Document and Entity Information [Abstract] Document And Entity Information Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Class A Common Stock Class B Common Stock Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Trading Symbol 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 Series A Preferred Stock Series B Preferred Stock ASSETS Cash and cash equivalents CASH AND CASH EQUIVALENTS-June 30 CASH AND CASH EQUIVALENTS-January 1 Cash and Cash Equivalents, at Carrying Value, Total Deposits with banks Banks Banks Cash And Securities Segregated Under Federal And Other Regulations Cash deposited with clearing organizations and other segregated cash Cash and Securities Segregated under Federal and Other Regulations, Total Receivables, Net [Abstract] Receivables - Net Receivables-net: Fees 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. Receivables from Customers and other Customers and other Due from Related Parties Amounts receivables from related parties Due from Related Parties, Total Related parties Represents receivables from fees, customer and other and related parties, net of allowance for doubtful accounts. Receivables, Net Total receivables, net Other Investments Other investments Other Investments, Total Other Investments, net Total Investments Investments, total Investments Property Plant And Equipment Net Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property (net of accumulated amortization and depreciation of $264,238 and $250,898 at March 31, 2011 and December 31, 2010, respectively) Property, Plant and Equipment, Net, Total Property (net of accumulated amortization and depreciation of $272,369 and $250,898 at June 30, 2011 and December 31, 2010, 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. Goodwill And Intangible Assets Net Goodwill and other intangible assets (net of accumulated amortization of $12,398 and $7,140 at September 30, 2010 and December 31, 2009, respectively) Goodwill and intangible assets net Goodwill and other intangible assets (net of accumulated amortization of $18,187 and $15,007 at June 30, 2011 and December 31, 2010, respectively) Other assets Other Assets, Total Total assets Total Assets Total assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities: 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. Deposits and other customer payables Employee Related Liabilities Current And Noncurrent Accrued compensation and benefits Employee-related Liabilities, Total Senior debt Senior Debt, Outstanding Senior Notes, Total Capital lease obligations Capital Lease Obligations, Total Related party payables Amounts payables to related parties Due to Related Parties, Total Other liabilities Other Liabilities, Total Subordinated debt Subordinated Debt, Ending Balance Subordinated Debt, Beginning Balance Subordinated Debt, Total Total liabilities Total liabilities Commitments and contingencies 2009 Commitments and contingencies Stockholders' Equity Attributable to Parent [Abstract] Preferred Stock Value [Abstract] Preferred Stock: Preferred Stock, Value, Issued Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred Stock, Value, Issued, Total Preferred stock Common Stock, Value [Abstract] Common Stock Value Abstract Common stock: Common Stock, Value, Issued Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common Stock, Value, Issued, Total Common stock Additional P-I-Cl Additional Paid in Capital, Ending Balance Additional Paid in Capital, Beginning Balance Additional paid-in-capital Additional Paid in Capital, Total Retained Earnings (Accumulated Deficit) Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Total Retained earnings Accumulated other comprehensive income (loss), net of tax ELEMENT Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated other comprehensive income (loss), net of tax Total Lazard Ltd AOCI Accumulated other comprehensive income loss, net of tax Stockholders Equity Subtotal Before Common Stock Held By Subsidiary Stockholders Equity Subtotal Before Common Stock Held By Subsidiary Stockholders Equity Subtotal Before Common Stock Held By Subsidiary, Total Class A common stock held by a subsidiary, at cost (5,865,580 and 5,850,775 shares at September 30, 2010 and December 31, 2009, respectively) Class A common stock held by a subsidiary, at cost (4,339,875 and 6,847,508 shares at June 30, 2011 and December 31, 2010, respectively) Class A common stock held by a subsidiary, at cost (4,339,875 and 6,847,508 shares at June 30, 2011 and December 31, 2010, respectively) Class A common stock held by a subsidiary, at cost (4,339,875 and 6,847,508 shares at June 30, 2011 and December 31, 2010, respectively) Stockholders' Equity Attributable to Parent Stockholders' Equity Attributable to Parent, Ending Balance Stockholders' Equity Attributable to Parent, Beginning Balance Total Lazard Ltd stockholders' equity Stockholders' Equity Attributable to