Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 1,494	$ 1,381	$ 2,964	$ 2,903
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 490	$ 454	$ 967	$ 1,025
Percentage of revenues	33.00%	33.00%	33.00%	35.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,004	$ 927	$ 1,997	$ 1,878
Percentage of revenues	67.00%	67.00%	67.00%	65.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 747	$ 675	$ 1,484	$ 1,370
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 334	$ 294	$ 668	$ 608
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 217	$ 203	$ 432	$ 406
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 196	$ 178	$ 384	$ 356
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 47	$ 42	$ 92	$ 86
Percentage of revenues	6.00%	6.00%	6.00%	6.00%
MA | Transaction Revenue | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 43	$ 38	$ 83	$ 78
Percentage of revenues	13.00%	13.00%	12.00%	13.00%
MA | Transaction Revenue | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 4	$ 8	$ 8
Percentage of revenues	1.00%	2.00%	2.00%	2.00%
MA | Transaction Revenue | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 0	$ 1	$ 0
Percentage of revenues	1.00%	0.00%	0.00%	0.00%
MA | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 700	$ 633	$ 1,392	$ 1,284
Percentage of revenues	94.00%	94.00%	94.00%	94.00%
MA | Recurring Revenue | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 291	$ 256	$ 585	$ 530
Percentage of revenues	87.00%	87.00%	88.00%	87.00%
MA | Recurring Revenue | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 214	$ 199	$ 424	$ 398
Percentage of revenues	99.00%	98.00%	98.00%	98.00%
MA | Recurring Revenue | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 195	$ 178	$ 383	$ 356
Percentage of revenues	99.00%	100.00%	100.00%	100.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 747	$ 706	$ 1,480	$ 1,533
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 365	$ 322	$ 721	$ 739
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 102	$ 123	$ 201	$ 267
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 145	$ 128	$ 287	$ 259
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 127	$ 122	$ 256	$ 245
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 8	$ 11	$ 15	$ 23
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 443	$ 412	$ 875	$ 939
Percentage of revenues	59.00%	58.00%	59.00%	61.00%
MIS | Transaction Revenue | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 236	$ 199	$ 466	$ 492
Percentage of revenues	65.00%	62.00%	65.00%	67.00%
MIS | Transaction Revenue | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 48	$ 73	$ 94	$ 166
Percentage of revenues	47.00%	59.00%	47.00%	62.00%
MIS | Transaction Revenue | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 73	$ 57	$ 143	$ 118
Percentage of revenues	50.00%	45.00%	50.00%	46.00%
MIS | Transaction Revenue | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 84	$ 82	$ 169	$ 161
Percentage of revenues	66.00%	67.00%	66.00%	66.00%
MIS | Transaction Revenue | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 2	$ 1	$ 3	$ 2
Percentage of revenues	25.00%	9.00%	20.00%	9.00%
MIS | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 304	$ 294	$ 605	$ 594
Percentage of revenues	41.00%	42.00%	41.00%	39.00%
MIS | Recurring Revenue | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 129	$ 123	$ 255	$ 247
Percentage of revenues	35.00%	38.00%	35.00%	33.00%
MIS | Recurring Revenue | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 54	$ 50	$ 107	$ 101
Percentage of revenues	53.00%	41.00%	53.00%	38.00%
MIS | Recurring Revenue | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 72	$ 71	$ 144	$ 141
Percentage of revenues	50.00%	55.00%	50.00%	54.00%
MIS | Recurring Revenue | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 43	$ 40	$ 87	$ 84
Percentage of revenues	34.00%	33.00%	34.00%	34.00%
MIS | Recurring Revenue | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 6	$ 10	$ 12	$ 21
Percentage of revenues	75.00%	91.00%	80.00%	91.00%