Segment Reporting - Schedule of Sales from Products (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Sales	$ 17,276	$ 16,657	$ 48,611	$ 48,544
Increase in hedge revenue			(61)	156
Revenue related to the sale of the marketing rights			111	91
U.S.
Segment Reporting Information [Line Items]
Sales	10,012	8,736	27,371	24,089
Non-US
Segment Reporting Information [Line Items]
Sales	7,264	7,922	21,240	24,455
Operating Segments
Segment Reporting Information [Line Items]
Sales	17,226	16,430	48,148	47,838
Operating Segments \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	15,611	14,943	43,299	43,358
Operating Segments \| Animal Health
Segment Reporting Information [Line Items]
Sales	1,615	1,487	4,849	4,480
Operating Segments \| U.S.
Segment Reporting Information [Line Items]
Sales	9,997	8,714	27,252	23,980
Operating Segments \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	9,493	8,227	25,747	22,563
Operating Segments \| U.S. \| Animal Health
Segment Reporting Information [Line Items]
Sales	504	487	1,505	1,417
Operating Segments \| Non-US
Segment Reporting Information [Line Items]
Sales	7,230	7,716	20,897	23,858
Operating Segments \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	6,118	6,717	17,552	20,795
Operating Segments \| Non-US \| Animal Health
Segment Reporting Information [Line Items]
Sales	1,112	999	3,345	3,063
Operating Segments \| Keytruda \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	8,142	7,429	23,303	21,646
Operating Segments \| Keytruda \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	4,879	4,500	13,936	13,031
Operating Segments \| Keytruda \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	3,263	2,929	9,367	8,614
Operating Segments \| Alliance revenue - Lynparza \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	379	337	1,061	947
Operating Segments \| Alliance revenue - Lynparza \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	184	161	503	449
Operating Segments \| Alliance revenue - Lynparza \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	195	177	558	498
Operating Segments \| Alliance revenue - Lenvima \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	258	251	781	755
Operating Segments \| Alliance revenue - Lenvima \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	177	173	545	523
Operating Segments \| Alliance revenue - Lenvima \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	81	78	236	233
Operating Segments \| Welireg \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	196	139	496	349
Operating Segments \| Welireg \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	161	127	422	320
Operating Segments \| Welireg \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	35	12	74	29
Operating Segments \| Alliance Revenue - Reblozyl \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	136	100	361	261
Operating Segments \| Alliance Revenue - Reblozyl \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	111	82	299	215
Operating Segments \| Alliance Revenue - Reblozyl \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	25	18	62	45
Operating Segments \| Gardasil/Gardasil 9 \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	1,749	2,306	4,202	7,032
Operating Segments \| Gardasil/Gardasil 9 \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	1,154	1,020	2,235	2,045
Operating Segments \| Gardasil/Gardasil 9 \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	595	1,285	1,967	4,988
Operating Segments \| ProQuad/M-M-R II/Varivax \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	684	703	1,832	1,891
Operating Segments \| ProQuad/M-M-R II/Varivax \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	554	572	1,457	1,500
Operating Segments \| ProQuad/M-M-R II/Varivax \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	130	131	374	391
Operating Segments \| Vaxneuvance \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	226	239	685	647
Operating Segments \| Vaxneuvance \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	134	137	409	397
Operating Segments \| Vaxneuvance \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	91	103	276	251
Operating Segments \| RotaTeq \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	204	193	554	572
Operating Segments \| RotaTeq \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	141	131	366	388
Operating Segments \| RotaTeq \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	63	62	187	185
Operating Segments \| Capvaxive \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	244	47	480	47
Operating Segments \| Capvaxive \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	238	47	473	47
Operating Segments \| Capvaxive \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	7	0	8	0
Operating Segments \| Pneumovax 23 \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	45	68	124	188
Operating Segments \| Pneumovax 23 \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	10	19	13	36
Operating Segments \| Pneumovax 23 \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	35	49	111	152
Operating Segments \| Bridion \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	439	420	1,341	1,315
Operating Segments \| Bridion \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	392	339	1,181	1,020
Operating Segments \| Bridion \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	47	81	161	296
Operating Segments \| Prevymis \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	266	208	702	570
Operating Segments \| Prevymis \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	128	101	345	265
Operating Segments \| Prevymis \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	138	107	357	305
Operating Segments \| Zerbaxa \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	81	64	225	182
Operating Segments \| Zerbaxa \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	49	39	136	106
Operating Segments \| Zerbaxa \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	32	26	89	77
Operating Segments \| Dificid \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	43	96	222	261
Operating Segments \| Dificid \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	30	83	185	231
Operating Segments \| Dificid \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	13	13	37	30
Operating Segments \| Winrevair \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	360	149	976	219
Operating Segments \| Winrevair \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	335	147	926	216
Operating Segments \| Winrevair \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	25	3	49	3
Operating Segments \| Alliance revenue - Adempas/Verquvo \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	112	102	340	306
Operating Segments \| Alliance revenue - Adempas/Verquvo \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	103	96	308	283
Operating Segments \| Alliance revenue - Adempas/Verquvo \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	8	7	32	22
Operating Segments \| Adempas \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	82	72	229	214
Operating Segments \| Adempas \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Operating Segments \| Adempas \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	82	72	229	214
Operating Segments \| Lagevrio \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	138	383	323	843
Operating Segments \| Lagevrio \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	24	84	90	144
Operating Segments \| Lagevrio \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	114	299	233	699
Operating Segments \| Isentress/Isentress HD \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	82	102	258	302
Operating Segments \| Isentress/Isentress HD \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	44	54	144	147
Operating Segments \| Isentress/Isentress HD \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	37	48	114	155
Operating Segments \| Delstrigo \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	77	65	228	180
Operating Segments \| Delstrigo \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	13	15	42	42
Operating Segments \| Delstrigo \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	64	50	185	139
Operating Segments \| Pifeltro \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	43	42	128	123
Operating Segments \| Pifeltro \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	29	31	86	86
Operating Segments \| Pifeltro \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	14	12	43	37
Operating Segments \| Belsomra \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	47	78	137	177
Operating Segments \| Belsomra \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	28	20	59	53
Operating Segments \| Belsomra \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	19	58	77	124
Operating Segments \| Simponi \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	189	0	545
Operating Segments \| Simponi \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Operating Segments \| Simponi \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	189	0	545
Operating Segments \| Remicade \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	41	0	115
Operating Segments \| Remicade \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Operating Segments \| Remicade \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	0	41	0	115
Operating Segments \| Januvia \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	382	278	1,302	1,102
Operating Segments \| Januvia \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	258	67	819	428
Operating Segments \| Januvia \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	124	211	483	674
Operating Segments \| Janumet \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	243	204	741	679
Operating Segments \| Janumet \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	78	15	210	70
Operating Segments \| Janumet \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	165	190	530	610
Operating Segments \| Other pharmaceutical \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	953	638	2,268	1,890
Operating Segments \| Other pharmaceutical \| U.S. \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	239	167	558	521
Operating Segments \| Other pharmaceutical \| Non-US \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	716	466	1,713	1,364
Operating Segments \| Livestock \| Animal Health
Segment Reporting Information [Line Items]
Sales	1,023	886	2,909	2,573
Operating Segments \| Livestock \| U.S. \| Animal Health
Segment Reporting Information [Line Items]
Sales	213	194	598	529
Operating Segments \| Livestock \| Non-US \| Animal Health
Segment Reporting Information [Line Items]
Sales	811	692	2,312	2,044
Operating Segments \| Companion Animal \| Animal Health
Segment Reporting Information [Line Items]
Sales	592	601	1,940	1,907
Operating Segments \| Companion Animal \| U.S. \| Animal Health
Segment Reporting Information [Line Items]
Sales	291	293	907	888
Operating Segments \| Companion Animal \| Non-US \| Animal Health
Segment Reporting Information [Line Items]
Sales	301	307	1,033	1,019
Operating Segments \| Alliance revenue - Koselugo \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	214	39	301	114
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Sales	50	227	463	706
Corporate, Non-Segment \| U.S.
Segment Reporting Information [Line Items]
Sales	15	22	119	109
Corporate, Non-Segment \| Non-US
Segment Reporting Information [Line Items]
Sales	$ 34	$ 206	$ 343	$ 597