Revenues - Revenue by Category (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
Eliminations
Disaggregation of Revenue [Line Items]
Revenue	(210)	(206)	(199)
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	7,718	7,088	5,916
Eliminations
Disaggregation of Revenue [Line Items]
Revenue	(210)	(206)	(199)
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 | Eliminations
Disaggregation of Revenue [Line Items]
Revenue	12	13	13
MA | Total Decision Solutions | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,692	1,516	1,383
MA | Total Decision Solutions | Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	569	551	521
MA | Total Decision Solutions | Insurance | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	685	598	550
MA | Total Decision Solutions | KYC | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	438	367	312
MA | Research and Insights | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	995	926	884
MA | Data and Information | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	912	853	789
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 | Eliminations
Disaggregation of Revenue [Line Items]
Revenue	198	193	186
MIS | Corporate finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	2,132	1,950	1,404
MIS | Corporate finance (CFG) | Investment-grade | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	573	488	335
MIS | Corporate finance (CFG) | High-yield | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	324	285	150
MIS | Corporate finance (CFG) | Bank loans | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	503	527	292
MIS | Corporate finance (CFG) | Other accounts | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	732	650	627
MIS | Structured finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	558	518	405
MIS | Structured finance (SFG) | Asset-backed securities | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	142	130	121
MIS | Structured finance (SFG) | RMBS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	111	98	92
MIS | Structured finance (SFG) | CMBS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	99	94	60
MIS | Structured finance (SFG) | Structured credit | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	202	193	129
MIS | Structured finance (SFG) | Other accounts | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4	3	3
MIS | Financial institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	759	727	545
MIS | Financial institutions (FIG) | Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	500	450	378
MIS | Financial institutions (FIG) | Insurance | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	186	214	123
MIS | Financial institutions (FIG) | Managed investments | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	59	49	32
MIS | Financial institutions (FIG) | Other accounts | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	14	14	12
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) | Public finance / sovereign | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	275	240	205
MIS | Public, project and infrastructure finance (PPIF) | Project and infrastructure | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	360	324	271
MIS | Rating Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4,084	3,759	2,830
MIS | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 35	$ 34	$ 30