Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 1,786	$ 1,470
Percentage of revenues	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 719	$ 476
Percentage of revenues	40.00%	32.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,067	$ 994
Percentage of revenues	60.00%	68.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 799	$ 737
MA | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 802	$ 740
Percentage of revenues	100.00%	100.00%
MA | Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 365	$ 334
MA | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 365	$ 334
Percentage of revenues	100.00%	100.00%
MA | Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 222	$ 215
MA | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 222	$ 215
Percentage of revenues	100.00%	100.00%
MA | Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 212	$ 188
MA | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 212	$ 188
Percentage of revenues	100.00%	100.00%
MA | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 42	$ 45
MA | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	5.00%	6.00%
MA | Transaction Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 37	$ 40
Percentage of revenues	10.00%	12.00%
MA | Transaction Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 4	$ 5
Percentage of revenues	2.00%	2.00%
MA | Transaction Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 0
Percentage of revenues	0.00%	0.00%
MA | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 757	$ 692
MA | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	95.00%	94.00%
MA | Recurring Revenue | Decision Solutions (DS) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 328	$ 294
Percentage of revenues	90.00%	88.00%
MA | Recurring Revenue | Research and Insights (R&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 218	$ 210
Percentage of revenues	98.00%	98.00%
MA | Recurring Revenue | Data and Information (D&I) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 211	$ 188
Percentage of revenues	100.00%	100.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 987	$ 733
MIS | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,034	$ 778
Percentage of revenues	100.00%	100.00%
MIS | Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 529	$ 356
MIS | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 529	$ 356
Percentage of revenues	100.00%	100.00%
MIS | Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 114	$ 99
MIS | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 114	$ 99
Percentage of revenues	100.00%	100.00%
MIS | Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 195	$ 142
MIS | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 195	$ 142
Percentage of revenues	100.00%	100.00%
MIS | Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 141	$ 129
MIS | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 141	$ 129
Percentage of revenues	100.00%	100.00%
MIS | MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 8	$ 7
MIS | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 8	$ 7
Percentage of revenues	100.00%	100.00%
MIS | Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 677	$ 431
MIS | Transaction Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	69.00%	59.00%
MIS | Transaction Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 399	$ 230
Percentage of revenues	75.00%	65.00%
MIS | Transaction Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 59	$ 45
Percentage of revenues	52.00%	45.00%
MIS | Transaction Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 122	$ 70
Percentage of revenues	63.00%	49.00%
MIS | Transaction Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 96	$ 86
Percentage of revenues	68.00%	67.00%
MIS | Transaction Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 0
Percentage of revenues	12.00%	0.00%
MIS | Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 310	$ 302
MIS | Recurring Revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	31.00%	41.00%
MIS | Recurring Revenue | Corporate Finance (CFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 130	$ 126
Percentage of revenues	25.00%	35.00%
MIS | Recurring Revenue | Structured Finance (SFG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 55	$ 54
Percentage of revenues	48.00%	55.00%
MIS | Recurring Revenue | Financial Institutions (FIG) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 73	$ 72
Percentage of revenues	37.00%	51.00%
MIS | Recurring Revenue | Public, Project and Infrastructure Finance (PPIF) | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 45	$ 43
Percentage of revenues	32.00%	33.00%
MIS | Recurring Revenue | MIS Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 7
Percentage of revenues	88.00%	100.00%