Segment Reporting - Sales from Products (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Sales	$ 15,529	$ 15,775
Increase in hedge revenue	58	54
Revenue related to the sale of the marketing rights	95	61
U.S.
Segment Reporting Information [Line Items]
Sales	8,522	7,478
Non-US
Segment Reporting Information [Line Items]
Sales	7,007	8,297
Operating Segments
Segment Reporting Information [Line Items]
Sales	15,226	15,517
Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	8,429	7,410
Operating Segments \| Non-US
Segment Reporting Information [Line Items]
Sales	6,797	8,107
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Sales	303	258
Corporate, Non-Segment \| U.S.
Segment Reporting Information [Line Items]
Sales	93	68
Corporate, Non-Segment \| Non-US
Segment Reporting Information [Line Items]
Sales	210	190
Pharmaceutical \| Operating Segments
Segment Reporting Information [Line Items]
Sales	13,638	14,006
Pharmaceutical \| Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	7,927	6,936
Pharmaceutical \| Operating Segments \| Non-US
Segment Reporting Information [Line Items]
Sales	5,711	7,070
Pharmaceutical \| Operating Segments \| Keytruda
Segment Reporting Information [Line Items]
Sales	7,205	6,947
Pharmaceutical \| Operating Segments \| Keytruda \| U.S.
Segment Reporting Information [Line Items]
Sales	4,308	4,119
Pharmaceutical \| Operating Segments \| Keytruda \| Non-US
Segment Reporting Information [Line Items]
Sales	2,897	2,828
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	312	292
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza \| U.S.
Segment Reporting Information [Line Items]
Sales	145	135
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza \| Non-US
Segment Reporting Information [Line Items]
Sales	168	157
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	258	255
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima \| U.S.
Segment Reporting Information [Line Items]
Sales	186	173
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima \| Non-US
Segment Reporting Information [Line Items]
Sales	72	82
Pharmaceutical \| Operating Segments \| Welireg
Segment Reporting Information [Line Items]
Sales	137	85
Pharmaceutical \| Operating Segments \| Welireg \| U.S.
Segment Reporting Information [Line Items]
Sales	123	77
Pharmaceutical \| Operating Segments \| Welireg \| Non-US
Segment Reporting Information [Line Items]
Sales	15	7
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl
Segment Reporting Information [Line Items]
Sales	119	71
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl \| U.S.
Segment Reporting Information [Line Items]
Sales	101	58
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl \| Non-US
Segment Reporting Information [Line Items]
Sales	18	12
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,327	2,249
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9 \| U.S.
Segment Reporting Information [Line Items]
Sales	536	488
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9 \| Non-US
Segment Reporting Information [Line Items]
Sales	790	1,761
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	539	570
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax \| U.S.
Segment Reporting Information [Line Items]
Sales	423	438
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax \| Non-US
Segment Reporting Information [Line Items]
Sales	116	133
Pharmaceutical \| Operating Segments \| Vaxneuvance
Segment Reporting Information [Line Items]
Sales	230	219
Pharmaceutical \| Operating Segments \| Vaxneuvance \| U.S.
Segment Reporting Information [Line Items]
Sales	139	161
Pharmaceutical \| Operating Segments \| Vaxneuvance \| Non-US
Segment Reporting Information [Line Items]
Sales	92	58
Pharmaceutical \| Operating Segments \| RotaTeq
Segment Reporting Information [Line Items]
Sales	228	216
Pharmaceutical \| Operating Segments \| RotaTeq \| U.S.
Segment Reporting Information [Line Items]
Sales	164	149
Pharmaceutical \| Operating Segments \| RotaTeq \| Non-US
Segment Reporting Information [Line Items]
Sales	64	67
Pharmaceutical \| Operating Segments \| Capvaxive
Segment Reporting Information [Line Items]
Sales	107	0
Pharmaceutical \| Operating Segments \| Capvaxive \| U.S.
Segment Reporting Information [Line Items]
Sales	106	0
Pharmaceutical \| Operating Segments \| Capvaxive \| Non-US
Segment Reporting Information [Line Items]
Sales	1	0
Pharmaceutical \| Operating Segments \| Pneumovax 23
Segment Reporting Information [Line Items]
Sales	41	61
Pharmaceutical \| Operating Segments \| Pneumovax 23 \| U.S.
Segment Reporting Information [Line Items]
Sales	(2)	6
Pharmaceutical \| Operating Segments \| Pneumovax 23 \| Non-US
Segment Reporting Information [Line Items]
Sales	42	55
Pharmaceutical \| Operating Segments \| Bridion
Segment Reporting Information [Line Items]
Sales	441	440
Pharmaceutical \| Operating Segments \| Bridion \| U.S.
Segment Reporting Information [Line Items]
Sales	378	329
Pharmaceutical \| Operating Segments \| Bridion \| Non-US
Segment Reporting Information [Line Items]
Sales	63	111
Pharmaceutical \| Operating Segments \| Prevymis
Segment Reporting Information [Line Items]
Sales	208	174
Pharmaceutical \| Operating Segments \| Prevymis \| U.S.
Segment Reporting Information [Line Items]
Sales	102	74
Pharmaceutical \| Operating Segments \| Prevymis \| Non-US
Segment Reporting Information [Line Items]
Sales	106	100
Pharmaceutical \| Operating Segments \| Dificid
Segment Reporting Information [Line Items]
Sales	83	73
Pharmaceutical \| Operating Segments \| Dificid \| U.S.
Segment Reporting Information [Line Items]
Sales	72	68
Pharmaceutical \| Operating Segments \| Dificid \| Non-US
Segment Reporting Information [Line Items]
Sales	11	5
Pharmaceutical \| Operating Segments \| Zerbaxa
Segment Reporting Information [Line Items]
Sales	70	56
Pharmaceutical \| Operating Segments \| Zerbaxa \| U.S.
