Entity Central Index Key Lessee operating lease liability payments due year six. Lessee operating lease liability payments due after year six. Cover [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 Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Shell Company Entity Shell Company Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Document Quarterly Report Document Quarterly Report Document Transition Report Document Transition Report Entity Incorporation, State or Country Code Entity Incorporation State Country Code Entity File Number Entity File Number Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address Address Line1 Entity Address, Address Line Two Entity Address Address Line2 Entity Address, City or Town Entity Address City Or Town Entity Address, State or Province Entity Address Postal Zip Code Entity Address, Country Entity Address Country City Area Code City Area Code Local Phone Number Local Phone Number Title of each class Security12b Title Trading Symbol(s) Trading Symbol Name of each exchange on which registered Security Exchange Name Represents deposits with banks and investments with a maturity of less than 90 days. 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. Stockholders equity subtotal before common stock held by subsidiaries and noncontrolling interests. 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. Payable pursuant to the tax receivable agreement. Statement Of Financial Position [Abstract] Statement [Table] Statement [Table] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Series A Preferred Stock [Member] Series A Preferred Stock [Member] Series B Preferred Stock [Member] Series B Preferred Stock [Member] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] LTBP Trust. LTBP Trust [Member] Ltbp Trust [Member] Statement [Line Items] Statement [Line Items] 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 $31,288 and $40,164 at September 30, 2019 and December 31, 2018, respectively): Accounts Receivable Net [Abstract] Fees Accrued Fees And Other Revenue Receivable Customers and other Receivables From Customers And Other Total receivables, net Accounts Receivable Net Investments Investments Property (net of accumulated amortization and depreciation of $352,104 and $339,770 at September 30, 2019 and December 31, 2018, respectively) Property Plant And Equipment Net Operating lease right-of-use assets Operating Lease Right Of Use Asset Goodwill and other intangible assets (net of accumulated amortization of $67,973 and $65,949 at September 30, 2019 and December 31, 2018, 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 AND STOCKHOLDERS’ EQUITY Liabilities And Stockholders Equity [Abstract] Liabilities: Liabilities [Abstract] Deposits and other customer payables Deposits And Other Customer Payables Accrued compensation and benefits Employee Related Liabilities Current And Noncurrent Operating lease liabilities Operating Lease Liability Senior debt Long Term Debt Tax receivable agreement obligation Payable Pursuant To Tax Receivable Agreement Deferred tax liabilities Deferred Income Tax Liabilities Net Other liabilities Other Liabilities Total Liabilities Liabilities Commitments and contingencies Commitments And Contingencies STOCKHOLDERS’ EQUITY Stockholders Equity [Abstract] Preferred stock: Preferred Stock Number Of Shares Par Value And Other Disclosures [Abstract] Preferred stock Preferred Stock Value Common stock: Common Stock Number Of Shares Par Value And Other Disclosures [Abstract] Class A, par value $.01 per share (500,000,000 shares authorized; 129,766,091 shares issued at September 30, 2019 and December 31, 2018, including shares held by subsidiaries as indicated below) Common Stock Value Additional paid-in-capital Additional Paid In Capital Common Stock Retained earnings Retained Earnings Accumulated Deficit Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income Loss Net Of Tax Stockholders' equity subtotal before common stock held by subsidiaries and Noncontrolling interests, total Stockholders Equity Before Common Stock Held By Subsidiaries And Noncontrolling Interests Class A common stock held by subsidiaries, at cost (23,950,582 and 17,574,805 shares at September 30, 2019 and December 31, 2018, respectively) Common Stock Held By Subsidiary Total Lazard Ltd Stockholders’ Equity Stockholders Equity Noncontrolling interests Minority Interest Total Stockholders’ Equity Stockholders Equity Including Portion Attributable To Noncontrolling Interest Total Liabilities and Stockholders’ Equity Liabilities And Stockholders Equity Number of shares held by subsidiary, which are purchased for the purpose of granting the shares to senior employees as part of an employee stock option plan approved by the Entity's Board of Directors. Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock held by subsidiaries, shares Common Stock Held By Subsidiary Shares Amount of expense relating to occupancy and equipment costs which can include such expenses as rent, utilities, depreciation and amortization, and repairs and maintenance costs. Amount of expense related to technology and information expense and can include such costs as depreciation and amortization, subscriptions to electronic services such as Bloomberg and consulting services related to technology. Fund administration and outsourced services expense. Amount of amortization and other acquisition related benefits costs related to intangible assets and contingent consideration. Income Statement [Abstract] 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] 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 Benefits Costs 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 LTD Net Income Loss WEIGHTED AVERAGE SHARES OF COMMON STOCK OUTSTANDING: Weighted Average Number Of Shares Outstanding [Abstract] Basic Weighted Average Number Of Shares Outstanding Basic Diluted Weighted Average Number Of Diluted Shares Outstanding NET INCOME PER SHARE OF COMMON STOCK: Earnings Per Share [Abstract] Basic Earnings Per Share Basic Diluted Earnings Per Share Diluted 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] Actuarial gain (net of tax expense (benefit) of $(1,607) and $214 for the three months ended September 30, 2019 and 2018, respectively, and $1,113 and $618 for the nine months ended September 30, 2019 and 2018, 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 $172 and $264 for the three months ended September 30, 2019 and 2018, respectively, and $524 and $948 for the nine months ended September 30, 2019 and 2018, respectively) Other Comprehensive Income Loss Reclassification Adjustment From A O C I Pension And Other Postretirement Benefit Plans Net Of Tax OTHER COMPREHENSIVE 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 LTD Comprehensive Income Net Of Tax Tax expense (benefit) on actuarial gain, 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 The amount of lease expense incurred between from the time of adoption of new accounting guidance and the end of the current period. Amortization of deferred expenses and share- based compensation. Proceeds relating to customer deposits. Amount of cash outflow made in accordance with the tax receivable agreement obligation. 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. 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 To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization of property Depreciation Depletion And Amortization Noncash lease expense Non Cash Lease Expense 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 (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] Issuance of senior debt, net of expenses Proceeds From Issuance Of Senior Long Term Debt Customer deposits, net Proceeds From Customer Deposits Contributions from noncontrolling interests Proceeds From Minority Shareholders Payments for: Payments For Financing Activities [Abstract] Senior debt Repayments Of Senior Debt Distributions to noncontrolling interests Payments To Minority Shareholders Payments under tax receivable agreement Payments For Tax Receivable Agreement Obligation Purchase of Class A common stock Payments For Repurchase Of Common Stock Class A common stock dividends Payments Of Dividends Common Stock 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 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—September 30 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 Value of shares delivered from treasury stock during the period as a result of an equity-based compensation plan and related tax benefit (expense). Number 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. Dividend-equivalents, business acquisitions. Business acquisitions and related equity transactions. The amount included in stockholders equity due to the consolidation of variable interest entities. Statement Of Stockholders Equity [Abstract] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-In-Capital [Member] Additional Paid In Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss), Net of Tax [Member] Accumulated Other Comprehensive Income [Member] Common Stock Held by Subsidiary Class A Common Stock Held By Subsidiaries [Member] Common Stock Held By Subsidiary [Member] Total Lazard Ltd Stockholders' Equity [Member] Parent [Member] Noncontrolling Interests [Member] Noncontrolling Interest [Member] Balance Balance (in shares) Shares Issued 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 Dividend equivalents Dividends Sharebased Compensation Stock Class A common stock dividends Dividends Common Stock Purchase of Class A common stock Stock Repurchased During Period Value Purchase of Class A common stock (in shares) Stock Repurchased During Period Shares Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit) Delivery Of Shares From Treasury Stock During The Period Net Of Tax On Share Based Compensation Value Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit) (in shares) Delivery Of Shares From Treasury Stock During The Period Net Of Tax On Share Based Compensation Shares Business acquisitions and related equity transactions: Business Acquisitions And Related Equity Transactions [Abstract] Delivery of Class A common stock Stock Issued During Period Value Acquisitions Delivery of Class A common stock (in shares) Stock Issued During Period Shares Acquisitions Class A common stock issuable (including related amortization) Stock Issued Issuable During Period Value Business Acquisitions Mergers And Amortization Dividend equivalents Dividend Equivalents Business Acquisitions Distributions to noncontrolling interests, net Minority Interest Decrease From Distributions To Noncontrolling Interest Holders Consolidation of VIEs Consolidation Of Variable Interest Entities Balance Balance (in shares) Tax expense (benefit) from stock issued in connection with share-based incentive compensation. Class A common stock dividends per share Common Stock Dividends Per Share Declared 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 Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization and Basis of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [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 Recognition [Abstract] Revenue Recognition Revenue From Contract With Customer [Text Block] Receivables [Abstract] Receivables Loans Notes Trade And Other Receivables Disclosure [Text Block] Schedule Of Investments [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] Leases [Abstract] Leases Lessee Operating Leases [Text Block] Goodwill And Intangible Assets Disclosure [Abstract] Goodwill and Other Intangible Assets Goodwill And Intangible Assets Disclosure [Text Block] Debt Disclosure [Abstract] Senior Debt Debt Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Equity [Abstract] Stockholders' Equity Stockholders Equity Note Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Incentive Plans Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Compensation And Retirement Disclosure [Abstract] Employee Benefit Plans Pension And Other Postretirement Benefits Disclosure [Text Block] Restructuring And Related Activities [Abstract] Business Realignment Restructuring Impairment And Other Activities Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Net Income Per Share of Class A Common Stock Earnings Per Share [Text Block] Related Party Transactions [Abstract] Related Parties Related Party Transactions Disclosure [Text Block] The entire disclosure for regulatory transactions. Regulatory Capital Requirements [Abstract] Regulatory Authorities Regulatory Authorities [Text Block] Segment Reporting [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Variable Interest Entity Consolidated Carrying Amount Assets And Liabilities [Abstract] Consolidated VIEs Variable Interest Entity Disclosure [Text Block] Disclosure of accounting policy for the nature of an entity's business, major products or services, principal markets including location and relative importance of its operation in each reporting segment and basis of determination. Organization Organization Policy [Text Block] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Recent Accounting Developments New Accounting Pronouncements Policy Policy [Text Block] Revenue Recognition Policy Revenue From Contract With Customer Policy [Text Block] Fair Value Measurement Policy Fair Value Measurement Policy Policy [Text Block] Derivative Instruments Derivatives Policy [Text Block] Share-Based Incentive Plan Awards Share Based Compensation Option And Incentive Plans Policy Employer Contributions to Pension Plans Pension And Other Postretirement Plans Policy Revenue Based on Business Segment Results Disaggregation Of Revenue Table [Text Block] Tabular disclosure of activity in the allowance for doubtful accounts. Schedule of Activity in Allowance for Doubtful Accounts Schedule Of Allowance For Doubtful Accounts Table [Text Block] Tabular disclosure of investments including debt​ equity​ securities funds and interest bearing deposits as well as investments accounted for under equity method and securities sold not yet purchased. Company's Investments and Securities Sold, Not Yet Purchased Investments Including Debt Equity Securities Funds And Interest Bearing Deposits As Well As Investments Accounted For Under Equity Method And Securities Sold Not Yet Purchased Table [Text Block] Schedule of Equity Securities and Trading Debt Securities Net Unrealized Investment Gains and Losses Unrealized Gain Loss On Investments Table [Text Block] Schedule of Classification of Investments and Certain Other Assets and Liabilities Measured at Fair Value on Recurring Basis and Investments Measured at NAV Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Tabular disclosure of fair value assets and liabilities measured on recurring basis unobservable input reconciliation. Summary of Changes in Fair Value of Company's Level 3 Assets and Liabilities Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Table [Text Block] Fair Value of Certain Investments Based on NAV Fair Value Investments Entities That Calculate Net Asset Value Per Share Table [Text Block] Fair Values of Derivatives Reported on Condensed Consolidated Statements of Financial Condition Schedule Of Derivative Instruments In Statement Of Financial Position Fair Value [Text Block] Net Gains and (Losses) With Respect To Derivative Instruments (Including Derivatives Not Designed As Hedging