$MCO
MOODYS CORP /DE/ Stock $mco

$mco Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000105955621000010 Filed on February 22, 2021

Income Statement

Concept	2019 Q4	2018 Q4	2018 Q3
Revenue	$1.233B	$1.060B	$1.081B
YoY Change	16.32%	-9.05%	1.68%
Cost Of Revenue	$355.2M	$304.1M	$306.3M
YoY Change	16.8%	-9.55%	-3.44%
Gross Profit	$877.6M	$756.0M	$774.5M
YoY Change	16.08%	-8.84%	3.86%
Gross Profit Margin	71.18%	71.32%	71.66%
Selling, General & Admin	$318.9M	$278.2M	$260.3M
YoY Change	14.63%	-6.99%	5.94%
% of Gross Profit	36.34%	36.8%	33.61%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$50.10M	$48.30M	$46.10M
YoY Change	3.73%	-3.21%	7.21%
% of Gross Profit	5.71%	6.39%	5.95%
Operating Expenses	$369.0M	$326.5M	$614.0M
YoY Change	13.02%	-6.45%	-0.07%
Operating Profit	$504.0M	$376.0M	$467.0M
YoY Change	34.04%	-19.23%	4.12%
Interest Expense	-$23.00M	-$72.40M	-$56.40M
YoY Change	-68.23%	58.42%	6.21%
% of Operating Profit	-4.56%	-19.26%	-12.08%
Other Income/Expense, Net	-$28.60M	$17.40M	-$54.00M
YoY Change	-264.37%	-182.46%	-412.14%
Pretax Income	$452.4M	$321.6M	$412.8M
YoY Change	40.67%	-21.12%	-11.38%
Income Tax	$91.40M	$63.20M	$100.8M
% Of Pretax Income	20.2%	19.65%	24.42%
Net Earnings	$359.0M	$251.0M	$310.0M
YoY Change	43.03%	884.31%	-2.3%
Net Earnings / Revenue	29.12%	23.68%	28.68%
Basic Earnings Per Share	$1.91	$1.31	$1.62
Diluted Earnings Per Share	$1.88	$1.29	$1.59
COMMON SHARES
Basic Shares Outstanding		191.3M shares	191.8M shares
Diluted Shares Outstanding			194.5M shares

Balance Sheet

Concept	2019 Q4	2018 Q4	2018 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments	$1.930B	$1.818B	$1.146B
YoY Change	6.16%	53.68%	7.0%
Cash & Equivalents	$1.832B	$1.685B	$1.035B
Short-Term Investments	$98.00M	$133.0M	$111.0M
Other Short-Term Assets	$330.0M	$282.0M	$238.9M
YoY Change	17.02%	12.75%	19.15%
Inventory
Prepaid Expenses	$71.00M	$67.00M	$78.90M
Receivables	$1.419B	$1.287B	$1.132B
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$3.679B	$3.387B	$2.516B
YoY Change	8.62%	31.25%	10.41%
LONG-TERM ASSETS
Property, Plant & Equipment	$292.0M	$320.0M	$311.1M
YoY Change	-8.75%	-1.57%	-6.32%
Goodwill	$3.722B	$3.781B	$3.661B
YoY Change	-1.56%	0.75%	-1.63%
Intangibles	$1.498B	$1.566B	$1.518B
YoY Change	-4.34%	-4.02%	-7.07%
Long-Term Investments	$127.0M	$124.0M	$144.0M
YoY Change	2.42%	2.48%	30.91%
Other Assets	$389.0M	$275.0M	$243.6M
YoY Change	41.45%	71.98%	44.57%
Total Long-Term Assets	$6.586B	$5.668B	$5.923B
YoY Change	16.2%	-0.74%	-1.71%
TOTAL ASSETS
Total Short-Term Assets	$3.679B	$3.387B	$2.516B
Total Long-Term Assets	$6.586B	$5.668B	$5.923B
Total Assets	$10.27B	$9.526B	$8.439B
YoY Change	7.76%	10.84%	1.62%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$38.00M	$30.00M	$16.20M
YoY Change	26.67%	37.61%	-44.52%
Accrued Expenses	$608.0M	$452.0M	$332.0M
YoY Change	34.51%	-14.72%	-13.09%
Deferred Revenue	$1.050B	$953.0M	$771.5M
YoY Change	10.18%	7.85%
Short-Term Debt	$0.00	$0.00	$25.00M
YoY Change		-100.0%	-92.06%
Long-Term Debt Due	$0.00	$450.0M	$445.6M
YoY Change	-100.0%	50.25%	48.88%
Total Short-Term Liabilities	$1.912B	$2.099B	$1.824B
YoY Change	-8.91%	1.73%	-8.02%
LONG-TERM LIABILITIES
Long-Term Debt	$5.581B	$5.226B	$4.484B
YoY Change	6.79%	2.25%	-12.2%
Other Long-Term Liabilities	$504.0M	$576.0M	$574.9M
YoY Change	-12.5%	-13.25%	28.53%
Total Long-Term Liabilities	$6.085B	$5.802B	$5.059B
YoY Change	4.88%	0.47%	-8.92%
TOTAL LIABILITIES
Total Short-Term Liabilities	$1.912B	$2.099B	$1.824B
Total Long-Term Liabilities	$6.085B	$5.802B	$5.059B
Total Liabilities	$9.428B	$8.870B	$7.833B
YoY Change	6.29%	1.85%	-7.43%
SHAREHOLDERS EQUITY
Retained Earnings	$9.656B	$8.594B	$8.429B
YoY Change	12.36%	15.12%	12.19%
Common Stock	$645.0M	$604.0M	$573.1M
YoY Change	6.79%	13.53%	15.64%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$9.250B	$8.313B	$8.260B
YoY Change	11.27%	1.96%	1.68%
Treasury Stock Shares	155.2M shares	151.6M shares	151.3M shares
Shareholders Equity	$612.0M	$459.0M	$400.1M
YoY Change
Total Liabilities & Shareholders Equity	$10.27B	$9.526B	$8.439B
YoY Change	7.76%	10.84%	1.62%

Cashflow Statement

Concept	2019 Q4	2018 Q4	2018 Q3
OPERATING ACTIVITIES
Net Income	$359.0M	$251.0M	$310.0M
YoY Change	43.03%	884.31%	-2.3%
Depreciation, Depletion And Amortization	$50.10M	$48.30M	$46.10M
YoY Change	3.73%	-3.21%	7.21%
Cash From Operating Activities	$490.6M	$376.5M	$307.3M
YoY Change	30.31%	-8.59%	-21.29%
INVESTING ACTIVITIES
Capital Expenditures	-$8.100M	-$27.50M	-$25.00M
YoY Change	-70.55%	29.72%	-6.02%
Acquisitions
YoY Change
Other Investing Activities	$193.6M	-$265.1M	-$43.50M
YoY Change	-173.03%	-3182.56%	-98.73%
Cash From Investing Activities	$185.5M	-$292.6M	-$68.50M
YoY Change	-163.4%	2222.22%	-98.01%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-46.00M	568.7M	-512.6M
YoY Change	-108.09%	-291.74%	-171.28%
NET CHANGE
Cash From Operating Activities	490.6M	376.5M	307.3M
Cash From Investing Activities	185.5M	-292.6M	-68.50M
Cash From Financing Activities	-46.00M	568.7M	-512.6M
Net Change In Cash	630.1M	652.6M	-273.8M
YoY Change	-3.45%	535.44%	-88.29%
FREE CASH FLOW
Cash From Operating Activities	$490.6M	$376.5M	$307.3M
Capital Expenditures	-$8.100M	-$27.50M	-$25.00M
Free Cash Flow	$498.7M	$404.0M	$332.3M
YoY Change	23.44%	-6.72%	-20.31%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Local Phone Number LocalPhoneNumber	553-0300
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Central Index Key EntityCentralIndexKey	0001059556
CY2018	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201802Member
CY2019	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201613Member
CY2019Q1	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201602Member
CY2019Q1	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201602Member
CY2019	us-gaap	Accounting Standards Update Extensible List AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201613Member
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	1-14037
CY2020	dei	Entity Registrant Name EntityRegistrantName	MOODY’S CORPORATION
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	13-3998945
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	7 World Trade Center at 250 Greenwich Street
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	New York
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	NY
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	10007
CY2020	dei	City Area Code CityAreaCode	212
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2020	dei	Entity Small Business EntitySmallBusiness	false
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2020	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020Q2	dei	Entity Public Float EntityPublicFloat	51000000000	USD
CY2021Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	187100000	shares
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2020	us-gaap	Cost Of Revenue CostOfRevenue	1475000000	USD
CY2019	us-gaap	Cost Of Revenue CostOfRevenue	1387000000	USD
CY2018	us-gaap	Cost Of Revenue CostOfRevenue	1246000000	USD
CY2020	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	1229000000	USD
CY2019	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	1167000000	USD
CY2018	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	1080000000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	50000000	USD
CY2019	us-gaap	Restructuring Charges RestructuringCharges	60000000	USD
CY2018	us-gaap	Restructuring Charges RestructuringCharges	49000000	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	220000000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	200000000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	192000000	USD
CY2020	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	0	USD
CY2019	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	3000000	USD
CY2018	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	8000000	USD
CY2020	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-9000000	USD
CY2019	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-14000000	USD
CY2018	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
CY2020	us-gaap	Costs And Expenses CostsAndExpenses	2983000000	USD
CY2019	us-gaap	Costs And Expenses CostsAndExpenses	2831000000	USD
CY2018	us-gaap	Costs And Expenses CostsAndExpenses	2575000000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	2388000000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	1998000000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	1868000000	USD
CY2020	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-205000000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-208000000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-215000000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	46000000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	20000000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	19000000	USD
CY2020	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-159000000	USD
CY2019	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-188000000	USD
CY2018	us-gaap	Nonoperating Income Expense NonoperatingIncomeExpense	-196000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	2229000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	1810000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	1672000000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	452000000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	381000000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	352000000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	1777000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1429000000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1320000000	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	-1000000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	7000000	USD
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	10000000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1778000000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1422000000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1310000000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	9.48
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	7.51
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.84
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	9.39
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	7.42
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.74
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	187600000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	189300000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	191600000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	189300000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	191600000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	194400000	shares
CY2020	us-gaap	Profit Loss ProfitLoss	1777000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1429000000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1320000000	USD
CY2020	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification And Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationAndTax	361000000	USD
CY2020	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationTax	13000000	USD
CY2020	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationNetOfTax	348000000	USD
CY2019	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationNetOfTax	-23000000	USD
CY2019	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification And Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationAndTax	-22000000	USD
CY2019	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationTax	1000000	USD
CY2018	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification And Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationAndTax	-315000000	USD
CY2018	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationTax	0	USD
CY2018	mco	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Before Reclassification Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentBeforeReclassificationNetOfTax	-315000000	USD
CY2020	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentBeforeTax	0	USD
CY2020	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentTax	0	USD
CY2020	us-gaap	Translation Adjustment Functional To Reporting Currency Gain Loss Reclassified To Earnings Net Of Tax TranslationAdjustmentFunctionalToReportingCurrencyGainLossReclassifiedToEarningsNetOfTax	0	USD
CY2019	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentBeforeTax	-32000000	USD
CY2019	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentTax	0	USD
CY2019	us-gaap	Translation Adjustment Functional To Reporting Currency Gain Loss Reclassified To Earnings Net Of Tax TranslationAdjustmentFunctionalToReportingCurrencyGainLossReclassifiedToEarningsNetOfTax	-32000000	USD
CY2018	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Before Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentBeforeTax	0	USD
CY2018	mco	Other Comprehensive Income Loss Foreign Currency Translation Reclassification Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationReclassificationAdjustmentTax	0	USD
CY2018	us-gaap	Translation Adjustment Functional To Reporting Currency Gain Loss Reclassified To Earnings Net Of Tax TranslationAdjustmentFunctionalToReportingCurrencyGainLossReclassifiedToEarningsNetOfTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax	-364000000	USD
CY2020	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationTax	-91000000	USD
CY2020	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Net Of Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationNetOfTax	-273000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax	35000000	USD
CY2019	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationTax	9000000	USD
CY2019	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Net Of Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationNetOfTax	26000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax	41000000	USD
CY2018	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationTax	7000000	USD
CY2018	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Before Reclassification Net Of Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationNetOfTax	34000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax	1000000	USD
CY2020	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationTax	0	USD
CY2020	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Netof Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationNetofTax	1000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax	3000000	USD
CY2019	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationTax	1000000	USD
CY2019	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Netof Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationNetofTax	2000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax	0	USD
CY2018	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationTax	0	USD
CY2018	mco	Other Comprehensive Income Loss Net Investment Hedge Gain Loss Reclassification Netof Tax OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationNetofTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-68000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-51000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-17000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-1000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-1000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	-3000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	-1000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	-2000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	8000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	2000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	6000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	3000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	1000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	2000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax	5000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	1000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	4000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-42000000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-10000000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-32000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-32000000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-8000000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-24000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	6000000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	2000000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	4000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-103000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-102000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-1000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	13000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	2000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	11000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax OtherComprehensiveIncomeLossBeforeTax	-264000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	10000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-274000000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	1776000000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	1440000000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	1046000000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	-8000000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	11000000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	-12000000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1784000000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1429000000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1058000000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	2597000000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1832000000	USD
CY2020Q4	us-gaap	Short Term Investments ShortTermInvestments	99000000	USD
CY2019Q4	us-gaap	Short Term Investments ShortTermInvestments	98000000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	34000000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2020Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	1430000000	USD
CY2019Q4	us-gaap	Accounts Receivable Net Current AccountsReceivableNetCurrent	1419000000	USD
CY2020Q4	us-gaap	Other Assets Current OtherAssetsCurrent	383000000	USD
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	330000000	USD
CY2020Q4	us-gaap	Assets Current AssetsCurrent	4509000000	USD
CY2019Q4	us-gaap	Assets Current AssetsCurrent	3679000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	278000000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	292000000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	393000000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	456000000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	4556000000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	3722000000	USD
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1824000000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1498000000	USD
CY2020Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	334000000	USD
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	229000000	USD
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	515000000	USD
CY2019Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	389000000	USD
CY2020Q4	us-gaap	Assets Assets	12409000000	USD
CY2019Q4	us-gaap	Assets Assets	10265000000	USD
CY2020Q4	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	1039000000	USD
CY2019Q4	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	773000000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	94000000	USD
CY2019Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	89000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1089000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1050000000	USD
CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	2222000000	USD
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	1912000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	98000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	112000000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	6422000000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	5581000000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	404000000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities Net DeferredIncomeTaxLiabilitiesNet	357000000	USD
CY2020Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	483000000	USD
CY2019Q4	us-gaap	Liability For Uncertain Tax Positions Noncurrent LiabilityForUncertainTaxPositionsNoncurrent	477000000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	427000000	USD
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	485000000	USD
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	590000000	USD
CY2019Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	504000000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	10646000000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	9428000000	USD
CY2020Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2019Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		USD
CY2020Q4	us-gaap	Redeemable Noncontrolling Interest Equity Carrying Amount RedeemableNoncontrollingInterestEquityCarryingAmount	0	USD
CY2019Q4	us-gaap	Redeemable Noncontrolling Interest Equity Carrying Amount RedeemableNoncontrollingInterestEquityCarryingAmount	6000000	USD
CY2019Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000	shares
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000	shares
CY2019Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2019Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Outstanding PreferredStockSharesOutstanding	0	shares
CY2020Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2019Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	USD
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	1000000000	shares
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	1000000000	shares
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	342902272	shares
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	342902272	shares
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	3000000	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	3000000	USD
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	735000000	USD
CY2019Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	642000000	USD
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	11011000000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	9656000000	USD
CY2020Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	155808563	shares
CY2019Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	155215143	shares
CY2020Q4	us-gaap	Treasury Stock Value TreasuryStockValue	9748000000	USD
CY2019Q4	us-gaap	Treasury Stock Value TreasuryStockValue	9250000000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-432000000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-439000000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	1569000000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	612000000	USD
CY2020Q4	us-gaap	Minority Interest MinorityInterest	194000000	USD
CY2019Q4	us-gaap	Minority Interest MinorityInterest	219000000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1763000000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	831000000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	12409000000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	10265000000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	1777000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1429000000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1320000000	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	220000000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	200000000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	192000000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	154000000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	136000000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	130000000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-44000000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-38000000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-99000000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-24000000	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-12000000	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2020	mco	Settlement Of Treasury Rate Lock SettlementOfTreasuryRateLock	68000000	USD
CY2019	mco	Settlement Of Treasury Rate Lock SettlementOfTreasuryRateLock	0	USD
CY2018	mco	Settlement Of Treasury Rate Lock SettlementOfTreasuryRateLock	0	USD
CY2020	mco	Operating Lease Impairment Loss And Non Cash Restructuring Charge OperatingLeaseImpairmentLossAndNonCashRestructuringCharge	36000000	USD
CY2019	mco	Operating Lease Impairment Loss And Non Cash Restructuring Charge OperatingLeaseImpairmentLossAndNonCashRestructuringCharge	38000000	USD
CY2018	mco	Operating Lease Impairment Loss And Non Cash Restructuring Charge OperatingLeaseImpairmentLossAndNonCashRestructuringCharge	0	USD
CY2020	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-9000000	USD
CY2019	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-14000000	USD
CY2018	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	0	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-31000000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	134000000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	136000000	USD
CY2020	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	38000000	USD
CY2019	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	88000000	USD
CY2018	us-gaap	Increase Decrease In Prepaid Deferred Expense And Other Assets IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets	9000000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	49000000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	69000000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	17000000	USD
CY2020	mco	Increase Decrease In Lease Obligations IncreaseDecreaseInLeaseObligations	10000000	USD
CY2019	mco	Increase Decrease In Lease Obligations IncreaseDecreaseInLeaseObligations	16000000	USD
CY2018	mco	Increase Decrease In Lease Obligations IncreaseDecreaseInLeaseObligations	0	USD
CY2018	mco	Increase Decreasein Contractwith Customer Liability Excluding Effectof Exchange Rate IncreaseDecreaseinContractwithCustomerLiabilityExcludingEffectofExchangeRate	139000000	USD
CY2020	mco	Unrecognized Tax Benefits And Other Non Current Tax Liabilities Period Increase Decrease UnrecognizedTaxBenefitsAndOtherNonCurrentTaxLiabilitiesPeriodIncreaseDecrease	-12000000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	42000000	USD
CY2020	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	247000000	USD
CY2019	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	65000000	USD
CY2018	us-gaap	Increase Decrease In Accounts Payable And Accrued Liabilities IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	-99000000	USD
CY2020	mco	Increase Decreasein Contractwith Customer Liability Excluding Effectof Exchange Rate IncreaseDecreaseinContractwithCustomerLiabilityExcludingEffectofExchangeRate	-29000000	USD
CY2019	mco	Increase Decreasein Contractwith Customer Liability Excluding Effectof Exchange Rate IncreaseDecreaseinContractwithCustomerLiabilityExcludingEffectofExchangeRate	76000000	USD
CY2019	mco	Unrecognized Tax Benefits And Other Non Current Tax Liabilities Period Increase Decrease UnrecognizedTaxBenefitsAndOtherNonCurrentTaxLiabilitiesPeriodIncreaseDecrease	8000000	USD
CY2018	mco	Unrecognized Tax Benefits And Other Non Current Tax Liabilities Period Increase Decrease UnrecognizedTaxBenefitsAndOtherNonCurrentTaxLiabilitiesPeriodIncreaseDecrease	59000000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-102000000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-19000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	2146000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1675000000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1461000000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	103000000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	69000000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	91000000	USD
CY2020	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	897000000	USD
CY2020	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	181000000	USD
CY2019	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	138000000	USD
CY2018	us-gaap	Payments To Acquire Investments PaymentsToAcquireInvestments	193000000	USD
CY2020	us-gaap	Proceeds From Sale Maturity And Collection Of Shortterm Investments ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments	104000000	USD
CY2019	us-gaap	Proceeds From Sale Maturity And Collection Of Shortterm Investments ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments	174000000	USD
CY2018	us-gaap	Proceeds From Sale Maturity And Collection Of Shortterm Investments ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments	161000000	USD
CY2020	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	0	USD
CY2019	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	226000000	USD
CY2018	us-gaap	Proceeds From Divestiture Of Businesses Net Of Cash Divested ProceedsFromDivestitureOfBusinessesNetOfCashDivested	6000000	USD
CY2019	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	162000000	USD
CY2018	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	289000000	USD
CY2020	us-gaap	Proceeds From Hedge Investing Activities ProceedsFromHedgeInvestingActivities	2000000	USD
CY2019	us-gaap	Proceeds From Hedge Investing Activities ProceedsFromHedgeInvestingActivities	12000000	USD
CY2018	us-gaap	Proceeds From Hedge Investing Activities ProceedsFromHedgeInvestingActivities	0	USD
CY2020	us-gaap	Payments For Hedge Investing Activities PaymentsForHedgeInvestingActivities	2000000	USD
CY2019	us-gaap	Payments For Hedge Investing Activities PaymentsForHedgeInvestingActivities	7000000	USD
CY2018	us-gaap	Payments For Hedge Investing Activities PaymentsForHedgeInvestingActivities	0	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1077000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	36000000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-406000000	USD
CY2020	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	1491000000	USD
CY2019	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	824000000	USD
CY2018	us-gaap	Proceeds From Notes Payable ProceedsFromNotesPayable	1090000000	USD
CY2020	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	800000000	USD
CY2019	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	950000000	USD
CY2018	us-gaap	Repayments Of Notes Payable RepaymentsOfNotesPayable	800000000	USD
CY2020	us-gaap	Proceeds From Issuance Of Commercial Paper ProceedsFromIssuanceOfCommercialPaper	789000000	USD
CY2019	us-gaap	Proceeds From Issuance Of Commercial Paper ProceedsFromIssuanceOfCommercialPaper	1317000000	USD
CY2018	us-gaap	Proceeds From Issuance Of Commercial Paper ProceedsFromIssuanceOfCommercialPaper	989000000	USD
CY2020	us-gaap	Repayments Of Commercial Paper RepaymentsOfCommercialPaper	792000000	USD
CY2019	us-gaap	Repayments Of Commercial Paper RepaymentsOfCommercialPaper	1320000000	USD
CY2018	us-gaap	Repayments Of Commercial Paper RepaymentsOfCommercialPaper	1120000000	USD
CY2020	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	51000000	USD
CY2019	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	45000000	USD
CY2018	us-gaap	Proceeds From Stock Plans ProceedsFromStockPlans	47000000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	104000000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	77000000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	62000000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	503000000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	991000000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	203000000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	420000000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	378000000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	337000000	USD
CY2020	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	1000000	USD
CY2019	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	3000000	USD
CY2018	us-gaap	Payments Of Dividends Minority Interest PaymentsOfDividendsMinorityInterest	5000000	USD
CY2020	mco	Cash Paid Resulting In Reduction Of Noncontrolling Interest Ownership CashPaidResultingInReductionOfNoncontrollingInterestOwnership	23000000	USD
CY2019	mco	Cash Paid Resulting In Reduction Of Noncontrolling Interest Ownership CashPaidResultingInReductionOfNoncontrollingInterestOwnership	12000000	USD
CY2018	mco	Cash Paid Resulting In Reduction Of Noncontrolling Interest Ownership CashPaidResultingInReductionOfNoncontrollingInterestOwnership	0	USD
CY2020	mco	Payments Of Debt Issuance And Debt Extinguishment Or Debt Prepayment Costs PaymentsOfDebtIssuanceAndDebtExtinguishmentOrDebtPrepaymentCosts	39000000	USD
CY2019	mco	Payments Of Debt Issuance And Debt Extinguishment Or Debt Prepayment Costs PaymentsOfDebtIssuanceAndDebtExtinguishmentOrDebtPrepaymentCosts	18000000	USD
CY2018	mco	Payments Of Debt Issuance And Debt Extinguishment Or Debt Prepayment Costs PaymentsOfDebtIssuanceAndDebtExtinguishmentOrDebtPrepaymentCosts	11000000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-351000000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1563000000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-412000000	USD
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	47000000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-1000000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-30000000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	765000000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	147000000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	613000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1832000000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1685000000	USD
CY2018	us-gaap	Dividends Dividends	343000000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1832000000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	131000000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	-16000000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1072000000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2597000000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	1685000000	USD
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	-115000000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	1320000000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.76
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	203000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax	7000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-281000000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	2000000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	4000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	1000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-1000000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	136000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	4000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-1000000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	656000000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	656000000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	1429000000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.00
CY2019	us-gaap	Dividends Dividends	383000000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	-32000000	USD
CY2019	us-gaap	Minority Interest Decrease From Redemptions MinorityInterestDecreaseFromRedemptions	12000000	USD
CY2019	us-gaap	Noncontrolling Interest Increase From Business Combination NoncontrollingInterestIncreaseFromBusinessCombination	17000000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	991000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax	9000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	33000000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-8000000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-24000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	1000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	2000000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	831000000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	831000000	USD
CY2020	us-gaap	Net Income Loss Including Portion Attributable To Nonredeemable Noncontrolling Interest NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest	1778000000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.24
CY2020	us-gaap	Dividends Dividends	424000000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	154000000	USD
CY2020	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	-53000000	USD
CY2020	us-gaap	Minority Interest Decrease From Redemptions MinorityInterestDecreaseFromRedemptions	17000000	USD
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	503000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Translation Adjustment Tax OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax	-78000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	74000000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-10000000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax	-32000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax	2000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax	6000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-16000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-49000000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1763000000	USD
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020	us-gaap	Number Of Reporting Units NumberOfReportingUnits	7	reportingUnit
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	26000000	USD
CY2020	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	<div style="margin-bottom:6pt;margin-top:6pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:700;line-height:120%">Concentration of Credit Risk</span></div><div style="margin-bottom:6pt;margin-top:6pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">Financial instruments that potentially subject the Company to concentration of credit risk principally consist of cash and cash equivalents, short-term investments, trade receivables and derivatives.</span></div><div style="margin-bottom:6pt;margin-top:6pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">The Company manages its credit risk exposure by allocating its cash equivalents among various money market mutual funds, money market deposit accounts, certificates of deposits and high-grade commercial paper. Short-term investments primarily consist of certificates of deposit as of December 31, 2020 and 2019. The Company manages its credit risk exposure on cash equivalents and short-term investments by limiting the amount it can invest with any single entity. No customer accounted for 10% or more of accounts receivable at December 31, 2020 or 2019.</span></div>
CY2020Q4	mco	Number Of Customers Greater Than10 Percent Or More Of Accounts Receivable NumberOfCustomersGreaterThan10PercentOrMoreOfAccountsReceivable	0	customer
CY2019Q4	mco	Number Of Customers Greater Than10 Percent Or More Of Accounts Receivable NumberOfCustomersGreaterThan10PercentOrMoreOfAccountsReceivable	0	customer
CY2020	us-gaap	Use Of Estimates UseOfEstimates	Use of EstimatesThe preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the period. Actual results could differ from those estimates.
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2020	mco	Percentage Of Revenues PercentageOfRevenues	1
CY2019	mco	Percentage Of Revenues PercentageOfRevenues	1
CY2018	mco	Percentage Of Revenues PercentageOfRevenues	1
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	1162000000	USD
CY2020	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	1029000000	USD
CY2020	us-gaap	Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	1007000000	USD
CY2020	us-gaap	Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination ContractWithCustomerLiabilityIncreaseDecreaseForContractAcquiredInBusinessCombination	24000000	USD
CY2020	mco	Effect Of Exchange Rate On Deferred Revenue EffectOfExchangeRateOnDeferredRevenue	23000000	USD
CY2020	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	25000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	1187000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1089000000	USD
CY2020Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	98000000	USD
CY2018Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	1075000000	USD
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	923000000	USD
CY2019	us-gaap	Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	991000000	USD
CY2019	us-gaap	Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination ContractWithCustomerLiabilityIncreaseDecreaseForContractAcquiredInBusinessCombination	9000000	USD
CY2019	mco	Effect Of Exchange Rate On Deferred Revenue EffectOfExchangeRateOnDeferredRevenue	10000000	USD
CY2019	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	87000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	1162000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	1050000000	USD
CY2019Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	112000000	USD
CY2017Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	946000000	USD
CY2018	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	808000000	USD
CY2018	us-gaap	Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress	946000000	USD
CY2018	us-gaap	Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination ContractWithCustomerLiabilityIncreaseDecreaseForContractAcquiredInBusinessCombination	16000000	USD
CY2018	mco	Effect Of Exchange Rate On Deferred Revenue EffectOfExchangeRateOnDeferredRevenue	-25000000	USD
CY2018	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	129000000	USD
CY2018Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	1075000000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Current ContractWithCustomerLiabilityCurrent	953000000	USD
CY2018Q4	us-gaap	Contract With Customer Liability Noncurrent ContractWithCustomerLiabilityNoncurrent	122000000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	187600000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	189300000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	191600000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	1700000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	2300000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	2800000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	189300000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	191600000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	194400000	shares
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	200000	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	200000	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	400000	shares
CY2020	us-gaap	Accelerated Share Repurchases Final Price Paid Per Share AcceleratedShareRepurchasesFinalPricePaidPerShare	180.33
CY2020Q4	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	17000000	USD
CY2020	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-205000000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-208000000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-215000000	USD
CY2020	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossBeforeReclassificationAfterTax	-325000000	USD
CY2019	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossBeforeReclassificationAfterTax	26000000	USD
CY2018	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossBeforeReclassificationAfterTax	34000000	USD
CY2020	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossReclassificationAfterTax	-2000000	USD
CY2019	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossReclassificationAfterTax	2000000	USD
CY2018	mco	Other Comprehensive Income Loss Cash Flow Hedgeand Net Investment Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeandNetInvestmentHedgeGainLossReclassificationAfterTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Derivative Excluded Component Increase Decrease After Adjustments And Tax OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax	50000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Derivative Excluded Component Increase Decrease After Adjustments And Tax OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax	52000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Derivative Excluded Component Increase Decrease After Adjustments And Tax OtherComprehensiveIncomeLossDerivativeExcludedComponentIncreaseDecreaseAfterAdjustmentsAndTax	11000000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1403000000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	88000000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	92000000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1716000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1206000000	USD
CY2019	us-gaap	Depreciation Nonproduction DepreciationNonproduction	97000000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	292000000	USD
CY2020	us-gaap	Depreciation Nonproduction DepreciationNonproduction	96000000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1131000000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	928000000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	839000000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	278000000	USD
CY2018	us-gaap	Depreciation Nonproduction DepreciationNonproduction	90000000	USD
CY2020	us-gaap	Acquired Finite Lived Intangible Assets Weighted Average Useful Life AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife	P14Y
CY2019Q4	us-gaap	Goodwill Gross GoodwillGross	3734000000	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	12000000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	3722000000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	626000000	USD
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	626000000	USD
CY2020	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	208000000	USD
CY2020	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	208000000	USD
CY2020Q4	us-gaap	Goodwill Gross GoodwillGross	4568000000	USD
CY2020Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	12000000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	4556000000	USD
CY2018Q4	us-gaap	Goodwill Gross GoodwillGross	3793000000	USD
CY2018Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	12000000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	3781000000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	114000000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	114000000	USD
CY2019	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	-10000000	USD
CY2019Q4	us-gaap	Goodwill Gross GoodwillGross	3734000000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	102000000	USD
CY2019	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	-10000000	USD
CY2019	us-gaap	Goodwill Written Off Related To Sale Of Business Unit GoodwillWrittenOffRelatedToSaleOfBusinessUnit	163000000	USD
CY2019	us-gaap	Goodwill Written Off Related To Sale Of Business Unit GoodwillWrittenOffRelatedToSaleOfBusinessUnit	163000000	USD
CY2019Q4	us-gaap	Goodwill Impaired Accumulated Impairment Loss GoodwillImpairedAccumulatedImpairmentLoss	12000000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	3722000000	USD
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1824000000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1498000000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	124000000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	103000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	131000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	131000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	126000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	119000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	117000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	1200000000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	1824000000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	50000000	USD
CY2019	us-gaap	Restructuring Charges RestructuringCharges	60000000	USD
CY2018	us-gaap	Restructuring Charges RestructuringCharges	49000000	USD
CY2019Q4	us-gaap	Long Term Investments LongTermInvestments	10000000	USD
CY2018Q4	us-gaap	Restructuring Reserve RestructuringReserve	42000000	USD
CY2019Q4	us-gaap	Restructuring Reserve RestructuringReserve	24000000	USD
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	21000000	USD
CY2020Q4	us-gaap	Restructuring Reserve RestructuringReserve	21000000	USD
CY2020Q4	us-gaap	Derivative Assets DerivativeAssets	88000000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	60000000	USD
CY2020Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	148000000	USD
CY2020Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	186000000	USD
CY2020Q4	us-gaap	Liabilities Fair Value Disclosure LiabilitiesFairValueDisclosure	186000000	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	92000000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	3000000	USD
CY2019Q4	us-gaap	Assets Fair Value Disclosure AssetsFairValueDisclosure	95000000	USD
CY2020Q4	us-gaap	Prepaid Taxes PrepaidTaxes	94000000	USD
CY2019Q4	us-gaap	Business Combination Indemnification Assets Amount As Of Acquisition Date BusinessCombinationIndemnificationAssetsAmountAsOfAcquisitionDate	16000000	USD
CY2020Q4	us-gaap	Long Term Investments LongTermInvestments	66000000	USD
CY2019Q4	us-gaap	Prepaid Taxes PrepaidTaxes	79000000	USD
CY2020Q4	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	91000000	USD
CY2019Q4	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	71000000	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net Current CapitalizedContractCostNetCurrent	93000000	USD
CY2019Q4	us-gaap	Capitalized Contract Cost Net Current CapitalizedContractCostNetCurrent	91000000	USD
CY2020Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	31000000	USD
CY2019Q4	us-gaap	Derivative Assets Current DerivativeAssetsCurrent	9000000	USD
CY2020Q4	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	74000000	USD
CY2019Q4	us-gaap	Other Assets Miscellaneous Current OtherAssetsMiscellaneousCurrent	80000000	USD
CY2020Q4	us-gaap	Other Assets Current OtherAssetsCurrent	383000000	USD
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	330000000	USD
CY2020Q4	us-gaap	Investments In Affiliates Subsidiaries Associates And Joint Ventures InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures	135000000	USD
CY2019Q4	us-gaap	Investments In Affiliates Subsidiaries Associates And Joint Ventures InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures	117000000	USD
CY2020Q4	us-gaap	Deposit Assets DepositAssets	19000000	USD
CY2019Q4	us-gaap	Deposit Assets DepositAssets	13000000	USD
CY2020Q4	us-gaap	Business Combination Indemnification Assets Amount As Of Acquisition Date BusinessCombinationIndemnificationAssetsAmountAsOfAcquisitionDate	15000000	USD
CY2020Q4	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	17000000	USD
CY2019Q4	us-gaap	Cash Surrender Value Of Life Insurance CashSurrenderValueOfLifeInsurance	0	USD
CY2020Q4	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	134000000	USD
CY2019Q4	us-gaap	Capitalized Contract Cost Net Noncurrent CapitalizedContractCostNetNoncurrent	119000000	USD
CY2020Q4	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	57000000	USD
CY2019Q4	us-gaap	Derivative Assets Noncurrent DerivativeAssetsNoncurrent	83000000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	21000000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Assets For Plan Benefits Noncurrent DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent	0	USD
CY2020Q4	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	51000000	USD
CY2019Q4	us-gaap	Other Assets Miscellaneous Noncurrent OtherAssetsMiscellaneousNoncurrent	31000000	USD
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	515000000	USD
CY2019Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	389000000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	197000000	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current EmployeeRelatedLiabilitiesCurrent	152000000	USD
CY2020Q4	us-gaap	Accrued Bonuses Current AccruedBonusesCurrent	226000000	USD
CY2019Q4	us-gaap	Accrued Bonuses Current AccruedBonusesCurrent	208000000	USD
CY2019Q4	us-gaap	Dividends Payable Current DividendsPayableCurrent	7000000	USD
CY2020Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	53000000	USD
CY2019Q4	us-gaap	Accrued Professional Fees Current AccruedProfessionalFeesCurrent	43000000	USD
CY2020Q4	mco	Customer Billings And Payments Received In Advance CustomerBillingsAndPaymentsReceivedInAdvance	42000000	USD
CY2019Q4	mco	Customer Billings And Payments Received In Advance CustomerBillingsAndPaymentsReceivedInAdvance	28000000	USD
CY2020Q4	us-gaap	Dividends Payable Current DividendsPayableCurrent	11000000	USD
CY2020Q4	us-gaap	Interest Payable Current InterestPayableCurrent	82000000	USD
CY2019Q4	us-gaap	Interest Payable Current InterestPayableCurrent	63000000	USD
CY2020Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	39000000	USD
CY2019Q4	us-gaap	Accounts Payable Current AccountsPayableCurrent	38000000	USD
CY2020Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	128000000	USD
CY2019Q4	us-gaap	Accrued Income Taxes Current AccruedIncomeTaxesCurrent	73000000	USD
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	45000000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Current Liabilities PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities	7000000	USD
CY2020Q4	us-gaap	Accrued Royalties Current AccruedRoyaltiesCurrent	19000000	USD
CY2019Q4	us-gaap	Accrued Royalties Current AccruedRoyaltiesCurrent	25000000	USD
CY2020Q4	us-gaap	Foreign Currency Contracts Liability Fair Value Disclosure ForeignCurrencyContractsLiabilityFairValueDisclosure	2000000	USD
CY2019Q4	us-gaap	Foreign Currency Contracts Liability Fair Value Disclosure ForeignCurrencyContractsLiabilityFairValueDisclosure	0	USD
CY2020Q4	us-gaap	Restructuring Reserve Current RestructuringReserveCurrent	18000000	USD
CY2019Q4	us-gaap	Restructuring Reserve Current RestructuringReserveCurrent	21000000	USD
CY2020Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	39000000	USD
CY2019Q4	us-gaap	Derivative Liabilities Current DerivativeLiabilitiesCurrent	0	USD
CY2020Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	138000000	USD
CY2019Q4	us-gaap	Other Accrued Liabilities Current OtherAccruedLiabilitiesCurrent	108000000	USD
CY2020Q4	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	1039000000	USD
CY2019Q4	us-gaap	Accounts Payable And Accrued Liabilities Current AccountsPayableAndAccruedLiabilitiesCurrent	773000000	USD
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	244000000	USD
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	299000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	113000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	82000000	USD
CY2020Q4	mco	Disposal Group Including Discontinued Operation Indemnification Provision Liability DisposalGroupIncludingDiscontinuedOperationIndemnificationProvisionLiability	33000000	USD
CY2019Q4	mco	Disposal Group Including Discontinued Operation Indemnification Provision Liability DisposalGroupIncludingDiscontinuedOperationIndemnificationProvisionLiability	43000000	USD
CY2020Q4	us-gaap	Income Tax Examination Liability Refund Adjustment From Settlement With Taxing Authority IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority	18000000	USD
CY2019Q4	us-gaap	Income Tax Examination Liability Refund Adjustment From Settlement With Taxing Authority IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority	51000000	USD
CY2020Q4	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	145000000	USD
CY2019Q4	us-gaap	Derivative Liabilities Noncurrent DerivativeLiabilitiesNoncurrent	0	USD
CY2020Q4	us-gaap	Restructuring Reserve Noncurrent RestructuringReserveNoncurrent	3000000	USD
CY2019Q4	us-gaap	Restructuring Reserve Noncurrent RestructuringReserveNoncurrent	3000000	USD
CY2020Q4	us-gaap	Other Accrued Liabilities Noncurrent OtherAccruedLiabilitiesNoncurrent	34000000	USD
CY2019Q4	us-gaap	Other Accrued Liabilities Noncurrent OtherAccruedLiabilitiesNoncurrent	26000000	USD
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	590000000	USD
CY2019Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	504000000	USD
CY2020	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	0	USD
CY2020	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-7000000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	7000000	USD
CY2019	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	-25000000	USD
CY2019	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-32000000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-13000000	USD
CY2018	us-gaap	Oci Before Reclassifications Net Of Tax Attributable To Parent OciBeforeReclassificationsNetOfTaxAttributableToParent	-256000000	USD
CY2018	us-gaap	Reclassification From Aoci Current Period Net Of Tax Attributable To Parent ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent	-4000000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-254000000	USD
CY2019Q4	us-gaap	Employee Stock Ownership Plan Esop Shares In Esop EmployeeStockOwnershipPlanESOPSharesInESOP	411100	shares
CY2018	us-gaap	Employee Stock Ownership Plan Esop Dividends Paid To Esop EmployeeStockOwnershipPlanESOPDividendsPaidToESOP	1000000	USD
CY2020	us-gaap	Employee Stock Ownership Plan Esop Dividends Paid To Esop EmployeeStockOwnershipPlanESOPDividendsPaidToESOP	1000000	USD
CY2019	us-gaap	Employee Stock Ownership Plan Esop Dividends Paid To Esop EmployeeStockOwnershipPlanESOPDividendsPaidToESOP	1000000	USD
CY2020Q4	us-gaap	Employee Stock Ownership Plan Esop Shares In Esop EmployeeStockOwnershipPlanESOPSharesInESOP	360600	shares
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	154000000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	136000000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	130000000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	30000000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	29000000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	32000000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0080
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0114
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate	0.0105
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.23
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.24
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.26
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0143
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0256
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	38000000	USD
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P6Y2M12D
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.0282
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P5Y8M12D
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P6Y2M12D
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	60.66
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	43.29
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	45.73
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	1600000	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	93.51
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	100000	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	280.37
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	700000	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	59.57
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	1000000.0	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	133.95
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y7M6D
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	160000000	USD
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber	1000000.0	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	132.80
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1	P5Y7M6D
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	158000000	USD
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	700000	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	101.13
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P4Y7M6D
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	125000000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	39000000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	36000000	USD
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	132000000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	114000000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	99000000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	32000000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	27000000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Exercise Of Stock Options EmployeeServiceShareBasedCompensationTaxBenefitFromExerciseOfStockOptions	24000000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	213000000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	179000000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	168000000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	68000000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	59000000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	50000000	USD
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	215000000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	181000000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	233000000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	496000000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	419000000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	451000000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	6000000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-19000000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-59000000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	0	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-3000000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-2000000	USD
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-50000000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-16000000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-38000000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-44000000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-38000000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-99000000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	452000000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	381000000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	352000000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.023
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.022
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.022
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.015
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.001
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.018
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	0
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.028
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.015
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.021
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.011
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.203
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.210
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.211
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	514000000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	458000000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	442000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1349000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	1039000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	936000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	880000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	771000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	89000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	736000000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	2229000000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	1810000000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	1672000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	9000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	6000000	USD
CY2020Q4	mco	Deferred Tax Assets Accumulated Depreciation And Amortization Non Current DeferredTaxAssetsAccumulatedDepreciationAndAmortizationNonCurrent	2000000	USD
CY2019Q4	mco	Deferred Tax Assets Accumulated Depreciation And Amortization Non Current DeferredTaxAssetsAccumulatedDepreciationAndAmortizationNonCurrent	1000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	42000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	46000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Benefits DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits	99000000	USD
CY2020Q4	mco	Deferred Tax Assets Capitalized Cost DeferredTaxAssetsCapitalizedCost	39000000	USD
CY2019Q4	mco	Deferred Tax Assets Capitalized Cost DeferredTaxAssetsCapitalizedCost	0	USD
CY2020Q4	mco	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	122000000	USD
CY2019Q4	mco	Deferred Tax Assets Operating Lease Liabilities DeferredTaxAssetsOperatingLeaseLiabilities	136000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Deferred Income DeferredTaxAssetsDeferredIncome	30000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Deferred Income DeferredTaxAssetsDeferredIncome	37000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	17000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	13000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Restructuring Charges DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsRestructuringCharges	3000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Restructuring Charges DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsRestructuringCharges	4000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Contingencies DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsContingencies	98000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Contingencies DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsContingencies	94000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Self Insurance DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsSelfInsurance	10000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Self Insurance DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsSelfInsurance	8000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	93000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	10000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	13000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	574000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	447000000	USD
CY2020Q4	mco	Deferred Tax Liabilities Accumulated Depreciation And Amortization Non Current DeferredTaxLiabilitiesAccumulatedDepreciationAndAmortizationNonCurrent	468000000	USD
CY2019Q4	mco	Deferred Tax Liabilities Accumulated Depreciation And Amortization Non Current DeferredTaxLiabilitiesAccumulatedDepreciationAndAmortizationNonCurrent	389000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	90000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	107000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	23000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Investments DeferredTaxLiabilitiesInvestments	23000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	10000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	8000000	USD
CY2020Q4	us-gaap	Deferred Compensation Sharebased Arrangements Liability Current And Noncurrent DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent	0	USD
CY2019Q4	us-gaap	Deferred Compensation Sharebased Arrangements Liability Current And Noncurrent DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent	2000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	10000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	12000000	USD
CY2018Q4	mco	Deferred Tax Asset For Potential Transition Tax Benefit If Foreign Unrecognized Tax Benefits Not Sustained DeferredTaxAssetForPotentialTransitionTaxBenefitIfForeignUnrecognizedTaxBenefitsNotSustained	50000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	16000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	0	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	8000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	22000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	4000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	3000000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	629000000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	566000000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	55000000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	119000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	15000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	9000000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	70000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	128000000	USD
CY2017Q4	us-gaap	Tax Cuts And Jobs Act Of2017 Transition Tax For Accumulated Foreign Earnings Income Tax Expense TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense	247000000	USD
CY2018Q3	us-gaap	Tax Cuts And Jobs Act Of2017 Transition Tax For Accumulated Foreign Earnings Income Tax Expense TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense	236000000	USD
	us-gaap	Tax Cuts And Jobs Act Of2017 Measurement Period Adjustment Income Tax Expense Benefit TaxCutsAndJobsActOf2017MeasurementPeriodAdjustmentIncomeTaxExpenseBenefit	-11000000	USD
CY2018	mco	Estimated Repatriation Tax Liability Resulting From The Tax Act Pay Period EstimatedRepatriationTaxLiabilityResultingFromTheTaxActPayPeriod	P8Y
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	-60000000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Percent EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent	-0.0269
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	-44000000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Percent EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent	-0.0242
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	15000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	9000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	483000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	432000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	477000000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	495000000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	389000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	37000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	35000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	80000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	17000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	22000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	89000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	2000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	2000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	13000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	5000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	1000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	2000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	41000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	44000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	48000000	USD
CY2020	mco	Unrecognized Tax Benefits Decrease Resulting From Divestiture UnrecognizedTaxBenefitsDecreaseResultingFromDivestiture	0	USD
CY2019	mco	Unrecognized Tax Benefits Decrease Resulting From Divestiture UnrecognizedTaxBenefitsDecreaseResultingFromDivestiture	28000000	USD
CY2018	mco	Unrecognized Tax Benefits Decrease Resulting From Divestiture UnrecognizedTaxBenefitsDecreaseResultingFromDivestiture	0	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	483000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	477000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	0	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	500000000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	495000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	31000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Expense UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense	28000000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	113000000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	82000000	USD
CY2020Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	6430000000	USD
CY2020Q4	us-gaap	Interest Rate Derivatives At Fair Value Net InterestRateDerivativesAtFairValueNet	-56000000	USD
CY2020Q4	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	24000000	USD
CY2020Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	40000000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	6422000000	USD
CY2019Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	5603000000	USD
CY2019Q4	us-gaap	Interest Rate Derivatives At Fair Value Net InterestRateDerivativesAtFairValueNet	-27000000	USD
CY2019Q4	us-gaap	Debt Instrument Unamortized Discount Premium Net DebtInstrumentUnamortizedDiscountPremiumNet	17000000	USD
CY2019Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	32000000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	5581000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	500000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	500000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	700000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	4230000000	USD
CY2020Q4	us-gaap	Debt Instrument Face Amount DebtInstrumentFaceAmount	6430000000	USD
CY2020	us-gaap	Interest And Other Income InterestAndOtherIncome	11000000	USD
CY2019	us-gaap	Interest And Other Income InterestAndOtherIncome	17000000	USD
CY2018	us-gaap	Interest And Other Income InterestAndOtherIncome	15000000	USD
CY2020	us-gaap	Interest Expense Borrowings InterestExpenseBorrowings	163000000	USD
CY2019	us-gaap	Interest Expense Borrowings InterestExpenseBorrowings	176000000	USD
CY2018	us-gaap	Interest Expense Borrowings InterestExpenseBorrowings	197000000	USD
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	34000000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	28000000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	15000000	USD
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	19000000	USD
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	22000000	USD
CY2018	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	19000000	USD
CY2020	us-gaap	Interest Costs Capitalized Adjustment InterestCostsCapitalizedAdjustment	0	USD
CY2019	us-gaap	Interest Costs Capitalized Adjustment InterestCostsCapitalizedAdjustment	1000000	USD
CY2018	us-gaap	Interest Costs Capitalized Adjustment InterestCostsCapitalizedAdjustment	1000000	USD
CY2020	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-205000000	USD
CY2019	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-208000000	USD
CY2018	us-gaap	Interest Income Expense Nonoperating Net InterestIncomeExpenseNonoperatingNet	-215000000	USD
CY2020	us-gaap	Interest Paid InterestPaid	132000000	USD
CY2019	us-gaap	Interest Paid InterestPaid	167000000	USD
CY2018	us-gaap	Interest Paid InterestPaid	183000000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	6422000000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	5581000000	USD
CY2020Q4	us-gaap	Capital Units Authorized CapitalUnitsAuthorized	1020000000.00	shares
CY2020Q4	mco	Shares Of All Classes Of Stock Par Value SharesOfAllClassesOfStockParValue	0.01
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	1000000000.0	shares
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000.0	shares
CY2020	us-gaap	Schedule Of Repurchase Agreements ScheduleOfRepurchaseAgreements	The table below summarizes the Company’s remaining authority under its share repurchase program as of December 31, 2020:<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:99.707%"><tr><td style="width:1.0%"/><td style="width:62.243%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.533%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:16.495%"/><td style="width:0.1%"/><td style="width:0.1%"/><td style="width:0.533%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:16.496%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:8pt;font-weight:700;line-height:120%">Date Authorized</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:8pt;font-weight:700;line-height:120%">Amount Authorized</span></td><td colspan="3" style="padding:0 1pt"/><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:8pt;font-weight:700;line-height:120%">Remaining Authority</span></td></tr><tr><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/></tr><tr><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">December 16, 2019</span></td><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">1,000 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="3" style="background-color:#cceeff;padding:0 1pt"/><td colspan="2" style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:9pt;font-weight:400;line-height:120%">831 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/><td colspan="3" style="display:none"/></tr></table>
CY2020	us-gaap	Stock Issued During Period Shares Share Based Compensation Gross StockIssuedDuringPeriodSharesShareBasedCompensationGross	1400000	shares
CY2020Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.56
CY2020Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.56
CY2019Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.50
CY2019Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.50
CY2018Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.44
CY2018Q1	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.44
CY2020Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.56
CY2020Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.56
CY2019Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.50
CY2019Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.50
CY2018Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.44
CY2018Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.44
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.56
CY2020Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.56
CY2019Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.50
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.50
CY2018Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.44
CY2018Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.44
CY2020Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.56
CY2020Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.56
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.50
CY2019Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.50
CY2018Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.44
CY2018Q4	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.44
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.24
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	2.24
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.00
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	2.00
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.76
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.76
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	96000000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	97000000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	5000000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	2000000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	19000000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	17000000	USD
CY2020	us-gaap	Lease Cost LeaseCost	110000000	USD
CY2019	us-gaap	Lease Cost LeaseCost	112000000	USD
CY2020	us-gaap	Operating Lease Impairment Loss OperatingLeaseImpairmentLoss	21000000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	108000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	579000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	58000000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	106000000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	36000000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	41000000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P6Y9M18D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.036
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.036
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	110000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	99000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	93000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	84000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	76000000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	117000000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	521000000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	200000000	USD
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	94000000	USD
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	427000000	USD
CY2020	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	2	segment
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2020	us-gaap	Costs And Expenses CostsAndExpenses	2983000000	USD
CY2019	us-gaap	Costs And Expenses CostsAndExpenses	2831000000	USD
CY2020	us-gaap	Operating Income Loss OperatingIncomeLoss	2388000000	USD
CY2019	us-gaap	Operating Income Loss OperatingIncomeLoss	1998000000	USD
CY2020	us-gaap	Restructuring Charges RestructuringCharges	50000000	USD
CY2019	us-gaap	Restructuring Charges RestructuringCharges	60000000	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	220000000	USD
CY2020	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	0	USD
CY2019	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	3000000	USD
CY2020	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-9000000	USD
CY2019	us-gaap	Gain Loss On Sale Of Business GainLossOnSaleOfBusiness	-14000000	USD
CY2020	us-gaap	Litigation Settlement Amount Awarded To Other Party LitigationSettlementAmountAwardedToOtherParty	0	USD
CY2019	us-gaap	Litigation Settlement Amount Awarded To Other Party LitigationSettlementAmountAwardedToOtherParty	16000000	USD
CY2020	mco	Adjusted Operating Income AdjustedOperatingIncome	2667000000	USD
CY2019	mco	Adjusted Operating Income AdjustedOperatingIncome	2291000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2018	us-gaap	Costs And Expenses CostsAndExpenses	2575000000	USD
CY2018	us-gaap	Operating Income Loss OperatingIncomeLoss	1868000000	USD
CY2018	us-gaap	Restructuring Charges RestructuringCharges	49000000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	192000000	USD
CY2018	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	8000000	USD
CY2018	mco	Adjusted Operating Income AdjustedOperatingIncome	2117000000	USD
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	5371000000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4829000000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	4443000000	USD
CY2020Q4	us-gaap	Noncurrent Assets NoncurrentAssets	7051000000	USD
CY2019Q4	us-gaap	Noncurrent Assets NoncurrentAssets	5968000000	USD
CY2018Q4	us-gaap	Noncurrent Assets NoncurrentAssets	5667000000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2020	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	26000000	USD
CY2020	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	14000000	USD
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	34000000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	9000000	USD
CY2020	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	6000000	USD
CY2020	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	15000000	USD
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2019	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	10000000	USD
CY2019	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	10000000	USD
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	5000000	USD
CY2019	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	4000000	USD
CY2019	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	9000000	USD
CY2017Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	14000000	USD
CY2018	us-gaap	Provision For Doubtful Accounts ProvisionForDoubtfulAccounts	15000000	USD
CY2018	us-gaap	Allowance For Doubtful Accounts Receivable Write Offs AllowanceForDoubtfulAccountsReceivableWriteOffs	9000000	USD
CY2018Q4	us-gaap	Allowance For Doubtful Accounts Receivable Current AllowanceForDoubtfulAccountsReceivableCurrent	20000000	USD
CY2017Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	6000000	USD
CY2018	us-gaap	Valuation Allowance Deferred Tax Asset Change In Amount ValuationAllowanceDeferredTaxAssetChangeInAmount	0	USD
CY2018	us-gaap	Valuation Allowances And Reserves Deductions ValuationAllowancesAndReservesDeductions	1000000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	5000000	USD
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	2000000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-18000000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-11000000	USD
CY2020	mco	Pension Expense Net Periodic Pension Costs Other PensionExpenseNetPeriodicPensionCostsOther	13000000	USD
CY2019	mco	Pension Expense Net Periodic Pension Costs Other PensionExpenseNetPeriodicPensionCostsOther	18000000	USD
CY2018	mco	Pension Expense Net Periodic Pension Costs Other PensionExpenseNetPeriodicPensionCostsOther	10000000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	6000000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	13000000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	14000000	USD
CY2020	mco	Other Non Operating Income Expense Other OtherNonOperatingIncomeExpenseOther	25000000	USD
CY2019	mco	Other Non Operating Income Expense Other OtherNonOperatingIncomeExpenseOther	7000000	USD
CY2018	mco	Other Non Operating Income Expense Other OtherNonOperatingIncomeExpenseOther	6000000	USD
CY2020	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	46000000	USD
CY2019	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	20000000	USD
CY2018	us-gaap	Other Nonoperating Income Expense OtherNonoperatingIncomeExpense	19000000	USD

Files In Submission

Name	View Source	Status
0001059556-21-000010-index-headers.html	Edgar Link	pending
0001059556-21-000010-index.html	Edgar Link	pending
0001059556-21-000010.txt	Edgar Link	pending
0001059556-21-000010-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
mco-20201231.htm	Edgar Link	pending
mco-20201231.xsd	Edgar Link	pending
mco-20201231xexx1010.htm	Edgar Link	pending
mco-20201231xexx1011.htm	Edgar Link	pending
mco-20201231xexx105.htm	Edgar Link	pending
mco-20201231xexx21.htm	Edgar Link	pending
mco-20201231xexx231.htm	Edgar Link	pending
mco-20201231xexx311.htm	Edgar Link	pending
mco-20201231xexx312.htm	Edgar Link	pending
mco-20201231xexx321.htm	Edgar Link	pending
mco-20201231xexx322.htm	Edgar Link	pending
mco-20201231xexx41.htm	Edgar Link	pending
mco-20201231_cal.xml	Edgar Link	unprocessable
mco-20201231_def.xml	Edgar Link	unprocessable
mco-20201231_g1.jpg	Edgar Link	pending
mco-20201231_g10.jpg	Edgar Link	pending
mco-20201231_g100.jpg	Edgar Link	pending
mco-20201231_g101.jpg	Edgar Link	pending
mco-20201231_g102.jpg	Edgar Link	pending
mco-20201231_g103.jpg	Edgar Link	pending
mco-20201231_g104.jpg	Edgar Link	pending
mco-20201231_g105.jpg	Edgar Link	pending
mco-20201231_g106.jpg	Edgar Link	pending
mco-20201231_g107.jpg	Edgar Link	pending
mco-20201231_g108.jpg	Edgar Link	pending
mco-20201231_g109.jpg	Edgar Link	pending
mco-20201231_g11.jpg	Edgar Link	pending
mco-20201231_g110.jpg	Edgar Link	pending
mco-20201231_g111.jpg	Edgar Link	pending
mco-20201231_g112.jpg	Edgar Link	pending
mco-20201231_g113.jpg	Edgar Link	pending
mco-20201231_g114.jpg	Edgar Link	pending
mco-20201231_g115.jpg	Edgar Link	pending
mco-20201231_g116.jpg	Edgar Link	pending
mco-20201231_g117.jpg	Edgar Link	pending
mco-20201231_g118.jpg	Edgar Link	pending
mco-20201231_g119.jpg	Edgar Link	pending
mco-20201231_g12.jpg	Edgar Link	pending
mco-20201231_g120.jpg	Edgar Link	pending
mco-20201231_g121.jpg	Edgar Link	pending
mco-20201231_g122.jpg	Edgar Link	pending
mco-20201231_g123.jpg	Edgar Link	pending
mco-20201231_g124.jpg	Edgar Link	pending
mco-20201231_g125.jpg	Edgar Link	pending
mco-20201231_g126.jpg	Edgar Link	pending
mco-20201231_g127.jpg	Edgar Link	pending
mco-20201231_g128.jpg	Edgar Link	pending
mco-20201231_g129.jpg	Edgar Link	pending
mco-20201231_g13.jpg	Edgar Link	pending
mco-20201231_g130.jpg	Edgar Link	pending
mco-20201231_g131.jpg	Edgar Link	pending
mco-20201231_g132.jpg	Edgar Link	pending
mco-20201231_g133.jpg	Edgar Link	pending
mco-20201231_g134.jpg	Edgar Link	pending
mco-20201231_g135.jpg	Edgar Link	pending
mco-20201231_g136.jpg	Edgar Link	pending
mco-20201231_g137.jpg	Edgar Link	pending
mco-20201231_g138.jpg	Edgar Link	pending
mco-20201231_g139.jpg	Edgar Link	pending
mco-20201231_g14.jpg	Edgar Link	pending
mco-20201231_g140.jpg	Edgar Link	pending
mco-20201231_g141.jpg	Edgar Link	pending
mco-20201231_g142.jpg	Edgar Link	pending
mco-20201231_g143.jpg	Edgar Link	pending
mco-20201231_g144.jpg	Edgar Link	pending
mco-20201231_g145.jpg	Edgar Link	pending
mco-20201231_g146.jpg	Edgar Link	pending
mco-20201231_g147.jpg	Edgar Link	pending
mco-20201231_g148.jpg	Edgar Link	pending
mco-20201231_g149.jpg	Edgar Link	pending
mco-20201231_g15.jpg	Edgar Link	pending
mco-20201231_g150.jpg	Edgar Link	pending
mco-20201231_g151.jpg	Edgar Link	pending
mco-20201231_g152.jpg	Edgar Link	pending
mco-20201231_g153.jpg	Edgar Link	pending
mco-20201231_g154.jpg	Edgar Link	pending
mco-20201231_g155.jpg	Edgar Link	pending
mco-20201231_g156.jpg	Edgar Link	pending
mco-20201231_g157.jpg	Edgar Link	pending
mco-20201231_g158.jpg	Edgar Link	pending
mco-20201231_g159.jpg	Edgar Link	pending
mco-20201231_g16.jpg	Edgar Link	pending
mco-20201231_g160.jpg	Edgar Link	pending
mco-20201231_g161.jpg	Edgar Link	pending
mco-20201231_g162.jpg	Edgar Link	pending
mco-20201231_g163.jpg	Edgar Link	pending
mco-20201231_g164.jpg	Edgar Link	pending
mco-20201231_g165.jpg	Edgar Link	pending
mco-20201231_g166.jpg	Edgar Link	pending
mco-20201231_g167.jpg	Edgar Link	pending
mco-20201231_g168.jpg	Edgar Link	pending
mco-20201231_g17.jpg	Edgar Link	pending
mco-20201231_g18.jpg	Edgar Link	pending
mco-20201231_g19.jpg	Edgar Link	pending
mco-20201231_g2.jpg	Edgar Link	pending
mco-20201231_g20.jpg	Edgar Link	pending
mco-20201231_g21.jpg	Edgar Link	pending
mco-20201231_g22.jpg	Edgar Link	pending
mco-20201231_g23.jpg	Edgar Link	pending
mco-20201231_g24.jpg	Edgar Link	pending
mco-20201231_g25.jpg	Edgar Link	pending
mco-20201231_g26.jpg	Edgar Link	pending
mco-20201231_g27.jpg	Edgar Link	pending
mco-20201231_g28.jpg	Edgar Link	pending
mco-20201231_g29.jpg	Edgar Link	pending
mco-20201231_g3.jpg	Edgar Link	pending
mco-20201231_g30.jpg	Edgar Link	pending
mco-20201231_g31.jpg	Edgar Link	pending
mco-20201231_g32.jpg	Edgar Link	pending
mco-20201231_g33.jpg	Edgar Link	pending
mco-20201231_g34.jpg	Edgar Link	pending
mco-20201231_g35.jpg	Edgar Link	pending
mco-20201231_g36.jpg	Edgar Link	pending
mco-20201231_g37.jpg	Edgar Link	pending
mco-20201231_g38.jpg	Edgar Link	pending
mco-20201231_g39.jpg	Edgar Link	pending
mco-20201231_g4.jpg	Edgar Link	pending
mco-20201231_g40.jpg	Edgar Link	pending
mco-20201231_g41.jpg	Edgar Link	pending
mco-20201231_g42.jpg	Edgar Link	pending
mco-20201231_g43.jpg	Edgar Link	pending
mco-20201231_g44.jpg	Edgar Link	pending
mco-20201231_g45.jpg	Edgar Link	pending
mco-20201231_g46.jpg	Edgar Link	pending
mco-20201231_g47.jpg	Edgar Link	pending
mco-20201231_g48.jpg	Edgar Link	pending
mco-20201231_g49.jpg	Edgar Link	pending
mco-20201231_g5.jpg	Edgar Link	pending
mco-20201231_g50.jpg	Edgar Link	pending
mco-20201231_g51.jpg	Edgar Link	pending
mco-20201231_g52.jpg	Edgar Link	pending
mco-20201231_g53.jpg	Edgar Link	pending
mco-20201231_g54.jpg	Edgar Link	pending
mco-20201231_g55.jpg	Edgar Link	pending
mco-20201231_g56.jpg	Edgar Link	pending
mco-20201231_g57.jpg	Edgar Link	pending
mco-20201231_g58.jpg	Edgar Link	pending
mco-20201231_g59.jpg	Edgar Link	pending
mco-20201231_g6.jpg	Edgar Link	pending
mco-20201231_g60.jpg	Edgar Link	pending
mco-20201231_g61.jpg	Edgar Link	pending
mco-20201231_g62.jpg	Edgar Link	pending
mco-20201231_g63.jpg	Edgar Link	pending
mco-20201231_g64.jpg	Edgar Link	pending
mco-20201231_g65.jpg	Edgar Link	pending
mco-20201231_g66.jpg	Edgar Link	pending
mco-20201231_g67.jpg	Edgar Link	pending
mco-20201231_g68.jpg	Edgar Link	pending
mco-20201231_g69.jpg	Edgar Link	pending
mco-20201231_g7.jpg	Edgar Link	pending
mco-20201231_g70.jpg	Edgar Link	pending
mco-20201231_g71.jpg	Edgar Link	pending
mco-20201231_g72.jpg	Edgar Link	pending
mco-20201231_g73.jpg	Edgar Link	pending
mco-20201231_g74.jpg	Edgar Link	pending
mco-20201231_g75.jpg	Edgar Link	pending
mco-20201231_g76.jpg	Edgar Link	pending
mco-20201231_g77.jpg	Edgar Link	pending
mco-20201231_g78.jpg	Edgar Link	pending
mco-20201231_g79.jpg	Edgar Link	pending
mco-20201231_g8.jpg	Edgar Link	pending
mco-20201231_g80.jpg	Edgar Link	pending
mco-20201231_g81.jpg	Edgar Link	pending
mco-20201231_g82.jpg	Edgar Link	pending
mco-20201231_g83.jpg	Edgar Link	pending
mco-20201231_g84.jpg	Edgar Link	pending
mco-20201231_g85.jpg	Edgar Link	pending
mco-20201231_g86.jpg	Edgar Link	pending
mco-20201231_g87.jpg	Edgar Link	pending
mco-20201231_g88.jpg	Edgar Link	pending
mco-20201231_g89.jpg	Edgar Link	pending
mco-20201231_g9.jpg	Edgar Link	pending
mco-20201231_g90.jpg	Edgar Link	pending
mco-20201231_g91.jpg	Edgar Link	pending
mco-20201231_g92.jpg	Edgar Link	pending
mco-20201231_g93.jpg	Edgar Link	pending
mco-20201231_g94.jpg	Edgar Link	pending
mco-20201231_g95.jpg	Edgar Link	pending
mco-20201231_g96.jpg	Edgar Link	pending
mco-20201231_g97.jpg	Edgar Link	pending
mco-20201231_g98.jpg	Edgar Link	pending
mco-20201231_g99.jpg	Edgar Link	pending
mco-20201231_htm.xml	Edgar Link	completed
mco-20201231_lab.xml	Edgar Link	unprocessable
mco-20201231_pre.xml	Edgar Link	unprocessable
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
R101.htm	Edgar Link	pending
R102.htm	Edgar Link	pending
R103.htm	Edgar Link	pending
R104.htm	Edgar Link	pending
R105.htm	Edgar Link	pending
R106.htm	Edgar Link	pending
R107.htm	Edgar Link	pending
R108.htm	Edgar Link	pending
R109.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R110.htm	Edgar Link	pending
R111.htm	Edgar Link	pending
R112.htm	Edgar Link	pending
R113.htm	Edgar Link	pending
R114.htm	Edgar Link	pending
R115.htm	Edgar Link	pending
R116.htm	Edgar Link	pending
R117.htm	Edgar Link	pending
R118.htm	Edgar Link	pending
R119.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R120.htm	Edgar Link	pending
R121.htm	Edgar Link	pending
R122.htm	Edgar Link	pending
R123.htm	Edgar Link	pending
R124.htm	Edgar Link	pending
R125.htm	Edgar Link	pending
R126.htm	Edgar Link	pending
R127.htm	Edgar Link	pending
R128.htm	Edgar Link	pending
R129.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R130.htm	Edgar Link	pending
R131.htm	Edgar Link	pending
R132.htm	Edgar Link	pending
R133.htm	Edgar Link	pending
R134.htm	Edgar Link	pending
R135.htm	Edgar Link	pending
R136.htm	Edgar Link	pending
R137.htm	Edgar Link	pending
R138.htm	Edgar Link	pending
R139.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R140.htm	Edgar Link	pending
R141.htm	Edgar Link	pending
R142.htm	Edgar Link	pending
R143.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R96.htm	Edgar Link	pending
R97.htm	Edgar Link	pending
R98.htm	Edgar Link	pending
R99.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$MCO
MOODYS CORP /DE/ Stock $mco

2019 Q4 Form 10-K Financial Statement

#000105955621000010 Filed on February 22, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MCO MOODYS CORP /DE/ Stock $mco

2019 Q4 Form 10-K Financial Statement

#000105955621000010 Filed on February 22, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$MCO
MOODYS CORP /DE/ Stock $mco