Transfers and Servicing [Abstract] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [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] Debt and Equity Securities, FV-NI [Line Items] Debt and Equity Securities, FV-NI [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 Instruments and Hedging Activities Disclosure [Abstract] 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. Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Subsidiary Of Jefferies Subsidiary Of Jefferies Financial Group Inc. [Member] Subsidiary Of Jefferies Financial Group Inc. [Member] 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] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Corporate debt securities Corporate Debt Securities [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Jefferies Jefferies Financial Group Inc. [Member] Jefferies Financial Group Inc. [Member] Affiliate of Jefferies Affiliate Of Jefferies Financial Group Inc. [Member] Affiliate Of Jefferies Financial Group Inc. [Member] Hedge Fund Managed By Jefferies Hedge Fund Managed By Jefferies Financial Group Inc. [Member] Hedge Fund Managed By Jefferies Financial Group Inc. [Member] Landcadia Holdings Inc. Landcadia Holdings Inc. [Member] Landcadia Holdings Inc. [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated Entity Affiliated Entity [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Commissions and other fees Capital Markets And Asset Management Services, Commissions And Other Fees [Member] Capital Markets And Asset Management Services, Commissions And Other Fees [Member] 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] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Charges to Jefferies for services provided Revenue from Related Parties Charges from Jefferies for services received Related Party Transaction, Expenses from Transactions with Related Party Receivable from Jefferies Accounts Receivable, Related Parties, Current Payable to Jefferies 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 Dividends payable Dividends Payable 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 Payables-brokers, dealers and clearing organizations Payables to Broker-Dealers and Clearing Organizations Financial instruments sold, not yet purchased Financial Instruments Sold, Not yet Purchased, at Fair Value Investment in related party Related Party Transaction, Investment Amount Related Party Transaction, Investment Amount 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 Payments to acquire investments Payments to Acquire Investments Proceeds from sale of securities Proceeds from Sale of Available-for-sale Securities Gain (loss) on sale of securities Debt and Equity Securities, Gain (Loss) Equity Method Investments and Joint Ventures [Abstract] Investments Investment [Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swaps Interest Rate Swap [Member] 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] Secured Debt Secured Debt [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Debt principal amount Debt Instrument, Face Amount Increase (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 Compensation Related Costs [Abstract] 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] Commitments and Contingencies Disclosure [Abstract] Commitments, Contingencies and Guarantees Commitments Contingencies and Guarantees [Text Block] Document And Entity Information [Abstract] Document and Entity Information Abstract. Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Jefferies Finance, LLC Jefferies Finance Llc [Member] Jefferies Finance LLC. 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] Guarantee Obligations [Line Items] Guarantor Obligations [Line Items] 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 Brokers, dealers and clearing organizations Receivables from Brokers-Dealers and Clearing Organizations Berkadia Commercial Mortgage, LLC Berkadia Commercial Mortgage, LLC [Member] Berkadia Commercial Mortgage, LLC [Member] Purchase commitment amount Purchase Commitment Amount Purchase Commitment Amount 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] Derivative Instruments with Contingent Features Derivative Instruments With Contingent Features [Table Text Block] Derivative Instruments With Contingent Features [Table Text Block] Accounting Policies [Abstract] Consolidation Consolidation, Policy [Policy Text Block] Principal Transactions Revenues Revenue Recognition, Policy [Policy Text Block] Accounting Standards to be Adopted in Future Periods and Adopted Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Equity Method Investee Equity Method Investee [Member] Equity Investments in Jefferies Capital Partners Related Funds Equity Investments in Jefferies Capital Partners Related Funds [Member] Equity Investments in Jefferies Capital Partners Related Funds [Member] Equity investments loans in related funds Equity Investments Loans In Related Funds Equity investments in and loans to related funds, in aggregate. Other revenues and investment income (loss) Other Revenues And Investment Income Loss On Private Equity Related Investments Other Revenues And Investment Income Loss On Private Equity Related Investments Service charges Related Party Transaction, Other Revenues from Transactions with Related Party Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Long-term debt Long-term Debt [Member] CDOs and CLOs Collateralized Debt Obligations and Collateralized Loan Obligations [Member] Collateralized Debt Obligations and Collateralized Loan Obligations [Member] Municipal securities Municipal Bonds [Member] RMBS Residential Mortgage Backed Securities [Member] Investments