| Debt (Details 2) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | 
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| SIRIUS XM | |
| Debt Instrument [Line Items] | |
| Shares pledged as collateral under loan | 150.0lmca_Sharespledgedascollateralunderloan / invest_InvestmentIssuerAxis = lmca_SiriusXmMember | 
| Share value | $ 525us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue / invest_InvestmentIssuerAxis = lmca_SiriusXmMember | 
| Live Nation | |
| Debt Instrument [Line Items] | |
| Shares pledged as collateral under loan | 12.0lmca_Sharespledgedascollateralunderloan / invest_InvestmentIssuerAxis = lmca_LiveNationMember | 
| Share value | 313us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue / invest_InvestmentIssuerAxis = lmca_LiveNationMember | 
| Time Warner Inc | |
| Debt Instrument [Line Items] | |
| Shares pledged as collateral under loan | 3.6lmca_Sharespledgedascollateralunderloan / invest_InvestmentIssuerAxis = lmca_TimeWarnerIncMember | 
| Share value | 309us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue / invest_InvestmentIssuerAxis = lmca_TimeWarnerIncMember | 
| Viacom, Inc. | |
| Debt Instrument [Line Items] | |
| Shares pledged as collateral under loan | 3.5lmca_Sharespledgedascollateralunderloan / invest_InvestmentIssuerAxis = lmca_ViacomIncMember | 
| Share value | 266us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue / invest_InvestmentIssuerAxis = lmca_ViacomIncMember | 
| Time, Inc. [Member] | |
| Debt Instrument [Line Items] | |
| Shares pledged as collateral under loan | 1.0lmca_Sharespledgedascollateralunderloan / invest_InvestmentIssuerAxis = lmca_TimeInc.Member | 
| Share value | $ 13us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAtFairValue / invest_InvestmentIssuerAxis = lmca_TimeInc.Member | 
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- Definition Shares pledged as collateral under loan No definition available. 
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- Definition The fair value as of the balance sheet date of financial instruments and other positions owned by the entity and pledged to counterparties as collateral, including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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