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 Fees Property, accumulated amortization and depreciation Accumulated other comprehensive income (loss), net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax Noncontrolling interest acquired in a business acquisition, net of distributions to noncontrolling interests. Acquisitions of and distributions to noncontrolling interests Additional paid-in-capital Additional Paid-in- Capital Noncash items included in net income: Amortization of share-based incentive compensation Adjustments to reconcile net income to net cash provided by operating activities: Amendment Flag Amortization of Deferred Expenses, Stock Units and Interest Rate Hedge. Amortization of deferred expenses, share-based incentive compensation and interest rate hedge Amortization of intangible assets related to acquisitions Money management fees Total assets Total assets ASSETS BUSINESS ACQUISITIONS Capital lease obligations Acquisition of businesses, cash acquired Cash and cash equivalents CASH AND CASH EQUIVALENTS - September 30 CASH AND CASH EQUIVALENTS - January 1 NET DECREASE IN CASH AND CASH EQUIVALENTS NET DECREASE IN CASH AND CASH EQUIVALENTS Cash deposited with clearing organizations and other segregated cash Cash Flow, Noncash Investing Disclosure [Abstract] Supplemental investing non-cash transaction: Class of Stock [Domain] Commitments and contingencies Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES Class A Common stock Class B common stock The cash outflow to repurchase common membership interests. Repurchase of common membership interests from members of LAZ-MD Holdings Repurchase of common membership interests from members of LAZ-MD Holdings Repurchase of common membership interests during the period. Repurchase of common membership interests from LAZ-MD Holdings Repurchase of common membership interests from LAZ-MD Holdings DIVIDENDS DECLARED PER SHARE OF COMMON STOCK 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 (5,865,580 and 5,850,775 shares at September 30, 2010 and December 31, 2009, respectively) Common Stock Held by Subsidiary Class A Common Stock Held By A Subsidiary 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. Class A common stock held by a subsidiary, shares Number of shares issued or issuable in connection with acquisitions and mergers and related amortization. Class A common stock issued/issuable in connection with business acquisitions and LAM Merger and related amortization (in shares) Common Stock Common stock, par value Common stock, shares authorized Common stock, shares issued Common stock, shares outstanding Common Stock, Value, Issued Common stock Common Stock, Value [Abstract] Common stock: Comprehensive income Comprehensive income Comprehensive income (loss): Total operating expenses Total operating expenses OPERATING EXPENSES Current Fiscal Year End Date SENIOR AND SUBORDINATED DEBT Debt securities [Abstract] Debt: 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 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 DERIVATIVES INCENTIVE PLANS 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 Dividend equivalents. Dividend-equivalents Dividends, Common Stock Class A common stock dividends Document - Document and Entity Information [Abstract] Document - Document and Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Year Focus Document Period End Date Document Type Due from Related Parties Related parties Related party payables NET INCOME PER SHARE OF COMMON STOCK: Earnings Per Share, Basic Basic Earnings Per Share, Diluted Diluted NET INCOME PER SHARE OF CLASS A COMMON STOCK EFFECT OF EXCHANGE RATE CHANGES ON CASH Accrued compensation and benefits Entity Central Index Key Entity Common Stock, Shares Outstanding Entity [Domain] Entity Filer Category Entity Registrant Name Equity Component [Domain] FAIR VALUE MEASUREMENTS Equities Goodwill and other intangible assets, accumulated amortization 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 (Gain) loss on extinguishment of debt (Gain) loss on extinguishment of debt GOODWILL AND OTHER INTANGIBLE ASSETS 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 other intangible assets (net of accumulated amortization of $12,398 and $7,140 at September 30, 2010 and December 31, 2009, respectively) Income Statement [Abstract] INCOME TAXES Provision for income taxes 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 Increase (Decrease) In Deposits And Other Customer Payables Deposits and other payables Increase (Decrease) in Financial Instruments Used in Operating Activities Investments (Increase) decrease in operating assets: Increase (decrease) in operating liabilities: Increase (Decrease) in Other Operating Assets Other assets Receivables - net Receivables - net Banks 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 Interest income 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 Investments Investments, Total Investments: Investments, including debt and equity securities, other investments as well as investments accounted for under the equity method. INVESTMENTS Compensation and benefits Legal Entity [Axis] Total liabilities Total liabilities Liabilities: Total liabilities and stockholders' equity Total liabilities and stockholders' equity LIABILITIES AND STOCKHOLDERS' EQUITY 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 