XML 92 R77.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Retirement Benefits (Reconciliation of Net Actuarial Loss) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Pension Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Total recognized as component of net periodic benefit cost (credit) | $ (240) | $ (222) | $ (234)
Post-retirement Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Total recognized as component of net periodic benefit cost (credit) | 2 | 1 | 0
Net Actuarial (Loss) Gain |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Amortization of net loss | 208 | 161 | 102
U.S. | Pension Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Other | 0 | 0 |
U.S. | Post-retirement Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Other | 0 | 1 |
U.S. | Net Actuarial (Loss) Gain | Pension Benefits |  |  |
Reconciliation of unrecognized net actuarial gain loss [Roll Forward] |  |  |
Beginning balance | (2,446) | (2,114) |
Recognized as component of net periodic benefit cost (credit): |  |  |
Amortization of net loss | 90 | 72 |
Liability experience | 227 | (650) |
Asset experience | 353 | 246 |
Other | (1) | 0 |
Total amount recognized as change in plan assets and benefit obligations | 579 | (404) |
Ending balance | (1,777) | (2,446) | (2,114)
U.S. | Net Actuarial (Loss) Gain | Post-retirement Benefits |  |  |
Reconciliation of unrecognized net actuarial gain loss [Roll Forward] |  |  |
Beginning balance | 3 | 4 |
Recognized as component of net periodic benefit cost (credit): |  |  |
Amortization of net loss | (1) | 0 |
Liability experience | 1 | (1) |
Asset experience | 0 | 0 |
Other | 0 | 0 |
Total amount recognized as change in plan assets and benefit obligations | 1 | (1) |
Ending balance | 3 | 3 | 4
Non-U.S. | Pension Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Total recognized as component of net periodic benefit cost (credit) | (187) | (162) | (176)
Non-U.S. | Post-retirement Benefits |  |  |
Recognized as component of net periodic benefit cost (credit): |  |  |
Total recognized as component of net periodic benefit cost (credit) | 2 | 0 | 0
Non-U.S. | Net Actuarial (Loss) Gain | Pension Benefits |  |  |
Reconciliation of unrecognized net actuarial gain loss [Roll Forward] |  |  |
Beginning balance | (3,467) | (3,055) |
Recognized as component of net periodic benefit cost (credit): |  |  |
Amortization of net loss | 116 | 89 |
Effect of settlement | 5 | 3 |
Total recognized as component of net periodic benefit cost (credit) | 121 | 92 |
Liability experience | 617 | (1,273) |
Asset experience | (199) | 916 |
Effect of curtailment | 2 | 0 |
Total amount recognized as change in plan assets and benefit obligations | 420 | (357) |
Exchange rate adjustments | 22 | (147) |
Ending balance | (2,904) | (3,467) | (3,055)
Non-U.S. | Net Actuarial (Loss) Gain | Post-retirement Benefits |  |  |
Reconciliation of unrecognized net actuarial gain loss [Roll Forward] |  |  |
Beginning balance | (16) | (5) |
Recognized as component of net periodic benefit cost (credit): |  |  |
Amortization of net loss | 2 | 0 |
Effect of settlement | 0 | 0 |
Total recognized as component of net periodic benefit cost (credit) | 2 | 0 |
Liability experience | 4 | (10) |
Asset experience | 0 | 0 |
Effect of curtailment | 0 | 0 |
Total amount recognized as change in plan assets and benefit obligations | 4 | (10) |
Exchange rate adjustments | 0 | (1) |
Ending balance | $ (10) | $ (16) | $ (5)

X
- Definition Accumulated Other Comprehensive Income (Loss) [Roll Forward] + References No definition available. + Details
Name: | mmc_AccumulatedOtherComprehensiveIncomeLossRollForward
Namespace Prefix: | mmc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Finalization Of Pension And Non Pension Postretirement Plan Valuation, Settlement, Before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationSettlementBeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Pension And Other Postretirement Benefit Plans Adjustment Excluding Foreign Currency Transaction, Adjustment, Before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentExcludingForeignCurrencyTransactionAdjustmentBeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Other, Before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansOtherBeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Foreign Currency Exchange Adjustments Arising During Period, Before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyExchangeAdjustmentsArisingDuringPeriodBeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) On Plan Assets Arising During Period, before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansNetUnamortizedGainLossOnPlanAssetsArisingDuringPeriodbeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) On Plan Obligations Arising During Period, before Tax + References No definition available. + Details
Name: | mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansNetUnamortizedGainLossOnPlanObligationsArisingDuringPeriodbeforeTax
Namespace Prefix: | mmc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, including portion attributable to noncontrolling interest. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners). + References No definition available. + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTaxAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, before tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e689-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount before tax of reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442411-227067 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32136-110900 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124442407-227067 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669686-108580 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900 + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanSponsorLocationAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanSponsorLocationAxis=us-gaap_ForeignPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |