Revenues - Revenues Disaggregated by Line of Business and Geographical Area (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 1,470	$ 1,522
United States
Disaggregation of Revenue [Line Items]
Revenue	770	823
Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	700	699
MA
Disaggregation of Revenue [Line Items]
Revenue	737	695
MA | United States
Disaggregation of Revenue [Line Items]
Revenue	324	310
MA | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	413	385
MA | Decision Solutions
Disaggregation of Revenue [Line Items]
Revenue	354	334
MA | Decision Solutions | United States
Disaggregation of Revenue [Line Items]
Revenue	152	147
MA | Decision Solutions | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	202	187
MA | Research and Insights
Disaggregation of Revenue [Line Items]
Revenue	195	183
MA | Research and Insights | United States
Disaggregation of Revenue [Line Items]
Revenue	105	103
MA | Research and Insights | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	90	80
MA | Data and Information
Disaggregation of Revenue [Line Items]
Revenue	188	178
MA | Data and Information | United States
Disaggregation of Revenue [Line Items]
Revenue	67	60
MA | Data and Information | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	121	118
MIS
Disaggregation of Revenue [Line Items]
Revenue	733	827
MIS | United States
Disaggregation of Revenue [Line Items]
Revenue	446	513
MIS | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	287	314
MIS | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	356	417
MIS | Corporate Finance (CFG) | United States
Disaggregation of Revenue [Line Items]
Revenue	246	275
MIS | Corporate Finance (CFG) | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	110	142
MIS | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	99	144
MIS | Structured Finance (SFG) | United States
Disaggregation of Revenue [Line Items]
Revenue	61	97
MIS | Structured Finance (SFG) | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	38	47
MIS | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	142	131
MIS | Financial Institutions (FIG) | United States
Disaggregation of Revenue [Line Items]
Revenue	63	65
MIS | Financial Institutions (FIG) | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	79	66
MIS | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	129	123
MIS | Public, Project and Infrastructure Finance (PPIF) | United States
Disaggregation of Revenue [Line Items]
Revenue	76	75
MIS | Public, Project and Infrastructure Finance (PPIF) | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	53	48
MIS | Total ratings revenue
Disaggregation of Revenue [Line Items]
Revenue	726	815
MIS | Total ratings revenue | United States
Disaggregation of Revenue [Line Items]
Revenue	446	512
MIS | Total ratings revenue | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	280	303
MIS | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	7	12
MIS | MIS Other | United States
Disaggregation of Revenue [Line Items]
Revenue	0	1
MIS | MIS Other | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 11