at fair value Investments [Member] Other ABS Other Asset Backed Securities [Member] Other asset-backed securities. Corporate equity securities Equity Securities [Member] CMBS Commercial Mortgage Backed Securities [Member] Loans and other receivables Loans and Finance Receivables [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Level 1 Fair Value, Inputs, Level 1 [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] 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 Transfers of liabilities from Level 2 to Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Transfers, Net 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 Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Related party private equity vehicles Private Equity Vehicles [Member] Private equity vehicles. Other private investment vehicles Other Private Investment Vehicles [Member] Other Private Investment Vehicles [Member] ERROR in label resolution. Mortgage And Asset Backed Securitization Activity Agency [Member] Mortgage and asset backed securitization activity agency. ERROR in label resolution. Mortgage And Asset Backed Securitization Activity Non Agency [Member] Mortgage and asset backed securitization activity non agency. JCP Entities JCP Entities [Member] JCP Entities [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Equity investments Equity Commitments Committed equity capitalization. Funded equity commitments Funded Equity Commitments Funded amount of the committed equity capitalization at the balance sheet date. Carrying amount of equity investment Carrying Amount Of Equity Investments Carrying amount of equity investments. Maximum exposure Guarantee Obligations Maximum Exposure Fair Value Guarantee obligations maximum exposure fair value. Carrying amount Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets Loss Contingencies [Table] Loss Contingencies [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] 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 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 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] Banking and Thrift [Abstract] Securities received as collateral Securities Received as Collateral Fair value of securities received as collateral Fair Value of Securities Received as Collateral that Can be Resold or Repledged Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations Other Commitments [Table] Other Commitments [Table] 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] Forward starting securities purchased under agreements to resell settled within three business days Forward Starting Securities Purchased Under Agreements To Resell Settled [Member] Forward Starting Securities Purchased Under Agreements To Resell Settled [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 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 Derivative instrument liabilities with credit-risk-related contingent features Derivative, Net Liability Position, Aggregate Fair Value Collateral posted Collateral Already Posted, Aggregate Fair Value Collateral received Collateral Received, Aggregate Fair Value Collateral Received, Aggregate Fair Value Return of and additional collateral required in the event of a credit rating downgrade below investment grade Additional Collateral, Aggregate Fair Value 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, Disclosures [Table Text Block] Fair Value Disclosures Fair Value Disclosures [Text Block] Related Party Transactions Related Party Transactions Disclosure [Text Block] Statement of Cash Flows [Abstract] Cash, Cash Equivalents and Restricted Cash by Category [Abstract] Cash and Cash Equivalents [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value 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 Cash, Cash Equivalents And Restricted Cash, At Carrying Value Cash, Cash Equivalents And Restricted Cash, At Carrying Value 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 Total Return Swap [Member] 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. 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] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Net revenues Revenues, Net of Interest Expense Non-interest expenses Noninterest Expense Earnings before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Segment assets Assets 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] Minimum Minimum [Member] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value Alternative Investment Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded 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. Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Interest rate swaps Derivative Financial Instruments, Assets [Member] Interest rate contracts Interest Rate Contract [Member] Foreign exchange contracts Foreign Exchange Contract [Member] Equity contracts Equity Contract [Member] Commodity contracts Commodity Contract [Member] Credit contracts Credit Risk Contract [Member] Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Gains (losses) recognized in interest expense on fair value hedge Gain (Loss) on Fair Value Hedges Recognized in Earnings Unrealized and realized gains (losses) Gain (Loss) on Derivative Instruments, Net, Pretax Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Variable Interest Entities Variable Interest Entities [Member] Variable Interest Entities [Member] Statement [Line Items] Statement [Line Items] Pledged financial instruments Pledged Financial Instruments, Not Separately Reported, Securities Fees, interest and other 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. Other assets Other Assets Short-term borrowings at fair value