Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
Dec. 31, 2025 reportingUnit customer	Dec. 31, 2024 customer reportingUnit
Capitalized Contract Cost [Line Items]
Number of reporting units	3
Number of customers greater than 10% or more of accounts receivable \| customer	0	0
MIS
Capitalized Contract Cost [Line Items]
Number of reporting units	2
MIS \| Moodys Other Ratings Operations
Capitalized Contract Cost [Line Items]
Number of reporting units	1
MA
Capitalized Contract Cost [Line Items]
Number of reporting units	1	2
Subscription and Maintenance Contracts \| MA \| Minimum
Capitalized Contract Cost [Line Items]
Revenue, contractual coverage period (years)	3 years
General customer contract payment condition (days)	30 days
Subscription and Maintenance Contracts \| MA \| Maximum
Capitalized Contract Cost [Line Items]
Revenue, contractual coverage period (years)	5 years
General customer contract payment condition (days)	60 days

The days in which payment is required under the general terms and conditions of a revenue contract with customers.

No definition available.

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Customers Greater Than 10 Percent or More of Accounts Receivable

+ References

No definition available.

+ Details

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Namespace Prefix:	mco_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Revenue, Contractual Coverage Period

+ References

No definition available.

+ Details

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Namespace Prefix:	mco_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479483/340-40-50-3

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mco_MoodysAnalyticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
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