| Investments In Available-For-Sale Securities And Other Cost Investments (Details 1) (USD $) In Millions, unless otherwise specified | 12 Months Ended | |
|---|---|---|
| Dec. 31, 2014 | Dec. 31, 2013 | |
| Equity Securities | 听 | 听 | 
| Gross unrealized holding gains | 听 | $ 6us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember | 
| Debt Securities | 听 | 听 | 
| Gross unrealized holding gains | 听 | 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember | 
| SIRIUS XM [Member] | 听 | 听 | 
| Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net | $ 40us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = lmca_SiriusXmDebtSecuritiesMember | 听 | 
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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