Segment Information - Financial Information by Segment (Detail) - USD ($) $ in Millions	12 Months Ended			36 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2025
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	$ 7,718	$ 7,088	$ 5,916
Compensation expense	2,574	2,539	2,241
Non-compensation expense	1,202	1,141	1,078
Operating, SG&A	3,776	3,680	3,319
Adjusted Operating Income	3,942	3,408	2,597
Depreciation and amortization	480	431	373
Restructuring	108	59	87
Charges related to asset abandonment	3	43	0	$ 46
Operating income	3,351	2,875	2,137
Non-operating expense, net	(221)	(176)	(202)
Income before provision for income taxes	3,130	2,699	1,935
Eliminations
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	(210)	(206)	(199)
Intersegment expense	(210)	(206)	(199)
Operating, SG&A	(210)	(206)	(199)
Adjusted Operating Income	0	0	0
Depreciation and amortization	0	0	0
Restructuring	0	0	0
Operating Segments
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	7,718	7,088	5,916
MA
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	3,599	3,295	3,056
Compensation expense	1,438	1,370	1,238
Non-compensation expense	779	731	708
MA | Eliminations
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	12	13	13
Intersegment expense	198	193	186
MA | Operating Segments
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	3,611	3,308	3,069
Operating, SG&A	2,415	2,294	2,132
Adjusted Operating Income	1,196	1,014	937
Depreciation and amortization	393	353	298
Restructuring	77	42	59
Charges related to asset abandonment	3	43
MIS
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	4,119	3,793	2,860
Compensation expense	1,136	1,169	1,003
Non-compensation expense	423	410	370
MIS | Eliminations
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	198	193	186
Intersegment expense	12	13	13
MIS | Operating Segments
Segment Reporting Information, Operating Income (Loss) [Abstract]
Revenue	4,317	3,986	3,046
Operating, SG&A	1,571	1,592	1,386
Adjusted Operating Income	2,746	2,394	1,660
Depreciation and amortization	87	78	75
Restructuring	31	17	$ 28
Charges related to asset abandonment	$ 0	$ 0