Goodwill And Other Acquired Intangible Assets - Activity in Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Beginning balance, Goodwill gross	$ 3,734	$ 3,793
Beginning balance, Accumulated impairment charge	(12)	(12)
Beginning balance, goodwill net	3,722	3,781
Additions/adjustments	626	114
Foreign currency translation adjustments	208	(10)
Divestiture of MAKS		(163)
Ending balance, Goodwill gross	4,568	3,734
Ending balance, Accumulated impairment charge	(12)	(12)
Ending balance, goodwill net	4,556	3,722
MIS
Goodwill [Roll Forward]
Beginning balance, Goodwill gross	315	258
Beginning balance, Accumulated impairment charge	0	0
Beginning balance, goodwill net	315	258
Additions/adjustments	(2)	53
Foreign currency translation adjustments	(2)	4
Ending balance, Goodwill gross	311	315
Ending balance, Accumulated impairment charge	0	0
Ending balance, goodwill net	311	315
MA
Goodwill [Roll Forward]
Beginning balance, Goodwill gross	3,419	3,535
Beginning balance, Accumulated impairment charge	(12)	(12)
Beginning balance, goodwill net	3,407	3,523
Additions/adjustments	628	61
Foreign currency translation adjustments	210	(14)
Divestiture of MAKS		(163)
Ending balance, Goodwill gross	4,257	3,419
Ending balance, Accumulated impairment charge	(12)	(12)
Ending balance, goodwill net	$ 4,245	$ 3,407

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of increase (decrease) from foreign currency translation adjustments and purchase accounting adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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