XML 84 R43.htm IDEA: XBRL DOCUMENT
v3.19.3

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2019
Risk and Insurance Services Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | $ 2,206 | $ 7,203
Fiduciary interest income | 31 | 80
Risk and Insurance Services Segment | EMEA |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 536 | 1,821
Risk and Insurance Services Segment | Asia Pacific |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 242 | 698
Risk and Insurance Services Segment | Latin America |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 110 | 304
Risk and Insurance Services Segment | Total International |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 888 | 2,823
Risk and Insurance Services Segment | U.S./Canada |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 1,014 | 2,972
Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 1,785 | 5,258
Wealth | Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 592 | 1,748
Health | Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 441 | 1,341
Career | Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 247 | 606
Marsh Insurance Group | Risk and Insurance Services Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 1,902 | 5,795
Guy Carpenter Reinsurance Group | Risk and Insurance Services Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 273 | 1,328
Marsh & Guy Carpenter | Risk and Insurance Services Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 2,175 | 7,123
Mercer Consulting Group | Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | 1,280 | 3,695
Oliver Wyman Group Consulting Group | Consulting Segment |  |
Disaggregation of Revenue [Line Items] |  |
Revenue | $ 505 | $ 1,563

X
- Definition Interest income earned on both U.S. and foreign fiduciary funds held in trust. + References No definition available. + Details
Name: | mmc_InterestIncomeFiduciaryAssets
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mmc_RiskandInsuranceServicesSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=us-gaap_EMEAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=srt_AsiaPacificMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=srt_LatinAmericaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=mmc_InternationalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=mmc_UnitedStatesandCanadaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mmc_ConsultingSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=mmc_WealthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=mmc_HealthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=mmc_CareerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=mmc_MarshInsuranceGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=mmc_GuyCarpenterReinsuranceGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=mmc_MarshGuyCarpenterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=mmc_MercerConsultingGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsegmentsAxis=mmc_OliverWymanGroupConsultingGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |