1.0.0.3 false CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data 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 Operating Revenues 2 us-gaap_RevenuesAbstract 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 Separate accounts 3 lm_InvestmentAdvisoryFeesSeparateAccounts lm false credit duration monetary Revenue recognized in the period for asset-based fees earned for providing investment advice, research and other services for... false false false false false false false false false 1 true true 190888000 190888 false false 2 true true 316675000 316675 false false Revenue recognized in the period for asset-based fees earned for providing investment advice, research and other services for customers relating to separately managed accounts. These fees are generally determined as a percentage of assets under management. No authoritative reference available. false 6 Funds 3 lm_InvestmentAdvisoryFeesFunds lm false credit duration monetary Revenue recognized in the period for asset-based fees earned for providing investment advice, research and other services for... false false false false false false false false false 1 false true 328024000 328024 false false 2 false true 569558000 569558 false false Revenue recognized in the period for asset-based fees earned for providing investment advice, research and other services for customers relating to management of mutual funds and closed-end funds. No authoritative reference available. false 7 Performance fees 3 us-gaap_PerformanceFees us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 5684000 5684 false false 2 false true 10145000 10145 false false No definition available. No authoritative reference available. false 8 Distribution and service fees 3 lm_DistributionAndServiceFees lm false credit duration monetary Fees earned from funds (including 12b-1 fees) to reimburse the distributor for the costs of marketing and selling fund shares... false false false false false false false false false 1 false true 86701000 86701 false false 2 false true 153499000 153499 false false Fees earned from funds (including 12b-1 fees) to reimburse the distributor for the costs of marketing and selling fund shares and servicing proprietary funds. These fees are generally determined as a percentage of retail and institutional client assets. Reported amounts also include fees earned from providing client or shareholder servicing, record keeping, or administrative services to proprietary funds. No authoritative reference available. false 9 Other 3 us-gaap_RevenueOtherFinancialServices us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1787000 1787 false false 2 false true 4154000 4154 false false No definition available. No authoritative reference available. false 10 Total operating revenues 3 us-gaap_Revenues us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 613084000 613084 false false 2 false true 1054031000 1054031 false false No definition available. No authoritative reference available. true 11 Operating Expenses 2 us-gaap_CostsAndExpensesAbstract 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 12 Compensation and benefits 3 us-gaap_LaborAndRelatedExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 268812000 268812 false false 2 false true 377668000 377668 false false No definition available. No authoritative reference available. false 13 Distribution and servicing 3 lm_DistributionAndServicing lm false debit duration monetary Costs related to the marketing and selling of fund shares and servicing proprietary funds. Fees are generally determined as... false false false false false false false false false 1 false true 172464000 172464 false false 2 false true 307873000 307873 false false Costs related to the marketing and selling of fund shares and servicing proprietary funds. Fees are generally determined as a percentage of client assets. No authoritative reference available. false 14 Communications and technology 3 us-gaap_CommunicationsAndInformationTechnology us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 40490000 40490 false false 2 false true 50286000 50286 false false No definition available. No authoritative reference available. false 15 Occupancy 3 us-gaap_OccupancyNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 32584000 32584 false false 2 false true 34144000 34144 false false No definition available. No authoritative reference available. false 16 Amortization of intangible assets 3 us-gaap_AmortizationOfIntangibleAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 5628000 5628 false false 2 false true 9624000 9624 false false No definition available. No authoritative reference available. false 17 Other 3 us-gaap_OtherExpenses us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 34791000 34791 false false 2 false true 45489000 45489 false false No definition available. No authoritative reference available. false 18 Total operating expenses 3 us-gaap_CostsAndExpenses us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 554769000 554769 false false 2 false true 825084000 825084 false false No definition available. No authoritative reference available. true 19 Operating Income (Loss) 2 us-gaap_OperatingIncomeLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 58315000 58315 false false 2 false true 228947000 228947 false false No definition available. No authoritative reference available. true 20 Other Income (Expense) 2 us-gaap_NonoperatingIncomeExpenseAbstract 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 21 Interest income 3 us-gaap_InvestmentIncomeInterest us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1821000 1821 false false 2 false true 23268000 23268 false false No definition available. No authoritative reference available. false 22 Interest expense 3 us-gaap_InterestExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -43390000 -43390 false false 2 false true -44463000 -44463 false false No definition available. No authoritative reference available. false 23 Fund support 3 lm_FundSupportIncomeExpense lm false credit duration monetary Represents the aggregate amount of realized and unrealized gains and (losses) on fund support, including letters of credit,... false false false false false false false false false 1 false true 17558000 17558 false false 2 false true -266874000 -266874 false false Represents the aggregate amount of realized and unrealized gains and (losses) on fund support, including letters of credit, total return swaps, and capital support agreements, relating to certain proprietary liquidity funds. Amounts include the contractual obligations and benefits relating to the change in fair value of supported assets and related financing costs. No authoritative reference available. false 24 Other 3 us-gaap_OtherNonoperatingIncomeExpense us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 46400000 46400 false false 2 false true 1307000 1307 false false No definition available. No authoritative reference available. false 25 Total other income (expense) 3 us-gaap_NonoperatingIncomeExpense us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 22389000 22389 false false 2 false true -286762000 -286762 false false No definition available. No authoritative reference available. true 26 Income (Loss) from Operations before Income Tax Provision (Benefit) 2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 80704000 80704 false false 2 false true -57815000 -57815 false false No definition available. No authoritative reference available. true 27 Income tax provision (benefit) 2 us-gaap_IncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 28380000 28380 false false 2 false true -21734000 -21734 false false No definition available. No authoritative reference available. false 28 Net Income (Loss) 2 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 52324000 52324 false false 2 false true -36081000 -36081 false false No definition available. No authoritative reference available. true 29 Less: Net income attributable to noncontrolling interests 2 us-gaap_NetIncomeLossAttributableToNoncontrollingInterest us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 2270000 2270 false false 2 false true 46000 46 false false No definition available. No authoritative reference available. false 30 Net Income (Loss) attributable to Legg Mason, Inc. 2 us-gaap_NetIncomeLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 50054000 50054 false false 2 true true -36127000 -36127 false false No definition available. No authoritative reference available. true 31 Net Income (Loss) per Share attributable to Legg Mason, Inc. common shareholders: 2 us-gaap_EarningsPerShareAbstract 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 32 Basic (in dollars per share) 3 us-gaap_EarningsPerShareBasic us-gaap true na duration decimal No definition available. false false false false false false false false true 1 true true 0.35 0.35 false false 2 true true -0.26 -0.26 false false No definition available. No authoritative reference available. false 33 Diluted (in dollars per share) 3 us-gaap_EarningsPerShareDiluted us-gaap true na duration decimal No definition available. false false false false false false false false true 1 true true 0.35 0.35 false false 2 true true -0.26 -0.26 false false No definition available. No authoritative reference available. false 34 Weighted Average Number of Shares Outstanding: 2 us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract 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 35 Basic (in shares) 3 us-gaap_WeightedAverageNumberOfSharesOutstandingBasic us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 142006000 142006 false false 2 false true 140505000 140505 false false No definition available. No authoritative reference available. false 36 Diluted (in shares) 3 us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 143126000 143126 false false 2 false true 140505000 140505 false false No definition available. No authoritative reference available. false 37 Dividends Declared per Share (in dollars per share) 2 us-gaap_CommonStockDividendsPerShareDeclared us-gaap true na duration decimal No definition available. false false false false false false false false true 1 true true 0.03 0.03 false false 2 true true 0.24 0.24 false false No definition available. No authoritative reference available. false false 2 34 false Thousands Thousands Hundreds false true