Segment Reporting Information [Line Items]
Sales	42	33
Pharmaceutical \| Operating Segments \| Zerbaxa \| Non-US
Segment Reporting Information [Line Items]
Sales	28	23
Pharmaceutical \| Operating Segments \| Winrevair
Segment Reporting Information [Line Items]
Sales	280	0
Pharmaceutical \| Operating Segments \| Winrevair \| U.S.
Segment Reporting Information [Line Items]
Sales	268	0
Pharmaceutical \| Operating Segments \| Winrevair \| Non-US
Segment Reporting Information [Line Items]
Sales	12	0
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo
Segment Reporting Information [Line Items]
Sales	106	98
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo \| U.S.
Segment Reporting Information [Line Items]
Sales	97	90
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo \| Non-US
Segment Reporting Information [Line Items]
Sales	9	8
Pharmaceutical \| Operating Segments \| Adempas
Segment Reporting Information [Line Items]
Sales	68	70
Pharmaceutical \| Operating Segments \| Adempas \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Adempas \| Non-US
Segment Reporting Information [Line Items]
Sales	68	70
Pharmaceutical \| Operating Segments \| Lagevrio
Segment Reporting Information [Line Items]
Sales	102	350
Pharmaceutical \| Operating Segments \| Lagevrio \| U.S.
Segment Reporting Information [Line Items]
Sales	35	45
Pharmaceutical \| Operating Segments \| Lagevrio \| Non-US
Segment Reporting Information [Line Items]
Sales	67	305
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	90	111
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD \| U.S.
Segment Reporting Information [Line Items]
Sales	51	50
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD \| Non-US
Segment Reporting Information [Line Items]
Sales	39	61
Pharmaceutical \| Operating Segments \| Delstrigo
Segment Reporting Information [Line Items]
Sales	67	56
Pharmaceutical \| Operating Segments \| Delstrigo \| U.S.
Segment Reporting Information [Line Items]
Sales	15	12
Pharmaceutical \| Operating Segments \| Delstrigo \| Non-US
Segment Reporting Information [Line Items]
Sales	52	44
Pharmaceutical \| Operating Segments \| Pifeltro
Segment Reporting Information [Line Items]
Sales	45	42
Pharmaceutical \| Operating Segments \| Pifeltro \| U.S.
Segment Reporting Information [Line Items]
Sales	32	29
Pharmaceutical \| Operating Segments \| Pifeltro \| Non-US
Segment Reporting Information [Line Items]
Sales	13	13
Pharmaceutical \| Operating Segments \| Belsomra
Segment Reporting Information [Line Items]
Sales	50	46
Pharmaceutical \| Operating Segments \| Belsomra \| U.S.
Segment Reporting Information [Line Items]
Sales	13	15
Pharmaceutical \| Operating Segments \| Belsomra \| Non-US
Segment Reporting Information [Line Items]
Sales	37	32
Pharmaceutical \| Operating Segments \| Simponi
Segment Reporting Information [Line Items]
Sales	0	184
Pharmaceutical \| Operating Segments \| Simponi \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Simponi \| Non-US
Segment Reporting Information [Line Items]
Sales	0	184
Pharmaceutical \| Operating Segments \| Remicade
Segment Reporting Information [Line Items]
Sales	0	39
Pharmaceutical \| Operating Segments \| Remicade \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Remicade \| Non-US
Segment Reporting Information [Line Items]
Sales	0	39
Pharmaceutical \| Operating Segments \| Januvia
Segment Reporting Information [Line Items]
Sales	549	419
Pharmaceutical \| Operating Segments \| Januvia \| U.S.
Segment Reporting Information [Line Items]
Sales	344	183
Pharmaceutical \| Operating Segments \| Januvia \| Non-US
Segment Reporting Information [Line Items]
Sales	204	236
Pharmaceutical \| Operating Segments \| Janumet
Segment Reporting Information [Line Items]
Sales	247	251
Pharmaceutical \| Operating Segments \| Janumet \| U.S.
Segment Reporting Information [Line Items]
Sales	65	39
Pharmaceutical \| Operating Segments \| Janumet \| Non-US
Segment Reporting Information [Line Items]
Sales	182	212
Pharmaceutical \| Operating Segments \| Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	729	632
Pharmaceutical \| Operating Segments \| Other pharmaceutical \| U.S.
Segment Reporting Information [Line Items]
Sales	184	165
Pharmaceutical \| Operating Segments \| Other pharmaceutical \| Non-US
Segment Reporting Information [Line Items]
Sales	545	467
Animal Health \| Operating Segments
Segment Reporting Information [Line Items]
Sales	1,588	1,511
Animal Health \| Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	502	474
Animal Health \| Operating Segments \| Non-US
Segment Reporting Information [Line Items]
Sales	1,086	1,037
Animal Health \| Operating Segments \| Livestock
Segment Reporting Information [Line Items]
Sales	924	850
Animal Health \| Operating Segments \| Livestock \| U.S.
Segment Reporting Information [Line Items]
Sales	194	166
Animal Health \| Operating Segments \| Livestock \| Non-US
Segment Reporting Information [Line Items]
Sales	730	683
Animal Health \| Operating Segments \| Companion Animal
Segment Reporting Information [Line Items]
Sales	664	661
Animal Health \| Operating Segments \| Companion Animal \| U.S.
Segment Reporting Information [Line Items]
Sales	308	308
Animal Health \| Operating Segments \| Companion Animal \| Non-US
Segment Reporting Information [Line Items]
Sales	$ 356	$ 354