Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] JCP Fund V JCP Funds [Member] JCP Funds [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Net gains (losses) from our investments in JCP Fund V Unrealized Gain (Loss) on Securities Net increase (decrease) in net assets resulting from operations Equity Method Investment, Increase (Decrease) in Net Assets Resulting from Operations Equity Method Investment, Increase (Decrease) in Net Assets Resulting from Operations Fair Value Disclosures [Abstract] Financial instruments owned: Financial Instruments, Owned, at Fair Value [Abstract] Loans and other receivables Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables Loans and other receivables on nonaccrual status and/or 90 days or greater past due Fair Value, Option, Loans Held as Assets, Aggregate Amount in Nonaccrual Status, Aggregated Difference Long-term debt and short-term borrowings Fair Value, Option, Aggregate Differences, Long-term And Short-Term Debt Instruments Fair Value, Option, Aggregate Differences, Long-term And Short-Term Debt Instruments Loans and other receivables 90 days or greater past due Fair Value, Option, Loans Held as Assets, 90 Days or More Past Due, Aggregate Difference Statement of Comprehensive Income [Abstract] Statement [Table] Statement [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Adjustment related to 2017 Tax Cuts and Jobs Act Adjustment Related To 2017 Tax Cuts And Jobs Act [Member] Adjustment Related To 2017 Tax Cuts And Jobs Act [Member] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] German Pension Plan Foreign Pension Plan [Member] Statement [Line Items] Statement [Line Items] Currency translation and other adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Changes in instrument specific credit risk, tax expense (benefit) Other Comprehensive Income (Loss), Changes in Instrument Specific Credit Risk, Tax Other Comprehensive Income (Loss), Changes in Instrument Specific Credit Risk, Tax Cash flow hedges Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Schedule of Components of Total Revenue Schedule Of Components Of Revenue [Table Text Block] Schedule Of Components Of Revenue [Table Text Block] Disaggregation of Revenue Disaggregation Of Revenue [Table Text Block] Disaggregation Of Revenue [Table Text Block] Statement of Stockholders' Equity [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Changes in instrument specific credit risk Other Comprehensive Income Loss Changes in Instrument Specific Credit Risk, Net of Tax Other Comprehensive Income Loss Changes in Instrument Specific Credit Risk, Net of Tax Pension adjustments Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block] Guarantees Schedule of Guarantor Obligations [Table Text Block] Other Commitments [Table] Other Commitments [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Equity commitments Equity Commitments [Member] Equity commitments. Loan commitments Loan Commitments [Member] Loan commitments. Mortgage-related and other purchase commitments Mortgage Related Commitments [Member] Mortgage-related commitments. Underwriting commitments Underwriting Commitments [Member] Underwriting Commitments [Member] Forward starting reverse repos Forward Starting Reverse Repos [Member] Forward Starting Reverse Repos [Member] Forward starting repos Forward Starting Repos [Member] Forward Starting Repos [Member] Other unfunded commitments Other Commitments [Member] Other Commitments [Member] Other Commitments [Line Items] Other Commitments [Line Items] 2018 Contractual Obligation, Future Minimum Payments Due, Remainder of Fiscal Year 2019 Contractual Obligation, Due in Second Year 2020 and 2021 Contractual Obligation, Due in Third and Fourth Year Contractual Obligation, Due in Third and Fourth Year 2022 and 2023 Contractual Obligation, Due in fifth and Sixth Year Contractual Obligation, Due in fifth and Sixth Year 2024 and Later Contractual Obligation, Due After Sixth Year Contractual Obligation, Due After Sixth Year Maximum Payout Contractual Obligation Guarantor obligation settled period (in days) Guarantor Obligation Settled Period Guarantor Obligation Settled Period Banking and Thrift [Abstract] Offsetting Assets and Liabilities [Table] Offsetting Assets and Liabilities [Table] Offsetting Assets and Liabilities [Table] Securities Borrowed Type [Axis] Securities Borrowed Type [Axis] Securities Borrowed Type [Axis] Securities Borrowed Type [Domain] Securities Borrowed Type [Domain] [Domain] for Securities Borrowed Type [Axis] Securities Received As Collateral [Member] Securities Received As Collateral [Member] Securities Received As Collateral [Member] Securities Loaned Type [Axis] Securities Loaned Type [Axis] Securities Loaned Type [Axis] Securities Loaned Type [Domain] Securities Loaned Type [Domain] [Domain] for Securities Loaned Type [Axis] Obligation To Return Securities Received As Collateral [Member] Obligation To Return Securities Received As Collateral [Member] Obligation To Return Securities Received As Collateral [Member] Offsetting Assets and Liabilities [Line Items] Offsetting Assets and Liabilities [Line Items] [Line Items] for Offsetting Assets and Liabilities [Table] Securities borrowing arrangements Securities Borrowed [Abstract] Gross Amounts Securities Borrowed, Gross Netting in Consolidated Statement of Financial Condition Securities Borrowed, Liability Net Amounts in Consolidated Statement of Financial Condition Securities Borrowed Additional Amounts Available for Setoff Securities Borrowed, Collateral, Obligation to Return Cash Available Collateral Securities Borrowed, Collateral, Obligation to Return Securities Net Amount Securities Borrowed, Amount Offset Against Collateral Reverse repurchase agreements Offsetting Securities Purchased under Agreements to Resell [Abstract] Gross Amounts Securities Purchased under Agreements to Resell, Gross Netting in Consolidated Statement of Financial Condition Securities Purchased under Agreements to Resell, Liability Net Amounts in Consolidated Statement of Financial Condition Securities Purchased under Agreements to Resell Additional Amounts Available for Setoff Securities Purchased under Agreements to Resell, Not Offset, Policy Election Deduction Available Collateral Securities Purchased under Agreements to Resell, Fair Value of Collateral Net Amount Securities Purchased under Agreements to Resell, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election Securities lending arrangements Securities Loaned [Abstract] Gross Amounts Securities Loaned, Gross Netting in Consolidated Statement of Financial Condition Securities Loaned, Asset Net Amounts in Consolidated Statement of Financial Condition Securities Loaned Additional Amounts Available for Setoff Securities Loaned, Collateral, Right to Reclaim Cash Available Collateral Securities Loaned, Collateral, Right to Reclaim Securities Net Amount Securities Loaned, Amount Offset Against Collateral Repurchase agreements Offsetting Securities Sold under Agreements to Repurchase [Abstract] Gross Amounts Securities Sold under Agreements to Repurchase, Gross Netting in Consolidated Statement of Financial Condition Securities Sold under Agreements to Repurchase, Asset Net Amounts in Consolidated Statement of Financial Condition Securities Sold under Agreements to Repurchase Additional Amounts Available for Setoff Securities Sold under Agreements to Repurchase, Not Offset, Policy Election Deduction Available Collateral Securities Sold under Agreements to Repurchase, Fair Value of Collateral Net Amount Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral Securities borrowing arrangements Collateralized Financing Transactions Securities Borrowing Arrangements Collateralized Financing Transactions Securities Borrowing Arrangements Securities borrowing arrangements, collateral Collateralized Financing Transactions Securities Borrowing Arrangements Collateral Collateralized Financing Transactions Securities Borrowing Arrangements Securities Collateral Received Securities borrowing arrangements, repurchase agreements Collateralized Financing Transactions Securities Borrowing Arrangements Repurchase Agreements Collateralized