Revenues - Transaction and Relationship Revenue (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
Percentage of Revenues	100.00%	100.00%	100.00%
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7,718	$ 7,088	$ 5,916
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
Percentage of Revenues	100.00%	100.00%	100.00%
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
Percentage of Revenues	100.00%	100.00%	100.00%
Banking | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 569	$ 551	$ 521
Percentage of Revenues	100.00%	100.00%	100.00%
Insurance | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 685	$ 598	$ 550
Percentage of Revenues	100.00%	100.00%	100.00%
KYC | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 438	$ 367	$ 312
Percentage of Revenues	100.00%	100.00%	100.00%
Corporate finance (CFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 2,132	$ 1,950	$ 1,404
Percentage of Revenues	100.00%	100.00%	100.00%
Structured finance (SFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 558	$ 518	$ 405
Percentage of Revenues	100.00%	100.00%	100.00%
Financial institutions (FIG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 759	$ 727	$ 545
Percentage of Revenues	100.00%	100.00%	100.00%
Public, project and infrastructure finance (PPIF) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 635	$ 564	$ 476
Percentage of Revenues	100.00%	100.00%	100.00%
MIS Other | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 35	$ 34	$ 30
Percentage of Revenues	100.00%	100.00%	100.00%
Total Decision Solutions | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,692	$ 1,516	$ 1,383
Percentage of Revenues	100.00%	100.00%	100.00%
Research and Insights | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 995	$ 926	$ 884
Percentage of Revenues	100.00%	100.00%	100.00%
Data and Information | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 912	$ 853	$ 789
Percentage of Revenues	100.00%	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 2,878	$ 2,687	$ 1,837
Percentage of Revenues	37.00%	38.00%	31.00%
Transaction Revenue | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 137	$ 170	$ 199
Transaction Revenue | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of Revenues	4.00%	5.00%	7.00%
Transaction Revenue | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 2,741	$ 2,517	$ 1,638
Transaction Revenue | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of Revenues	67.00%	66.00%	57.00%
Transaction Revenue | Banking | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 93	$ 113	$ 126
Percentage of Revenues	16.00%	21.00%	24.00%
Transaction Revenue | Insurance | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 21	$ 26	$ 47
Percentage of Revenues	3.00%	4.00%	9.00%
Transaction Revenue | KYC | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 7	$ 5
Percentage of Revenues	1.00%	2.00%	2.00%
Transaction Revenue | Corporate finance (CFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,559	$ 1,415	$ 887
Percentage of Revenues	73.00%	73.00%	63.00%
Transaction Revenue | Structured finance (SFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 315	$ 292	$ 190
Percentage of Revenues	56.00%	56.00%	47.00%
Transaction Revenue | Financial institutions (FIG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 422	$ 418	$ 254
Percentage of Revenues	56.00%	57.00%	47.00%
Transaction Revenue | Public, project and infrastructure finance (PPIF) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 438	$ 384	$ 301
Percentage of Revenues	69.00%	68.00%	63.00%
Transaction Revenue | MIS Other | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 8	$ 6
Percentage of Revenues	20.00%	24.00%	20.00%
Transaction Revenue | Total Decision Solutions | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 117	$ 146	$ 178
Percentage of Revenues	7.00%	10.00%	13.00%
Transaction Revenue | Research and Insights | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 12	$ 12	$ 14
Percentage of Revenues	1.00%	1.00%	2.00%
Transaction Revenue | Data and Information | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 8	$ 12	$ 7
Percentage of Revenues	1.00%	1.00%	1.00%
Relationship Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 4,840	$ 4,401	$ 4,079
Percentage of Revenues	63.00%	62.00%	69.00%
Relationship Revenue | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 3,462	$ 3,125	$ 2,857
Relationship Revenue | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of Revenues	96.00%	95.00%	93.00%
Relationship Revenue | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 1,378	$ 1,276	$ 1,222
Relationship Revenue | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of Revenues	33.00%	34.00%	43.00%
Relationship Revenue | Banking | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 476	$ 438	$ 395
Percentage of Revenues	84.00%	79.00%	76.00%
Relationship Revenue | Insurance | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 664	$ 572	$ 503
Percentage of Revenues	97.00%	96.00%	91.00%
Relationship Revenue | KYC | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 435	$ 360	$ 307
Percentage of Revenues	99.00%	98.00%	98.00%
Relationship Revenue | Corporate finance (CFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 573	$ 535	$ 517
Percentage of Revenues	27.00%	27.00%	37.00%
Relationship Revenue | Structured finance (SFG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 243	$ 226	$ 215
Percentage of Revenues	44.00%	44.00%	53.00%
Relationship Revenue | Financial institutions (FIG) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 337	$ 309	$ 291
Percentage of Revenues	44.00%	43.00%	53.00%
Relationship Revenue | Public, project and infrastructure finance (PPIF) | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 197	$ 180	$ 175
Percentage of Revenues	31.00%	32.00%	37.00%
Relationship Revenue | MIS Other | MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 28	$ 26	$ 24
Percentage of Revenues	80.00%	76.00%	80.00%
Relationship Revenue | Total Decision Solutions | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,575	$ 1,370	$ 1,205
Percentage of Revenues	93.00%	90.00%	87.00%
Relationship Revenue | Research and Insights | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 983	$ 914	$ 870
Percentage of Revenues	99.00%	99.00%	98.00%
Relationship Revenue | Data and Information | MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 904	$ 841	$ 782
Percentage of Revenues	99.00%	99.00%	99.00%