Short-term Debt, Fair Value Other secured financings Other Secured Financings Accrued expenses and other liabilities Accounts Payable and Accrued Liabilities Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Interest income Investments in and Advances to Affiliates, Dividend or Interest Credited to Income Unfunded commitment fees Line of Credit Facility, Unfunded Commitment Fee Income Line of Credit Facility, Unfunded Commitment Fee Income Our total equity balance Equity Method Investments Net earnings Equity Method Investment, Summarized Financial Information, Net Income (Loss) Origination and syndication fee revenues Fees Earned To Joint Venture Related To Loan Origination Fees paid to joint venture related to loan origination. Origination fee expenses Fees Paid To Joint Venture Related To Loan Origination Fees paid to joint venture related to loan origination. CLO placement fee revenues Brokerage Commissions Revenue Derivative losses Derivative, Gain (Loss) on Derivative, Net Underwriting fees Underwriting Fees Underwriting Fees Service fees Service Fees Earned Service Fees Earned Epic Gas Epic Gas [Member] Epic Gas [Member] Ownership percentage Equity Method Investment, Ownership Percentage Our investment in Epic Gas Net losses JCP Fund V JCP Funds [Member] JCP Funds [Member] Total committed equity capitalization Percent of financial information presented Equity Method Investment, Percent of Financial Information Presented Equity Method Investment, Percent of Financial Information Presented 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. Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] 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. Financial instruments owned: Financial Instruments, Owned, at Fair Value [Abstract] 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: Financial Instruments Sold, Not yet Purchased, at Fair Value [Abstract] 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 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 Counterparty and Cash Collateral Netting Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset Short-term borrowings Long-term debt Obligation to return securities received as collateral Obligation to Return Securities Received as Collateral Level 1 to Level 2 transfers, amount Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Securitization Activities Transfers and Servicing of Financial Assets [Text Block] Segment Reporting Segment Reporting Disclosure [Text Block] Number of operating segments Number of Operating Segments 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. Accounting Changes and Error Corrections [Abstract] Schedule of New Accounting Pronouncements Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Brokers and Dealers [Abstract] Net Capital, Adjusted and Excess Net Capital Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile net earnings to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization 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 provided by (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 proceeds from (payments on) other secured financings Proceeds from (Payments for) Other Financing Activities Net change in bank overdrafts Proceeds from (Repayments of) Bank Overdrafts Proceeds from noncontrolling interests Proceeds from Noncontrolling Interests 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 (decrease) in cash, cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash at end of period Supplemental disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid during the period for Cash Paid Received During Period [Abstract] Cash paid (received) during the period for: Interest Interest Paid, Including Capitalized Interest, Operating and Investing Activities Income taxes, net Income Taxes Paid, Net Income Tax Disclosure [Abstract] Earliest Tax Year Subject to Examination in the Major Tax Jurisdictions in which the Company Operates Summary of Income Tax Examinations [Table Text Block] 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 Long-Term Debt Long-term Debt [Text Block] Net Revenues, Expenses and Total Assets by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Net Revenues by Geographic Region Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block] Aggregate amortization expense Amortization of Intangible Assets Remainder of fiscal 2018 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Year ending November 30, 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Two Year ending November 30, 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Three Year ending November 30, 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Four Year ending November 30, 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Five Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Equities Equities [Member] Equities [Member] Fixed Income 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] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Americas Americas [Member] Europe Europe [Member] Asia Asia [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenues from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] 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. Derivatives Derivative [Member] 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 Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Domain] Retirement Plan Sponsor Location [Domain] German Plan Foreign Plan [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Pension Plan Pension Plan [Member] Jefferies Bache Limited Jefferies Bache Limited [Member] Jefferies Bache Limited [Member] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Domain] Adjustments for Change