XML 86 R74.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Segment Information (Details of Operating Segment Revenue) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ 3,504 | $ 3,341 | $ 11,238 | $ 10,339
Operating Segments |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 3,519 | 3,350 | 11,277 | 10,373
Operating Segments | Risk and Insurance Services Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,863 | 1,763 | 6,303 | 5,668
Operating Segments | Risk and Insurance Services Segment | Marsh Insurance Group |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,643 | 1,490 | 5,106 | 4,713
Operating Segments | Risk and Insurance Services Segment | Guy Carpenter Reinsurance Group |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 220 | 273 | 1,197 | 955
Operating Segments | Consulting Segment |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,656 | 1,587 | 4,974 | 4,705
Operating Segments | Consulting Segment | Mercer Consulting Group |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 1,175 | 1,149 | 3,504 | 3,335
Operating Segments | Consulting Segment | Oliver Wyman Group Consulting Group |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | 481 | 438 | 1,470 | 1,370
Corporate and Eliminations |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Revenue | $ (15) | $ (9) | $ (39) | $ (34)

X
- Definition Amount, including 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix: | us-gaap_
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_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mmc_RiskandInsuranceServicesSegmentMember
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_StatementBusinessSegmentsAxis=mmc_ConsultingSegmentMember
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: |

X
- Details
Name: | srt_ConsolidationItemsAxis=mmc_CorporateAndEliminationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |