| Investments In Affiliates Accounted For Using The Equity Method (Details) (USD $)Share data in Millions, unless otherwise specified
 | 12 Months Ended | 1 Months Ended | 3 Months Ended |  | 
      
        | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | May 31, 2013 | Jan. 18, 2013 | Mar. 31, 2013 | May 01, 2013 | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Investments in affiliates, accounted for using the equity method | $ 851,000,000us-gaap_EquityMethodInvestments | $ 3,299,000,000us-gaap_EquityMethodInvestments |  |  |  |  |  | 
      
        | Share of earnings (losses) of affiliates, net | (113,000,000)us-gaap_IncomeLossFromEquityMethodInvestments | (32,000,000)us-gaap_IncomeLossFromEquityMethodInvestments | 1,346,000,000us-gaap_IncomeLossFromEquityMethodInvestments |  |  |  |  | 
      
        | Income Tax Expense (Benefit) | 66,000,000us-gaap_IncomeTaxExpenseBenefit | (135,000,000)us-gaap_IncomeTaxExpenseBenefit | 469,000,000us-gaap_IncomeTaxExpenseBenefit |  |  |  |  | 
      
        | Charter Communications |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Equity Method Investment, Aggregate Cost |  |  |  |  |  |  | 2,600,000,000us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 | 
      
        | excess amortization in share of earnings (loss) | 60,000,000lmca_ExcessAmortizationInShareOfEarningsLoss / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 | 51,000,000lmca_ExcessAmortizationInShareOfEarningsLoss / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 |  |  |  |  |  | 
      
        | Percentage ownership |  |  |  |  |  |  | 27.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 | 
      
        | Investments in affiliates, accounted for using the equity method |  | 2,395,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 |  |  |  |  |  | 
      
        | Purchase of shares in equity method investee |  |  |  | 26.9lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 |  |  |  | 
      
        | Share of earnings (losses) of affiliates, net | (94,000,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 | (83,000,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_CharterCommunicationsMember
 |  |  |  |  |  | 
      
        | SIRIUS XM |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Purchase of shares in equity method investee |  |  |  |  | 50.0lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 | 50.0lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 |  | 
      
        | Share of earnings (losses) of affiliates, net |  | 8,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 | 1,367,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 |  |  |  |  | 
      
        | Share of tax benefit of affiliates |  |  | 1,229,000,000lmca_IncomeTaxBenefitFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 |  |  |  |  | 
      
        | Live Nation |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Percentage ownership | 27.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  |  |  | 
      
        | Investments in affiliates, accounted for using the equity method | 396,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | 409,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  |  | 
      
        | Equity Method Investment, Quoted Market Value | 1,403,000,000us-gaap_EquityMethodInvestmentQuotedMarketValue / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  |  |  | 
      
        | Purchase of shares in equity method investee | 1.7lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | 1.7lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | 11.0lmca_PurchaseOfSharesInEquityMethodInvestee / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  | 
      
        | Payments to Acquire Equity Method Investments | 39,000,000us-gaap_PaymentsToAcquireEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | 19,000,000us-gaap_PaymentsToAcquireEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | 107,000,000us-gaap_PaymentsToAcquireEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  | 
      
        | Share of earnings (losses) of affiliates, net | (30,000,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | (18,000,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 | (45,000,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_LiveNationMember
 |  |  |  |  | 
      
        | Sirius XM Canada |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Percentage ownership | 37.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 |  |  |  |  |  |  | 
      
        | Investments in affiliates, accounted for using the equity method | 237,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 | 273,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 |  |  |  |  |  | 
      
        | Equity Method Investment, Quoted Market Value | 247,000,000us-gaap_EquityMethodInvestmentQuotedMarketValue / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 |  |  |  |  |  |  | 
      
        | Share of earnings (losses) of affiliates, net | 5,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 | 7,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmCanadaMember
 |  |  |  |  |  | 
      
        | Equity method investment, other |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Investments in affiliates, accounted for using the equity method | 218,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_EquityMethodInvestmentOtherMember
 | 222,000,000us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_EquityMethodInvestmentOtherMember
 |  |  |  |  |  | 
      
        | Share of earnings (losses) of affiliates, net | 6,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_EquityMethodInvestmentOtherMember
 | 54,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_EquityMethodInvestmentOtherMember
 | 24,000,000us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_EquityMethodInvestmentOtherMember
 |  |  |  |  | 
      
        | SIRIUS XM | SIRIUS XM |  |  |  |  |  |  |  | 
      
        | Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  | 
      
        | Income Tax Expense (Benefit) |  |  | $ 3,000,000,000us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis
 = lmca_SiriusXmMember
 / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
 = lmca_SiriusXmMember
 |  |  |  |  |