in Accounting Principle [Domain] Changes to presentation of Consolidated Statements of Cash Flows Changes To Presentation Of Consolidated Statements Of Cash Flows [Member] Changes To Presentation Of Consolidated Statements Of Cash Flows [Member] Payment to transfer defined benefit obligation and insurance contracts Defined Benefit Plan, Payment To Transfer Defined Benefit Obligation And Insurance Contracts Defined Benefit Plan, Payment To Transfer Defined Benefit Obligation And Insurance Contracts Consideration for release of indemnity relating to pension obligations Consideration For Release of Indemnity Relating To Pension Obligations Consideration For Release of Indemnity Relating To Pension Obligations Proceeds from short-term borrowings Payments on short-term borrowings Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Securitization Vehicles Securitization Activity [Member] Securitization Activity [Member] Other Other Activity [Member] Other activity. Cash Cash [Member] Financial instruments owned Financial Instruments Owned [Member] Financial Instruments Owned [Member] Securities purchased under agreement to resell Securities Purchased Under Agreement [Member] Securities Purchased Under Agreement [Member] Fees, interest and other receivables Fees, Interest and Other Receivables [Member] Fees, Interest and Other Receivables [Member] Other secured financings Other Secured Financings [Member] Other Secured Financings [Member] Other liabilities Other Liabilities [Member] Assets Variable Interest Entity, Consolidated, Carrying Amount, Assets Liabilities Variable Interest Entity, Consolidated, Carrying Amount, Liabilities Secured financing included in inventory and eliminated Vie Secured Financing Eliminated In Consolidation Secured financing held by The Company in Inventory and eliminated in consolidation. New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-18 Accounting Standards Update 2016-18 [Member] Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Member's paid-in capital Additional Paid-in Capital [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] 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 Net cash used in operating activities Cumulative effect of the adoption of the new revenue standard Cumulative Effect of New Accounting Principle in Period of Adoption Loans Loans [Member] 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 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 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 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value 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 Ending Balance Change in unrealized gains/ (losses) relating to instruments still held Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) 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] Non-vested share-based awards Nonvested Share Awards [Member] Nonvested Share Awards [Member] Restricted cash awards Restricted Cash Awards [Member] Restricted Cash Awards [Member] Compensation Plans [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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 Statement of Stockholders' Equity [Abstract] Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] 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] Adjustment related to foreign currency gains reclassified to earnings Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax Changes in instrument specific credit risk reclassified to earnings Other Comprehensive Income (Loss) Changes In Instrument Specific Credit Risk Reclassified To Earnings, Net of Tax Other Comprehensive Income (Loss) Changes In Instrument Specific Credit Risk Reclassified To Earnings, Net of Tax 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 Cash flow hedges Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Pension adjustments Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Accounting Developments New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Jefferies Capital Partners V L.P. Jefferies Capital Partners V L.P [Member] Jefferies Capital Partners V L.P [Member] SBI USA Fund L.P. SBI USA Fund L.P. [Member] SBI USA Fund L.P. [Member] KCG KCG Holdings, Inc [Member] KCG Holdings, Inc [Member] Net gain on change in fair value of investment 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 Income Taxes Income Tax Disclosure [Text Block] Statement of Comprehensive Income [Abstract] 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 Nonconsolidated VIEs Variable Interest Entity, Not Primary Beneficiary [Member] 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. 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] Floating rate puttable notes matured April 8, 2018 Floating Rate Puttable Notes Matured April 8, 2018 [Member] Floating Rate Puttable Notes Matured April 8, 2018 [Member] Floating rate puttable notes matured May 3, 2018 Floating Rate Puttable Notes Matured May 3, 2018 [Member] Floating Rate Puttable Notes Matured May 3, 2018 [Member] Equity-linked notes Equity-linked Notes [Member] Equity-linked Notes [Member] Equity-inked Notes Matured On December 7, 2017 Equity-Linked Notes Matured On December 7, 2017 [Member] Equity-Linked Notes Matured On December 7, 2017 [Member] Equity-linked Notes Due July 12, 2018 Equity-linked Notes Due July 12, 2018 [Member] Equity-linked Notes Due July 12, 2018 [Member] Intraday Credit Facility Intraday Credit Facility [Member] Intraday Credit Facility [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, at Point in Time 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 Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Restricted stock and RSUs Restricted