XML 78 R63.htm IDEA: XBRL DOCUMENT v2.4.1.9
Debt (Estimated Fair Value of Significant Financial Instruments) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Carrying Amount [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term debt $ 61mmc_LongTermDebtandCapitalLeaseObligationCurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 $ 11mmc_LongTermDebtandCapitalLeaseObligationCurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
Long-term debt 3,828mmc_LongTermDebtandCapitalLeaseObligationNoncurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 3,376mmc_LongTermDebtandCapitalLeaseObligationNoncurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Short-term debt 61mmc_LongTermDebtandCapitalLeaseObligationCurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 11mmc_LongTermDebtandCapitalLeaseObligationCurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
Long-term debt $ 4,009mmc_LongTermDebtandCapitalLeaseObligationNoncurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 $ 3,493mmc_LongTermDebtandCapitalLeaseObligationNoncurrentFairValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember