$MMC
MARSH & MCLENNAN COMPANIES, INC. Stock $mmc

$mmc Overview Financials Valuation SEC Filings Company Website

2021 Q4 Form 10-K Financial Statement

#000006270922000009 Filed on February 16, 2022

Income Statement

Concept	2021 Q4	2021	2020 Q4
Revenue	$5.137B	$19.82B	$4.416B
YoY Change	16.33%	15.07%	3.56%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin	$2.905B	$11.43B	$2.650B
YoY Change	9.62%	12.79%	6.94%
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$178.0M	$747.0M	$194.0M
YoY Change	-8.25%	0.81%	16.17%
% of Gross Profit
Operating Expenses	$4.119B	$15.51B	$3.775B
YoY Change	9.11%	9.54%	6.97%
Operating Profit		$4.312B	$571.0M
YoY Change		40.64%	-3.55%
Interest Expense	-$91.00M	$444.0M	-$101.0M
YoY Change	-9.9%	-13.79%	-17.89%
% of Operating Profit		10.3%	-17.69%
Other Income/Expense, Net	$66.00M	$277.0M	$70.00M
YoY Change	-5.71%	7.78%	12.9%
Pretax Income	$961.0M	$4.208B	$540.0M
YoY Change	77.96%	50.66%	1.69%
Income Tax	$154.0M	$1.034B	$161.0M
% Of Pretax Income	16.02%	24.57%	29.81%
Net Earnings	$803.0M	$3.143B	$374.0M
YoY Change	114.71%	55.9%	-4.35%
Net Earnings / Revenue	15.63%	15.86%	8.47%
Basic Earnings Per Share		$6.20	$0.74
Diluted Earnings Per Share	$1.565M	$6.13	$0.73
COMMON SHARES
Basic Shares Outstanding	504.9M shares	507.0M shares	507.2M shares
Diluted Shares Outstanding		513.0M shares

Balance Sheet

Concept	2021 Q4	2021	2020 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$1.752B	$1.752B	$2.089B
YoY Change	-16.13%	-16.13%	80.87%
Cash & Equivalents	$1.752B	$1.752B	$2.089B
Short-Term Investments
Other Short-Term Assets	$926.0M	$636.0M	$740.0M
YoY Change	25.14%	-14.05%	9.31%
Inventory
Prepaid Expenses
Receivables	$5.876B	$5.876B	$5.326B
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$8.264B	$8.264B	$8.155B
YoY Change	1.34%	1.34%	15.38%
LONG-TERM ASSETS
Property, Plant & Equipment	$847.0M	$2.715B	$856.0M
YoY Change	-1.05%	-1.27%	-0.23%
Goodwill	$16.32B		$15.52B
YoY Change	5.16%		5.77%
Intangibles	$2.810B		$2.699B
YoY Change	4.11%		-2.7%
Long-Term Investments	$207.0M	$207.0M	$280.0M
YoY Change	-26.07%		-35.48%
Other Assets	$1.461B	$4.075B	$1.458B
YoY Change	0.21%	3.74%	-17.02%
Total Long-Term Assets	$26.12B	$26.12B	$24.89B
YoY Change	4.94%	4.94%	2.49%
TOTAL ASSETS
Total Short-Term Assets	$8.264B	$8.264B	$8.155B
Total Long-Term Assets	$26.12B	$26.12B	$24.89B
Total Assets	$34.39B	$34.39B	$33.05B
YoY Change	4.05%	4.05%	5.4%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$3.165B	$3.165B	$3.050B
YoY Change	3.77%	3.77%	11.07%
Accrued Expenses	$3.274B	$3.274B	$2.742B
YoY Change	19.4%	19.4%	8.0%
Deferred Revenue
YoY Change
Short-Term Debt	$17.00M	$0.00	$517.0M
YoY Change	-96.71%		-57.45%
Long-Term Debt Due	$17.00M	$17.00M	$517.0M
YoY Change	-96.71%	-96.71%	-57.45%
Total Short-Term Liabilities	$6.654B	$6.654B	$6.556B
YoY Change	1.49%	1.49%	-1.84%
LONG-TERM LIABILITIES
Long-Term Debt	$10.93B	$10.93B	$10.80B
YoY Change	1.27%	1.27%	0.51%
Other Long-Term Liabilities	$1.712B	$5.579B	$1.485B
YoY Change	15.29%	-13.33%	6.3%
Total Long-Term Liabilities	$12.65B	$16.51B	$12.28B
YoY Change	2.96%	-4.18%	1.18%
TOTAL LIABILITIES
Total Short-Term Liabilities	$6.654B	$6.654B	$6.556B
Total Long-Term Liabilities	$12.65B	$16.51B	$12.28B
Total Liabilities	$19.30B	$23.38B	$18.84B
YoY Change	2.45%	-2.36%	0.11%
SHAREHOLDERS EQUITY
Retained Earnings	$18.39B		$16.27B
YoY Change	13.01%		7.06%
Common Stock	$1.673B		$1.504B
YoY Change	11.24%		5.69%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$4.478B		$3.562B
YoY Change	25.72%		-5.62%
Treasury Stock Shares	57.11M shares		52.91M shares
Shareholders Equity	$11.01B	$11.01B	$9.104B
YoY Change
Total Liabilities & Shareholders Equity	$34.39B	$34.39B	$33.05B
YoY Change	4.05%	4.05%	5.4%

Cashflow Statement

Concept	2021 Q4	2021	2020 Q4
OPERATING ACTIVITIES
Net Income	$803.0M	$3.143B	$374.0M
YoY Change	114.71%	55.9%	-4.35%
Depreciation, Depletion And Amortization	$178.0M	$747.0M	$194.0M
YoY Change	-8.25%	0.81%	16.17%
Cash From Operating Activities	$1.442B	$3.516B	$1.383B
YoY Change	4.27%	3.96%	29.25%
INVESTING ACTIVITIES
Capital Expenditures	-$138.0M	$406.0M	-$70.00M
YoY Change	97.14%	16.67%	-48.91%
Acquisitions		$859.0M
YoY Change		32.77%
Other Investing Activities	-$437.0M	-$4.000M	-$98.00M
YoY Change	345.92%	-233.33%	226.67%
Cash From Investing Activities	-$575.0M	-$1.164B	-$168.0M
YoY Change	242.26%	46.78%	0.6%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$1.159B
YoY Change
Debt Paid & Issued, Net		$1.016B
YoY Change		-59.6%
Cash From Financing Activities	749.0M	-$1.297B	-1.717B
YoY Change	-143.62%	40.22%	66.54%
NET CHANGE
Cash From Operating Activities	1.442B	$3.516B	1.383B
Cash From Investing Activities	-575.0M	-$1.164B	-168.0M
Cash From Financing Activities	749.0M	-$1.297B	-1.717B
Net Change In Cash	1.616B	$700.0M	-502.0M
YoY Change	-421.91%	-67.82%	292.19%
FREE CASH FLOW
Cash From Operating Activities	$1.442B	$3.516B	$1.383B
Capital Expenditures	-$138.0M	$406.0M	-$70.00M
Free Cash Flow	$1.580B	$3.110B	$1.453B
YoY Change	8.74%	2.5%	20.38%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2021Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2021	dei	Entity Central Index Key EntityCentralIndexKey	0000062709
CY2021	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
CY2021	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2021	dei	Amendment Flag AmendmentFlag	false
CY2021	dei	City Area Code CityAreaCode	212
CY2021	dei	Local Phone Number LocalPhoneNumber	345-5000
CY2021	dei	Document Annual Report DocumentAnnualReport	true
CY2021	dei	Document Period End Date DocumentPeriodEndDate	2021-12-31
CY2021	dei	Security12b Title Security12bTitle	Common Stock, par value $1.00 per share
CY2021	dei	Trading Symbol TradingSymbol	MMC
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
CY2021	dei	Document Type DocumentType	10-K
CY2021	dei	Document Period End Date DocumentPeriodEndDate	2021-12-31
CY2021	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2021	dei	Document Transition Report DocumentTransitionReport	false
CY2021	dei	Entity File Number EntityFileNumber	1-5998
CY2021	dei	Entity Registrant Name EntityRegistrantName	Marsh & McLennan Companies, Inc.
CY2021	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2021	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	36-2668272
CY2021	dei	Entity Address Address Line1 EntityAddressAddressLine1	1166 Avenue of the Americas
CY2021	dei	Entity Address City Or Town EntityAddressCityOrTown	New York
CY2021	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
CY2021	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	10036
CY2021	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2021	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2021	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
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CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	6556000000	USD
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CY2020Q4	mmc	Fiduciary Liabilities Gross Noncurrent FiduciaryLiabilitiesGrossNoncurrent	8585000000	USD
CY2021Q4	mmc	Cashand Investments Heldin Fiduciary Capacity Noncurrent CashandInvestmentsHeldinFiduciaryCapacityNoncurrent	9622000000	USD
CY2020Q4	mmc	Cashand Investments Heldin Fiduciary Capacity Noncurrent CashandInvestmentsHeldinFiduciaryCapacityNoncurrent	8585000000	USD
CY2021Q4	mmc	Fiduciary Liabilities Net Noncurrent FiduciaryLiabilitiesNetNoncurrent	0	USD
CY2020Q4	mmc	Fiduciary Liabilities Net Noncurrent FiduciaryLiabilitiesNetNoncurrent	0	USD
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CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	1924000000	USD
CY2021Q4	mmc	Liability For Errors And Omissions LiabilityForErrorsAndOmissions	355000000	USD
CY2020Q4	mmc	Liability For Errors And Omissions LiabilityForErrorsAndOmissions	366000000	USD
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CY2021Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
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CY2021Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1
CY2021Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	1600000000	shares
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	1600000000	shares
CY2021Q4	us-gaap	Minority Interest MinorityInterest	213000000	USD
CY2020Q4	us-gaap	Minority Interest MinorityInterest	156000000	USD
CY2021Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	560641640	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	560641640	shares
CY2021Q4	us-gaap	Common Stock Value CommonStockValue	561000000	USD
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	561000000	USD
CY2021Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	1112000000	USD
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	943000000	USD
CY2021Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	18389000000	USD
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CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-5110000000	USD
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CY2021Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	57105619	shares
CY2020Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	52914550	shares
CY2021Q4	us-gaap	Treasury Stock Value TreasuryStockValue	4478000000	USD
CY2020Q4	us-gaap	Treasury Stock Value TreasuryStockValue	3562000000	USD
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	11222000000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	9260000000	USD
CY2021Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	34388000000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	33049000000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	3174000000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	2046000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1773000000	USD
CY2021	us-gaap	Depreciation Depreciation	382000000	USD
CY2020	us-gaap	Depreciation Depreciation	390000000	USD
CY2019	us-gaap	Depreciation Depreciation	333000000	USD
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	365000000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	351000000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	314000000	USD
CY2021	mmc	Leases Right Of Use Asset Amortization LeasesRightOfUseAssetAmortization	327000000	USD
CY2019	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	27000000	USD
CY2021	us-gaap	Deconsolidation Gain Or Loss Amount DeconsolidationGainOrLossAmount	267000000	USD
CY2020	us-gaap	Deconsolidation Gain Or Loss Amount DeconsolidationGainOrLossAmount	0	USD
CY2019	us-gaap	Deconsolidation Gain Or Loss Amount DeconsolidationGainOrLossAmount	0	USD
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-63000000	USD
CY2020	mmc	Leases Right Of Use Asset Amortization LeasesRightOfUseAssetAmortization	355000000	USD
CY2019	mmc	Leases Right Of Use Asset Amortization LeasesRightOfUseAssetAmortization	315000000	USD
CY2021	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	27000000	USD
CY2020	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	-22000000	USD
CY2021	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
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CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	40000000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	84000000	USD
CY2021	us-gaap	Gain Loss On Investments GainLossOnInvestments	61000000	USD
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CY2021	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	252000000	USD
CY2020	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	75000000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	108000000	USD
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CY2019	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-56000000	USD
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	348000000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	290000000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	252000000	USD
CY2021	mmc	Acquisition Related Hedging Expense AcquisitionRelatedHedgingExpense	0	USD
CY2020	mmc	Acquisition Related Hedging Expense AcquisitionRelatedHedgingExpense	0	USD
CY2019	mmc	Acquisition Related Hedging Expense AcquisitionRelatedHedgingExpense	8000000	USD
CY2019	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	130000000	USD
CY2021	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	166000000	USD
CY2020	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	66000000	USD
CY2019	us-gaap	Increase Decrease In Other Current Assets IncreaseDecreaseInOtherCurrentAssets	13000000	USD
CY2021	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	215000000	USD
CY2020	us-gaap	Increase Decrease In Other Noncurrent Assets IncreaseDecreaseInOtherNoncurrentAssets	-86000000	USD
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CY2021	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	225000000	USD
