Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 1,817	$ 1,494	$ 3,603	$ 2,964
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 731	$ 490	$ 1,450	$ 967
Percentage of revenues	40.00%	33.00%	40.00%	33.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,086	$ 1,004	$ 2,153	$ 1,997
Percentage of revenues	60.00%	67.00%	60.00%	67.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 802	$ 747	$ 1,601	$ 1,484
MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 806	$ 751	$ 1,608	$ 1,491
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 366	$ 334
MA | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 366	$ 334	$ 731	$ 668
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 226	$ 217
MA | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 226	$ 217	$ 448	$ 432
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 210	$ 196
MA | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 210	$ 196	$ 422	$ 384
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 39	$ 47	$ 81	$ 92
MA | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	5.00%	6.00%	5.00%	6.00%
MA | Transaction Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 35	$ 43	$ 72	$ 83
Percentage of revenues	10.00%	13.00%	10.00%	12.00%
MA | Transaction Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 3	$ 7	$ 8
Percentage of revenues	1.00%	1.00%	2.00%	2.00%
MA | Transaction Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 1	$ 2	$ 1
Percentage of revenues	0.00%	1.00%	0.00%	0.00%
MA | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 763	$ 700	$ 1,520	$ 1,392
MA | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	95.00%	94.00%	95.00%	94.00%
MA | Recurring Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 331	$ 291	$ 659	$ 585
Percentage of revenues	90.00%	87.00%	90.00%	88.00%
MA | Recurring Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 223	$ 214	$ 441	$ 424
Percentage of revenues	99.00%	99.00%	98.00%	98.00%
MA | Recurring Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 209	$ 195	$ 420	$ 383
Percentage of revenues	100.00%	99.00%	100.00%	100.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 1,015	$ 747	$ 2,002	$ 1,480
MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,064	$ 793	$ 2,098	$ 1,571
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 525	$ 365
MIS | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 525	$ 365	$ 1,054	$ 721
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 131	$ 102
MIS | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 131	$ 102	$ 245	$ 201
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 195	$ 145
MIS | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 195	$ 145	$ 390	$ 287
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 154	$ 127
MIS | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 154	$ 127	$ 295	$ 256
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 10	$ 8
MIS | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 10	$ 8	$ 18	$ 15
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 692	$ 443	$ 1,369	$ 875
MIS | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	68.00%	59.00%	68.00%	59.00%
MIS | Transaction Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 388	$ 236	$ 787	$ 466
Percentage of revenues	74.00%	65.00%	75.00%	65.00%
MIS | Transaction Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 76	$ 48	$ 135	$ 94
Percentage of revenues	58.00%	47.00%	55.00%	47.00%
MIS | Transaction Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 115	$ 73	$ 237	$ 143
Percentage of revenues	59.00%	50.00%	61.00%	50.00%
MIS | Transaction Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 110	$ 84	$ 206	$ 169
Percentage of revenues	71.00%	66.00%	70.00%	66.00%
MIS | Transaction Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 2	$ 4	$ 3
Percentage of revenues	30.00%	25.00%	22.00%	20.00%
MIS | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 323	$ 304	$ 633	$ 605
MIS | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	32.00%	41.00%	32.00%	41.00%
MIS | Recurring Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 137	$ 129	$ 267	$ 255
Percentage of revenues	26.00%	35.00%	25.00%	35.00%
MIS | Recurring Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 55	$ 54	$ 110	$ 107
Percentage of revenues	42.00%	53.00%	45.00%	53.00%
MIS | Recurring Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 80	$ 72	$ 153	$ 144
Percentage of revenues	41.00%	50.00%	39.00%	50.00%
MIS | Recurring Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 44	$ 43	$ 89	$ 87
Percentage of revenues	29.00%	34.00%	30.00%	34.00%
MIS | Recurring Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 6	$ 14	$ 12
Percentage of revenues	70.00%	75.00%	78.00%	80.00%