1.0.0.3 false CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 4 Cash Flows from Operating Activities 2 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 5 Net income (loss) 3 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 52324000 52324 false false 2 true true -36081000 -36081 false false No definition available. No authoritative reference available. false 6 Non-cash items included in net income (loss): 3 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 7 Depreciation and amortization 4 lm_DepreciationAndAmortizationExcludingAmortizationOfDeferredSalesCommissions lm false debit duration monetary The aggregate amount of depreciation expense and amortization expense. Depreciation expense is the noncash expense recognized... false false false false false false false false false 1 false true 27644000 27644 false false 2 false true 32450000 32450 false false The aggregate amount of depreciation expense and amortization expense. Depreciation expense is the noncash expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Amortization expense is the noncash expense charged against earnings in the current period that reflects the allocation of the cost of definite lived intangible assets and leasehold improvements over the shorter of their estimated remaining economic lives or the lease term. Excludes the amortization of deferred sales commissions. No authoritative reference available. false 8 Imputed interest for 2.5% convertible senior notes 4 lm_ImputedInterestForConvertibleSeniorNotes lm false debit duration monetary This amount represents the imputed interest, which is a non-cash expense, on contingent convertible debt required by FSP APB... false false false false false false false false false 1 false true 8364000 8364 false false 2 false true 7853000 7853 false false This amount represents the imputed interest, which is a non-cash expense, on contingent convertible debt required by FSP APB 14-1. No authoritative reference available. false 9 Amortization of deferred sales commissions 4 us-gaap_AmortizationOfDeferredSalesCommissions us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 7011000 7011 false false 2 false true 9508000 9508 false false No definition available. No authoritative reference available. false 10 Accretion and amortization of securities discounts and premiums, net 4 us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 2910000 2910 false false 2 false true 1738000 1738 false false No definition available. No authoritative reference available. false 11 Stock-based compensation 4 us-gaap_ShareBasedCompensation us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 12872000 12872 false false 2 false true 15523000 15523 false false No definition available. No authoritative reference available. false 12 Unrealized losses (gains) on investments 4 us-gaap_UnrealizedGainLossOnInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -49287000 -49287 false false 2 false true 13475000 13475 false false No definition available. No authoritative reference available. false 13 Unrealized losses (gains) on fund support 4 lm_UnrealizedGainsLossesOnFundSupport lm false debit duration monetary The aggregate decrease (increase) in the fair value of fund support, including letters of credit, total return swap, and... false false false false false false false false false 1 false true -16502000 -16502 false false 2 false true 266874000 266874 false false The aggregate decrease (increase) in the fair value of fund support, including letters of credit, total return swap, and capital support agreements, for certain proprietary liquidity funds during the period. Amounts also include related financing costs. No authoritative reference available. false 14 Deferred income taxes 4 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 34442000 34442 false false 2 false true -77613000 -77613 false false No definition available. No authoritative reference available. false 15 Other 4 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOther us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1020000 1020 false false 2 false true 154000 154 false false No definition available. No authoritative reference available. false 16 Decrease (increase) in assets excluding acquisitions: 3 us-gaap_IncreaseDecreaseInOperatingAssetsAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 17 Investment advisory and related fees receivable 4 us-gaap_IncreaseDecreaseInAccountsReceivable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -2864000 -2864 false false 2 false true 16689000 16689 false false No definition available. No authoritative reference available. false 18 Net sales (purchases) of trading investments 4 us-gaap_ProceedsFromPaymentsForTradingSecurities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 34603000 34603 false false 2 false true -36353000 -36353 false false No definition available. No authoritative reference available. false 19 Refundable income taxes 4 us-gaap_IncreaseDecreaseInIncomeTaxesReceivable us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 579968000 579968 false false 2 false true 1868000 1868 false false No definition available. No authoritative reference available. false 20 Other receivables 4 us-gaap_IncreaseDecreaseInOtherReceivables us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 79751000 