Long-Term Debt, Maturity, after Year Four

No definition available.

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Namespace Prefix:	mco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in remainder of current fiscal year.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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Indebtedness - Principal Payments Due on Long-Term Borrowings (Detail) - USD ($) $ in Millions	6 Months Ended	9 Months Ended
	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
2020 (After September 30,)		$ 0
2021		0
2022		500
2023		500
2024		500
Thereafter		4,865
Total principal payment		6,365	$ 5,603
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
2022		500
Total principal payment		500	500
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
2024		500
Total principal payment		500	500
5.25% 2014 Senior Notes (30-Year), due 2044
Debt Instrument [Line Items]
Thereafter		600
Total principal payment		$ 600	600
Debt instrument, term	30 years	30 years
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Thereafter		$ 586
Total principal payment		586	561
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
2023		500
Total principal payment		500	500
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Thereafter		500
Total principal payment		500	500
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Thereafter		400
Total principal payment		400	400
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Thereafter		400
Total principal payment		400	400
0.950% Senior Notes Due 2030
Debt Instrument [Line Items]
Thereafter		879
Total principal payment		879	$ 842
3.75% 2020 Senior Notes, due 2025
Debt Instrument [Line Items]
Thereafter		700
Total principal payment		$ 700
Debt instrument, term		5 years
3.25% 2020 Senior Notes, due 2050
Debt Instrument [Line Items]
Thereafter		$ 300
Total principal payment		$ 300
Debt instrument, term		30 years
2.55% 2020 Senior Notes, due 2060
Debt Instrument [Line Items]
Thereafter		$ 500
Total principal payment		$ 500
Debt instrument, term		40 years