Noncontrolling Interest Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Noncontrolling Interests Stockholders' Equity Attributable to Noncontrolling Interest, Total Noncontrolling interests Balance - January 1, 2008, value Balance Balance Total stockholders' equity Total liabilities and stockholders' equity Total liabilities and stockholders' equity Property, accumulated amortization and depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Other intangible assets (net of accumulated amortization) Other intangible assets, Accumulated Amortization Goodwill and other intangible assets, accumulated amortization 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. Common stock held by subsidiary, shares Class A common stock held by a subsidiary, shares Common stock in exchange of RSUs Preferred stock, par value Par value of preferred stock Preferred stock, shares authorized Authorized shares of preferred stock Preferred stock, shares issued Preferred Stock, Shares Issued, Total Preferred stock, shares outstanding Preferred Stock, Shares Outstanding, Ending Balance Preferred Stock, Shares Outstanding, Beginning Balance Outstanding shares of preferred stock Common stock, par value Common stock, shares authorized Common stock, shares issued Common Stock, Shares, Issued, Total Common stock, shares outstanding Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Condensed Consolidated Statements Of Operations REVENUE 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. Investment banking and other advisory fees Money management fees Asset Management Fees, Total Interest income Other Income Other Total revenue Total revenue The cost of borrowed funds accounted for as interest that was charged against earnings during the period and aggregate amount of interest expense on all deposits. Interest expense and interest expense deposits Interest expense Revenue, net of interest expense. Net Revenue Net revenue OPERATING EXPENSES Compensation and benefits Labor and Related Expense, Total Occupancy and equipment 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 expense Marketing and business development Captures expenses relating to investments in technology including software development and maintenance, acquisition of hardware through purchase or lease, and expenses relating to voice, network data and market data. Also includes consulting fees related to technology. Technology and information services expense Technology and information services Fees relating to legal, audit, consulting, advisory and compliance services. Professional 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. Fund administration and outsourced services Amortization of intangible assets related to acquisitions Amortization expenses of intangible assets Amortization of Intangible Assets, Total Restructuring Restructuring expense Other Expenses Other Expenses, Total Other Total operating expenses Operating Expenses Total operating expenses OPERATING INCOME Operating Income OPERATING INCOME Operating income, as reported above Provision for income taxes Provision for income taxes, total Net income (loss) Net income NET INCOME Net income Net Income Loss Attributable To Noncontrolling Interest LESS - NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTERESTS Net Income (Loss) Attributable to Noncontrolling Interest, Total Net Income (Loss) Attributable To Noncontrolling Interests NET INCOME ATTRIBUTABLE TO LAZARD LTD NET INCOME ATTRIBUTABLE TO LAZARD LTD Net income attributable to Lazard Ltd Share Information Attributable To Parent Company CLass A Stockholders [Abstract] Share Information Attributable To Parent Company CLass Stockholders [Abstract] ATTRIBUTABLE TO LAZARD LTD CLASS A COMMON STOCKHOLDERS: WEIGHTED AVERAGE SHARES OF COMMON STOCK OUTSTANDING: Weighted Average Number of Shares Outstanding, Basic Weighted average number of shares of Class A common stock outstanding - basic Weighted Average Number of Shares Outstanding, Basic, Total Basic Weighted Average Number of Shares Outstanding, Diluted Weighted average number of shares of Class A common stock outstanding - diluted Weighted Average Number of Shares Outstanding, Diluted, Total Diluted Net Income Per Share Of Class A Common Stock NET INCOME PER SHARE OF COMMON STOCK: Earnings Per Share, Basic Net income attributable to Lazard Ltd per share of Class A common stock, Basic Earnings Per Share, Basic, Total Basic Earnings Per Share, Diluted Net income attributable to Lazard Ltd per share of Class A common stock, Diluted Earnings Per Share, Diluted, Total Diluted DIVIDENDS DECLARED PER SHARE OF COMMON STOCK Quarterly dividend declared per share Condensed Consolidated Statements Of Cash Flows CASH FLOWS FROM OPERATING ACTIVITIES: Adjustments to reconcile net income to net cash provided by operating activities: Noncash items included in net income: Noncash items included in net income: The