Segment Information - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) segment lineOfBusiness
Segment Reporting Information [Line Items]
Number of operating segments \| segment	2
Number of reportable segments \| segment	2
MIS
Segment Reporting Information [Line Items]
Number of lines of business \| lineOfBusiness	5
MA
Segment Reporting Information [Line Items]
Number of lines of business \| lineOfBusiness	2
2018 Restructuring Program \| MIS
Segment Reporting Information [Line Items]
Cumulative expense incurred to date	$ 61
2018 Restructuring Program \| MA
Segment Reporting Information [Line Items]
Cumulative expense incurred to date	44
2020 Real Estate Rationalization Restructuring Program \| MIS
Segment Reporting Information [Line Items]
Cumulative expense incurred to date	21
2020 Real Estate Rationalization Restructuring Program \| MA
Segment Reporting Information [Line Items]
Cumulative expense incurred to date	15
2020 MA Strategic Reorganization Restructuring Program \| MA
Segment Reporting Information [Line Items]
Cumulative expense incurred to date	$ 18

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

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- Definition

Amount of costs incurred to date for the specified restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
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-Name Accounting Standards Codification
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- 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

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