Financing Transactions Securities Borrowing Arrangements Repurchase Agreements Securities borrowing arrangements, repurchase agreements, pledged securities collateral Collateralized Financing Transactions Securities Borrowing Arrangements Pledged Securities Collateral Collateralized Financing Transactions Securities Borrowing Arrangements Pledged Securities Collateral Compensation Related Costs [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted cash awards Restricted Cash Awards [Member] Restricted Cash Awards [Member] Restricted stock and RSUs Restricted Stock and Restricted Stock Units [Member] Restricted Stock and Restricted Stock Units [Member] Compensation Plans [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Restricted cash awards Deferred Compensation Arrangement with Individual, Compensation Expense Restricted stock and RSUs Share-based Compensation Profit sharing plan Compensation Cost Related To Profit Sharing Plan Compensation cost related to profit sharing plan. Total compensation cost Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost Transfers and Servicing [Abstract] Transferred assets Assets Transferred Due To Securitization Assets transferred due to securitization activities in which the Company had continuing involvement. Proceeds on new securitizations Proceeds On New Securitizations Proceeds On New Securitizations Cash flows received on retained interests Cash Flows Between Transferor and Transferee, Proceeds from New Transfers Revenues from Contracts with Customers Revenue From Contract With Customer [Text Block] Revenue From Contract With Customer [Text Block] Commitments, Contingencies and Guarantees Commitments Contingencies and Guarantees [Text Block] Member's paid-in capital Additional Paid-in Capital [Member] Total Jefferies Group LLC member’s equity Parent [Member] Noncontrolling interests Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance, beginning of period Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Cumulative effect of the adoption of the new revenue standard, net of tax Cumulative Effect of New Accounting Principle in Period of Adoption Net earnings (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Distribution to Leucadia National Corporation Distributed Earnings Tax Cuts and Jobs Act adjustment Tax Cuts And Jobs Act of 2017, Reclassification from Aoci to Additional Paid-in Capital Tax Effect Tax Cuts And Jobs Act of 2017, Reclassification from Aoci to Additional Paid-in Capital Tax Effect Currency adjustments Balance, end of period Related Party Transactions [Abstract] Summary of Interest Income, Other Revenues and Investment Income Attributable to Related Party Private Equity Funds Interest and Other Income [Table Text Block] Schedule of related party transactions Schedule of Related Party Transactions [Table Text Block] Schedule of Components of Compensation Cost Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Schedule of Remaining Unamortized Amounts Related to Certain Compensation Plans Schedule Of Share Based Compensation Allocation Of Period Costs And Amortization Period Table [Table Text Block] Schedule Of Share Based Compensation Allocation Of Period Costs And Amortization Period Table [Table Text Block] Jefferies Finance, LLC Jefferies Finance Llc [Member] Jefferies Finance LLC. Epic Gas Epic Gas [Member] Epic Gas [Member] Summary of Selected Financial Information Equity Method Investments [Table Text Block] Accounting Policies [Abstract] Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Securitization Activities Transfers and Servicing of Financial Assets [Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Fair value of derivative instruments in a liability position Derivative, Net Liability Position, Aggregate Fair Value Collateral posted for derivative instruments in a liability position Collateral Already Posted, Aggregate Fair Value Additional collateral required for derivative instruments in a liability position Additional Collateral, Aggregate Fair Value Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Capital Markets Capital Markets [Member] Capital markets. Asset Management Asset Management Segment [Member] Asset Management Segment [Member] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Goodwill, Beginning Balance Goodwill Translation adjustments Goodwill, Foreign Currency Translation Gain (Loss) Goodwill, Ending Balance Accounting Changes and Error Corrections [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Axis] Information about effect of transition method for cumulative effect in initial period of application. Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] [Domain] for Information about effect of transition method for cumulative effect in initial period of application. ASC 606 Impact Difference Between Revenue Guidance In Effect Before And After Topic 606 [Member] Effect in current period from application of guidance for revenue from contract with customer compared with guidance for revenue recognition applicable prior to change when using transition method for cumulative effect in period including initial date of application. Adjusted Calculated Under Revenue Guidance In Effect Before Topic 606 [Member] Calculated under guidance for revenue recognition in effect prior to change to new guidance for revenue from contract with customer when using transition method for cumulative effect in period including initial date of application. Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Investment banking Investment Banking Revenue Total revenues Revenues Net revenues Revenues, Net of Interest Expense Underwriting costs Underwriting Costs Underwriting Costs Technology and communications Communications and Information Technology Business development Business Development Professional services Professional Fees Other Other Expenses Total non-compensation expenses Non Compensation Expenses Non Compensation Expenses Total non-interest expenses Noninterest Expense Segment Reporting [Abstract] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Americas Americas [Member] Europe Europe [Member] Asia Asia [Member] Revenue from External Customer [Line Items] Revenue from External Customer [Line Items] Revenues: Revenues [Abstract] Non-vested share-based awards Nonvested Share Awards [Member] Nonvested Share Awards [Member] Remaining Unamortized Amounts Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted Average Vesting Period (in Years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Disaggregation of Revenue [Table] Disaggregation Of Revenue [Table] Disaggregation Of Revenue [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Equities (1) Equities [Member] Equities [Member] Fixed Income (1) Fixed Income Services [Member] Fixed Income Services [Member] Investment Banking - Capital Markets Investment Banking, Capital Markets [Member] Investment Banking, Capital Markets [Member] Investment Banking - Advisory Investment Banking, Advisory [Member] Investment Banking, Advisory [Member] Asset Management Asset Management Services [Member] Asset Management Services [Member] Disaggregation Of Revenue [Line Items] Disaggregation Of Revenue [Line Items] [Line Items] for Disaggregation Of Revenue [Table] Revenues from contracts with customers Revenue From Contract With Customer Excluding Assessed Tax Revenue From Contract With Customer Excluding Assessed Tax Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Total other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Net earnings (loss) attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Comprehensive income (loss) attributable to Jefferies Group LLC Comprehensive Income (Loss), Net of Tax, Attributable to Parent Fair Value and Related Number of Derivative Contracts Categorized by Type of Derivative Contract Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Unrealized and Realized Gains (Losses) on Derivative Contracts Derivative Instruments, Gain (Loss) [Table Text Block] Remaining Contract Maturity of Fair Value of OTC Derivative Assets and Liabilities Remaining Contract Maturity Of Fair Value Of Over Counter Derivative Assets And Liabilities Table [Table Text Block] OTC