Revenues - Revenues Disaggregated by Line of Business and Geographical Area (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenue	$ 1,898	$ 1,817	$ 3,822	$ 3,603
United States
Disaggregation of Revenue [Line Items]
Revenue	992	974	2,057	1,943
Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	906	843	1,765	1,660
MA
Disaggregation of Revenue [Line Items]
Revenue	888	802	1,747	1,601
MA \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	891	806	1,753	1,608
MA \| United States
Disaggregation of Revenue [Line Items]
Revenue	381	338	756	675
MA \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	381	338	756	675
MA \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	507	464	991	926
MA \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	507	464	991	926
MA \| Decision Solutions (DS)
Disaggregation of Revenue [Line Items]
Revenue	413	366
MA \| Decision Solutions (DS) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	413	366	818	731
MA \| Decision Solutions (DS) \| United States
Disaggregation of Revenue [Line Items]
Revenue	162	138
MA \| Decision Solutions (DS) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			329	276
MA \| Decision Solutions (DS) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	251	228
MA \| Decision Solutions (DS) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			489	455
MA \| Research and Insights (R&I)
Disaggregation of Revenue [Line Items]
Revenue	249	226
MA \| Research and Insights (R&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	249	226	485	448
MA \| Research and Insights (R&I) \| United States
Disaggregation of Revenue [Line Items]
Revenue	139	124
MA \| Research and Insights (R&I) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			267	246
MA \| Research and Insights (R&I) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	110	102
MA \| Research and Insights (R&I) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			218	202
MA \| Data and Information (D&I)
Disaggregation of Revenue [Line Items]
Revenue	226	210
MA \| Data and Information (D&I) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	226	210	444	422
MA \| Data and Information (D&I) \| United States
Disaggregation of Revenue [Line Items]
Revenue	80	76
MA \| Data and Information (D&I) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			160	153
MA \| Data and Information (D&I) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	146	134
MA \| Data and Information (D&I) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			284	269
MIS
Disaggregation of Revenue [Line Items]
Revenue	1,010	1,015	2,075	2,002
MIS \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,060	1,064	2,174	2,098
MIS \| United States
Disaggregation of Revenue [Line Items]
Revenue	611	636	1,301	1,268
MIS \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	611	636	1,301	1,268
MIS \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	399	379	774	734
MIS \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	399	379	774	734
MIS \| Corporate Finance (CFG)
Disaggregation of Revenue [Line Items]
Revenue	512	525
MIS \| Corporate Finance (CFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	512	525	1,076	1,054
MIS \| Corporate Finance (CFG) \| United States
Disaggregation of Revenue [Line Items]
Revenue	314	342
MIS \| Corporate Finance (CFG) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			705	714
MIS \| Corporate Finance (CFG) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	198	183
MIS \| Corporate Finance (CFG) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			371	340
MIS \| Structured Finance (SFG)
Disaggregation of Revenue [Line Items]
Revenue	135	131
MIS \| Structured Finance (SFG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	135	131	273	245
MIS \| Structured Finance (SFG) \| United States
Disaggregation of Revenue [Line Items]
Revenue	91	92
MIS \| Structured Finance (SFG) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			191	168
MIS \| Structured Finance (SFG) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	44	39
MIS \| Structured Finance (SFG) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			82	77
MIS \| Financial Institutions (FIG)
Disaggregation of Revenue [Line Items]
Revenue	191	195
MIS \| Financial Institutions (FIG) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	191	195	382	390
MIS \| Financial Institutions (FIG) \| United States
Disaggregation of Revenue [Line Items]
Revenue	99	104
MIS \| Financial Institutions (FIG) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			194	202
MIS \| Financial Institutions (FIG) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	92	91
MIS \| Financial Institutions (FIG) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			188	188
MIS \| Public, Project and Infrastructure Finance (PPIF)
Disaggregation of Revenue [Line Items]
Revenue	162	154
MIS \| Public, Project and Infrastructure Finance (PPIF) \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	162	154	325	295
MIS \| Public, Project and Infrastructure Finance (PPIF) \| United States
Disaggregation of Revenue [Line Items]
Revenue	107	98
MIS \| Public, Project and Infrastructure Finance (PPIF) \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			211	184
MIS \| Public, Project and Infrastructure Finance (PPIF) \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	55	56
MIS \| Public, Project and Infrastructure Finance (PPIF) \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			114	111
MIS \| Total ratings revenue
Disaggregation of Revenue [Line Items]
Revenue	1,000	1,005
MIS \| Total ratings revenue \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	1,000	1,005	2,056	1,984
MIS \| Total ratings revenue \| United States
Disaggregation of Revenue [Line Items]
Revenue	611	636
MIS \| Total ratings revenue \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			1,301	1,268
MIS \| Total ratings revenue \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	389	369
MIS \| Total ratings revenue \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			755	716
MIS \| MIS Other
Disaggregation of Revenue [Line Items]
Revenue	10	10
MIS \| MIS Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	10	10	19	18
MIS \| MIS Other \| United States
Disaggregation of Revenue [Line Items]
Revenue	0	0
MIS \| MIS Other \| United States \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			0	0
MIS \| MIS Other \| Non-U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 10	$ 10
MIS \| MIS Other \| Non-U.S. \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenue			$ 19	$ 18

MOODYS CORP /DE/ 10-Q