79751 false false 2 false true -10172000 -10172 false false No definition available. No authoritative reference available. false 21 Other assets 4 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 59370000 59370 false false 2 false true 9486000 9486 false false No definition available. No authoritative reference available. false 22 Increase (decrease) in liabilities excluding acquisitions: 3 us-gaap_IncreaseDecreaseInOperatingLiabilitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 23 Accrued compensation 4 lm_IncreaseDecreaseInAccruedCompensation lm false debit duration monetary The net change during the reporting period in the total obligations incurred and payable for obligations related to services... false false false false false false false false false 1 false true -187538000 -187538 false false 2 false true -328839000 -328839 false false The net change during the reporting period in the total obligations incurred and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. No authoritative reference available. false 24 Deferred compensation 4 us-gaap_IncreaseDecreaseInDeferredCompensation us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -5225000 -5225 false false 2 false true -8668000 -8668 false false No definition available. No authoritative reference available. false 25 Accounts payable and accrued expenses 4 lm_IncreaseDecreaseInAccountsPayableAndAccruedExpenses lm false debit duration monetary The net change during the reporting period in the obligation created by or pertaining to goods and services received from... false false false false false false false false false 1 false true -3853000 -3853 false false 2 false true 31396000 31396 false false The net change during the reporting period in the obligation created by or pertaining to goods and services received from vendors; are incurred in connection with contractual obligations, or accumulate over time and for which invoices have not yet been received. This also includes payables for distribution and servicing costs related to the marketing and selling of fund shares. Distribution and servicinig fees are generally determined as a percentage of client assets. No authoritative reference available. false 26 Other liabilities 4 us-gaap_IncreaseDecreaseInOtherOperatingLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -131991000 -131991 false false 2 false true 12981000 12981 false false No definition available. No authoritative reference available. false 27 Cash Provided by (Used for) Operating Activities 3 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 503019000 503019 false false 2 false true -77731000 -77731 false false No definition available. No authoritative reference available. true 28 Cash Flows from Investing Activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 29 Payments for fixed assets 3 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -34037000 -34037 false false 2 false true -26027000 -26027 false false No definition available. No authoritative reference available. false 30 Proceeds from the sale of assets 3 lm_ProceedsFromTheSaleOfAssets lm false debit duration monetary The cash inflow associated with the amount received from the sale of assets or a portion of the company's business, for... false false false false false false false false false 1 false true 0 0 false false 2 false true 181147000 181147 false false The cash inflow associated with the amount received from the sale of assets or a portion of the company's business, for example a segment, division, branch or other business, during the period. No authoritative reference available. false 31 Fund Support: 3 lm_FundSupportInvestingActivitiesAbstract lm false na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 32 Restricted cash, net (principally fund support collateral) 4 us-gaap_IncreaseDecreaseInRestrictedCash us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 6966000 6966 false false 2 false true -264987000 -264987 false false No definition available. No authoritative reference available. false 33 Payments under liquidity fund support arrangements 4 lm_PaymentsUnderLiquidityFundSupportArrangements lm false credit duration monetary The cash outflow for the reporting period associated with Liquidity Fund Support Arrangements. false false false false false false false false false 1 false true 0 0 false false 2 false true -5231000 -5231 false false The cash outflow for the reporting period associated with Liquidity Fund Support Arrangements. No authoritative reference available. false 34 Proceeds from sale of SIV securities 4 lm_FundSupportProceedsFromSaleOfStructuredInvestmentVehicleSecurities lm false debit duration monetary The cash inflow for the reporting period associated with sales of securities issued by Structured Investment Vehicles... false false false false false false false false false 1 false true 0 0 false false 2 false true 81834000 81834 false false The cash inflow for the reporting period associated with sales of securities issued by Structured Investment Vehicles (SIVS's), including SIV's supported under letters of credit, total return swaps, and capital support agreements. No authoritative reference available. false 35 Purchases of SIV securities, net of distributions 4 lm_FundSupportPurchasesOfStructuredInvestmentVehicleSecuritiesNetOfDistributions