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CY2020	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	207000000	USD
CY2019	us-gaap	Increase Decrease In Employee Related Liabilities IncreaseDecreaseInEmployeeRelatedLiabilities	154000000	USD
CY2021	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-45000000	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	60000000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	42000000	USD
CY2021	mmc	Pensionand Other Postretirement Benefit Contributions In Excessof Current Year Expense PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense	372000000	USD
CY2020	mmc	Pensionand Other Postretirement Benefit Contributions In Excessof Current Year Expense PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense	356000000	USD
CY2019	mmc	Pensionand Other Postretirement Benefit Contributions In Excessof Current Year Expense PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense	369000000	USD
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CY2020	mmc	Increase Decreasein Operating Lease Liabilities IncreaseDecreaseinOperatingLeaseLiabilities	-351000000	USD
CY2019	mmc	Increase Decreasein Operating Lease Liabilities IncreaseDecreaseinOperatingLeaseLiabilities	-327000000	USD
CY2021	mmc	Effectof Exchange Rateon Cashand Cash Equivalentsfrom Operating Activities EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities	-38000000	USD
CY2020	mmc	Effectof Exchange Rateon Cashand Cash Equivalentsfrom Operating Activities EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities	32000000	USD
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CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	3382000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	2361000000	USD
CY2021	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	1159000000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	485000000	USD
CY2021	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	0	USD
CY2020	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	1000000000	USD
CY2019	us-gaap	Proceeds From Lines Of Credit ProceedsFromLinesOfCredit	300000000	USD
CY2021	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	743000000	USD
CY2020	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	737000000	USD
CY2019	us-gaap	Proceeds From Issuance Of Debt ProceedsFromIssuanceOfDebt	6459000000	USD
CY2021	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1016000000	USD
CY2020	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	2515000000	USD
CY2019	us-gaap	Repayments Of Long Term Debt RepaymentsOfLongTermDebt	1064000000	USD
CY2021	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2019	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	80000000	USD
CY2021	us-gaap	Payments For Derivative Instrument Financing Activities PaymentsForDerivativeInstrumentFinancingActivities	0	USD
CY2020	us-gaap	Payments For Derivative Instrument Financing Activities PaymentsForDerivativeInstrumentFinancingActivities	0	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	585000000	USD
CY2021	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	0	USD
CY2020	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	3000000	USD
CY2019	us-gaap	Payments For Derivative Instrument Financing Activities PaymentsForDerivativeInstrumentFinancingActivities	337000000	USD
CY2021	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	101000000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	132000000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	89000000	USD
CY2021	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	161000000	USD
CY2020	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	132000000	USD
CY2019	us-gaap	Proceeds From Issuance Or Sale Of Equity ProceedsFromIssuanceOrSaleOfEquity	158000000	USD
CY2021	mmc	Paymentsfor Acquisitions Deferredand Contingent Consideration PaymentsforAcquisitionsDeferredandContingentConsideration	117000000	USD
CY2020	mmc	Paymentsfor Acquisitions Deferredand Contingent Consideration PaymentsforAcquisitionsDeferredandContingentConsideration	122000000	USD
CY2019	mmc	Paymentsfor Acquisitions Deferredand Contingent Consideration PaymentsforAcquisitionsDeferredandContingentConsideration	65000000	USD
CY2021	mmc	Receipts Of Contingent Consideration For Dispositions ReceiptsOfContingentConsiderationForDispositions	71000000	USD
CY2020	mmc	Receipts Of Contingent Consideration For Dispositions ReceiptsOfContingentConsiderationForDispositions	0	USD
CY2019	mmc	Receipts Of Contingent Consideration For Dispositions ReceiptsOfContingentConsiderationForDispositions	0	USD
CY2021	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	36000000	USD
CY2020	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	34000000	USD
CY2019	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	16000000	USD
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	1026000000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	943000000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	890000000	USD
CY2021	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	1183000000	USD
CY2020	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	955000000	USD
CY2019	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	1025000000	USD
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1297000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-925000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	4331000000	USD
CY2019	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	-183000000	USD
CY2021	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	406000000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	348000000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	421000000	USD
CY2021	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	-18000000	USD
CY2020	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	-107000000	USD
CY2021	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	5000000	USD
CY2020	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	0	USD
CY2019	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	91000000	USD
CY2021	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	84000000	USD
CY2020	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	98000000	USD
CY2019	us-gaap	Proceeds From Divestiture Of Businesses And Interests In Affiliates ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates	229000000	USD
CY2021	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	859000000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	647000000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	4229000000	USD
CY2021	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-4000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8499000000	USD
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	3000000	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	66000000	USD
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1164000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-793000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-4395000000	USD
CY2021	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-355000000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	511000000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	135000000	USD
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	700000000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	2175000000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	2432000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8499000000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	6067000000	USD
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	11374000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	8585000000	USD
CY2021Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1752000000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	2089000000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1155000000	USD
CY2021Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	9622000000	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	7344000000	USD
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	11374000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8499000000	USD
CY2021	mmc	Dividend Equivalents Per Share Cash Declared DividendEquivalentsPerShareCashDeclared	2.00
CY2020	mmc	Dividend Equivalents Per Share Cash Declared DividendEquivalentsPerShareCashDeclared	1.84
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CY2019	mmc	Common Stock Dividends Per Share Cash Declared CommonStockDividendsPerShareCashDeclared	1.74
CY2021Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	11222000000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	9260000000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	7943000000	USD
CY2021	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2021Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	303000000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents At Carrying Value RestrictedCashAndCashEquivalentsAtCarryingValue	270000000	USD
CY2020	us-gaap	Gain Loss On Investments GainLossOnInvestments	-22000000	USD
