Segment Reporting - Sales from Products (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Sales	$ 15,775	$ 14,487
Increase in hedge revenue	54	99
Revenue related to the sale of the marketing rights	61	51
U.S.
Segment Reporting Information [Line Items]
Sales	7,478	6,659
Int’l
Segment Reporting Information [Line Items]
Sales	8,297	7,828
Operating Segments
Segment Reporting Information [Line Items]
Sales	15,517	14,212
Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	7,410	6,599
Operating Segments \| Int’l
Segment Reporting Information [Line Items]
Sales	8,107	7,614
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Sales	258	275
Corporate, Non-Segment \| U.S.
Segment Reporting Information [Line Items]
Sales	68	60
Corporate, Non-Segment \| Int’l
Segment Reporting Information [Line Items]
Sales	190	214
Pharmaceutical \| Operating Segments
Segment Reporting Information [Line Items]
Sales	14,006	12,721
Pharmaceutical \| Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	6,936	6,117
Pharmaceutical \| Operating Segments \| Int’l
Segment Reporting Information [Line Items]
Sales	7,070	6,604
Pharmaceutical \| Operating Segments \| Keytruda
Segment Reporting Information [Line Items]
Sales	6,947	5,795
Pharmaceutical \| Operating Segments \| Keytruda \| U.S.
Segment Reporting Information [Line Items]
Sales	4,119	3,485
Pharmaceutical \| Operating Segments \| Keytruda \| Int’l
Segment Reporting Information [Line Items]
Sales	2,828	2,310
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	292	275
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza \| U.S.
Segment Reporting Information [Line Items]
Sales	135	142
Pharmaceutical \| Operating Segments \| Alliance revenue - Lynparza \| Int’l
Segment Reporting Information [Line Items]
Sales	157	133
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	255	232
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima \| U.S.
Segment Reporting Information [Line Items]
Sales	173	153
Pharmaceutical \| Operating Segments \| Alliance revenue - Lenvima \| Int’l
Segment Reporting Information [Line Items]
Sales	82	79
Pharmaceutical \| Operating Segments \| Welireg
Segment Reporting Information [Line Items]
Sales	85	42
Pharmaceutical \| Operating Segments \| Welireg \| U.S.
Segment Reporting Information [Line Items]
Sales	77	41
Pharmaceutical \| Operating Segments \| Welireg \| Int’l
Segment Reporting Information [Line Items]
Sales	7	1
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl
Segment Reporting Information [Line Items]
Sales	71	43
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl \| U.S.
Segment Reporting Information [Line Items]
Sales	58	30
Pharmaceutical \| Operating Segments \| Alliance Revenue - Reblozyl \| Int’l
Segment Reporting Information [Line Items]
Sales	12	12
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	2,249	1,972
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9 \| U.S.
Segment Reporting Information [Line Items]
Sales	488	416
Pharmaceutical \| Operating Segments \| Gardasil/Gardasil 9 \| Int’l
Segment Reporting Information [Line Items]
Sales	1,761	1,556
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	570	528
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax \| U.S.
Segment Reporting Information [Line Items]
Sales	438	421
Pharmaceutical \| Operating Segments \| ProQuad/M-M-R II/Varivax \| Int’l
Segment Reporting Information [Line Items]
Sales	133	107
Pharmaceutical \| Operating Segments \| Vaxneuvance
Segment Reporting Information [Line Items]
Sales	219	106
Pharmaceutical \| Operating Segments \| Vaxneuvance \| U.S.
Segment Reporting Information [Line Items]
Sales	161	94
Pharmaceutical \| Operating Segments \| Vaxneuvance \| Int’l
Segment Reporting Information [Line Items]
Sales	58	13
Pharmaceutical \| Operating Segments \| RotaTeq
Segment Reporting Information [Line Items]
Sales	216	297
Pharmaceutical \| Operating Segments \| RotaTeq \| U.S.
Segment Reporting Information [Line Items]
Sales	149	180
Pharmaceutical \| Operating Segments \| RotaTeq \| Int’l
Segment Reporting Information [Line Items]
Sales	67	117
Pharmaceutical \| Operating Segments \| Pneumovax 23
Segment Reporting Information [Line Items]
Sales	61	96
Pharmaceutical \| Operating Segments \| Pneumovax 23 \| U.S.
Segment Reporting Information [Line Items]
Sales	6	40
Pharmaceutical \| Operating Segments \| Pneumovax 23 \| Int’l
Segment Reporting Information [Line Items]
Sales	55	56
Pharmaceutical \| Operating Segments \| Bridion
Segment Reporting Information [Line Items]
Sales	440	487
Pharmaceutical \| Operating Segments \| Bridion \| U.S.
Segment Reporting Information [Line Items]
Sales	329	276
Pharmaceutical \| Operating Segments \| Bridion \| Int’l
Segment Reporting Information [Line Items]
Sales	111	210
Pharmaceutical \| Operating Segments \| Prevymis
Segment Reporting Information [Line Items]
Sales	174	129
Pharmaceutical \| Operating Segments \| Prevymis \| U.S.
Segment Reporting Information [Line Items]
Sales	74	54
Pharmaceutical \| Operating Segments \| Prevymis \| Int’l
Segment Reporting Information [Line Items]
Sales	100	75
Pharmaceutical \| Operating Segments \| Dificid
Segment Reporting Information [Line Items]
Sales	73	65
Pharmaceutical \| Operating Segments \| Dificid \| U.S.
Segment Reporting Information [Line Items]
Sales	68	62
Pharmaceutical \| Operating Segments \| Dificid \| Int’l
Segment Reporting Information [Line Items]
Sales	5	3
Pharmaceutical \| Operating Segments \| Zerbaxa
Segment Reporting Information [Line Items]
Sales	56	50
Pharmaceutical \| Operating Segments \| Zerbaxa \| U.S.
Segment Reporting Information [Line Items]
Sales	33	27
Pharmaceutical \| Operating Segments \| Zerbaxa \| Int’l
Segment Reporting Information [Line Items]
Sales	23	23
Pharmaceutical \| Operating Segments \| Noxafil
Segment Reporting Information [Line Items]
Sales	56	60
Pharmaceutical \| Operating Segments \| Noxafil \| U.S.
Segment Reporting Information [Line Items]
Sales	8	14
Pharmaceutical \| Operating Segments \| Noxafil \| Int’l
Segment Reporting Information [Line Items]
Sales	48	46
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo
Segment Reporting Information [Line Items]
Sales	98	99
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo \| U.S.
Segment Reporting Information [Line Items]
Sales	90	83
Pharmaceutical \| Operating Segments \| Alliance revenue - Adempas/Verquvo \| Int’l
Segment Reporting Information [Line Items]
Sales	8	16
Pharmaceutical \| Operating Segments \| Adempas
Segment Reporting Information [Line Items]
Sales	70	59
Pharmaceutical \| Operating Segments \| Adempas \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Adempas \| Int’l
Segment Reporting Information [Line Items]
Sales	70	59
Pharmaceutical \| Operating Segments \| Lagevrio
Segment Reporting Information [Line Items]
Sales	350	392
Pharmaceutical \| Operating Segments \| Lagevrio \| U.S.
Segment Reporting Information [Line Items]
Sales	45	(2)
Pharmaceutical \| Operating Segments \| Lagevrio \| Int’l
Segment Reporting Information [Line Items]
Sales	305	394
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	111	123
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD \| U.S.
Segment Reporting Information [Line Items]
Sales	50	52
Pharmaceutical \| Operating Segments \| Isentress/Isentress HD \| Int’l
Segment Reporting Information [Line Items]
Sales	61	71
Pharmaceutical \| Operating Segments \| Delstrigo
Segment Reporting Information [Line Items]
Sales	56	44
Pharmaceutical \| Operating Segments \| Delstrigo \| U.S.
Segment Reporting Information [Line Items]
Sales	12	11
Pharmaceutical \| Operating Segments \| Delstrigo \| Int’l
Segment Reporting Information [Line Items]
Sales	44	33
Pharmaceutical \| Operating Segments \| Pifeltro
Segment Reporting Information [Line Items]
Sales	42	34
Pharmaceutical \| Operating Segments \| Pifeltro \| U.S.
Segment Reporting Information [Line Items]
Sales	29	24
Pharmaceutical \| Operating Segments \| Pifeltro \| Int’l
Segment Reporting Information [Line Items]
Sales	13	10
Pharmaceutical \| Operating Segments \| Belsomra
Segment Reporting Information [Line Items]
Sales	46	56
Pharmaceutical \| Operating Segments \| Belsomra \| U.S.
Segment Reporting Information [Line Items]
Sales	15	16
Pharmaceutical \| Operating Segments \| Belsomra \| Int’l
Segment Reporting Information [Line Items]
Sales	32	40
Pharmaceutical \| Operating Segments \| Simponi
Segment Reporting Information [Line Items]
Sales	184	180
Pharmaceutical \| Operating Segments \| Simponi \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Simponi \| Int’l
Segment Reporting Information [Line Items]
Sales	184	180
Pharmaceutical \| Operating Segments \| Remicade
Segment Reporting Information [Line Items]
Sales	39	51
Pharmaceutical \| Operating Segments \| Remicade \| U.S.
Segment Reporting Information [Line Items]
Sales	0	0
Pharmaceutical \| Operating Segments \| Remicade \| Int’l
Segment Reporting Information [Line Items]
Sales	39	51
Pharmaceutical \| Operating Segments \| Januvia
Segment Reporting Information [Line Items]
Sales	419	551
Pharmaceutical \| Operating Segments \| Januvia \| U.S.
Segment Reporting Information [Line Items]
Sales	183	271
Pharmaceutical \| Operating Segments \| Januvia \| Int’l
Segment Reporting Information [Line Items]
Sales	236	280
Pharmaceutical \| Operating Segments \| Janumet
Segment Reporting Information [Line Items]
Sales	251	329
Pharmaceutical \| Operating Segments \| Janumet \| U.S.
Segment Reporting Information [Line Items]
Sales	39	56
Pharmaceutical \| Operating Segments \| Janumet \| Int’l
Segment Reporting Information [Line Items]
Sales	212	272
Pharmaceutical \| Operating Segments \| Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	576	626
Pharmaceutical \| Operating Segments \| Other pharmaceutical \| U.S.
Segment Reporting Information [Line Items]
Sales	157	171
Pharmaceutical \| Operating Segments \| Other pharmaceutical \| Int’l
Segment Reporting Information [Line Items]
Sales	419	457
Animal Health \| Operating Segments
Segment Reporting Information [Line Items]
Sales	1,511	1,491
Animal Health \| Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	474	482
Animal Health \| Operating Segments \| Int’l
Segment Reporting Information [Line Items]
Sales	1,037	1,010
Animal Health \| Operating Segments \| Livestock
Segment Reporting Information [Line Items]
Sales	850	849
Animal Health \| Operating Segments \| Livestock \| U.S.
Segment Reporting Information [Line Items]
Sales	166	174
Animal Health \| Operating Segments \| Livestock \| Int’l
Segment Reporting Information [Line Items]
Sales	683	676
Animal Health \| Operating Segments \| Companion Animal
Segment Reporting Information [Line Items]
Sales	661	642
Animal Health \| Operating Segments \| Companion Animal \| U.S.
Segment Reporting Information [Line Items]
Sales	308	308
Animal Health \| Operating Segments \| Companion Animal \| Int’l
Segment Reporting Information [Line Items]
Sales	$ 354	$ 334