derivatives by risk exposure and maturity profile. Counterparty Credit Quality with Respect to Fair Value of OTC Derivatives Assets Counterparty Credit Quality With Respect To Fair Value Of Otc Derivatives Assets Table [Table Text Block] Counterparty credit quality with respect to the fair value of OTC derivatives assets. Credit Related Derivative Contracts Disclosure of Credit Derivatives [Table Text Block] A- or higher Fair Value Of Over Counter Derivatives Assets Counterparty Credit QualityA Or Higher Fair Value Of Over Counter Derivatives Assets Counterparty Credit QualityA Or Higher BBB- to BBB Fair Value Of Over Counter Derivatives Assets Counterparty Credit Quality Bbb To Bbb Fair value of OTC derivatives assets, counterparty credit quality BBB- to BBB. BB or lower Fair Value Of Over Counter Derivatives Assets Counterparty Credit Quality Bb or Lower Fair value of OTC derivatives assets, counterparty credit quality BB or lower. Unrated Fair Value Of Over Counter Derivatives Assets Counterparty Credit Quality Unrated Fair value of OTC derivatives assets, counterparty credit quality unrated. Total OTC derivative assets included in Financial instruments owned Otc Derivative Assets Included In Financial Instruments Owned OTC Derivative Assets Included In Financial Instruments Owned. Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Non-interest expenses Earnings before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Segment assets Assets Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Table] Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Table] Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer relationships Customer Relationships [Member] Trade name Trade Names [Member] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Exchange and clearing organization membership interests and registrations Exchange And Clearing Organization Membership Interests And Registrations [Member] Exchange and clearing organization membership interests and registrations. Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Line Items] Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Line Items] [Line Items] for Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Table] [Table] Gross costs - finite lived intangible assets Finite-Lived Intangible Assets, Gross Gross costs - indefinite lived intangible assets Indefinite Lived Intangible Assets Gross Indefinite lived Intangible asset Gross (before impairment). Total gross costs - intangible assets Intangible Assets, Gross (Excluding Goodwill) Accumulated amortization - finite lived intangible assets Finite-Lived Intangible Assets, Accumulated Amortization Net carrying amount - finite lived intangible assets Finite-Lived Intangible Assets, Net Net carrying amount - indefinite lived intangible assets Indefinite Lived Intangible Asset Net Cost (After Impairment) Indefinite Lived Intangible Asset Net Cost (After Impairment) Total net carrying amount - intangible assets Intangible Assets, Net (Excluding Goodwill) Weighted average remaining lives (years) Finite-Lived Intangible Asset, Useful Life Schedule of Collateralized Financing Transactions Schedule of Collateralized Financing Transactions [Table Text Block] Schedule of Collateralized Financing Transactions [Table Text Block] Summary of Repurchase Agreements and Securities Borrowing and Lending Arrangements Offsetting Assets and Liabilities [Table Text Block] Offsetting Assets and Liabilities [Table Text Block] Revenue related to performance obligations satisfied Contract With Customer, Performance Obligation Satisfied Contract With Customer, Performance Obligation Satisfied Revenue associated with distribution services, a portion of which related to prior periods Contract With Customer, Performance Obligation Satisfied In Previous Period Contract With Customer, Performance Obligation Satisfied In Previous Period Receivables related to revenue from contracts with customers Contract With Customer Asset, Net Contract With Customer Asset, Net Deferred revenue Deferred Revenue Deferred revenue, revenue recognized Deferred Revenue, Revenue Recognized Capitalized contract cost Capitalized Contract Cost, Net Capitalized Contract Cost, Net Expenses related to capitalized costs to fulfill a contract Capitalized Contract Cost, Amortization Capitalized Contract Cost, Amortization Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 3 Fair Value, Inputs, Level 3 [Member] Security Owned and Sold, Not yet Purchased, at Fair Value [Axis] Security Owned and Sold, Not yet Purchased, at Fair Value [Axis] Security Owned and Sold, Not yet Purchased Fair Value, Security Name [Domain] Security Owned and Sold, Not yet Purchased Fair Value, Security Name [Domain] Financial instruments owned Financial Instruments Owned [Member] Financial Instruments Owned [Member] Financial Instruments Sold, Not Yet Purchased Financial Instruments Sold, Not Yet Purchased [Member] Financial Instruments Sold, Not Yet Purchased [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Corporate equity securities Equity Securities [Member] Corporate debt securities Corporate Debt Securities [Member] CDOs and CLOs Collateralized Debt Obligations and Collateralized Loan Obligations [Member] Collateralized Debt Obligations and Collateralized Loan Obligations [Member] RMBS Residential Mortgage Backed Securities [Member] CMBS Commercial Mortgage Backed Securities [Member] Other ABS Other Asset Backed Securities [Member] Other asset-backed securities. Loans and other receivables Loans and Finance Receivables [Member] Investments at fair value Investments [Member] Loans Loans [Member] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Derivatives Derivative [Member] Eligible Item or Group for Fair Value Option [Axis] Fair Value, Option, Eligible Item or Group [Domain] Non-exchange-traded securities Non Exchange Traded Securities [Member] Non-exchange traded securities. Private equity securities Private Equity Securities [Member] Private equity securities. Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Total return swaps Total Return Swap [Member] Equity options Equity Option [Member] Unfunded commitments Unfunded Commitments [Member] Unfunded Commitments [Member] Variable funding note swaps Variable Funding Note Swaps [Member] Variable Funding Note Swaps [Member] Interest rate swaps Interest Rate Swap [Member] Valuation Technique [Axis] Valuation Technique [Axis] Valuation Technique [Domain] Valuation Technique [Domain] Market approach Market Approach Valuation Technique [Member] Comparable pricing Comparable Pricing Valuation Technique [Member] Comparable Pricing Valuation Technique [Member] Convertible bond model Convertible Bond Model [Member] Convertible Bond Model [Member] Discounted cash flows Discounted Cash Flow Approach [Member] Discounted Cash Flow Approach [Member] Scenario analysis Scenario Analysis [Member] Scenario Analysis [Member] Option model/default rate Option Model/Default Rate Valuation Technique [Member] Option Model/Default Rate Valuation Technique [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Weighted Average Weighted Average [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] Instruments owned, fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Instruments sold, not yet purchased, fair value Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Price Fair Value Inputs, Price Fair Value Inputs, Price Underlying stock price Share Price Comparable asset price Fair Value Inputs, Comparable Asset Price Fair Value Inputs, Comparable Asset Price Discount rate/yield Cash Flow Discount Rate Cash Flow Discount Rate Constant prepayment rate Fair Value Inputs, Prepayment Rate Constant default rate / Credit spread Fair Value Inputs, Entity Credit Risk Loss severity Fair Value Inputs, Loss Severity Volatility Fair Value Assumptions, Expected Volatility Rate Estimated recovery percentage Fair Value Assumptions Estimated Recovery Percentage Fair value assumptions estimated recovery percentage. Cumulative loss rate Fair Value Inputs, Cumulative Loss Rate Fair Value Inputs, Cumulative Loss Rate Duration (years) Fair Value Inputs, Duration Fair Value Inputs, Duration Transaction level