amount of expense recognized in the current period that reflects the allocation of the cost of property over the assets' useful lives. Depreciation and amortization of property Amortization of Deferred Expenses, Stock Units and Interest Rate Hedge. Amortization Of Deferred Expenses Stock Units And Interest Rate Hedge Amortization of deferred expenses, share-based incentive compensation and interest rate hedge (Gain) loss on extinguishment of debt Loss on extinguishment of debt Loss on extinguishment of debt Loss on Extinguishment of Debt, Total (Increase) decrease in operating assets: Proceeds from (Payments for) in Interest-bearing Deposits in Banks Deposits with banks Deposits with banks 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 Cash And Securities Segregated Under Federal And Other Regulations Cash deposited with clearing organizations and other segregated cash Cash deposited with clearing organizations and other segregated cash Increase Decrease in Receivables Receivables-net Increase (Decrease) in Receivables, Total Increase Decrease In Financial Instruments Used In Operating Activities Investments Increase (Decrease) in Financial Instruments Used in Operating Activities, Total Increase Decrease In Other Operating Assets Other assets Other assets Increase (decrease) in operating liabilities: Increase (Decrease) In Deposits And Other Customer Payables Increase Decrease In Deposits And Other Customer Payables Deposits and other payables Deposits and other payables 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. Accrued compensation and benefits and other liabilities Net cash provided by operating activities Net cash provided by (used in) operating activities Net cash provided by (used in) operating activities CASH FLOWS FROM INVESTING ACTIVITIES: This item represents (i) the cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence and (ii) distributions that constitute a return of investment. Disposition of and distributions from equity method investments Distributions relating to equity method investments Additions to property Additions to property Payments to Acquire Property, Plant, and Equipment, Total Disposals of property Proceeds from Sale of Property, Plant, and Equipment, Total Proceeds from sales and maturities of available-for-sale securities Proceeds from Sale and Maturity of Available-for-sale Securities, Total Net cash provided by (used in) investing activities Net cash provided by (used in) investing activities CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds From Financing Activities [Abstract] Proceeds From Financing Activities Abstract Proceeds from: Contributions from noncontrolling interests Contribution from noncontrolling interests Excess Tax Benefit from Share-based Compensation, Financing Activities Excess tax benefits from share-based incentive compensation The cash inflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Proceeds From Other Financing Activities ProceedsFromOtherFinancingActivities Proceeds From Other Financing Activities Other financing activities Payments For Financing Activities [Abstract] Payments For Financing Activities Abstract Payments for: Senior borrowings Senior borrowings Repayments of Senior Debt, Total Repayments Of Long Term Capital Lease Obligations Capital lease obligations The cash outflow to return capital to noncontrolled 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. Payments To Minority Shareholders Including Dividends Distributions to noncontrolling interests Distributions to noncontrolling interests The cash outflow to repurchase common membership interests. Common Membership Interest Repurchased Repurchase of common membership interests from members of LAZ-MD Holdings Repurchase of common membership interests from members of LAZ-MD Holdings Payments For Repurchase Of Common Stock Purchase of Class A common stock Class A common stock dividends Class A common stock dividends The cash outflow from the settlement of share-based incentive compensation. Settlement Of Share Based Incentive Compensation Settlement of vested 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. Payments For Other Financing Activities Other financing activities PaymentsForOtherFinancingActivities Other financing activities Net cash used in financing activities Net cash used in financing activities EFFECT OF EXCHANGE RATE CHANGES ON CASH Effect of Exchange Rate on Cash and Cash Equivalents, Total NET DECREASE IN CASH AND CASH EQUIVALENTS NET DECREASE IN CASH AND CASH EQUIVALENTS Condensed Consolidated Statements Of Changes In Stockholders' Equity Statement, Equity Components [Axis] Equity Component [Domain] Common Stock Additional Paid-In-Capital Retained Earnings Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax Common Stock Held by Subsidiary Class A Common Stock Held By A Subsidiary Total Lazard Ltd Stockholders' Equity Noncontrolling