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	22000000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	2436000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	3015000000	USD
CY2021Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1589000000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	2159000000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	847000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	856000000	USD
CY2021	us-gaap	Gain Loss On Investments GainLossOnInvestments	61000000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	10000000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	12000000	USD
CY2021Q4	us-gaap	Capitalized Computer Software Net CapitalizedComputerSoftwareNet	475000000	USD
CY2020Q4	us-gaap	Capitalized Computer Software Net CapitalizedComputerSoftwareNet	481000000	USD
CY2021Q4	us-gaap	Capitalized Computer Software Accumulated Amortization CapitalizedComputerSoftwareAccumulatedAmortization	1700000000	USD
CY2020Q4	us-gaap	Capitalized Computer Software Accumulated Amortization CapitalizedComputerSoftwareAccumulatedAmortization	1600000000	USD
CY2021Q4	mmc	Liability For Errors And Omissions Current And Noncurrent LiabilityForErrorsAndOmissionsCurrentAndNoncurrent	434000000	USD
CY2020Q4	mmc	Liability For Errors And Omissions Current And Noncurrent LiabilityForErrorsAndOmissionsCurrentAndNoncurrent	639000000	USD
CY2021	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	31000000	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	30000000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	31000000	USD
CY2021	us-gaap	Net Income Loss NetIncomeLoss	3143000000	USD
CY2021	us-gaap	Profit Loss ProfitLoss	3174000000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	2046000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1773000000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	2016000000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1742000000	USD
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	507000000	shares
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	506000000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	506000000	shares
CY2021	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	6000000	shares
CY2020	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	6000000	shares
CY2019	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	5000000	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	513000000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	512000000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	511000000	shares
CY2021	mmc	Average Share Price Common Stock AverageSharePriceCommonStock	141.57
CY2020	mmc	Average Share Price Common Stock AverageSharePriceCommonStock	109.12
CY2019	mmc	Average Share Price Common Stock AverageSharePriceCommonStock	97.23
CY2021Q4	mmc	Uncollected Premiumsand Claims Netof Related Payables UncollectedPremiumsandClaimsNetofRelatedPayables	13000000000	USD
CY2020Q4	mmc	Uncollected Premiumsand Claims Netof Related Payables UncollectedPremiumsandClaimsNetofRelatedPayables	11200000000	USD
CY2021	us-gaap	Use Of Estimates UseOfEstimates	<span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Estimates:</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The estimates are based on historical experience and on various other assumptions that the Company believes are reasonable. </span><div style="margin-top:5pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Such matters include:</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">estimates of revenue;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">impairment assessments and charges;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">recoverability of long-lived assets;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">liabilities for errors and omissions;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">deferred tax assets, uncertain tax positions and income tax expense;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">share-based and incentive compensation expense; </span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">the allowance for current expected credit losses on receivables;</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">useful lives assigned to long-lived assets, and depreciation and amortization; and</span></div><div style="margin-top:5pt;padding-left:36pt;text-indent:-18pt"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:14.5pt">fair value estimates of contingent consideration receivable or payable related to acquisitions or dispositions. </span></div><div style="margin-top:5pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The Company believes these estimates are reasonable based on information currently available at the time they are made. The Company also considered potential COVID-19 impacts to its customer base in various industries and geographies. Insurance exposures subject to variable factors are subject to mid-term and end of term adjustments, as well as policy audits, which may reduce premiums and corresponding commissions. Estimates were updated based on internal and industry specific economic data. The ultimate extent to which COVID-19 will directly or indirectly impact the Company’s businesses, results of operations and financial condition will depend on numerous evolving factors and future developments that it is not able to predict. Actual results may differ from these estimates</span><span style="color:#000000;font-family:'Calibri',sans-serif;font-size:11pt;font-weight:400;line-height:120%">.</span></div>
CY2021	mmc	Revenue Percent RevenuePercent	0.02
CY2021	mmc	Brokerage Revenue Number Of Annual Installments BrokerageRevenueNumberOfAnnualInstallments	4	installment
CY2021Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	290000000	USD
CY2020Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	236000000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	207000000	USD
CY2021Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	776000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	676000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	593000000	USD
CY2021	us-gaap	Contract With Customer Asset Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	547000000	USD
CY2021	us-gaap	Contract With Customer Asset Reclassified To Receivable ContractWithCustomerAssetReclassifiedToReceivable	493000000	USD
CY2020	us-gaap	Contract With Customer Asset Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerAssetCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	311000000	USD
CY2020	us-gaap	Contract With Customer Asset Reclassified To Receivable ContractWithCustomerAssetReclassifiedToReceivable	284000000	USD
CY2021	mmc	Contractwith Customer Liability Increase Decreasefor Cash Receivedfor Performance Obligations Not Yet Fulfilled ContractwithCustomerLiabilityIncreaseDecreaseforCashReceivedforPerformanceObligationsNotYetFulfilled	642000000	USD
CY2021	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	539000000	USD
CY2020	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	527000000	USD
CY2021	us-gaap	Contract With Customer Performance Obligation Satisfied In Previous Period ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod	84000000	USD
CY2020	us-gaap	Contract With Customer Performance Obligation Satisfied In Previous Period ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod	97000000	USD
CY2019	us-gaap	Contract With Customer Performance Obligation Satisfied In Previous Period ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod	79000000	USD
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	70000000	USD
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	63000000	USD
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	31000000	USD
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	14000000	USD
CY2021Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	9000000	USD
CY2021	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1500000000	USD
CY2020	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1300000000	USD
CY2019	us-gaap	Capitalized Contract Cost Amortization CapitalizedContractCostAmortization	1200000000	USD
CY2021	mmc	Business Combination Consideration Transferred Assets Acquired BusinessCombinationConsiderationTransferredAssetsAcquired	1697000000	USD
CY2020	mmc	Business Combination Consideration Transferred Assets Acquired BusinessCombinationConsiderationTransferredAssetsAcquired	929000000	USD
CY2019	mmc	Business Combination Consideration Transferred Assets Acquired BusinessCombinationConsiderationTransferredAssetsAcquired	8655000000	USD
CY2021	mmc	Business Combination Consideration Transferred Fiduciary Liabilities Assumed BusinessCombinationConsiderationTransferredFiduciaryLiabilitiesAssumed	18000000	USD
CY2020	mmc	Business Combination Consideration Transferred Fiduciary Liabilities Assumed BusinessCombinationConsiderationTransferredFiduciaryLiabilitiesAssumed	21000000	USD
CY2019	mmc	Business Combination Consideration Transferred Fiduciary Liabilities Assumed BusinessCombinationConsiderationTransferredFiduciaryLiabilitiesAssumed	1276000000	USD