Instruments) Schedule Of Other Derivatives Not Designated As Hedging Instruments Statements Of Financial Performance And Financial Position Location Table [Text Block] Components of Property Property Plant And Equipment [Text Block] Summary of Components of Operating Lease Expense Lease Cost Table [Text Block] Summary of supplemental cash flow information related to operating leases. Summary of Supplemental Cash Flow Information And Certain Other Information Related to Operating Leases Summary Of Supplemental Cash Flow Information Related To Operating Leases Table [Text Block] Summary of Maturities of Operating Lease Liabilities Outstanding Lessee Operating Lease Liability Maturity Table [Text Block] Schedule of Prior Adoption For Future Minimum Rental Payment for Operating Leases Schedule Of Future Minimum Rental Payments For Operating Leases Table [Text Block] Components of Goodwill and Other Intangible Assets Schedule Of Intangible Assets And Goodwill Table [Text Block] Changes in Carrying Amount of Goodwill Schedule Of Goodwill [Text Block] Gross Cost and Accumulated Amortization of Other Intangible Assets Schedule Of Finite Lived Intangible Assets Table [Text Block] Estimated Future Amortization Expense Scheduleof Finite Lived Intangible Assets Future Amortization Expense Table [Text Block] Senior Debt Schedule Of Debt Table [Text Block] Tabular disclosure of the share repurchases authorized by board of directors. Schedule of Share Repurchase Authorized by Board of Directors Schedule Of Share Repurchases Authorized By Board Of Directors Table [Text Block] Tabular disclosure of shares repurchased during the period under the share repurchased program. Schedule of Shares Repurchased Under the Share Repurchase Program Schedule Of Shares Repurchased Under Share Repurchase Program Table [Text Block] Accumulated Other Comprehensive Income (Loss), Net of Tax Schedule Of Accumulated Other Comprehensive Income Loss Table [Text Block] Adjustments for Items Reclassified Out of AOCI Reclassification Out Of Accumulated Other Comprehensive Income Table [Text Block] Tabular disclosure of noncontrolling interests during and as of end of reporting periods. Net Income Attributable to Noncontrolling Interests Schedule Of Noncontrolling Interests During And As Of End Of Reporting Periods Table [Text Block] Award Type Award Type [Axis] Award Type Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Restricted stock units and deferred stock units. Restricted Stock Units and Deferred Stock Units [Member] Restricted Stock Units And Deferred Stock Units [Member] Restricted stock awards class A. Restricted Stock Awards Class A [Member] Restricted Stock Awards Class A [Member] Performance based restricted stock unit PRSU. PRSUs [Member] Performance Based Restricted Stock Unit [Member] profits interest participation rights. Profits Interest Participation Rights [Member] Profits Interest Participation Rights [Member] Summary of Impact of Share-Based Incentive Plans on Compensation and Benefits Expense Schedule Of Compensation Cost For Share Based Payment Arrangements Allocation Of Share Based Compensation Costs By Plan Table [Text Block] Schedule of Activity Relating to Share-based Awards Schedule Of Share Based Compensation Activity Table [Text Block] Summary of LFI and Other Similar Deferred Compensation Arrangements Schedule Of Deferred Compensation Arrangement With Individual Share Based Payments [Text Block] Components of Net Periodic Benefit Cost (Credit) Schedule Of Net Benefit Costs Table [Text Block] Expenses Associated with Business Realignment Activity Schedule Of Restructuring And Related Costs [Text Block] Activity Related to the Obligations Pursuant to Business Realignment Schedule Of Restructuring Reserve By Type Of Cost [Text Block] Company's Basic and Diluted Net Income Per Share and Weighted Average Shares Outstanding Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Segment's Contribution with Respect to Net Revenue, Operating Expenses, Operating Income (Loss) and Total Assets Schedule Of Segment Reporting Information By Segment [Text Block] Summary of Consolidated VIE Assets and Liabilities Schedule Of Variable Interest Entities [Text Block] The enactment date of the governing operating agreement. Organization and basis of presentation. Organization and basis of presentation. Organization And Basis Of Presentation [Table] Organization And Basis Of Presentation [Table] Ownership Ownership [Axis] Ownership Ownership [Domain] Lazard Group LLC. Lazard Group LLC [Member] Lazard Group Llc [Member] Organization And Basis Of Presentation [Line Items] Organization And Basis Of Presentation [Line Items] Percentage of common membership interests held Minority Interest Ownership Percentage By Parent Governing operating agreement, date Governing Operating Agreement Date Number of business segments Number Of Operating Segments Operating lease right-of-use assets Operating lease liability U.S. federal statutory income tax rate Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate Disaggregation Of Revenue [Table] Disaggregation Of Revenue [Table] Segments Statement Business Segments [Axis] Segments Segment [Domain] Financial advisory segment. Financial Advisory Segment [Member] Financial Advisory Segment [Member] Asset management segment. Asset Management Segment [Member] Asset Management Segment [Member] Management fees and other. Management Fees and Other [Member] Management Fees And Other [Member] Incentive Fees. Incentive Fees [Member] Incentive Fees [Member] Disaggregation Of Revenue [Line Items] Disaggregation Of Revenue [Line Items] Net Revenue The amount of charge-offs, foreign currency translation and other adjustments made during the period to the allowance for doubtful accounts. Allowance For Doubtful Accounts Receivable Rollforward Allowance for doubtful accounts receivables, Beginning balance Bad debt expense, net of recoveries Provision For Doubtful Accounts Charge-offs, foreign currency translation and other adjustments Allowance For Doubtful Accounts Receivable Charge Offs Foreign Currency Translation And Other Adjustments Allowance for doubtful accounts receivables, Ending balance Receivables that are deemed past due or uncollectible. Schedule Of Accounts Notes Loans And Financing Receivable [Table] Schedule Of Accounts Notes Loans And Financing Receivable [Table] Receivable Type Accounts Notes Loans And Financing Receivable By Receivable Type [Axis] Receivable Receivable Type [Domain] Financing Receivables [Member] Finance Receivables [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts Notes And Loans Receivable [Line Items] Receivables past due or deemed uncollectible Receivable Deemed Past Due Or Uncollectible Interest-bearing financing fee receivables. Interest-bearing financing fee receivables Interest Bearing Financing Fee Receivables The aggregate carrying amount of non-interest bearing trade receivables. Aggregate carrying amount of non-interest bearing receivables Aggregate Carrying Amount Noninterest Bearing Trade Receivables Schedule Of Investments [Table] Schedule Of Investments [Table] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Interest-bearing Deposits [Member] Interest Bearing Deposits [Member] Debt [Member] Debt Securities [Member] Equities [Member] Equity Securities [Member] Alternative investments. Alternative Investment Funds [Member] Alternative Investments [Member] Debt Funds [Member] Fixed Income Funds [Member] Equity Funds [Member] Equity Funds [Member] Private Equity Funds [Member] Private Equity Funds [Member] Funds. Funds Total [Member] Funds [Member] Schedule of Investments [Line Items] Schedule Of Investments [Line Items] Total investments Investments, at fair value Investments Fair Value Disclosure Securities sold, not yet purchased, at fair value (included in "other liabilities") Financial Instruments Sold Not Yet Purchased At Fair Value Legal Entity Legal Entity [Axis] Entity Entity [Domain] Lazard fund interest. Lazard Fund Interests [Member] Lazard Fund Interest [Member] Period of time between issuance and maturity of treasury securities, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Statistical Measurement Range [Axis] Statistical Measurement Range [Member] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Financial Instrument Financial Instrument [Axis] Financial Instruments Transfers And Servicing Of Financial Instruments Types Of Financial Instruments [Domain] U.S. Treasury Securities [Member] U S Treasury Securities [Member] Deposits maturity period Maturity Of Time Deposits US Treasury securities maturity period Securities Maturity Date Net Realized Or Unrealized Gain Loss On Trading Securities [Abstract] Net unrealized investment gains (losses) Trading Securities Unrealized Holding Gain Loss Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level 1 [Member] Fair Value Inputs Level1 [Member] Level 2 [Member] Fair Value Inputs Level2 [Member] Level 3 [Member] Fair Value Inputs Level3 [Member] NAV [Member] Fair Value Measured At Net Asset Value Per Share [Member] Fair Value, Measurements, Recurring [Member] Fair Value By Measurement Frequency [Axis] Measurement Frequency Fair Value Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value Measurements Recurring [Member] Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Investments Total Derivative Assets Derivative Assets Total investments measured at fair value Assets Fair Value Disclosure Securities sold, not yet purchased Contingent consideration liability Business Combination Contingent Consideration Liability Total Derivative Liabilities Derivative Liabilities Total of Liabilities Measured at Fair Value Liabilities Fair Value Disclosure Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset, foreign currency translation adjustments. Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table] Liability Class Fair Value By Liability Class [Axis] Fair Value by Liability Class Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation By Liability Class [Domain] Contingent consideration liability. Contingent Consideration Liability [Member] Contingent Consideration Liability [Member] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Assets: Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward Beginning Balance Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Value Net Unrealized/Realized Gains/Losses Included In Earnings Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Gain Loss Included In Earnings1 Purchases/Acquisitions/Transfers Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Purchases Sales/ Dispositions/Settlements Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales Foreign Currency Translation Adjustments Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Foreign Currency Translation Adjustments Ending Balance Fair value measurement with unobservable inputs reconciliation recurring basis liability foreign currency translation adjustments. Liabilities: Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward Beginning Balance Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value Net Unrealized/Realized Gains/Losses Included In Earnings Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Included In Earnings Purchases/Acquisitions/ Transfers Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Purchases Sales/ Dispositions/Settlements Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Sales Foreign Currency Translation Adjustments Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Foreign Currency Translation Adjustments Ending Balance Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Schedule of information of fair value of assets and liabilities measured on recurring basis unobservable input reconciliation. Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Table] Fair Value of Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items] Fair Value Of Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] Net unrealized gains (losses) Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss Net unrealized (gains) losses Fair Value Liabilities Measured On Recurring Basis Change In Unrealized Gain Loss Fair value transfers between level one level two and level three amount. Fair Value Option Quantitative Disclosures [Table] Fair Value Option Quantitative Disclosures [Table] Edgewater Growth Capital Partners III, L.P. EGCP III [Member] Edgewater Growth Capital Partners Three Lp [Member] Fair Value Option Quantitative Disclosures [Line Items] Fair Value Option Quantitative Disclosures [Line Items] Transfers between Level 1, 2 and 3 in fair value measurement hierarchy Fair Value Transfers Between Level One Level Two And Level Three Amount Percentage of fair value not redeemable. Percentage of estimated liquidation period of investments not redeemable, next five years. Percentage of estimated liquidation period of investments not redeemable, five to ten years. Percentage of estimated liquidation period of investments not redeemable, thereafter. Fair Value Investments Entities That Calculate Net Asset Value Per Share [Table] Fair Value Investments Entities That Calculate Net Asset Value Per Share [Table] Hedge Funds [Member] Hedge Funds [Member] Funds of funds. Funds of Funds [Member] Funds Of Funds [Member] Other alternative investments. Other [Member] Other Alternative Investments [Member] Investment Secondary Categorization Investment Secondary Categorization [Axis] Investments by Secondary Categorization Investments By Secondary Categorization [Domain] Equity growth. Equity Growth [Member] Equity Growth [Member] Investment redemption frequency. Investment Redemption Frequency Investment Redemption Frequency [Axis] Investment redemption frequency. Investment Redemption Frequency Investment Redemption Frequency [Domain] Daily. Daily [Member] Daily [Member] Monthly. Monthly [Member] Monthly [Member] Quarterly. Quarterly [Member] Quarterly [Member] Annually. Annually [Member] Annually [Member] Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items] Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items] Fair Value Alternative Investment Unfunded Commitments Fair Value Investments Entities That Calculate Net Asset Value Per Share Unfunded Committments % of Fair Value Not Redeemable Percentage Of Fair Value Not Redeemable Estimated Liquidation Period of Investments Not Redeemable, % Next 5 Years Percentage Of Estimated Liquidation Period Of Investments Not Redeemable Next Five Years Estimated Liquidation Period of Investments Not Redeemable, % 5-10 Years Percentage Of Estimated Liquidation Period Of Investments Not Redeemable Five To Ten Years Estimated Liquidation Period of Investments Not Redeemable, % Thereafter Percentage Of Estimated Liquidation Period Of Investments Not Redeemable Thereafter Investments Redeemable, Redemption Notice Period Fair Value Investments Entities That Calculate Net Asset Value Per Share Investment Redemption Notice Period1 States the percentage with which the entity can redeem its investment, or portion thereof, per period (for example, annually, semi-annually, quarterly) for each of those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments), by major category. Investments Redeemable, Percent Fair Value Investments Entities That Calculate Net Asset Value Per Share Investment Redemption Frequency Percentage Consolidated but not owned. Consolidated But Not Owned [Member] Consolidated But Not Owned [Member] End of investment funding period. Remaining commitment date. End of the investment period End Of Investment Funding Period Remaining obligation date Remaining Commitment Date Fair Values Derivatives Balance Sheet Location By Derivative Contract Type By Hedging Designation [Table] Fair Values Derivatives Balance Sheet Location By Derivative Contract Type By Hedging Designation [Table] Derivative Instrument Derivative Instrument Risk [Axis] Derivative Contract Derivative Contract Type [Domain] Forward Foreign Currency Exchange Rate Contracts [Member] Foreign Exchange Forward [Member] Return swaps and other. Total Return Swaps and Other [Member] Return Swaps And Other [Member] Lazard fund interests and other similar deferred compensation arrangements. LFI and Other Similar Deferred Compensation Arrangements [Member] Lazard Fund Interests And Other Similar Deferred Compensation Arrangements [Member] Derivatives, Fair Value [Line Items] Derivatives Fair Value [Line Items] Derivative Assets Derivative Liabilities Represents receivables for net cash collateral under contracts. Total Return Swaps [Member] Total Return Swap [Member] Gross derivative assets Derivative Fair Value Of Derivative Asset Gross derivative liability Derivative Fair Value Of Derivative Liability Cash collateral pledged for total return swaps Derivative Cash Collateral For Return Swaps Derivative Instruments Gain Loss By Hedging Relationship By Income Statement Location By Derivative Instrument Risk [Table] Derivative Instruments Gain Loss By Hedging Relationship By Income Statement Location By Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments Gain Loss [Line Items] Gains (losses) on derivatives not designated as hedging instruments Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net Gains (losses) on derivatives instruments Derivative Gain Loss On Derivative Net Property Plant And Equipment [Abstract] Schedule Of Property Plant And Equipment [Table] Schedule Of Property Plant And Equipment [Table] Property, Plant and Equipment, Type Property Plant And Equipment By Type [Axis] Property, Plant and Equipment, Type Property Plant And Equipment Type [Domain] Buildings [Member] Building [Member] Leasehold Improvements [Member] Leasehold Improvements [Member] Furniture and equipment. Furniture and Equipment [Member] Furniture And Equipment [Member] Construction in Progress [Member] Construction In Progress [Member] Property, Plant and Equipment [Line Items] Property Plant And Equipment [Line Items] Property, plant and equipment, gross Property Plant And Equipment Gross Less - Accumulated depreciation and amortization Property Property, plant and equipment, useful life Property Plant And Equipment Useful Life Operating lease cost Operating Lease Cost Variable lease cost Variable Lease Cost Less - sublease income Sublease Income Total Lease Cost Supplemental cash flow information and other information relating to operating leases, Cash paid for amounts included in the measurement of lease liabilities: Supplemental Cash Flow Information And Other Information Relating To Operating Leases [Abstract] Operating cash flows from operating leases Operating Lease Payments Operating lease right-of-use assets obtained in exchange for operating lease liabilities Right Of Use Asset Obtained In Exchange For Operating Lease Liability Weighted average remaining lease term Operating Lease Weighted Average Remaining Lease Term1 Weighted average discount rate Operating Lease Weighted Average Discount Rate Percent 2019 (October 1 through December 31) Lessee Operating Lease Liability Payments Remainder Of Fiscal Year 2020 Lessee Operating Lease Liability Payments Due Year Two 2021 Lessee Operating Lease Liability Payments Due Year Three 2022 Lessee Operating Lease Liability Payments Due Year Four 2023 Lessee Operating Lease Liability Payments Due Year Five 2024 Lessee Operating Lease Liability Payments Due Year Six Thereafter Lessee Operating Lease Liability Payments Due After Year Six Total lease payments Lessee Operating Lease Liability Payments Due Less - Discount Lessee Operating Lease Liability Undiscounted Excess Amount Operating leases future minimum payments due net of sublease rentals. Minimum Rental Commitments Operating - 2019 Operating Leases Future Minimum Payments Due Current Minimum Rental Commitments Operating - 2020 Operating Leases Future Minimum Payments Due In Two Years Minimum Rental Commitments Operating - 2021 Operating Leases Future Minimum Payments Due In Three Years Minimum Rental Commitments Operating - 2022 Operating Leases Future Minimum Payments Due In Four Years Minimum Rental Commitments Operating - 2023 Operating Leases Future Minimum Payments Due In Five Years Minimum Rental Commitments Operating - Thereafter Operating Leases Future Minimum Payments Due Thereafter Total minimum rental commitments Operating Leases Future Minimum Payments Due Less - sublease proceeds Operating Leases Future Minimum Payments Due Future Minimum Sublease Rentals Net rental commitments Operating Leases Future Minimum Payments Due Net Of Sublease Rentals Goodwill Goodwill Other intangible assets (net of accumulated amortization) Other Intangible Assets Net Goodwill and other intangible assets, Total Goodwill and intangible assets. Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Table] Goodwill And Intangible Assets [Line Items] Goodwill And Intangible Assets [Line Items] Beginning Balance Foreign currency translation adjustments Goodwill Foreign Currency Translation Gain Loss Ending Balance Schedule Of Finite Lived Intangible Assets [Table] Schedule Of Finite Lived Intangible Assets [Table] Nature of Expense Nature Of Expense [Axis] Interim Period, Costs Not Allocable Interim Period Costs Not Allocable [Domain] Success or incentive fees. Success/Incentive Fees [Member] Success Or Incentive Fees [Member] Management fees, customer relationships and non-compete agreements. Management Fees, Customer Relationships and Non-Compete Agreements [Member] Management Fees Customer Relationships And Non Compete Agreements [Member] Finite-Lived Intangible Assets [Line Items] Finite Lived Intangible Assets [Line Items] Other intangible assets, Gross Cost Other Finite Lived Intangible Assets Gross Other intangible assets, Net Carrying Amount Amortization of intangible assets Amortization Of Intangible Assets 2019 (October 1 through December 31) Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year 2020 Finite Lived Intangible Assets Amortization Expense Year Two 2021 Finite Lived Intangible Assets Amortization Expense Year Three 2022 Finite Lived Intangible Assets Amortization Expense Year Four 2023 Finite Lived Intangible Assets Amortization Expense Year Five Thereafter Finite Lived Intangible Assets Amortization Expense After Year Five Total amortization expense Finite Lived Intangible Assets Net Debt Instrument [Table] Debt Instrument [Table] Debt Instrument Debt Instrument [Axis] Debt Instrument, Name Debt Instrument Name [Domain] Lazard Group four point two five percent senior notes. Lazard Group 4.25% Senior Notes [Member] Lazard Group Four Point Two Five Percent Senior Notes [Member] Lazard Group three point seven five percent senior notes. Lazard Group 3.75% Senior Notes [Member] Lazard Group Three Point Seven Five Percent Senior Notes [Member] Lazard Group 3.625% senior notes. Lazard Group 3.625% Senior Notes [Member] Lazard Group Three Point Six Two Five Percent Senior Notes [Member] Lazard Group four point five zero percent senior notes. Lazard Group 4.50% Senior Notes [Member] Lazard Group Four Point Five Zero Percent Senior Notes [Member] Lazard group four point three seven five percent senior notes. Lazard Group 4.375% Senior Notes [Member] Lazard Group Four Point Three Seven Five Percent Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Senior Debt, Initial Principal Amount Debt Instrument Face Amount Senior Debt, Maturity Date Debt Instrument Maturity Date Senior Debt, Annual Interest Rate Debt Instrument Interest Rate Stated Percentage Senior Debt, Outstanding Principal Debt Instrument Carrying Amount Senior Debt, Outstanding Unamortized Debt Costs Deferred Finance Costs Net Senior Debt, Outstanding Carrying Value Debt instrument interest rate payment date. Interest rate, payment terms Debt Instrument Interest Rate Payment Date Senior notes interest rate Redemption of senior debt aggregate principal amount Extinguishment Of Debt Amount Original Maturity Date Effective interest rates of senior notes Debt Instrument Interest Rate Effective Percentage Line of credit facility expiration. Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Amended and restated credit agreement. Amended and Restated Credit Agreement [Member] Amended And Restated Credit Agreement [Member] Lazard Freres Banque SA. LFB [Member] Lazard Freres Banque Sa [Member] Unused Lines of Credit [Member] Unused Lines Of Credit [Member] Senior Debt [Member] Senior Debt Obligations [Member] Senior revolving credit facility Line Of Credit Facility Maximum Borrowing Capacity Duration of senior revolving credit facility, in years Debt Instrument Term Expiration of credit facility Line Of Credit Facility Expiration Outstanding credit facility Line Of Credit Unused lines of credit Line Of Credit Facility Remaining Borrowing Capacity Fair value of senior debt Long Term Debt Fair Value Guarantor obligations collateral held. Other Commitments [Table] Other Commitments [Table] Business Acquisition Business Acquisition [Axis] Business Acquisition, Acquiree Business Acquisition Acquiree [Domain] Business acquisitions. Business Acquisitions [Member] Business Acquisitions [Member] Class A Common Stock [Member] Common Class A [Member] Contingent Consideration by Type Contingent Consideration By Type [Axis] Contingent Consideration Type Contingent Consideration Type [Domain] Non contingent. Non-Contingent [Member] Non Contingent [Member] Lazard Freres and company limited liability company. LFNY [Member] Lazard Freres And Company Limited Liability Company [Member] Other Commitments [Line Items] Other Commitments [Line Items] Guarantees indemnifications Guarantee Obligations Maximum Exposure Collateral/counter-guarantees Guarantor Obligations Collateral Held Business acquisition on remaining consideration equity interests issued or issuable number of shares issued. Business acquisition on remaining consideration equity interests issuable upon satisfaction of performance thresholds. Business acquisition contingent consideration shares earned including dividend equivalent. Common stock issued and issuable Business Acquisition Equity Interests Issued Or Issuable Number Of Shares Issued Number of contingent additional shares earned including dividend equivalent amount Business Acquisition Contingent Consideration Shares Earned Including Dividend Equivalent Common stock issued and issuable Business Acquisition On Remaining Consideration Equity Interests Issued Or Issuable Number Of Shares Issued Contingent shares issuable upon satisfaction of performance thresholds Business Acquisition On Remaining Consideration Equity Interests Issuable Upon Satisfaction Of Performance Thresholds Other commitments Other Commitment Share repurchase program. Share Repurchase Program [Abstract] Class Of Treasury Stock [Table] Class Of Treasury Stock [Table] Share Repurchase Program Share Repurchase Program [Axis] Share Repurchase Program Share Repurchase Program [Domain] Share repurchase program date October two thousand and seventeen. October, 2017 [Member] Share Repurchase Program Date October Two Thousand And Seventeen [Member] Share repurchase program date April two thousand and eighteen. April, 2018 [Member] Share Repurchase Program Date April Two Thousand And Eighteen [Member] Share repurchase program date October two thousand and eighteen. October, 2018 [Member] Share Repurchase Program Date October Two Thousand And Eighteen [Member] Share repurchase program date February two thousand and nineteen member February, 2019 [Member] Share Repurchase Program Date February Two Thousand And Nineteen [Member] Equity, Class of Treasury Stock [Line Items] Equity Class Of Treasury Stock [Line Items] Share Repurchase Authorization Stock Repurchase Program Authorized Amount1 Expiration Stock Repurchase Program Expiration Date Average price per common share. Average Price Per Share Average Price Per Common Share Schedule of stockholders equity. Schedule Of Stockholders' Equity [Table] Schedule Of Stockholders Equity [Table] Schedule Of Stockholders Equity [Table] Executive Officers [Member] Executive Officer [Member] 30 October, 2019 [Member] 30 October, 2019 [Member] Share Repurchase Program Date Thirty October Two Thousand And Nineteen [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Dividends Dividends [Axis] Dividends Dividends [Domain] Quarterly dividend declared by the board of directors to be distributed to shareholders. Quarterly Dividend [Member] Quarterly Dividend [Member] Schedule Of Stockholders Equity [Line Items] Schedule Of Stockholders Equity [Line Items] Aggregate value of all shares repurchased Share repurchase remaining authorization Stock Repurchase Program Remaining Authorized Repurchase Amount1 Share repurchase authorization expiration date Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Table] Currency Translation Adjustments [Member] Accumulated Foreign Currency Adjustment Including Portion Attributable To Noncontrolling Interest [Member] Employee Benefit Plans [Member] Accumulated Defined Benefit Plans Adjustment Including Portion Attributable To Noncontrolling Interest [Member] AOCI Attributable to Noncontrolling Interest [Member] Aoci Attributable To Noncontrolling Interest [Member] Total AOCI [Member] Aoci Including Portion Attributable To Noncontrolling Interest [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss [Line Items] Other comprehensive income (loss) before reclassifications Other Comprehensive Income Loss Before Reclassifications Net Of Tax Adjustments for items reclassified to earnings, net of tax Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract] Reclassification Out Of Accumulated Other Comprehensive Income [Table] Reclassification Out Of Accumulated Other Comprehensive Income [Table] Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items] Amortization relating to employee benefit plans Reclassification From Accumulated Other Comprehensive Income Current Period Before Tax Less - related income taxes Reclassification From Aoci Current Period Tax Total reclassifications, net of tax Minority Interest [Table] Minority Interest [Table] Edgewater. Edgewater [Member] Edgewater [Member] Other entity. Other [Member] Other Entity [Member] Variable Interest Entities Variable Interest Entities By Classification Of Entity [Axis] Variable Interest Entity, Classification Classification Of Variable Interest Entity [Domain] Consolidated VIEs [Member] Variable Interest Entity Primary Beneficiary [Member] Change In Ownership Interest [Line Items] Minority Interest [Line Items] Net Income Attributable to Noncontrolling Interests Number of shares distributed to the parent. Dividend declared per share of common stock Dividend payable date Dividend Payable Date To Be Paid Day Month And Year Dividend date of record Dividends Payable Date Of Record Day Month And Year Dividend declare date Dividends Payable Date Declared Day Month And Year Number of shares distributed to the parent Number Of Shares Distributed To The Parent Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Two thousand and eighteen plan. 2018 Equity Incentive Plan [Member] Two Thousand And Eighteen Plan [Member] Awarded under two thousand eight plan. Awarded Under 2008 Plan [Member] Awarded Under Two Thousand Eight Plan [Member] Two thousand and five plan. 2005 Equity Incentive Plan [Member] Two Thousand And Five Plan [Member] RSUs [Member] Restricted Stock Units R S U [Member] Title of Individual Title Of Individual [Axis] Title of Individual Title Of Individual With Relationship To Entity [Domain] Non-executive. Non-Executive [Member] Non Executive [Member] Deferred stock unit. DSUs [Member] Deferred Stock Unit [Member] Restricted Stock [Member] Restricted Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Shares authorized pertaining to share based compensation arrangements Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Percentage of outstanding shares available under an equity-based compensation award plan. Percentage of outstanding Class A common stock available under the plan Percentage Of Outstanding Shares Available Under An Equity Based Compensation Award Plan Compensation plan expiration period Share Based Compensation Arrangement By Share Based Payment Award Expiration Date Share-based incentive awards: Share Based Compensation Allocation And Classification In Financial Statements [Abstract] Share-based incentive awards Allocated Share Based Compensation Expense Common stock conversion basis Common Stock Conversion Basis Grant date fair value, amortized periods Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Rights Issuance of restricted stock units in connection with dividend participation rights. Charge to retained earnings pertaining to issuance of restricted stock units in connection with participation rights. Number of RSUs issued in connection with dividend participation rights Issuance Of Restricted Stock Units In Connection With Dividend Participation Rights Charges to retained earnings, net of estimated forfeitures Charge To Retained Earnings Pertaining To Issuance Of Restricted Stock Units In Connection With Participation Rights Percentage of annual compensation received by directors in deferred stock units. Percentage of annual compensation received by directors in the form of DSUs Percentage Of Annual Compensation Received By Directors In Deferred Stock Units Annual compensation received for service Deferred Compensation Arrangement With Individual Shares Issued Number of shares granted to directors under the Directors Fee deferral unit plan. Units granted under the directors deferred unit plan Units Granted Directors Deferred Unit Plan Share-based compensation arrangement by share-based payment award [Line Items] Units, Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Units, Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Units, Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period Units, Settled Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Units, Ending Balance Weighted Average Grant Date Fair Value, Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Weighted Average Grant Date Fair Value, Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value Weighted Average Grant Date Fair Value, Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value Weighted Average Grant Date Fair Value, Settled Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value Weighted Average Grant Date Fair Value, Ending Balance Dividend participation rights Withholding taxes in lieu of share delivery Shares Paid For Tax Withholding For Share Based Compensation Delivery of common stock associated with stock awards Restricted Stock Shares Issued Net Of Shares For Tax Withholdings Unrecognized compensation expense Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Unrecognized compensation expense, years Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Share based compensation arrangement by share based payment award award vesting terms. Percentage of target number of shares subject to each PRSU no longer subject to forfeiture due to threshold level of performance being achieved. Share based compensation arrangement by share based payment award target shares earned description. Percentage of target number of shares subject to each PRSU no longer subject to forfeiture due to threshold level of performance being achieved Percentage Of Target Number Of Shares Subject To Each Prsu No Longer Subject To Forfeiture Due To Threshold Level Of Performance Being Achieved Descriptions of vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Terms Vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 PRSUs target share distribution for Class A common stock, description Share Based Compensation Arrangement By Share Based Payment Award Target Shares Earned Description Percentage of target number of shares subject to applicable units no longer subject to forfeiture due to threshold level of performance being achieved. Percentage of target number of shares subject to the applicable units no longer subject to forfeiture due to threshold level of performance being achieved Percentage Of Target Number Of Shares Subject To Applicable Units No Longer Subject To Forfeiture Due To Threshold Level Of Performance Being Achieved Prepaid compensation asset, granted. Prepaid compensation asset, settled. Prepaid compensation asset forfeited. Prepaid compensation asset, amortization. Prepaid compensation asset decrease in fair value. Prepaid compensation asset, adjustment to forfeiture. Prepaid compensation asset, foreign currency translation and other adjustments. Prepaid compensation asset. Deferred Compensation Arrangements [Abstract] Schedule Of Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits By Title Of Individual And By Type Of Deferred Compensation [Table] Schedule Of Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits By Title Of Individual And By Type Of Deferred Compensation [Table] Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items] Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items] Prepaid Compensation Asset, Beginning Balance Prepaid Compensation Asset Prepaid Compensation Asset, Granted Prepaid Compensation Asset Granted Prepaid Compensation Asset, Settled Prepaid Compensation Asset Settled Prepaid Compensation Asset, Forfeited Prepaid Compensation Asset Forfeited Prepaid Compensation Asset, Amortization Prepaid Compensation Asset Amortization Prepaid Compensation Asset, Increase (decrease) in fair value of underlying investments Prepaid Compensation Asset Decrease In Fair Value Prepaid Compensation Asset, Adjustment for estimated forfeitures Prepaid Compensation Asset Adjustment To Forfeiture Prepaid Compensation Asset, Other Prepaid Compensation Asset Foreign Currency Translation And Other Adjustments Prepaid Compensation Asset, Ending Balance Derivative liability, granted. Derivative liability settled. Derivative liability forfeited. Derivative liability amortizations. Derivative liability, change in fair value. Derivative liability, adjustment to forfeiture. Derivative liability, foreign currency translation and other adjustments. Compensation Liability, Beginning Balance Compensation Liability, Granted Derivative Liability Granted Compensation Liability, Settled Derivative Liability Settled Compensation Liability, Forfeited Derivative Liability Forfeited Compensation Liability, Amortization Derivative Liability Amortizations Compensation Liability, Increase (decrease) in fair value of underlying investments Derivative Liability Change In Fair Value Compensation Liability, Adjustment for estimated forfeitures Derivative Liability Adjustment To Forfeiture Compensation Liability, Other Derivative Liability Foreign Currency Translation And Other Adjustments Compensation Liability, Ending Balance Amortization of awarded grants, net of forfeitures. Compensation expense related to the change in fair value of the underlying investments. Share Based Compensation [Abstract] Amortization, net of forfeitures Amortization Of Awarded Grants Net Of Forfeitures Change in the fair value of underlying investments Compensation Expense Related To Change In Fair Value Of Underlying Investments Total Deferred Compensation Arrangement With Individual Allocated Share Based Compensation Expense Defined Benefit Pension Plans And Defined Benefit Postretirement Plans Disclosure [Abstract] Schedule Of Defined Benefit Plans Disclosures [Table] Schedule Of Defined Benefit Plans Disclosures [Table] Pension Plans [Member] Retirement Plan Type [Axis] Retirement Plan Type Retirement Plan Type [Domain] Pension Plans [Member] Pension Plans Defined Benefit [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Components of Net Periodic Benefit Cost (Credit): Defined Benefit Plan Net Periodic Benefit Cost [Abstract] Service cost Defined Benefit Plan Service Cost Interest cost Defined Benefit Plan Interest Cost Expected return on plan assets Defined Benefit Plan Expected Return On Plan Assets Amortization of: Adjustment For Amortization [Abstract] Prior service cost Defined Benefit Plan Amortization Of Prior Service Cost Credit Net actuarial loss (gain) Defined Benefit Plan Amortization Of Gains Losses Settlement loss Defined Benefit Plan Recognized Net Gain Loss Due To Settlements1 Net periodic benefit cost (credit) Defined Benefit Plan Net Periodic Benefit Cost Corporate Segment [Member] Corporate [Member] Compensation and benefits Severance Costs1 Other Other Restructuring Costs Total Restructuring Charges Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Accrued compensation and benefits [member] Accrued Compensation and Benefits [Member] Accrued Compensation And Benefits [Member] Other Liabilities [Member] Other Liabilities [Member] Balance, July 1, 2019 Restructuring Reserve New charges Non-cash charges Restructuring Reserve Settled Without Cash2 Payments Payments For Restructuring Balance, September 30, 2019 Income tax provisions Effective income tax rates Effective Income Tax Rate Continuing Operations Weighted average number of shares outstanding basic before adjustments. The sum of the potential common shares or units used in the calculation of the basic per-share or per unit computation. Net income attributable to Lazard Ltd Add - adjustment for earnings attributable to participating securities Participating Securities Distributed And Undistributed Earnings Loss Basic Net income attributable to Lazard Ltd - basic Net Income Loss Available To Common Stockholders Basic Add - adjustment for earnings attributable to participating securities Participating Securities Distributed And Undistributed Earnings Loss Diluted Net income attributable to Lazard Ltd - diluted Net Income Loss Available To Common Stockholders Diluted Weighted average number of shares of Class A common stock outstanding Weighted Average Number Of Shares Outstanding Basic Before Adjustments Add - adjustment for shares of Class A common stock issuable on a non-contingent basis Weighted Average Number Of Basic Shares Outstanding Adjustment Weighted average number of shares of Class A common stock outstanding - basic Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average number of shares of Class A common stock outstanding - diluted Net income attributable to Lazard Ltd per share of Class A common stock: Earnings Per Share Basic And Diluted [Abstract] Schedule Of Related Party Transactions By Related Party [Table] Schedule Of Related Party Transactions By Related Party [Table] Affiliated funds. Sponsored Funds [Member] Affiliated Funds [Member] Member of the Company’s Board of Directors also served as a member of the client’s board of directors or in a management capacity. Member of Board of Directors of Company that Services were Provided to [Member] Member Of Board Of Directors Of Company That Services Were Provided To [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Type of Revenue [Extensible List] Type Of Revenue Extensible List Fees receivable Amount of cash savings in income or franchise tax that would be realized as a result of increases in tax basis and certain other tax benefits related to the amended and restated tax receivable agreement. Cash tax saving that may arise from tax benefits attributable to payments under the amended and restated tax receivable agreement. Amount of cash savings in income or franchise tax that would be realized as a result of increases in tax basis and certain other tax benefits related to the amended and restated tax receivable agreement Amount Of Cash Savings In Income Or Franchise Tax That Would Be Realized As Result Of Increases In Tax Basis And Certain Other Tax Benefits Related To Amended And Restated Tax Receivable Agreement Cash tax saving that may arise from tax benefits attributable to payments under the amended and restated tax receivable agreement Cash Tax Saving That May Arise From Tax Benefits Attributable To Payments Under Amended And Restated Tax Receivable Agreement Cumulative liability relating to obligations under Amended and Restated Tax Receivable Agreement Payments under tax receivable agreement Minimum net capital is fixed percentage of indebtedness recorded in focus report. Regulated Operations [Abstract] Regulatory requirements. Schedule of regulatory authorities. Schedule Of Regulatory Authorities [Table] Schedule Of Regulatory Authorities [Table] United Kingdom subsidiary. U.K. Subsidiaries [Member] United Kingdom Subsidiary [Member] Compagnie Financiere Lazard Freres SAS. CFLF [Member] Compagnie Financiere Lazard Freres Sas [Member] Combined European regulated group. Combined European Regulated Group [Member] Combined European Regulated Group [Member] Other U.S. and non-U.S. subsidiaries. Other U.S. and Non-U.S. Subsidiaries [Member] Other U S And Non U S Subsidiaries [Member] Regulatory Requirements [Line Items] Regulatory Requirements [Line Items] Specified fixed percentage, minimum required capital Minimum Net Capital Is Fixed Percentage Of Indebtedness Recorded In Focus Report Minimum net capital requirement as defined under exchange act Minimum Net Capital Required1 Regulatory capital Capital Regulatory capital in excess of minimum requirement Excess Capital Aggregate indebtedness to net capital ratio Ratio Of Indebtedness To Net Capital1 Schedule Of Segment Reporting Information By Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Consolidation Items Consolidation Items [Axis] Consolidation Items Consolidation Items [Domain] Operating Segments [Member] Operating Segments [Member] Corporate [Member] Corporate Non Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Net Revenue Operating Expenses Operating Income (Loss) Total Assets Schedule Of Variable Interest Entities [Table] Schedule Of Variable Interest Entities [Table] Variable Interest Entity, Primary Beneficiary [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] ASSETS Variable Interest Entity Consolidated Carrying Amount Assets [Abstract] Customers and other receivables Total Assets Variable Interest Entity Consolidated Carrying Amount Assets LIABILITIES Variable Interest Entity Consolidated Carrying Amount Liabilities [Abstract] Total Liabilities Variable Interest Entity Consolidated Carrying Amount Liabilities