Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue	$ 2,007	$ 1,813	$ 5,829	$ 5,416
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 787	$ 705	$ 2,255	$ 2,159
Percentage of revenues	39.00%	39.00%	39.00%	40.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,220	$ 1,108	$ 3,574	$ 3,257
Percentage of revenues	61.00%	61.00%	61.00%	60.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 909	$ 831	$ 2,656	$ 2,432
MA \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 912	$ 834	$ 2,665	$ 2,442
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| DS Banking Product and Service \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 140	$ 140	$ 419	$ 405
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| Insurance \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 171	$ 148	$ 502	$ 439
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| KYC \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 113	$ 95	$ 321	$ 270
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	$ 424	$ 383
MA \| Decision Solutions (DS) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 424	$ 383	$ 1,242	$ 1,114
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 252	$ 235
MA \| Research and Insights (R&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 252	$ 235	$ 737	$ 683
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	$ 233	$ 213
MA \| Data and Information (D&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 233	$ 213	$ 677	$ 635
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MA \| Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 34	$ 42	$ 107	$ 127
MA \| Transaction Revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	4.00%	5.00%	4.00%	5.00%
MA \| Transaction Revenue \| DS Banking Product and Service \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 25	$ 28	$ 76	$ 85
Percentage of revenues	18.00%	20.00%	18.00%	21.00%
MA \| Transaction Revenue \| Insurance \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 6	$ 15	$ 20
Percentage of revenues	2.00%	4.00%	3.00%	5.00%
MA \| Transaction Revenue \| KYC \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 3	$ 1	$ 6
Percentage of revenues	1.00%	3.00%	0.00%	2.00%
MA \| Transaction Revenue \| Decision Solutions (DS) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 29	$ 37	$ 92	$ 111
Percentage of revenues	7.00%	10.00%	7.00%	10.00%
MA \| Transaction Revenue \| Research and Insights (R&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 3	$ 9	$ 9
Percentage of revenues	1.00%	1.00%	1.00%	1.00%
MA \| Transaction Revenue \| Data and Information (D&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 2	$ 2	$ 6	$ 7
Percentage of revenues	1.00%	1.00%	1.00%	1.00%
MA \| Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 875	$ 789	$ 2,549	$ 2,305
MA \| Recurring Revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	96.00%	95.00%	96.00%	95.00%
MA \| Recurring Revenue \| DS Banking Product and Service \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 115	$ 112	$ 343	$ 320
Percentage of revenues	82.00%	80.00%	82.00%	79.00%
MA \| Recurring Revenue \| Insurance \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 168	$ 142	$ 487	$ 419
Percentage of revenues	98.00%	96.00%	97.00%	95.00%
MA \| Recurring Revenue \| KYC \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 112	$ 92	$ 320	$ 264
Percentage of revenues	99.00%	97.00%	100.00%	98.00%
MA \| Recurring Revenue \| Decision Solutions (DS) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 395	$ 346	$ 1,150	$ 1,003
Percentage of revenues	93.00%	90.00%	93.00%	90.00%
MA \| Recurring Revenue \| Research and Insights (R&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 249	$ 232	$ 728	$ 674
Percentage of revenues	99.00%	99.00%	99.00%	99.00%
MA \| Recurring Revenue \| Data and Information (D&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 231	$ 211	$ 671	$ 628
Percentage of revenues	99.00%	99.00%	99.00%	99.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 1,098	$ 982	$ 3,173	$ 2,984
MIS \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 1,148	$ 1,030	$ 3,322	$ 3,128
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 576	$ 515
MIS \| Corporate Finance (CFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 576	$ 515	$ 1,652	$ 1,569
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	$ 146	$ 135
MIS \| Structured Finance (SFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 146	$ 135	$ 419	$ 380
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	$ 208	$ 170
MIS \| Financial Institutions (FIG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 208	$ 170	$ 590	$ 560
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	$ 161	$ 154
MIS \| Public, Project and Infrastructure Finance (PPIF) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 161	$ 154	$ 486	$ 449
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| MIS Other
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 8
MIS \| MIS Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 8	$ 26	$ 26
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
MIS \| Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 753	$ 663	$ 2,148	$ 2,032
MIS \| Transaction Revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	69.00%	68.00%	68.00%	68.00%
MIS \| Transaction Revenue \| Corporate Finance (CFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 433	$ 382	$ 1,225	$ 1,169
Percentage of revenues	75.00%	74.00%	74.00%	75.00%
MIS \| Transaction Revenue \| Structured Finance (SFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 86	$ 78	$ 238	$ 213
Percentage of revenues	59.00%	58.00%	57.00%	56.00%
MIS \| Transaction Revenue \| Financial Institutions (FIG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 123	$ 92	$ 340	$ 329
Percentage of revenues	59.00%	54.00%	58.00%	59.00%
MIS \| Transaction Revenue \| Public, Project and Infrastructure Finance (PPIF) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 111	$ 109	$ 340	$ 315
Percentage of revenues	69.00%	71.00%	70.00%	70.00%
MIS \| Transaction Revenue \| MIS Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 2	$ 5	$ 6
Percentage of revenues	0.00%	25.00%	19.00%	23.00%
MIS \| Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 345	$ 319	$ 1,025	$ 952
MIS \| Recurring Revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Percentage of revenues	31.00%	32.00%	32.00%	32.00%
MIS \| Recurring Revenue \| Corporate Finance (CFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 143	$ 133	$ 427	$ 400
Percentage of revenues	25.00%	26.00%	26.00%	25.00%
MIS \| Recurring Revenue \| Structured Finance (SFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 60	$ 57	$ 181	$ 167
Percentage of revenues	41.00%	42.00%	43.00%	44.00%
MIS \| Recurring Revenue \| Financial Institutions (FIG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 85	$ 78	$ 250	$ 231
Percentage of revenues	41.00%	46.00%	42.00%	41.00%
MIS \| Recurring Revenue \| Public, Project and Infrastructure Finance (PPIF) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 50	$ 45	$ 146	$ 134
Percentage of revenues	31.00%	29.00%	30.00%	30.00%
MIS \| Recurring Revenue \| MIS Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 7	$ 6	$ 21	$ 20
Percentage of revenues	100.00%	75.00%	81.00%	77.00%