities [Abstract] Additions to property Payments To Acquire Property Plant And Equipment Disposals of property Proceeds From Sale Of Property Plant And Equipment Net cash used in investing activities Net Cash Provided By Used In Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from: Proceeds From Financing Activities [Abstract] Customer deposits Proceeds From Customer Deposits Contributions from noncontrolling interests Proceeds From Minority Shareholders Issuance of senior debt, net of expenses Proceeds From Issuance Of Senior Long Term Debt Excess tax benefits from share-based incentive compensation Excess Tax Benefit From Share Based Compensation Financing Activities Other financing activities Proceeds From Other Financing Activities Payments for: Payments For Financing Activities [Abstract] Senior debt Repayments Of Senior Debt Capital lease obligations Repayments Of Long Term Capital Lease Obligations Distributions to noncontrolling interests Payments To Minority Shareholders Purchase of Class A common stock Payments For Repurchase Of Common Stock Distribution to members Payments Of Distributions To Affiliates Settlement of share-based incentive compensation Settlement Of Share Based Incentive Compensation Other financing activities Payments For Other Financing Activities Net cash used in financing activities Net Cash Provided By Used In Financing Activities EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS AND RESTRICTED CASH Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CASH AND CASH EQUIVALENTS AND RESTRICTED CASH— January 1 Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CASH AND CASH EQUIVALENTS AND RESTRICTED CASH— December 31 Reconciliation of cash and cash equivalents and restricted cash within the condensed consolidated statements of financial condition. RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH WITHIN THE CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION: Reconciliation Of Cash And Cash Equivalents And Restricted Cash Within Condensed Consolidated Statements Of Financial Condition [Abstract] TOTAL CASH AND CASH EQUIVALENTS AND RESTRICTED CASH SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION: Supplemental Cash Flow Information [Abstract] Cash paid during the year for: Cash Paid During Year [Abstract] Interest Interest Paid Net Income taxes, net of refunds Income Taxes Paid Net Total distributions to members and non-controlling interest holders. Value of shares delivered from treasury stock during the period as a result of an equity-based compensation plan and related tax benefit (expense). Value of stock issued or issuable in connection with acquisitions and subsidiary merger and related amortization. Amount of ownership interest in a limited liability company (LLC), including portions attributable to both the parent and noncontrolling interests, after the cumulative effect adjustment of a new accounting principle applied in the period of adoption. Business acquisitions and related equity transactions. Statement Of Stockholders Equity [Abstract] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Members equity. Members' Equity [Member] Members Equity [Member] Accumulated Other Comprehensive Income (Loss), Net of Tax [Member] Accumulated Other Comprehensive Income [Member] Total Lazard Group LLC Members' Equity [Member] Parent [Member] Noncontrolling Interests [Member] Noncontrolling Interest [Member] Balance Adjustment for the cumulative effect on prior years from the adoption of new accounting guidance related to share-based incentive compensation Cumulative Effect Of New Accounting Principle In Period Of Adoption Balance, as adjusted Limited Liability Company Llc Members Equity Including Portion Attributable To Noncontrolling Interest Adjusted Balance1 Comprehensive income (loss) Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest [Abstract] Net income Other comprehensive income (loss) - net of tax Amortization of share-based incentive compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Distributions to members and noncontrolling interests, net Distributions To Members And Non Controlling Interest Holders Purchase of Class A common stock Stock Repurchased During Period Value Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense Delivery Of Shares From Treasury Stock During The Period Net Of Tax On Share Based Compensation Value Business acquisitions and related equity transactions: Business Acquisitions And Related Equity Transactions [Abstract] Delivery of Class A common stock and related tax benefit Stock Issued During Period Value Acquisitions Class A common stock issuable (including related amortization) Stock Issued Issuable During Period Value Business Acquisitions Mergers And Amortization Other Partners Capital Other Balance Tax expense (benefit) from stock issued in connection with share-based incentive compensation. Tax expense (benefit) on stock issued during period acquisitions. Tax expense (benefit) related to delivery of Class A Common Stock in connection with share-based incentive compensation Tax Expense Benefit From Stock Issued In Connection With Sharebased Incentive Compensation Tax benefit on delivery of Class A common stock in connection with business acquisitions Tax Expense Benefit On Stock Issued During Period Acquisitions Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization and Basis of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Policies [Abstract] Significant Accounting Policies Significant Accounting Policies [Text Block] New Accounting Pronouncements And Changes In Accounting Principles [Abstract] Recent Accounting Developments New Accounting Pronouncements And Changes In Accounting Principles [Text Block] Revenue From Contract With Customer [Abstract] Revenue Recognition Revenue From Contract With Customer [Text Block] Receivables [Abstract] Receivables Loans Notes Trade And Other Receivables Disclosure [Text Block] Investments Schedule [Abstract] Investments Investment [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Measurement Inputs Disclosure [Text Block] Derivative Instruments And Hedging Activities Disclosure [Abstract] Derivatives Derivative Instruments And Hedging Activities Disclosure [Text Block] Property Plant And Equipment [Abstract] Property Property Plant And Equipment Disclosure [Text Block] Goodwill And Intangible Assets Disclosure [Abstract] Goodwill and Other Intangible Assets Goodwill And Intangible Assets Disclosure [Text Block] Other assets and other liabilities disclosure. Text Block [Abstract] Other Assets and Other Liabilities Other Assets And Other Liabilities Disclosure [Text Block] Debt Disclosure [Abstract] Senior Debt Debt Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract]