Document and Entity Information [Abstract] Document and entity information. Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Common Class A [Member] Class A common stock [Member] Class A common stock Common Class B [Member] Class B common stock [Member] Class B common stock Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Condensed Consolidated Statements of Financial Condition [Abstract] Series A Preferred Stock [Member] Series A Preferred Stock [Member] Series A Preferred stock Series B Preferred Stock [Member] Series B Preferred stock Series B Preferred Stock [Member] Assets [Abstract] ASSETS Cash and Cash Equivalents, at Carrying Value CASH AND CASH EQUIVALENTS-June 30 CASH AND CASH EQUIVALENTS-January 1 Cash and cash equivalents Interest-bearing Deposits in Banks and Other Financial Institutions Deposits with banks Cash and Securities Segregated Under Federal and Other Regulations Cash deposited with clearing organizations and other segregated cash Receivables - Net [Abstract] Receivables (net of allowance for doubtful accounts of $20,756 and $19,450 at June 30, 2012 and December 31, 2011, respectively): Receivables net. Accrued Fees and Other Revenue Receivable Fees Receivables from Customers and other Customers and other Receivables from customers related to collateralized lending activities, loans granted by bank to third party clients, and managing directors and, employees in the ordinary course of business, and receivables from brokers-dealers and clearing organizations relating to unsettled securities transactions. Due from Related Parties Amounts receivables from related parties Related parties Receivables, Net Total receivables, net Represents receivables from fees, customer and other and related parties, net of allowance for doubtful accounts. Investments, net Total Investments Property Plant And Equipment Net Property - net Property (net of accumulated amortization and depreciation of $261,690 and $266,673 at June 30, 2012 and December 31, 2011, respectively) Goodwill And Intangible Assets Net Goodwill and other intangible assets, Total Goodwill and other intangible assets (net of accumulated amortization of $30,600 and $26,922 at June 30, 2012 and December 31, 2011, respectively) Sum of the carrying amounts of all goodwill and intangible assets as of the balance sheet date net of accumulated amortization and impairment charges. Other assets Other assets Total assets Total assets Total Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Liabilities [Abstract] Liabilities: Deposits and other customer payables Deposits and other customer payables Deposits and other customer payables principally related to customer-related interest-bearing time and demand deposits, short-term inter-bank borrowing with registered banks and amounts due on collateralized borrowing activities. Employee Related Liabilities Current And Noncurrent Accrued compensation and benefits Senior Notes Senior debt, Outstanding Senior debt Capital lease obligations Capital lease obligations Due to Related Parties Current and Noncurrent Amounts payables to related parties Related party payables Other liabilities Other liabilities Liabilities Total liabilities Commitments and contingencies 2009 Commitments and contingencies Stockholders Equity [Abstract] STOCKHOLDERS' EQUITY Preferred Stock [Abstract] Preferred stock: Preferred stock. Preferred Stock, Value Preferred stock Common Stock, Value Common stock Additional Paid in Capital Additional paid-in-capital Retained Earnings (Accumulated Deficit) Retained earnings Accumulated other comprehensive income loss, net of tax Total Lazard Ltd AOCI Accumulated other comprehensive loss, net of tax Common Stock Held by Subsidiary Common stock held by subsidiary Stockholders Equity Total Lazard Ltd stockholders' equity Stockholders' Equity Attributable to Noncontrolling Interest Noncontrolling interests Stockholders equity including portion attributable to Noncontrolling Interest Ending balance Beginning balance Total stockholders' equity Total liabilities and stockholders' equity Total liabilities and stockholders' equity Allowance for Doubtful Accounts Receivable Allowance for doubtful accounts receivables Accumulated Depreciation Depletion and Amortization Property Plant and Equipment Less - Accumulated depreciation and amortization Property, accumulated amortization and depreciation Finite Lived Intangible Assets Accumulated Amortization Other intangible assets, Accumulated Amortization Common stock held by subsidiary, shares Common stock held by subsidiaries, shares 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 or Stated Value Per Share Preferred stock, par value 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 or Stated Value Per Share Common stock, par value Common stock, shares authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Condensed Consolidated Statements of Operations [Abstract] Revenues [Abstract] REVENUE Investment Banking and Other Advisory Fees Investment banking and other advisory fees Includes advisory fees earned for providing advice and analysis related to corporate mergers, acquisitions, divestures, and funding. Also includes restructuring advisory fees earned involving a client or a client's portfolio company in bankruptcy, in financial distress and/or is significantly over leveraged. Asset Management Fees Money management fees Interest Income, Operating Interest income Other Income Other Revenues Total revenue Net Revenue Revenue, net of interest expense. Net revenue Costs and Expenses [Abstract] OPERATING EXPENSES Labor and Related Expense Compensation and benefits Occupancy, Net Occupancy and equipment Marketing and business development expense Captures expenses relating to business development such as travel and business meals, advertising, marketing and public relations, as well as fees paid to third parties retained by Lazard to introduce business or gather assets under management. Marketing and business development Fund Administration and Outsourced Services Fund administration and outsourced services Consisting of fees paid for outsourced services and asset management related expenses for mutual fund servicing, fund administration by third parties. In addition, custodial, clearing and settlement costs. Amortization of Intangible Assets Amortization of intangible assets related to acquisitions Other Expenses Other Costs and Expenses Operating Expenses Total operating expenses Operating Income (Loss) OPERATING INCOME Operating Income (loss) Income Tax Expense (Benefit) Provision for income taxes Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income NET INCOME NET INCOME Net Income (Loss) Attributable to Noncontrolling Interest Net Income (Loss) Attributable To Noncontrolling Interests LESS - NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS Net Income (Loss) Attributable to Parent NET INCOME ATTRIBUTABLE TO LAZARD LTD Net income attributable to Lazard Ltd Share Information Attributable To Parent Company Class Stockholders [Abstract] ATTRIBUTABLE TO LAZARD LTD CLASS A COMMON STOCKHOLDERS: Share information attributable to parent company Class A stockholders. Weighted Average Number of Shares Outstanding, Diluted [Abstract] WEIGHTED AVERAGE SHARES OF COMMON STOCK OUTSTANDING: Weighted Average Number of Shares Outstanding, Basic Weighted average number of shares common stock outstanding - basic Basic Weighted Average Number of Shares Outstanding, Diluted Weighted average number of shares of Class A common stock outstanding - diluted Diluted Net Income Per Share of Class A Common Stock [Abstract] NET INCOME PER SHARE OF COMMON STOCK: Earnings Per Share, Basic Basic Earnings Per Share, Diluted Diluted Common Stock, Dividends, Per Share, Declared Dividends declared per share of common stock DIVIDENDS DECLARED PER SHARE OF COMMON STOCK Condensed Consolidated Statements of Comprehensive Income [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive income (loss) - net of tax: OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX: Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Currency translation adjustments Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Amortization of interest rate hedge Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract] Employee benefit plans: Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax Net charges to OCI Net actuarial gain (loss) (net of tax benefit (expense) of $1,443 and $(29) for the three months ended June 30, 2012 and 2011, respectively, and $2,725 and $1,906 for the six months ended June 30, 2012 and 2011, respectively) Other Comprehensive Income Net Actuarial Gains Losses And Prior Service Cost Arising During Period Net Of Tax Adjustment for items reclassified to earnings (net of tax expense of $281 and $262 for the three months ended June 30, 2012 and 2011, respectively, and $578 and $517 for the six months ended June 30, 2012 and 2011, respectively) Includes the adjustment out of other comprehensive income for (1) actuarial gains (losses), and (2) prior service costs, both recognized as a component of net period benefit cost during the period, after tax. Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest COMPREHENSIVE INCOME Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest LESS - COMPREHENSIVE INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS Comprehensive Income (Loss), Net of Tax, Attributable to Parent COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD Tax Benefit Expense Associated With Actuary Loss Tax benefit (expense) Tax benefit expense associated with actuary loss. Tax expense associated with adjustment for item reclassified to earnings Tax expense associated with adjustment for item reclassified to earnings Tax expense associated with adjustment for item reclassified to earnings. Condensed Consolidated Statements of Cash Flows [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Adjustments to Reconcile Net Income (Loss) to 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] Noncash items included in net income: Depreciation and Amortization of Property Depreciation and amortization of property The amount of expense recognized in the current period that reflects the allocation of the cost of property over the assets' useful lives. Amortization Of Deferred Expenses Stock Units And Interest Rate Hedge Amortization of deferred expenses, share-based incentive compensation and interest rate hedge Amortization of deferred expenses, stock units and interest rate hedge. Increase (Decrease) in Operating Assets [Abstract] (Increase) decrease in operating assets: Proceeds from (Payments for) in Interest-bearing Deposits in Banks Deposits with banks Increase Decrease In Cash And Securities Segregated Under Federal And Other Regulations Cash deposited with clearing organizations and other segregated cash The net change during the reporting period in the amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers pursuant). Increase (Decrease) in Receivables Receivables-net Increase (Decrease) in Financial Instruments Used in Operating Activities Investments Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Operating Liabilities [Abstract] Increase (decrease) in operating liabilities: Increase Decrease In Deposits And Other Customer Payables Deposits and other payables Increase (Decrease) in deposits and other customer payables. Accrued Compensation and Benefits and Other Liabilities Accrued compensation and benefits and other liabilities Represents the net change of obligations incurred through that date and payable for obligations related to services received from employees such as accrued salaries, bonuses, payroll taxes and fringe benefits and the sum of other liabilities not individually reported in the financial statements or separately disclosed in the notes. Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] CASH FLOWS FROM INVESTING ACTIVITIES: Payments to Acquire Property, Plant, and Equipment, Total Additions to property Proceeds from Sale of Property, Plant, and Equipment Disposals of property Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds From Financing Activities [Abstract] Proceeds from: Proceeds from financing activities. Proceeds from Noncontrolling Interests Contribution from noncontrolling interests Excess Tax Benefit (Tax Deficiency) from Share-based Compensation, Financing Activities Excess tax benefits from share-based incentive compensation Proceeds From Other Financing Activities Other financing activities The cash inflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Payments For Financing Activities [Abstract] Payments for: Payments for financing activities. Repayments of Long-term Capital Lease Obligations Capital lease obligations Payments To Minority Shareholders Including Dividends Distributions to noncontrolling interests The cash outflow to return capital to non controlled interest, which generally occurs when noncontrolling shareholders reduce their ownership stake (in a subsidiary of the entity). This element includes dividends paid and other distributions to noncontrolling shareholders. Common Membership Interest Repurchased Repurchase of common membership interests from members of LAZ-MD Holdings The cash outflow to repurchase common membership interests. Payments for Repurchase of Common Stock Purchase of Class A common stock Payments of Ordinary Dividends, Common Stock Class A common stock dividends Settlement Of Share Based Incentive Compensation Settlement of vested share-based incentive compensation The cash outflow from the settlement of share-based incentive compensation. Payments For Other Financing Activities Other financing activities The cash outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Net Cash Provided by (Used in) Financing Activities Net cash used in financing activities Effect of Exchange Rate on Cash and Cash Equivalents EFFECT OF EXCHANGE RATE CHANGES ON CASH Cash and Cash Equivalents, Period Increase (Decrease) NET DECREASE IN CASH AND CASH EQUIVALENTS Condensed Consolidated Statements of Changes in Stockholders' Equity [Abstract] Statement, Equity Components [Axis] Common Stock [Member] Common Stock Additional Paid In Capital [Member] Additional Paid-In-Capital Retained Earnings [Member] Retained Earnings Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss), Net of Tax Common Stock Held By Subsidiary [Member] Class A Common Stock Held By a Subsidiary Common stock held by subsidiary. Parent [Member] Total Lazard Ltd Stockholders' Equity Noncontrolling Interest [Member] Noncontrolling Interests Shares, Issued Ending balance (in shares) Beginning balance (in shares) Common stock, issued Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Comprehensive income (loss): Stock Issued Issuable During Period Value Business Acquisitions Mergers And Amortization Class A common stock issued/issuable (including related amortization) Value of stock issued or issuable in connection with acquisitions and subsidiary merger and related amortization. Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Amortization of share-based incentive compensation Dividend Equivalents Dividend-equivalents Dividend equivalents. Dividends, Common Stock Class A common stock dividends Stock Repurchased During Period, Shares Purchase of Class A common stock (in shares) Purchase of Class A common stock Purchase of Class A common stock Stock Issued During Period Value Share Based Compensation And Related Tax Benefits Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefits of $972 and $2,178 for 2012 and 2011, respectively Value of stock issued during the period for share based compensation and related tax benefits. Stock Issued During Period Value Share Based Compensation And Related Tax Benefits Shares Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefits (in shares) Stock issued during period value share based compensation and related tax benefits shares Shares of stock issued during the period for share based compensation and related tax benefits. Common Membership Interest Repurchased During Period, Value Repurchase of common membership interests from LAZ-MD Holdings Repurchase of common membership interests during the period. Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Distributions to noncontrolling interests, net Noncontrolling Interest, Period Increase (Decrease) Adjustments related to noncontrolling interests Equity Component [Domain] Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options Share-based incentive compensation and related tax benefits Organization and Basis of Presentation [Abstract] Organization Consolidation and Presentation of Financial Statements Disclosure [Text Block] ORGANIZATION AND BASIS OF PRESENTATION RECENT ACCOUNTING DEVELOPMENTS [Abstract] Receivables Net [Text Block] RECEIVABLES - NET Disclosure related to receivables from fees, customer and other and related parties net of allowance for doubtful accounts. Investments [Abstract] Investment [Text Block] INVESTMENTS Fair Value Measurements [Abstract] Fair Value Measurement Inputs Disclosure [Text Block] FAIR VALUE MEASUREMENTS Derivatives [Abstract] Derivative instruments and hedging activities disclosure [Text Block] DERIVATIVES Business Acquisitions [Abstract] Business Combination Disclosure [Text Block] BUSINESS ACQUISITIONS Goodwill and Other Intangible Assets [Abstract] Goodwill and Intangible Assets Disclosure [Text Block] GOODWILL AND OTHER INTANGIBLE ASSETS Senior Debt [Abstract] Debt Disclosure [Text Block] SENIOR DEBT Commitments and Contingencies [Abstract] Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES Stockholders' Equity [Abstract] Stockholders' Equity Note Disclosure [Text Block] STOCKHOLDERS' EQUITY Incentive Plans [Abstract] Employee Benefit Plans [Abstract] Pension And Other Postretirement Benefits Disclosure [Text Block] EMPLOYEE BENEFIT PLANS Income Taxes [Abstract]