Stockholders' Equity Attributable to Noncontrolling Interest Noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Distributions to noncontrolling interests Adjustments related to noncontrolling interests Net cash used in financing activities Net cash used in financing activities CASH FLOWS FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Investing Activities Net cash provided by (used in) investing activities CASH FLOWS FROM INVESTING ACTIVITIES: Net cash provided by operating activities Net cash provided by operating activities CASH FLOWS FROM OPERATING ACTIVITIES: NET INCOME ATTRIBUTABLE TO LAZARD LTD NET INCOME ATTRIBUTABLE TO LAZARD LTD LESS - NET INCOME (LOSS) ATTRIBUTABLE TO NONCONTROLLING INTERESTS Revenue, net of interest expense. Net Revenue Net revenue Noncontrolling Interests Notes to Financial Statements [Abstract] Notes to Financial Statements [Abstract] Occupancy and equipment OPERATING INCOME OPERATING INCOME ORGANIZATION AND BASIS OF PRESENTATION Other assets Available-for-sale securities: Employee benefit plans: Net actuarial gain (loss) Amortization of interest rate hedge Currency translation adjustments Other comprehensive income (loss) - net of tax: 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. Adjustments for items reclassified to earnings Other Comprehensive Income, Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax Adjustments for items reclassified to earnings Net unrealized gain Represents investments in other debt securities not otherwise specified in the taxonomy carried at either fair value or amortized cost. Other (includes $10,135 and $10,217 of securities at amortized cost at September 30, 2010 and December 31, 2009, respectively) Represents investments in other debt securities not otherwise specified in the taxonomy carried at amortized cost. Other, securities at amortized cost Other Expenses Other Other Income Other Other Investments Other Other liabilities Total Lazard Ltd Stockholders' Equity Payments For Financing Activities [Abstract] Payments for: 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 Payments for Repurchase of Common Stock Purchase of Class A common stock Class A common stock dividends Class A common stock dividends Purchases of available-for-sale securities Purchases of available-for-sale securities Acquisition of businesses, net of cash acquired of $23,280, and equity method investments Acquisition of businesses, net of cash acquired of $23,280, and equity method investments Purchases of held-to-maturity securities Purchases of held-to-maturity securities Additions to property Additions to property 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. Distributions to noncontrolling interests Distributions to noncontrolling interests EMPLOYEE BENEFIT PLANS Preferred stock Preferred stock, par value Preferred stock, shares authorized Preferred stock, shares issued Preferred stock, shares outstanding Preferred Stock, Value, Issued Preferred stock Proceeds From Financing Activities [Abstract] Proceeds from: Contribution from noncontrolling interests The cash inflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. Other financing activities Proceeds from sales and maturities of available-for-sale securities Disposals of property Fees relating to legal, audit, consulting, advisory and compliance services. Professional services Net income Net income (loss) NET INCOME Property (net of accumulated amortization and depreciation of $248,690 and $239,603 at September 30, 2010 and December 31, 2009, respectively) 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. Customers and other Represents receivables from banks, fees, customer and other and related parties, net of allowance for doubtful accounts. Receivables, Net Receivables, Net, Total Receivables, Net [Abstract] Receivables-net: Disclosure related to receivables from banks, fees, customer and other and related parties, net of allowance for doubtful accounts. RECEIVABLES-NET REGULATORY AUTHORITIES Related Party Transactions Disclosure [Text Block] RELATED PARTIES Repayments of Long-term Capital Lease Obligations Capital lease obligations Senior borrowings Senior borrowings RESTRUCTURING PLANS Retained Earnings (Accumulated Deficit) Retained earnings Retained Earnings Total revenue Total revenue REVENUE RECENT ACCOUNTING DEVELOPMENTS SEGMENT INFORMATION Senior debt Series A Preferred stock Series B Preferred stock he cash outflow from the settlement of vested restricted stock units and deferred stock units. Settlement of vested share-based incentive compensation Settlement of vested share-based incentive compensation Restructuring Share Information Attributable To Parent Company CLass A Stockholders [Abstract] ATTRIBUTABLE TO LAZARD LTD CLASS A COMMON STOCKHOLDERS: Shares, Issued Ending Balance (in shares) Beginning Balance (in shares) Class of Stock [Axis] Statement, Equity Components [Axis] Statement [Line Items] Statement of Cash Flows [Abstract] Statement of Financial Position [Abstract] Statement of Stockholders' Equity [Abstract] Statement [Table] Stockholders' Equity Attributable to Parent Total Lazard Ltd stockholders' equity Total stockholders' equity Ending Balance Beginning Balance Total stockholders' equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] STOCKHOLDERS' EQUITY Stockholders' Equity Note Disclosure [Text Block] STOCKHOLDERS' EQUITY