Stock and Restricted Stock Units [Member] Restricted Stock and Restricted Stock Units [Member] 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 Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Schedule of Short-term Borrowings Schedule of Short-term Debt [Table Text Block] Income Statement [Abstract] Revenues: Revenues [Abstract] Commissions and other fees Principal transactions Principal Transactions Revenue, Net Investment banking Investment Banking Revenue Asset management fees Asset Management Fees And Investment Income Loss From Managed Funds Revenues earned from management, administrative and performance fees from funds managed by the firm, third-party managed funds, and investment income (loss) from investments in these funds. Interest Interest Income, Operating Other Other Operating Income (Expense), Net Total revenues Revenues Interest expense Interest Expense Net revenues Non-interest expenses: Noninterest Expense [Abstract] Compensation and benefits Labor and Related Expense Non-compensation expenses: Non Labor and Related Expense [Abstract] Non Labor and Related Expense [Abstract] Floor brokerage and clearing fees Floor Brokerage, Exchange and Clearance Fees Underwriting costs Underwriting Costs Underwriting Costs Technology and communications Communications and Information Technology Occupancy and equipment rental Occupancy, Net 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 Earnings before income taxes Income tax expense Income Tax Expense (Benefit) Net earnings Net earnings attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Net earnings attributable to Jefferies Group LLC Net Income (Loss) Attributable to Parent Goodwill and Other Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Revenue from External Customer [Line Items] Revenue from External Customer [Line Items] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] 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 Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Exchange-traded Exchange Traded Options [Member] Cleared OTC Otc Cleared [Member] OTC Cleared [Member] Bilateral OTC Bilateral Otc [Member] Bilateral OTC [Member] Rule change by London Clearing House Rule Change By London Clearing House [Member] Rule Change By London Clearing House [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Fair Value, Assets Derivative Asset, Fair Value, Gross Asset Number of Contracts, Assets Derivative Asset, Number of Instruments Held Fair Value, Liabilities Derivative Liability, Fair Value, Gross Liability Number of Contracts, Liabilities Derivative Liability, Number of Instruments Held Amounts offset in the Consolidated Statements of Financial Condition, Assets Derivative Asset, Fair Value, Amount Offset Against Collateral Amounts offset in the Consolidated Statements of Financial Condition, Liabilities Derivative Liability, Fair Value, Amount Offset Against Collateral Net amounts per Consolidated Statements of Financial Condition, Assets Net amounts per Consolidated Statements of Financial Condition, Liabilities Revenues from Contracts with Customers Revenue from Contract with Customer [Text Block] 8.500% Senior Notes Eight Point Five Percentage Senior Notes Due Two Thousand Nineteen [Member] 8.5% Senior Notes, due 2019. 2.375% Euro Medium Term Notes Two Point Three Seven Five Percentage Euro Medium Term Notes Due Two Thousand Twenty [Member] Two Point Three Seven Five Percentage Euro Medium Term Notes Due Two Thousand Twenty [Member] 6.875% Senior Notes Six Point Eight Seven Five Percentage Senior Notes Due Two Thousand Twenty One [Member] 6.875% Senior Note, due 2021. 2.250% Euro Medium Term Notes Two Point Two Five Percentage Euro Medium Term Notes Due Two Thousand Twenty Two [Member] 2.25 % Euro Medium Term Notes due 2022. 5.125% Senior Notes Five Point One Two Five Percentage Senior Notes Due Two Thousand Twenty Three [Member] 5.125 % Senior Notes due 2023. 6.450% Senior Debentures Six Point Four Five Percentage Senior Debentures Due Two Thousand Twenty Seven [Member] 6.45% Senior Debentures due 2027. 6.250% Senior Debentures Six Point Two Five Percentage Senior Debentures Due Two Thousand Thirty Six [Member] 6.25% Senior Debentures, due 2036. 6.500% Senior Notes Six Point Five Zero Percentage Senior Notes Due Two Thousand Forty Three [Member] 6.50% Senior Notes due 2043. Effective Interest Rate Debt Instrument, Interest Rate, Effective Percentage Commitments and Contingencies Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block] Guarantees Schedule of Guarantor Obligations [Table Text Block] Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Table] Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table] 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 Compensation Plans Compensation Related Costs, General [Text Block] 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 Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income attributable to Jefferies Group LLC Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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] Revenues Net Capital Requirements Regulatory Capital Requirements Disclosure [Text Block] Regulatory capital requirements disclosure. Net Capital Requirements [Table] Net Capital Requirements [Table] Net Capital Requirements [Table] Jefferies LLC 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 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] 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 Sold, Not Yet Purchased Financial Instruments Sold, Not Yet Purchased [Member] Financial Instruments Sold, Not Yet Purchased [Member] Eligible Item or Group for Fair Value Option [Axis]