lm false credit duration monetary The cash outflow for the reporting period associated with purchasing securities issued by Structured Investment Vehicles... false false false false false false false false false 1 false true 0 0 false false 2 false true -58527000 -58527 false false The cash outflow for the reporting period associated with purchasing securities issued by Structured Investment Vehicles (SIV's), including letters of credit, total return swaps, and capital support agreements. Amounts are net of any distribution received from SIV's. No authoritative reference available. false 36 Net increase in securities purchased under agreements to resell 3 us-gaap_ProceedsFromPaymentsForSecuritiesPurchasedUnderAgreementsToResell us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -54910000 -54910 false false No definition available. No authoritative reference available. false 37 Purchases of investment securities 3 lm_PurchasesOfInvestmentSecurities lm false credit duration monetary The cash outflow from purchases of available-for-sale securities and held-to-maturity securities. false false false false false false false false false 1 false true -361000 -361 false false 2 false true -252000 -252 false false The cash outflow from purchases of available-for-sale securities and held-to-maturity securities. No authoritative reference available. false 38 Proceeds from sales and maturities of investment securities 3 lm_ProceedsFromSalesAndMaturitiesOfInvestmentSecurities lm false debit duration monetary The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities... false false false false false false false false false 1 false true 688000 688 false false 2 false true 1237000 1237 false false The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity, or available-for-sale) during the period. No authoritative reference available. false 39 Cash Used for Investing Activities 3 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -26744000 -26744 false false 2 false true -145716000 -145716 false false No definition available. No authoritative reference available. true 40 Cash Flows from Financing Activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false No definition available. false 41 Proceeds from issuance of long-term debt, net 3 us-gaap_ProceedsFromIssuanceOfLongTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 1096362000 1096362 false false No definition available. No authoritative reference available. false 42 Third-party distribution financing, net 3 us-gaap_ProceedsFromRepaymentsOfOtherLongTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -779000 -779 false false 2 false true -598000 -598 false false No definition available. No authoritative reference available. false 43 Repayment of principal on long-term debt 3 us-gaap_RepaymentsOfLongTermDebt us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1287000 -1287 false false 2 false true -1186000 -1186 false false No definition available. No authoritative reference available. false 44 Issuance of common stock 3 us-gaap_ProceedsFromIssuanceOfCommonStock us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1958000 1958 false false 2 false true 13298000 13298 false false No definition available. No authoritative reference available. false 45 Dividends paid 3 us-gaap_PaymentsOfDividends us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -34337000 -34337 false false 2 false true -33816000 -33816 false false No definition available. No authoritative reference available. false 46 Net (redemptions/distributions paid)/subscriptions received from noncontrolling interest holders 3 us-gaap_ProceedsFromPaymentsToMinorityShareholders us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 3336000 3336 false false 2 false true -144000 -144 false false No definition available. No authoritative reference available. false 47 Excess tax benefit associated with stock-based compensation 3 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 1236000 1236 false false No definition available. No authoritative reference available. false 48 Cash (Used For) Provided by Financing Activities 3 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -31109000 -31109 false false 2 false true 1075152000 1075152 false false No definition available. No authoritative reference available. true 49 Effect of Exchange Rate Changes on Cash 2 us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 9655000 9655 false false 2 false true 696000 696 false false No definition available. No authoritative reference available. false 50 Net Increase in Cash and Cash Equivalents 2 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 454821000 454821 false false 2 false true 852401000 852401 false false No definition available. No authoritative reference available. true 51 Cash and Cash Equivalents at Beginning of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 1084474000 1084474 false false 2 false true 1463554000 1463554 false false No definition available. No authoritative reference available. false 52 Cash and Cash Equivalents at End of Period 2 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 true true 1539295000 1539295 false false 2 true true 2315955000 2315955 false false No definition available. No authoritative reference available. false false 2 49 false Thousands UnKnown UnKnown false true