Interests Shares, Issued Ending Balance (in shares) Ending balance (in shares) Beginning balance (in shares) Common membership interest activity in connection with secondary Offerings, Equity compensation Common stock, issued Comprehensive income (loss): Other comprehensive income (loss) - net of tax: Currency translation adjustments Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Amortization of interest rate hedge Other Comprehensive Income, Derivatives Qualifying as Hedges, Net of Tax, Total Available-for-sale securities: Net unrealized gain (loss) Net unrealized loss Adjustments for items reclassified to earnings Adjustments for items reclassified to earnings Employee benefit plans: Net actuarial gain (loss) Net actuarial loss 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 Net Actuarial Gains Losses And Prior Service Cost Arising During Period Net Of Tax Adjustments for items reclassified to earnings Comprehensive income Comprehensive income (loss) Value of stock issued or issuable in connection with acquisitions and subsidiary merger and related amortization. Stock Issued Issuable During Period Value Business Acquisitions Mergers And Amortization Class A common stock issued/issuable in connection with business acquisitions and LAM Merger and related amortization Amortization of share-based incentive compensation Dividend equivalents. Dividend-equivalents Dividends, Common Stock Class A common stock dividends Dividends, Common Stock, Total Purchase of Class A common stock (in shares) Purchase of Class A common Stock Purchase of Class A common stock Purchase of Class A common stock Delivery of Class A common stock in connection with share-based incentive compensation awards (in shares) Delivery of Class A common stock in connection with share-based incentive compensation (in shares) Delivery of Class A common stock in connection with share-based incentive compensation awards Delivery of Class A common stock in connection with share-based incentive compensation awards Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefits of $2,178 Repurchase of common membership interests during the period. Common Membership Interest Repurchased During Period, Value Repurchase of common membership interests from LAZ-MD Holdings Number of Class A shares issued during the period Stock Issued During Period Shares Class A New Issues Issuance of Class A common stock (in shares) Value of Class A stock issued during the period Stock Issued During Period Value Class A New Issues Issuance of Class A common stock Stock Issued In Exchange For Common Membership interests, Shares Stock issued in exchange for common membership interests, shares Class A common stock issued in exchange for Lazard Group common membership interests (in shares) Class A common stock issued in exchange for Lazard Group common membership interests] (in shares) Stock issued in exchange for common membership interests. Stock issued in exchange for common membership interests Class A common stock issued in exchange for Lazard Group common membership interests Adjustment related to the change in ownership in subsidiary. Adjustment Related To The Change In Ownership In Subsidiary Adjustment related to the change in Lazard Ltd's ownership in Lazard Group Adjustment related to the change in Lazard Ltd's ownership in Lazard Group Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Distributions to noncontrolling interests, net Distributions to noncontrolling interests Adjustments related to noncontrolling interests Adjustments related to noncontrolling interests Noncontrolling Interest, Period Increase (Decrease), Total Organization And Basis Of Presentation Organization And Basis Of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure Text Block ORGANIZATION AND BASIS OF PRESENTATION Organization And Basis Of Presentation Recent Accounting Developments RECENT ACCOUNTING DEVELOPMENTS Disclosure Text Block Recent Accounting Developments RECENT ACCOUNTING DEVELOPMENTS Disclosure related to receivables from fees, customer and other and related parties, net of allowance for doubtful accounts. RECEIVABLES-NET [Text Block] RECEIVABLES-NET AND DEPOSITS AND OTHER CUSTOMER PAYABLES Receivables - Net Investments Investments, including debt and equity securities, other investments as well as investments accounted for under the equity method. Investments Disclosure [Text Block] Investments Fair Value Measurements FAIR VALUE MEASUREMENTS Disclosure Text Block Fair Value Measurements Categorization of investments and certain other assets and liabilities measured at fair value on recuring basis Derivatives Derivative instruments and hedging activities disclosure [Text Block] Derivatives Merger Transaction Lam Merger Transaction Value of stock issued/issuable pursuant to a merger during the period. Stock issued/issuable during period merger [text block] Lam Merger Transaction