Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 1,472	$ 1,275	$ 4,436	$ 4,178
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 436	$ 334	$ 1,403	$ 1,359
Percentage of revenues	30.00%	26.00%	32.00%	33.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,036	$ 941	$ 3,033	$ 2,819
Percentage of revenues	70.00%	74.00%	68.00%	67.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 776	$ 685	$ 2,260	$ 2,055
MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 779	$ 687	$ 2,270	$ 2,060
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 354	$ 308
MA | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 354	$ 308	$ 1,022	$ 916
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 222	$ 201
MA | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 222	$ 201	$ 654	$ 607
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 200	$ 176
MA | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 200	$ 176	$ 584	$ 532
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 48	$ 38	$ 140	$ 124
MA | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	6.00%	6.00%	6.00%	6.00%
MA | Transaction Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 43	$ 34	$ 126	$ 112
Percentage of revenues	12.00%	11.00%	12.00%	12.00%
MA | Transaction Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 4	$ 4	$ 12	$ 12
Percentage of revenues	2.00%	2.00%	2.00%	2.00%
MA | Transaction Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 0	$ 2	$ 0
Percentage of revenues	1.00%	0.00%	0.00%	0.00%
MA | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 728	$ 647	$ 2,120	$ 1,931
MA | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	94.00%	94.00%	94.00%	94.00%
MA | Recurring Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 311	$ 274	$ 896	$ 804
Percentage of revenues	88.00%	89.00%	88.00%	88.00%
MA | Recurring Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 218	$ 197	$ 642	$ 595
Percentage of revenues	98.00%	98.00%	98.00%	98.00%
MA | Recurring Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 199	$ 176	$ 582	$ 532
Percentage of revenues	99.00%	100.00%	100.00%	100.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 696	$ 590	$ 2,176	$ 2,123
MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 743	$ 633	$ 2,314	$ 2,252
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 346	$ 277
MIS | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 346	$ 277	$ 1,067	$ 1,016
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 102	$ 101
MIS | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 102	$ 101	$ 303	$ 368
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 126	$ 109
MIS | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 126	$ 109	$ 413	$ 368
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 115	$ 92
MIS | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 115	$ 92	$ 371	$ 337
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 11
MIS | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 11	$ 22	$ 34
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 388	$ 296	$ 1,263	$ 1,235
MIS | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	56.00%	50.00%	58.00%	58.00%
MIS | Transaction Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 216	$ 153	$ 682	$ 645
Percentage of revenues	62.00%	55.00%	64.00%	63.00%
MIS | Transaction Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 48	$ 51	$ 142	$ 217
Percentage of revenues	47.00%	50.00%	47.00%	59.00%
MIS | Transaction Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 52	$ 41	$ 195	$ 159
Percentage of revenues	41.00%	38.00%	47.00%	43.00%
MIS | Transaction Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 71	$ 50	$ 240	$ 211
Percentage of revenues	62.00%	54.00%	65.00%	63.00%
MIS | Transaction Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 1	$ 4	$ 3
Percentage of revenues	14.00%	9.00%	18.00%	9.00%
MIS | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 308	$ 294	$ 913	$ 888
MIS | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	44.00%	50.00%	42.00%	42.00%
MIS | Recurring Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 130	$ 124	$ 385	$ 371
Percentage of revenues	38.00%	45.00%	36.00%	37.00%
MIS | Recurring Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 54	$ 50	$ 161	$ 151
Percentage of revenues	53.00%	50.00%	53.00%	41.00%
MIS | Recurring Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 74	$ 68	$ 218	$ 209
Percentage of revenues	59.00%	62.00%	53.00%	57.00%
MIS | Recurring Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 44	$ 42	$ 131	$ 126
Percentage of revenues	38.00%	46.00%	35.00%	37.00%
MIS | Recurring Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 6	$ 10	$ 18	$ 31
Percentage of revenues	86.00%	91.00%	82.00%	91.00%