Transaction Level Price Per Share Transaction Level Price Per Share Default probability Fair Value Inputs, Probability of Default Value of asset excluded from significant unobservable inputs Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Asset Exclusion Value Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Asset Exclusion Value Value of liability excluded from significant unobservable inputs Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Exclusion Value Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Exclusion Value Commissions and other fees Commissions And Other Fees [Member] Commissions And Other Fees [Member] Investment banking Investment Banking [Member] Investment Banking [Member] Asset management fees Asset Management Fees [Member] Asset Management Fees [Member] Other Revenue From Contract With Customers, Other [Member] Revenue From Contract With Customers, Other [Member] Principal transactions Principal Transactions Revenue [Member] Principal Transactions Revenue [Member] Interest Interest Revenue [Member] Interest Revenue [Member] Other Other Sources Of Revenue, Miscellaneous [Member] Other Sources Of Revenue, Miscellaneous [Member] Other sources of revenue Revenue, Other Financial Services Total revenues Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Derivative contracts—non-credit related Derivative Contracts Non Credit Related [Member] Derivative contracts - non credit related. Written derivative contracts—credit related Derivative Contracts Credit Related [Member] Derivative contracts - credit related. Guarantee Obligations [Line Items] Guarantor Obligations [Line Items] 2018 Guarantees Expected To Be Due Current Guarantees with a remaining term that matures during the fiscal year. These may include derivative guarantees, etc. 2019 Guarantees Expected To Be Due In Two Years Guarantees expected to be due within 2 fiscal years. These may include, derivative guarantees, etc. 2020 and 2021 Guarantees Expected To Be Due In Three And Four Years Guarantees expected to be due within 3 to 4 fiscal years. These may include, derivative guarantees, etc. 2022 and 2023 Guarantees Expected To Be Due In Five And Six Years Guarantees expected to be due within 5 to 6 fiscal years. These may include, derivative guarantees, etc. 2024 and Later Guarantees Expected To Be Due Thereafter Guarantees expected to be due within 7 fiscal years and thereafter. These may include, derivative guarantees, etc Notional/ Maximum Payout Guarantor Obligations, Maximum Exposure, Undiscounted Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 4.850% Senior Notes Four Point Eight Five Percentage Senior Notes, Due 2027 [Member] Four Point Eight Five Percentage Senior Notes, Due 2027 [Member] 3.875% Convertible Senior Debentures Three Point Eight Seven Five Percentage Convertible Senior Debentures Due Two Thousand Twenty Nine [Member] 3.875% Convertible Senior Debentures, due, 2029. Structured notes Structured Notes [Member] Structured Notes [Member] 4.150% Senior Notes Four Point One Five Zero Percent Senior Notes Due 2030 [Member] Four Point One Five Zero Percent Senior Notes Due 2030 [Member] 5.125% Senior Notes Five Point One Two Five Percentage Senior Notes Due Two Thousand Eighteen [Member] 5.125% Senior Notes, due 2018. Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Unsecured Debt Unsecured Debt [Member] Senior Notes Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt principal amount Debt Instrument, Face Amount Decrease of long-term debt Increase (Decrease) of Long-term Debt Increase (Decrease) of Long-term Debt Long-term debt at fair value Long-term Debt, Fair Value Long-term debt Long-term Debt Debt instrument interest rate Debt Instrument, Interest Rate, Stated Percentage Redemption price as percentage of principal amount redeemed Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Activity Related to Securitizations Accounted for as Sales Summary Of Securitization Arrangements Activity [Table Text Block] Tabular disclosure of the amount of financial assets securitized, proceeds and net revenues and cash flows received from retained interests. Summary of Retained Interests in SPEs Securitization Activities And Variable Interest Entity Table [Table Text Block] Total information regarding securitization vehicles to which Jefferies, acting as transferor, have transferred assets and for which the Company received sale accounting treatment. Brokers and Dealers [Abstract] Net Capital Requirements Regulatory Capital Requirements Disclosure [Text Block] Regulatory capital requirements disclosure. Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Number of operating segments Number of Operating Segments Accounting Developments New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Municipal securities Municipal Bonds [Member] Long-term debt Long-term Debt [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Investments at fair value Investments, Net Asset Value, Fair Value Disclosure Investments, Net Asset Value, Fair Value Disclosure Transfers of assets from Level 2 to Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Transfers of assets from Level 3 to Level 2 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Net gains/(losses) on Level 3 assets (realized and unrealized) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Net gains/(losses) on Level 3 liabilities (realized and unrealized) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Aggregate fair value of loans and other receivables on nonaccrual status and/or 90 days or greater past due Fair Value, Option, Loans Held as Assets, Aggregate Amount in Nonaccrual Status Loans and other receivables greater than 90 days past due Fair Value, Option, Loans Held as Assets, 90 Days or More Past Due Other changes in fair value Fair Value, Option, Changes in Fair Value, Gain (Loss) Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations Cash and Securities Segregated under Federal and Other Regulations Ownership percentage Equity Method Investment, Ownership Percentage Our investment in Epic Gas Equity Method Investments Net loss Equity Method Investment, Summarized Financial Information, Net Income (Loss) Related Party Transactions Related Party Transactions Disclosure [Text Block] Loss Contingencies [Table] Loss Contingencies [Table] Jefferies Capital Partners LLC Jefferies Capital Partners Llc [Member] Jefferies capital partners, LLC. Other Investments Investments, Other [Member] Investments, Other [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Standby Letters of Credit Standby Letters of Credit [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Outstanding equity commitments Equity Commitments Committed equity capitalization. Loan commitments outstanding to clients Loan Commitments Outstanding Loan commitments outstanding to clients. Fair value of mortgage-related commitments Mortgage Related Commitments At Fair Value Mortgage related commitments at fair value. Fair value of derivative contracts approximated deemed to meet the definition of a guarantee Guarantee Obligations Maximum Exposure Fair Value Guarantee obligations maximum exposure fair value. Letters of credit commitments Standby Letters Of Credit Commitments Standby Letters Of Credit Commitments Standby letters of credit expiration period Standby Letters of Credit Expiration Period Standby Letters of Credit Expiration Period Short-Term Borrowings Short-term Debt [Text Block] Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Number of years in which restricted stock awards amortized as compensation expense Period In Which Restricted Stock Awards Amortized As Compensation Expense Period In Which Restricted Stock Awards Amortized As Compensation Expense Minimum work hours required for part-time employees to purchase ESPP Share Based Compensation Arrangement By Employee Stock Purchase Plan, Minimum Work Hours Required for Part-time Employees Share Based Compensation Arrangement By Employee Stock Purchase Plan, Minimum Work Hours Required for Part-time Employees Annual employee contributions Share Based Compensation Arrangement By Employee Stock Purchase Plan Maximum Employee Contribution Share based compensation arrangement by maximum employee contributions to employee stock purchase plan. Employee service share based compensation plan stock price Share Based Compensation Arrangement By Employee Stock Purchase Plan Exercise Price Of Share Percentage of closing stock price used to purchase shares under the employee stock purchase plan. KCG KCG Holdings, Inc [Member] KCG Holdings, Inc [Member] Net earnings Loss on change in fair value of investment Unrealized Loss on Securities Carrying value of assets resulting from transfers Carrying Value Of Assets Resulting From Transfers Carrying Value Of Assets Resulting From Transfers Carrying value of liabilities resulting from transfers Carrying Value Of Liabilities Resulting From Transfers Carrying Value Of Liabilities Resulting From Transfers Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Collateralized Transactions Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Summary of Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Future Amortization Expense Related to Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Net derivatives Derivative Financial Instruments, Liabilities [Member] Other secured financings Other Secured Financings At Fair Value [Member] Other Secured Financings At Fair Value [Member] Assets: Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Beginning Balance Total gains/(losses) (realized and unrealized) Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances Net transfers into/ (out of) Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Ending Balance Change in unrealized gains/(losses) relating to instruments still held Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Liabilities: Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Beginning Balance Total gains/(losses) (realized and unrealized) Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances Net transfers into/ (out of) Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net Ending Balance Change in unrealized gains/ (losses) relating to instruments still held Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net earnings (loss) to net cash used in operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Income on loans to and investments in related parties Income On Loans To And Investments In Related Parties Income On Loans To And Investments In Related Parties Distributions received on investments in related parties Distributions Received On Investments In Related Parties Distributions Received On Investments In Related Parties Other adjustments Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Net change in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Securities deposited with clearing and depository organizations (Decrease) Increase In Cash And Securities Segregated And On Deposit For Regulatory Purposes Or Deposited With Clearing And Depository Organizations The net change during the reporting period of the amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances and cash and securities segregated in compliance with regulations. Receivables: Increase (Decrease) in Receivables [Abstract] Brokers, dealers and clearing organizations Increase (Decrease) in Receivables from Brokers-Dealers and Clearing Organizations Customers Increase Decrease In Customers Receivable The net change during the reporting period of the amounts due from customers for fees and charges arising from transactions related to the entity's brokerage activities and operations. Fees, interest and other Increase (Decrease) in Other Receivables Securities borrowed Increase (Decrease) in Securities Borrowed Financial instruments owned Increase (Decrease) in Financial Instruments Used in Operating Activities Securities purchased under agreements to resell Increase (Decrease) in Receivables under Repurchase Agreements Other assets Increase (Decrease) in Other Operating Assets Payables: Increase (Decrease) in Operating Liabilities [Abstract] Brokers, dealers and clearing organizations Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations Customers Increase (Decrease) in Payables to Customers Securities loaned Increase (Decrease) in Securities Loaned Transactions Financial instruments sold, not yet purchased Increase (Decrease) in Financial Instruments Sold, Not yet Purchased Securities sold under agreements to repurchase Increase (Decrease) in Payables under Repurchase Agreements Accrued expenses and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Contributions to loans to and investments in related parties Payments to Fund Long-term Loans to Related Parties Distributions from loans to and investments in related parties Proceeds from Collection of Long-term Loans to Related Parties Net payments on premises and equipment Payments to Acquire Property, Plant, and Equipment Cash received from contingent consideration Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset 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 short-term borrowings Proceeds from Short-term Debt Payments on short-term borrowings Repayments of Short-term Debt Proceeds from issuance of long-term debt, net of issuance costs Proceeds from Issuance of Senior Long-term Debt Repayment of long-term debt Repayments of Long-term Debt Dividend distribution Payments of Dividends Net payments on other secured financings Proceeds from (Payments for) Other Financing Activities Net change in bank overdrafts Proceeds from (Repayments of) Bank Overdrafts Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash, cash equivalents and restricted cash Effect of Exchange Rate on Cash and Cash Equivalents Net increase in cash, cash equivalents and restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Cash, cash equivalents and restricted cash at beginning of period Cash, Cash Equivalents And Restricted Cash, At Carrying Value Cash, Cash Equivalents And Restricted Cash, At Carrying Value Cash, cash equivalents and restricted cash at end of period Supplemental disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid (received) during the period for Cash Paid Received During Period [Abstract] Cash paid (received) during the period for: Interest Interest Paid Income taxes, net Income Taxes Paid, Net Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Investments Measured at Fair Value Based on Net Asset Value Per Share Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block] Summary of Changes in Fair Value of Financial Assets and Liabilities Classified as Level 3 Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Table [Table Text Block] Reconciliation of beginning Level 3 assets and liabilities to ending Level 3 assets and liabilities (specifically disaggregating purchases, sales, settlements, issuances, transfers to Level 3 and transfers out of Level 3). Quantitative Information about Significant Unobservable Inputs Used in Level 3 Fair Value Measurements Fair Value Inputs Assets And Liabilities Quantitative Information Table [Table Text Block] Tabular disclosure of quantitative information about significant unobservable inputs used in the fair value measurement of Level 3 financial assets and liabilities, including valuation technique and range of inputs Summary of Gains (Losses) Due to Changes in Instrument Specific Credit Risk and Summary of Contractual Principal Exceeds Fair Value for Loans and Other Receivables Fair Value, Option, Quantitative Disclosures [Table Text Block] Segment Reporting Segment Reporting Disclosure [Text Block] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Berkadia Commercial Mortgage, LLC Berkadia Commercial Mortgage, LLC [Member] Berkadia Commercial Mortgage, LLC [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated Entity Affiliated Entity [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Purchase commitment amount Purchase Commitment Amount Purchase Commitment Amount Trading Securities [Table] Trading Securities [Table] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] U.S. government agency RMBS Us Government Agency Issued Rmbs [Member] Us Government Agency Issued Rmbs [Member] U.S. government agency CMBS Us Government Agency Issued Cmbs [Member] Us Government Agency Issued Cmbs [Member] CLOs Collateralized Loan Obligations [Member] Consumer and other loans Other Debt Obligations [Member] Schedule of Trading Securities and Other Trading Assets [Line Items] Schedule of Trading Securities and Other Trading Assets [Line Items] Total RMBS securitization assets Rmbs Securitization Assets Represents unpaid principal amount of assets in residential mortgage backed securitization vehicles at the balance sheet date. Total CMBS securitization assets Cmbs Securitization Assets Represents unpaid principal amount of assets in commercial mortgage backed securitization vehicles at the balance sheet date. Total Collateralized loan obligations Collateralized Loan Obligations Securitization Assets Collateralized Loan Obligations Securitization Assets Consumer and other loans Other Securitization Assets Other Securitization Assets Retained Interests Retained Interest, Fair Value Disclosure Derivative [Table] Derivative [Table] Equity swaps and options Equity Swaps And Options [Member] Equity Swaps And Options [Member] Credit default swaps Credit Default Swap [Member] Total return swaps Foreign currency forwards, swaps and options Foreign Currency Forwards Swaps And Options [Member] Foreign currency forwards swaps and options. Fixed income forwards Fixed Income Forward Contracts [Member] Fixed Income Forward Contracts [Member] Interest rate swaps, options and forwards Interest Rate Swaps, Options and Forwards [Member] Interest Rate Swaps, Options and Forwards [Member] Derivative [Line Items] Derivative [Line Items] OTC derivative assets having maturity period of 0 to 12 months Otc Derivative Assets Having Maturity Period Of Zero To Twelve Months Over the counter derivative assets having maturity period of zero to twelve months. OTC derivative assets having maturity period of 1 to 5 years Otc Derivative Assets Having Maturity Period Of One To Five Years OTC derivative assets having maturity period of 1 to5 years. OTC derivative assets having maturity period of greater than 5 years Otc Derivative Assets Having Maturity Period Of Greater Than Five Years OTC derivative assets having maturity period of greater than five years. OTC derivative assets cross-maturity netting Otc Derivative Assets Cross Maturity Netting OTC derivative assets cross maturity netting. Total OTC derivative assets, net of cross-maturity netting Consolidated Otc Derivative Assets, Net Of Cross-Maturity Netting Total OTC derivative assets, net of cross-maturity netting. Cross product counterparty netting Derivative Assets Cross Product Counterparty Netting Derivative Assets Cross Product Counterparty Netting. OTC derivative liabilities having maturity period of 0 to 12 months Otc Derivative Liabilities Having Maturity Period Of Zero To Twelve Months OTC derivative liabilities having maturity period of zero to twelve months. OTC derivative liabilities having maturity period of 1 to 5 years Otc Derivative Liabilities Having Maturity Period Of One To Five Years OTC derivative liabilities having maturity period of 1 to 5 years. OTC derivative liabilities having maturity period of greater than 5 years Otc Derivative Liabilities Having Maturity Period Of Greater Than Five Years OTC derivative liabilities having maturity period of greater than 5 years. OTC derivative liabilities cross-maturity netting Otc Derivative Liabilities Cross Maturity Netting OTC derivative liabilities cross maturity netting. Total OTC derivative liabilities, net of cross-maturity netting Consolidated Otc Derivative Liabilities Net Of Cross Maturity Netting Total OTC derivative liabilities, net of cross-maturity netting. Cross product counterparty netting Derivative Liabilities Cross Product Counterparty Netting Derivative Liabilities Cross Product Counterparty Netting Total OTC derivative liabilities included in Financial instruments sold, not yet purchased Otc Derivative Liabilities Included In Financial Instruments Sold Not Yet Purchased OTC Derivative Liabilities Included In Financial Instruments Sold Not Yet Purchased. Exchange traded derivative assets Exchange Traded Derivative Assets Fair value of exchange traded derivative assets. Cash collateral received Cash Collateral Received Cash collateral received that was netted against OTC derivative assets. Exchange traded derivative liabilities, with fair value Exchange Traded Derivative Liabilities Fair value of exchange traded derivative liabilities. Cash collateral pledged Cash Collateral Pledge Cash collateral pledged that was netted against OTC derivative liabilities. Net Capital, Adjusted and Excess Net Capital Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Director Director [Member] Leucadia Leucadia [Member] Leucadia. Affiliate Of Leucadia Affiliate Of Leucadia [Member] Affiliate Of Leucadia [Member] Hedge Fund Managed by Subsidiary of Leucadia Hedge Fund Managed by Subsidiary of Leucadia [Member] Hedge Fund Managed by Subsidiary of Leucadia [Member] Hedge fund Managed by Leucadia Hedge Fund Managed By Leucadia [Member] Hedge Fund Managed By Leucadia [Member] Landcadia Holdings Inc. Landcadia Holdings Inc. [Member] Landcadia Holdings Inc. [Member] Subsidy of Leucadia Subsidy Of Leucadia [Member] Subsidy Of Leucadia [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Principal transactions Capital Markets And Asset Management Services, Principal Transactions [Member] Capital Markets And Asset Management Services, Principal Transactions [Member] Other revenues Capital Markets And Asset Management Services, Other [Member] Capital Markets And Asset Management Services, Other [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Accrued expenses and other liabilities Accounts Payable and Accrued Liabilities [Member] Loans outstanding to certain employees Loans and Leases Receivable, Related Parties Investment in related party Related Party Transaction, Investment Amount Related Party Transaction, Investment Amount Charges to Leucadia for services provided Revenue from Related Parties Charges from Leucadia for services received Related Party Transaction, Expenses from Transactions with Related Party Receivable from Leucadia Accounts Receivable, Related Parties, Current Payable to Leucadia Accounts Payable, Related Parties, Current Quarterly dividend as percentage of net earnings Quarterly Dividend As Percentage Of Net Earnings Quarterly Dividend As Percentage Of Net Earnings Tax payable Tax Payable, Related Parties, Current Tax Payable, Related Parties, Current Payment made to related party related to tax sharing agreement Related Party Transaction, Payment Made Related To Tax Sharing Agreement Related Party Transaction, Payment Made Related To Tax Sharing Agreement Brokers, dealers and clearing organizations Payables to Broker-Dealers and Clearing Organizations Financial instruments sold, not yet purchased, at fair value Financial Instruments Sold, Not yet Purchased, at Fair Value Net gain on investment in hedge fund Related Party Transaction, Gain (Loss) on Transaction Related Party Transaction, Gain (Loss) on Transaction Number of public offering units owned Relate Party Transaction, Number of Public Offering Units Owned Relate Party Transaction, Number of Public Offering Units Owned Number of common stock per public offering unit (in shares) Relate Party Transaction, Number of Common Stock Per Public Offering Unit Relate Party Transaction, Number of Common Stock Per Public Offering Unit Number of public warrant per public offering unit Relate Party Transaction, Number of Public Warrant Per Public Offering Unit Relate Party Transaction, Number of Public Warrant Per Public Offering Unit Financial instruments owned, at fair value Financial Instruments, Owned, at Fair Value Proceeds from sale of securities Proceeds from Sale of Available-for-sale Securities Gain (loss) on sale of securities Gain (Loss) on Sale of Securities, Net Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Table] Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] Cash Cash [Member] Mortgage- and asset-backed securities Mortgage and Asset-Backed Securities [Member] Mortgage and Asset-Backed Securities [Member] U.S. government and federal agency securities US Government Corporations and Agencies