CY2021	us-gaap	Business Combination Consideration Transferred Liabilities Incurred BusinessCombinationConsiderationTransferredLiabilitiesIncurred	213000000	USD
CY2020	us-gaap	Business Combination Consideration Transferred Liabilities Incurred BusinessCombinationConsiderationTransferredLiabilitiesIncurred	78000000	USD
CY2019	us-gaap	Business Combination Consideration Transferred Liabilities Incurred BusinessCombinationConsiderationTransferredLiabilitiesIncurred	2804000000	USD
CY2021	mmc	Business Combination Consideration Transferred Noncontrolling Interests Assumed BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed	64000000	USD
CY2020	mmc	Business Combination Consideration Transferred Noncontrolling Interests Assumed BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed	0	USD
CY2019	mmc	Business Combination Consideration Transferred Noncontrolling Interests Assumed BusinessCombinationConsiderationTransferredNoncontrollingInterestsAssumed	280000000	USD
CY2021	mmc	Business Combination Fair Value Of Previously Held Equity Method Investment BusinessCombinationFairValueOfPreviouslyHeldEquityMethodInvestment	390000000	USD
CY2020	mmc	Business Combination Fair Value Of Previously Held Equity Method Investment BusinessCombinationFairValueOfPreviouslyHeldEquityMethodInvestment	0	USD
CY2019	mmc	Business Combination Fair Value Of Previously Held Equity Method Investment BusinessCombinationFairValueOfPreviouslyHeldEquityMethodInvestment	0	USD
CY2021	mmc	Business Combination Contingentand Deferred Consideration BusinessCombinationContingentandDeferredConsideration	153000000	USD
CY2020	mmc	Business Combination Contingentand Deferred Consideration BusinessCombinationContingentandDeferredConsideration	183000000	USD
CY2019	mmc	Business Combination Contingentand Deferred Consideration BusinessCombinationContingentandDeferredConsideration	66000000	USD
CY2021	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	859000000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	647000000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	4229000000	USD
CY2021	us-gaap	Interest Paid Net InterestPaidNet	441000000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	481000000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	427000000	USD
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	1069000000	USD
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	673000000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	661000000	USD
CY2021	mmc	Paymentof Contingent Consideration PaymentofContingentConsideration	49000000	USD
CY2020	mmc	Paymentof Contingent Consideration PaymentofContingentConsideration	48000000	USD
CY2019	mmc	Paymentof Contingent Consideration PaymentofContingentConsideration	41000000	USD
CY2021	mmc	Proceeds From Contingent Consideration Prior Period Dispositions ProceedsFromContingentConsiderationPriorPeriodDispositions	19000000	USD
CY2020	mmc	Proceeds From Contingent Consideration Prior Period Dispositions ProceedsFromContingentConsiderationPriorPeriodDispositions	0	USD
CY2019	mmc	Proceeds From Contingent Consideration Prior Period Dispositions ProceedsFromContingentConsiderationPriorPeriodDispositions	0	USD
CY2021	mmc	Fair Value Measurementwith Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Includedin Earnings Net FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedinEarningsNet	-57000000	USD
CY2020	mmc	Fair Value Measurementwith Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Includedin Earnings Net FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedinEarningsNet	-26000000	USD
CY2019	mmc	Fair Value Measurementwith Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Includedin Earnings Net FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedinEarningsNet	-68000000	USD
CY2021	mmc	Adjustments And Payments Related To Contingent Consideration AdjustmentsAndPaymentsRelatedToContingentConsideration	-27000000	USD
CY2020	mmc	Adjustments And Payments Related To Contingent Consideration AdjustmentsAndPaymentsRelatedToContingentConsideration	22000000	USD
CY2019	mmc	Adjustments And Payments Related To Contingent Consideration AdjustmentsAndPaymentsRelatedToContingentConsideration	-27000000	USD
CY2021	mmc	Payments For Previous Acquisition Contingent Consideration PaymentsForPreviousAcquisitionContingentConsideration	28000000	USD
CY2020	mmc	Payments For Previous Acquisition Contingent Consideration PaymentsForPreviousAcquisitionContingentConsideration	54000000	USD
CY2019	mmc	Payments For Previous Acquisition Contingent Consideration PaymentsForPreviousAcquisitionContingentConsideration	22000000	USD
CY2021	mmc	Payments For Previous Acquisition Deferred Consideration PaymentsForPreviousAcquisitionDeferredConsideration	89000000	USD
CY2020	mmc	Payments For Previous Acquisition Deferred Consideration PaymentsForPreviousAcquisitionDeferredConsideration	68000000	USD
CY2019	mmc	Payments For Previous Acquisition Deferred Consideration PaymentsForPreviousAcquisitionDeferredConsideration	43000000	USD
CY2021	mmc	Payments For Previous Acquisition Deferredand Contingent Consideration PaymentsForPreviousAcquisitionDeferredandContingentConsideration	117000000	USD
CY2020	mmc	Payments For Previous Acquisition Deferredand Contingent Consideration PaymentsForPreviousAcquisitionDeferredandContingentConsideration	122000000	USD
CY2019	mmc	Payments For Previous Acquisition Deferredand Contingent Consideration PaymentsForPreviousAcquisitionDeferredandContingentConsideration	65000000	USD
CY2021	mmc	Proceeds From Previous Disposition Contingent Consideration ProceedsFromPreviousDispositionContingentConsideration	71000000	USD
CY2020	mmc	Proceeds From Previous Disposition Contingent Consideration ProceedsFromPreviousDispositionContingentConsideration	0	USD
CY2019	mmc	Proceeds From Previous Disposition Contingent Consideration ProceedsFromPreviousDispositionContingentConsideration	0	USD
CY2021	us-gaap	Stock Issued1 StockIssued1	228000000	USD
CY2020	us-gaap	Stock Issued1 StockIssued1	219000000	USD
CY2019	us-gaap	Stock Issued1 StockIssued1	165000000	USD
CY2021	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	348000000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	290000000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	252000000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	142000000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	140000000	USD
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	112000000	USD
CY2021	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	46000000	USD
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	47000000	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	32000000	USD
CY2021	mmc	Allowance For Doubtful Accounts Receivable Writeoffs Net Of Recoveries AllowanceForDoubtfulAccountsReceivableWriteoffsNetOfRecoveries	16000000	USD
CY2020	mmc	Allowance For Doubtful Accounts Receivable Writeoffs Net Of Recoveries AllowanceForDoubtfulAccountsReceivableWriteoffsNetOfRecoveries	30000000	USD
CY2019	mmc	Allowance For Doubtful Accounts Receivable Writeoffs Net Of Recoveries AllowanceForDoubtfulAccountsReceivableWriteoffsNetOfRecoveries	16000000	USD
CY2021	mmc	Allowance For Doubtful Accounts Receivable Effect Of Exchange Rate Changes And Other AllowanceForDoubtfulAccountsReceivableEffectOfExchangeRateChangesAndOther	-6000000	USD
CY2020	mmc	Allowance For Doubtful Accounts Receivable Effect Of Exchange Rate Changes And Other AllowanceForDoubtfulAccountsReceivableEffectOfExchangeRateChangesAndOther	-15000000	USD
CY2019	mmc	Allowance For Doubtful Accounts Receivable Effect Of Exchange Rate Changes And Other AllowanceForDoubtfulAccountsReceivableEffectOfExchangeRateChangesAndOther	12000000	USD
CY2021Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	166000000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	142000000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	140000000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	376000000	USD
CY2021	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-159000000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	535000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-180000000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-125000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-55000000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	840000000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	305000000	USD
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	535000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-225000000	USD
CY2020	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	694000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-146000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-170000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-55000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-554000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-408000000	USD
CY2021Q4	mmc	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax	13000000	USD
CY2020Q4	mmc	Accumulated Other Comprehensive Income Loss Foreign Currency Translation Adjustment Tax AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax	11000000	USD
CY2021Q4	mmc	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Adjustment Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansAdjustmentTax	1501000000	USD
CY2020Q4	mmc	Accumulated Other Comprehensive Income Loss Defined Benefit Pension And Other Postretirement Plans Adjustment Tax AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansAdjustmentTax	1805000000	USD
CY2021	us-gaap	Business Combination Consideration Transferred1 BusinessCombinationConsiderationTransferred1	1400000000	USD
CY2021	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	888000000	USD
CY2021	mmc	Business Combination Contingentand Deferred Consideration BusinessCombinationContingentandDeferredConsideration	153000000	USD
CY2021	mmc	Business Combination Fair Value Of Previously Held Equity Method Investment BusinessCombinationFairValueOfPreviouslyHeldEquityMethodInvestment	390000000	USD
CY2021	us-gaap	Finitelived Intangible Assets Acquired1 FinitelivedIntangibleAssetsAcquired1	508000000	USD
CY2021	us-gaap	Business Combination Pro Forma Information Revenue Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual	114000000	USD
CY2021	us-gaap	Business Combination Pro Forma Information Earnings Or Loss Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual	3000000	USD
CY2020	us-gaap	Business Combination Pro Forma Information Revenue Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual	169000000	USD
CY2020	us-gaap	Business Combination Pro Forma Information Earnings Or Loss Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual	11000000	USD
CY2019	us-gaap	Business Combination Pro Forma Information Revenue Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual	1200000000	USD
CY2019	us-gaap	Business Combination Pro Forma Information Earnings Or Loss Of Acquiree Since Acquisition Date Actual BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual	-40000000	USD
CY2021	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	5000000	USD
CY2020	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	3000000	USD
CY2019	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	125000000	USD
CY2020	us-gaap	Business Combination Consideration Transferred1 BusinessCombinationConsiderationTransferred1	877000000	USD
CY2020	mmc	Business Combination Contingentand Deferred Consideration BusinessCombinationContingentandDeferredConsideration	183000000	USD
CY2021	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	20008000000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	17586000000	USD
CY2019	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	17323000000	USD
CY2021	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	3179000000	USD
CY2020	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	2042000000	USD
CY2019	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	1877000000	USD
CY2021	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	6.27
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	4.03
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	3.71
CY2021	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	6.20
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	3.99
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	3.67
CY2020Q4	us-gaap	Goodwill Goodwill	15517000000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	14671000000	USD
CY2021	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	1045000000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	593000000	USD
CY2021	us-gaap	Goodwill Other Increase Decrease GoodwillOtherIncreaseDecrease	-245000000	USD
CY2020	us-gaap	Goodwill Other Increase Decrease GoodwillOtherIncreaseDecrease	253000000	USD
CY2021Q4	us-gaap	Goodwill Goodwill	16317000000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	15517000000	USD
CY2021Q4	us-gaap	Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount	96000000	USD
CY2020Q4	us-gaap	Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount	179000000	USD
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CY2021Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	1621000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2810000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	4099000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	1400000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2699000000	USD
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CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	351000000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	314000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	350000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	327000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	307000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	271000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	252000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	1303000000	USD
CY2021Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2810000000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1590000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1075000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	657000000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	2618000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	1718000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	1782000000	USD
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	4208000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	2793000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	2439000000	USD
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	251000000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	172000000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	70000000	USD
CY2021	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	714000000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	456000000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	455000000	USD
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	132000000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	79000000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	57000000	USD
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	1097000000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	707000000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	582000000	USD
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-40000000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	40000000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	69000000	USD
CY2021	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-12000000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-14000000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-16000000	USD
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-11000000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	14000000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	31000000	USD
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-63000000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	40000000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	84000000	USD
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1034000000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	747000000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	666000000	USD
CY2021Q4	mmc	Deferred Tax Assets Tax Deferred Expense Reservesand Accruals Netof Valuation Allowance DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsNetofValuationAllowance	647000000	USD
CY2020Q4	mmc	Deferred Tax Assets Tax Deferred Expense Reservesand Accruals Netof Valuation Allowance DeferredTaxAssetsTaxDeferredExpenseReservesandAccrualsNetofValuationAllowance	547000000	USD
CY2021Q4	mmc	Deferred Tax Assets Operating Loss Carryforwards Foreign Netof Valuation Allowance DeferredTaxAssetsOperatingLossCarryforwardsForeignNetofValuationAllowance	293000000	USD
CY2020Q4	mmc	Deferred Tax Assets Operating Loss Carryforwards Foreign Netof Valuation Allowance DeferredTaxAssetsOperatingLossCarryforwardsForeignNetofValuationAllowance	294000000	USD
CY2021Q4	mmc	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions And Postretirement Benefits Netof Valuation Allowance DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensionsAndPostretirementBenefitsNetofValuationAllowance	293000000	USD
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CY2021Q4	mmc	Deferred Tax Assets Operating Loss Carryforwards Domestic Net Of Valuation Allowance DeferredTaxAssetsOperatingLossCarryforwardsDomesticNetOfValuationAllowance	183000000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Deferred Expense DeferredTaxLiabilitiesDeferredExpense	98000000	USD
CY2020Q4	mmc	Deferred Tax Assets Operating Loss Carryforwards Domestic Net Of Valuation Allowance DeferredTaxAssetsOperatingLossCarryforwardsDomesticNetOfValuationAllowance	60000000	USD
CY2021Q4	mmc	Deferred Tax Assets Deferred Income Net Of Valuation Allowance DeferredTaxAssetsDeferredIncomeNetOfValuationAllowance	29000000	USD
CY2020Q4	mmc	Deferred Tax Assets Deferred Income Net Of Valuation Allowance DeferredTaxAssetsDeferredIncomeNetOfValuationAllowance	25000000	USD
