Revenues - Revenues Disaggregated by Line of Business and Geographical Area (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 7,718	$ 7,088	$ 5,916
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	7,718	7,088	5,916
U.S.
Disaggregation of Revenue [Line Items]
Revenue	4,171	3,836	3,071
Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	3,547	3,252	2,845
MA
Disaggregation of Revenue [Line Items]
Revenue	3,599	3,295	3,056
MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	3,611	3,308	3,069
MA | U.S.
Disaggregation of Revenue [Line Items]
Revenue	1,548	1,390	1,321
MA | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,548	1,390	1,321
MA | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	2,051	1,905	1,735
MA | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,051	1,905	1,735
MA | Total Decision Solutions | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,692	1,516	1,383
MA | Total Decision Solutions | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	674	570	550
MA | Total Decision Solutions | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,018	946	833
MA | Research and Insights | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	995	926	884
MA | Research and Insights | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	547	514	490
MA | Research and Insights | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	448	412	394
MA | Data and Information | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	912	853	789
MA | Data and Information | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	327	306	281
MA | Data and Information | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	585	547	508
MIS
Disaggregation of Revenue [Line Items]
Revenue	4,119	3,793	2,860
MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4,317	3,986	3,046
MIS | U.S.
Disaggregation of Revenue [Line Items]
Revenue	2,623	2,446	1,750
MIS | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,623	2,446	1,750
MIS | Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	1,496	1,347	1,110
MIS | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,496	1,347	1,110
MIS | Rating Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4,084	3,759	2,830
MIS | Rating Revenue | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,623	2,446	1,749
MIS | Rating Revenue | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,461	1,313	1,081
MIS | Corporate finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,132	1,950	1,404
MIS | Corporate finance (CFG) | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,427	1,333	952
MIS | Corporate finance (CFG) | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	705	617	452
MIS | Structured finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	558	518	405
MIS | Structured finance (SFG) | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	396	368	252
MIS | Structured finance (SFG) | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	162	150	153
MIS | Financial institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	759	727	545
MIS | Financial institutions (FIG) | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	384	386	253
MIS | Financial institutions (FIG) | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	375	341	292
MIS | Public, project and infrastructure finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	635	564	476
MIS | Public, project and infrastructure finance (PPIF) | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	416	359	292
MIS | Public, project and infrastructure finance (PPIF) | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	219	205	184
MIS | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	35	34	30
MIS | MIS Other | U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0	1
MIS | MIS Other | Non-U.S. | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 35	$ 34	$ 29