Securities [Member] Sovereign obligations Sovereign Debt [Member] Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items] Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items] Securities Lending Arrangements Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred Repurchase Agreements Financial Assets Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement Obligation To Return Securities Received As Collateral Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Amount Offset Against Collateral Total Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement Schedule of Gain (Loss) on Investments [Table] Schedule of Gain (Loss) on Investments [Table] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Assets Sold under Agreements to Repurchase, Type [Domain] Assets Sold under Agreements to Repurchase, Type [Domain] Gain (Loss) on Investments [Line Items] Gain (Loss) on Investments [Line Items] Loans and other receivables Fair Value, Option, Credit Risk, Gains (Losses) on Assets Financial Instruments Sold and Long-term Debt Financial Instruments Sold, Not yet Purchased, at Fair Value [Abstract] Gains (losses) due to changes in instrument specific credit risk Fair Value, Option, Credit Risk, Gains (Losses) on Liabilities Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Bank loans Notes Payable to Banks [Member] Line of credit Line of Credit [Member] Floating rate puttable notes Puttable Notes [Member] Puttable Notes [Member] Intraday Credit Facility Intraday Credit Facility [Member] Intraday Credit Facility [Member] Equity-linked notes Equity-linked Notes [Member] Equity-linked Notes [Member] Equity-Linked Notes Matured On December 7, 2017 Equity-Linked Notes Matured On December 7, 2017 [Member] Equity-Linked Notes Matured On December 7, 2017 [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Federal funds effective rate Federal Funds Effective Swap Rate [Member] Short-term Debt [Line Items] Short-term Debt [Line Items] Short-term borrowings Short-term Debt Interest rate on short-term borrowings outstanding Short-term Debt, Weighted Average Interest Rate Average daily short-term borrowings Short-term Debt, Average Outstanding Amount Credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Other Assets Other Assets [Member] Accrued expense and other liabilities Accrued Expense And Other Liabilities [Member] Accrued Expense And Other Liabilities [Member] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Equity commitment Equity Commitment, Amount Equity Commitment, Amount Total committed equity capitalization of JFIN Commitments Under Equity Capitalization Of Joint Venture Entity Commitments under equity capitalization of joint venture entity. Funded portion of equity commitment to subsidiary Equity Commitment To Joint Venture Funded Portion Equity commitment to joint venture funded portion. Unfunded portion of equity commitment to subsidiary Equity Commitment To Joint Venture Unfunded Portion Equity commitment to joint venture unfunded portion. Extension period Line Of Credit Extension Period Line of credit extension period. Termination notice period Line Of Credit Termination Notice Period Line of credit termination notice period. Committed line of credit facility amount Line Of Credit Facility Commitment Under Joint Venture Line of credit facility commitment under joint venture. Funded portion of loan commitment Loan Commitment To Joint Venture Funded Portion Loan Commitment To Joint Venture Funded Portion Loan commitment Aggregate Loan Commitment Aggregate loan commitment to joint venture. Receivables under service agreement Due from Related Parties Payables under service agreement Due to Related Parties Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Cash and cash equivalents ($5,106 and $7,514 at February 28, 2018 and November 30, 2017, respectively, related to consolidated VIEs) Cash and Cash Equivalents, at Carrying Value Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations Financial instruments owned, at fair value, (including securities pledged of $10,861,294 and $10,842,051 at February 28, 2018 and November 30, 2017, respectively; and $1,508 and $38,044 at February 28, 2018 and November 30, 2017, respectively, related to consolidated VIEs) Loans to and investments in related parties Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Securities borrowed Securities purchased under agreements to resell Securities received as collateral Securities Received as Collateral Receivables: Receivables [Abstract] Brokers, dealers and clearing organizations Receivables from Brokers-Dealers and Clearing Organizations Customers Receivables from Customers Fees, interest and other ($4 and $197 at February 28, 2018 and November 30, 2017, respectively, related to consolidated VIEs) Fees Interest And Other Represents accounts receivable from clients, counterparties and others, interest income receivable, dividend income receivable, fees receivable, and other receivables from suppliers, insurance companies and amounts due from third parties. Premises and equipment Property, Plant and Equipment, Net Goodwill Other assets ($2 at both February 28, 2018 and November 30, 2017, related to consolidated VIEs) Other Assets Total assets LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Short-term borrowings (includes $0 and $23,324 at fair value at February 28, 2018 and November 30, 2017, respectively) Collateralized financings: Collateralized Financings [Abstract] Securities loaned Securities sold under agreements to repurchase Other secured financings (includes $698,422 and $722,108 at February 28, 2018 and November 30, 2017, respectively, related to consolidated VIEs) Other Secured Financings Obligation to return securities received as collateral Obligation to Return Securities Received as Collateral Payables: Payables [Abstract] Payables. Customers Payables to Customers Accrued expenses and other liabilities ($534 and $1,391 at February 28, 2018 and November 30, 2017, respectively, related to consolidated VIEs) Accounts Payable and Accrued Liabilities Long-term debt (includes $735,456 and $606,956 at fair value at February 28, 2018 and November 30, 2017, respectively) Total liabilities Liabilities EQUITY Equity [Abstract] Member’s paid-in capital Additional Paid in Capital, Common Stock Accumulated other comprehensive loss: Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Currency translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Changes in instrument specific credit risk Accumulated Other Comprehensive Income (Loss), Changes in Instrument Specific Credit Risk, Net of Tax Accumulated Other Comprehensive Income (Loss), Changes in Instrument Specific Credit Risk, Net of Tax Cash flow hedges Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax Additional minimum pension liability Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax Total accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total Jefferies Group LLC member’s equity Members Common Stockholders Equity Members Common Stockholders Equity Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Equity And Members Equity Stockholders Equity Including Portion Attributable To Noncontrolling Interest Equity And Members Equity Stockholders Equity Including Portion Attributable To Noncontrolling Interest Total liabilities and equity Liabilities Equity And Members Equity Stockholders Equity Liabilities Equity And Members Equity Stockholders Equity Securities or Other Assets Sold under Agreements to Repurchase, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Assets Sold under Agreements to Repurchase, Maturity Period [Domain] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Overnight and Continuous Maturity Overnight [Member] Up to 30 Days Maturity Less than 30 Days [Member] 31-90 Days Maturity 30 to 90 Days [Member] Greater than 90 Days Maturity Greater than 90 Days [Member] Investments Investment [Text Block] Schedule of New Accounting Pronouncements Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Net Capital Requirements [Table] Net Capital Requirements [Table] Net Capital Requirements [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Jefferies Jefferies [Member] A registered broker dealer under the Securities and Exchange act of 1934 and a wholly owned subsidiary of the Parent (Jefferies). Net Capital Requirements [Line Items] Net Capital Requirements [Line Items] Net Capital Requirements [Line Items] Net Capital Net Capital Excess Net Capital Alternative Excess Net Capital Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Equity Long/Short Hedge Funds Hedge Funds, Equity Long (Short) [Member] Fixed Income and High Yield Hedge Funds High Yield Hedge Funds [Member] High Yield Hedge Funds. Fund of Funds Fund Of Funds [Member] Fund of Funds. Private equity funds Private Equity Funds [Member] Multi-asset Funds Multi-asset Funds [Member] Multi-asset Funds [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 Investments, Fair Value Disclosure Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Percentage of investment at fair value in liquidation Percentage of Investment at Fair Value in Liquidation Percentage of Investment at Fair Value in Liquidation Estimated period for the liquidation of the underlying assets, minimum Estimated Period For Liquidation Of Underlying Assets Minimum Estimated period for the liquidation of the underlying assets, Minimum. Estimated period for the liquidation of the underlying assets, maximum Estimated Period For Liquidation Of Underlying Assets Maximum Estimated period for the liquidation of the underlying assets, maximum. Percentage of redeemable investments Redeemable Investments Investments redeemable within 60-90 days Notice period redemption of investment prior written notice period Notice Period Redemption Of Investments Prior Written Notice Period Investments at fair value that cannot be redeemed at reporting date and are subject to a prior written redemption request. Fair Value Disclosures Fair Value Disclosures [Text Block] Cash, Cash Equivalents and Restricted Cash by Category [Abstract] Cash and Cash Equivalents [Abstract] Cash and cash equivalents Cash and securities segregated and on deposit for regulatory purposes with clearing and depository organizations Cash And Securities Segregated And On Deposit For Regulatory Purposes With Clearing And Depository Organizations Cash And Securities Segregated And On Deposit For Regulatory Purposes With Clearing And Depository Organizations Total cash, cash equivalents and restricted cash Accounting Standards Update 2016-18 Accounting Standards Update 2016-18 [Member] Accounting Standards Update 2016-18 [Member] Net cash used in operating activities Cumulative effect of the adoption of the new revenue standard Income Tax Disclosure [Abstract] Unrecognized tax benefits Unrecognized Tax Benefits Unrecognized tax benefits that would impact effective tax rate in future Unrecognized Tax Benefits that Would Impact Effective Tax Rate Accrued interest on unrecognized tax benefits Unrecognized Tax Benefits, Interest on Income Taxes Accrued Provisional estimate of impact of the Tax Act Tax Cuts And Jobs Act Of 2017 Incomplete Accounting Provisional Income Tax Expense (Benefit) Amount of reasonable estimate for income tax expense (benefit) from effect of Tax Cuts and Jobs Act of 2017 for which accounting for tax effect is incomplete. Provisional estimate of impact of the Tax Act related to revaluation of deferred tax asset Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense Provisional estimate of impact of the Tax Act related to deemed repatriation of foreign earnings Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Income Tax Expense Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Income Tax Expense Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Nonconsolidated VIEs Variable Interest Entity, Not Primary Beneficiary [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Assets and Liabilities of Consolidated VIEs Prior to Consolidation Variable Interest Entities Primary Beneficiary [Table Text Block] Variable Interest Entities Primary Beneficiary [Table Text Block] Variable Interests in Non-Consolidated Variable Interest Entities Non Consolidated Variable Interest Entities [Table Text Block] Non-consolidated variable interest entities aggregated by principal business activity. Compensation Plans Compensation Related Costs, General [Text Block] External Credit Rating by Grouping [Axis] External Credit Rating by Grouping [Axis] External Credit Rating by Grouping [Domain] External Credit Rating by Grouping [Domain] Investment Grade External Credit Rating, Investment Grade [Member] Non-investment Grade External Credit Rating, Non Investment Grade [Member] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Index credit default swaps Credit Index Product [Member] Single name credit default swaps Credit Default Swaption [Member] Total Notional Derivative, Notional Amount Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Level 2 Fair Value, Inputs, Level 2 [Member] Financial Instruments Owned and Pledged as Collateral by Type [Axis] Financial Instruments Owned and Pledged as Collateral by Type [Axis] Financial Instruments Owned and Pledged as Collateral, Type [Domain] Financial Instruments Owned and Pledged as Collateral, Type [Domain] Residential mortgage-backed securities Commercial mortgage-backed securities Other asset-backed securities Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets: Fair Value Assets Measured On Recurring Basis [Abstract] Fair value assets measured on recurring basis. Corporate equity securities Financial Instruments, Owned, Corporate Equities, at Fair Value Corporate debt securities Financial Instruments, Owned, Corporate Debt, at Fair Value Collateralized debt obligations and collateralized loan obligations Financial Instruments Owned Collateralized Debt Obligations At Fair Value The fair value as of the balance sheet date of firm holdings in structured asset - backed securities whose value and payments are derived from portfolio of fixed income underlying assets. U.S. government and federal agency securities Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value Municipal securities Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value Sovereign obligations Financial Instruments, Owned, Other Sovereign Government Obligations, at Fair Value Mortgage- and asset-backed securities, assets Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value Loans and other receivables Financial Instruments Owned Loans And Other Receivables The fair value as of the balance sheet date of firm holdings in corporate loans, participation certificates in GNMA project and construction loans, and escrow and trade claim receivables. Derivatives Financial Instruments, Owned, Derivatives and Other Contractual Agreements, at Fair Value Investments at fair value Financial Instruments, Owned, Principal Investments, at Fair Value Total financial instruments owned, excluding Investments at fair value based on NAV Financial Instruments, Owned, at Fair Value Excluding Investments at Net Asset Value Financial Instruments, Owned, at Fair Value Excluding Investments at Net Asset Value Counterparty and Cash Collateral Netting Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset Liabilities: Fair Value Liabilities Measured On Recurring Basis [Abstract] Fair value liabilities measured on recurring basis. Financial instruments sold, not yet purchased: Corporate equity securities Financial Instruments Sold, Not yet Purchased, Corporate Equities Corporate debt securities Financial Instruments Sold, Not yet Purchased, Corporate Debt U.S. government and federal agency securities Financial Instruments Sold, Not yet Purchased, US Government and Agency Obligations Municipal securities Financial Instruments Sold, Not yet Purchased, State and Municipal Government Obligations Sovereign obligations Financial Instruments Sold, Not yet Purchased, Other Sovereign Government Debt Commercial mortgage-backed securities Financial Instruments Sold, Not yet Purchased, Mortgages, Mortgage-backed and Asset-backed Securities Loans Fair Value Of Loan Obligations Fair value of loan obligations. Derivatives Financial Instruments Sold, Not yet Purchased, Derivatives and Other Contracts Total financial instruments sold, not yet purchased