CY2021Q4	mmc	Deferred Tax Assets Tax Deferred Expense Other Net Of Valuation Allowance DeferredTaxAssetsTaxDeferredExpenseOtherNetOfValuationAllowance	32000000	USD
CY2020Q4	mmc	Deferred Tax Assets Tax Deferred Expense Other Net Of Valuation Allowance DeferredTaxAssetsTaxDeferredExpenseOtherNetOfValuationAllowance	43000000	USD
CY2021Q4	mmc	Deferred Tax Assets Net Net Of Valuation Allowance DeferredTaxAssetsNetNetOfValuationAllowance	1477000000	USD
CY2020Q4	mmc	Deferred Tax Assets Net Net Of Valuation Allowance DeferredTaxAssetsNetNetOfValuationAllowance	1463000000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	624000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	569000000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	506000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	491000000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	403000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	143000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Deferred Expense DeferredTaxLiabilitiesDeferredExpense	87000000	USD
CY2021Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	32000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	32000000	USD
CY2021Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1663000000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	1322000000	USD
CY2021Q4	us-gaap	Undistributed Earnings Of Foreign Subsidiaries UndistributedEarningsOfForeignSubsidiaries	730000000	USD
CY2021	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
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CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.025
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.030
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.001
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CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.030
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0.026
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CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0
CY2021	mmc	Effective Income Tax Rate Reconciliation Gain On Deconsolidation Of Business Percent EffectiveIncomeTaxRateReconciliationGainOnDeconsolidationOfBusinessPercent	-0.015
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CY2021	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	36000000	USD
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CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	98000000	USD
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CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	78000000	USD
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CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	25000000	USD
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CY2021Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	94000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	98000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	86000000	USD
CY2021Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	87000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	90000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	75000000	USD
CY2021Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	45000000	USD
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CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	31000000	USD
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CY2021Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	19394000000	USD
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CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	61.42
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	200605	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	105.98
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	7217125	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	90.17
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P6Y4M24D
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	601999000	USD
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber	7128248	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice	89.98
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1	P6Y6M
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	595954000	USD
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	3988943	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	75.19
CY2021	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Remaining Contractual Term2 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2	P5Y1M6D
CY2021Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	392470000	USD
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	22.25
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	21.09
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	17.87
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	137500000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	159300000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	136700000	USD
CY2021	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	103000000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	72000000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	106500000	USD
CY2020Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	243000000	USD
CY2019Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	225000000	USD
CY2021	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases	107000000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Purchases FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases	107000000	USD
CY2021	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements	77000000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Settlements FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements	102000000	USD
CY2021	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Included In Earnings FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings	81000000	USD
CY2020	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Gain Loss Included In Earnings FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings	11000000	USD
CY2021	mmc	Fair Value Measurementwith Unobservable Inputs Reconciliation Recurring Basis Liability Other Adjustments FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments	-2000000	USD
CY2020	mmc	Fair Value Measurementwith Unobservable Inputs Reconciliation Recurring Basis Liability Other Adjustments FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments	2000000	USD
CY2021Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	352000000	USD
CY2020Q4	us-gaap	Fair Value Measurement With Unobservable Inputs Reconciliations Recurring Basis Liability Value FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue	243000000	USD
CY2021Q4	us-gaap	Equity Method Investments EquityMethodInvestments	207000000	USD
CY2020Q4	us-gaap	Equity Method Investments EquityMethodInvestments	280000000	USD
CY2021	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	5000000	USD
CY2020	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	27000000	USD
CY2021Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	36000000	USD
CY2020Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	33000000	USD
CY2021	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax	100000000	USD
CY2021	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	16000000	USD
CY2020	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	28000000	USD
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	374000000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	396000000	USD
CY2021	us-gaap	Short Term Lease Cost ShortTermLeaseCost	4000000	USD
CY2020	us-gaap	Short Term Lease Cost ShortTermLeaseCost	3000000	USD
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	144000000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	138000000	USD
CY2021	us-gaap	Sublease Income SubleaseIncome	20000000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	19000000	USD
CY2021	us-gaap	Lease Cost LeaseCost	502000000	USD
CY2020	us-gaap	Lease Cost LeaseCost	518000000	USD
CY2021	us-gaap	Operating Lease Payments OperatingLeasePayments	412000000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	420000000	USD
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	348000000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	261000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	389000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	350000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	307000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	276000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	253000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	924000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	2499000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	287000000	USD
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	2212000000	USD
CY2021Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	332000000	USD
CY2021Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	1880000000	USD
CY2021Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	2212000000	USD
CY2021Q4	mmc	Lessee Operating Lease Lease Notyet Commenced Amount LesseeOperatingLeaseLeaseNotyetCommencedAmount	13000000	USD
CY2021Q4	us-gaap	Lessee Operating Lease Lease Not Yet Commenced Term Of Contract1 LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1	P12M
CY2021Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	17000000	USD
CY2020Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	517000000	USD
CY2021Q4	us-gaap	Debt Current DebtCurrent	17000000	USD
CY2020Q4	us-gaap	Debt Current DebtCurrent	517000000	USD
CY2021Q4	us-gaap	Long Term Debt LongTermDebt	10950000000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	11313000000	USD
CY2021Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	17000000	USD
CY2020Q4	us-gaap	Long Term Debt Current LongTermDebtCurrent	517000000	USD
CY2021Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	10933000000	USD
CY2020Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	10796000000	USD
CY2021Q4	us-gaap	Commercial Paper CommercialPaper	0	USD
CY2021Q4	mmc	Number Of Facilities Terminated NumberOfFacilitiesTerminated	2	Facility
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	17000000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	616000000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	1600000000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	518000000	USD
CY2021Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	1200000000	USD
CY2021	us-gaap	Restructuring Charges RestructuringCharges	70000000	USD
CY2019Q4	us-gaap	Restructuring Reserve RestructuringReserve	102000000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	89000000	USD
CY2020	us-gaap	Payments For Restructuring PaymentsForRestructuring	100000000	USD
CY2020	us-gaap	Restructuring Reserve Translation Adjustment RestructuringReserveTranslationAdjustment	-10000000	USD
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	81000000	USD
CY2021	us-gaap	Restructuring Charges RestructuringCharges	70000000	USD
CY2021	us-gaap	Payments For Restructuring PaymentsForRestructuring	98000000	USD
CY2021	us-gaap	Restructuring Reserve Translation Adjustment RestructuringReserveTranslationAdjustment	-5000000	USD
CY2021Q4	us-gaap	Restructuring Reserve RestructuringReserve	48000000	USD
CY2021	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1200000000	USD
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	3800000	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Shares Issued In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod	4100000	shares
CY2020Q4	us-gaap	Loss Contingency Estimate Of Possible Loss LossContingencyEstimateOfPossibleLoss	155000000	GBP
CY2020Q4	us-gaap	Loss Contingency Estimate Of Possible Loss LossContingencyEstimateOfPossibleLoss	210000000	USD
CY2021	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	19820000000	USD
CY2021	us-gaap	Operating Income Loss OperatingIncomeLoss	4312000000	USD
CY2021Q4	us-gaap	Assets Assets	34388000000	USD
CY2021	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	747000000	USD
CY2021	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	406000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	17224000000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	3066000000	USD
CY2020Q4	us-gaap	Assets Assets	33049000000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	741000000	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	348000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	16652000000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	2677000000	USD
CY2019Q4	us-gaap	Assets Assets	31357000000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	647000000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	421000000	USD
CY2021	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	19820000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	17224000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	16652000000	USD
CY2021	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	19820000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	17224000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Including Assessed Tax RevenueFromContractWithCustomerIncludingAssessedTax	16652000000	USD
CY2021Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	847000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	856000000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	858000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	3382000000	USD
CY2020	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	955000000	USD
CY2020	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1880000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-925000000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	647000000	USD
CY2020	mmc	Payments For Proceeds From Other Lines Of Investing Activities PaymentsForProceedsFromOtherLinesOfInvestingActivities	146000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-793000000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	511000000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	2175000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8499000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	2361000000	USD
CY2019	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	1025000000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	3306000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	4331000000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	4229000000	USD
CY2019	mmc	Payments For Proceeds From Other Lines Of Investing Activities PaymentsForProceedsFromOtherLinesOfInvestingActivities	166000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-4395000000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	135000000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	2432000000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	6067000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	8499000000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	2074000000	USD
	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	1919000000	USD
	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-2046000000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-127000000	USD
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	384000000	USD
	mmc	Payments For Proceeds From Other Lines Of Investing Activities PaymentsForProceedsFromOtherLinesOfInvestingActivities	188000000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-572000000	USD
	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-243000000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	1132000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2021Q1	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0	USD
CY2021Q3	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	11806000000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	750000000	USD
	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	1277000000	USD
	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1491000000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-214000000	USD
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	350000000	USD
	mmc	Payments For Proceeds From Other Lines Of Investing Activities PaymentsForProceedsFromOtherLinesOfInvestingActivities	74000000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-424000000	USD
	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	38000000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	150000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2021Q2	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10824000000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	-408000000	USD
CY2021Q1	mmc	Increase Decrease In Fiduciary Liabilities IncreaseDecreaseInFiduciaryLiabilities	190000000	USD
CY2021Q1	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-451000000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-261000000	USD
CY2021Q1	mmc	Payments For Proceeds From Other Lines Of Investing Activities PaymentsForProceedsFromOtherLinesOfInvestingActivities	67000000	USD
CY2021Q1	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-67000000	USD
CY2021Q1	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-36000000	USD
CY2021Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-772000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	10674000000	USD
CY2021Q1	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	9902000000	USD

Files In Submission

Name	View Source	Status
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marshmclennanlogoa.jpg	Edgar Link	pending
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mmc12312021ex_321.htm	Edgar Link	pending
mmc123121ex_211.htm	Edgar Link	pending
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$MMC
MARSH & MCLENNAN COMPANIES, INC. Stock $mmc

2021 Q4 Form 10-K Financial Statement

#000006270922000009 Filed on February 16, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MMC MARSH & MCLENNAN COMPANIES, INC. Stock $mmc

2021 Q4 Form 10-K Financial Statement

#000006270922000009 Filed on February 16, 2022

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MMC
MARSH & MCLENNAN COMPANIES, INC. Stock $mmc