Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Sales	$ 64,168	$ 60,115	$ 59,283
Increase (decrease) in revenue hedging activities	195	244	810
Revenue related to the sale of the marketing rights	106	118	165
Operating Segments
Segment Reporting Information [Line Items]
Sales	63,277	59,208	57,555
Operating Segments \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	57,400	53,583	52,005
Operating Segments \| Pharmaceutical \| Keytruda
Segment Reporting Information [Line Items]
Sales	29,482	25,011	20,937
Operating Segments \| Pharmaceutical \| Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	1,311	1,199	1,116
Operating Segments \| Pharmaceutical \| Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	1,010	960	876
Operating Segments \| Pharmaceutical \| Welireg
Segment Reporting Information [Line Items]
Sales	509	218	123
Operating Segments \| Pharmaceutical \| Alliance revenue - Reblozyl
Segment Reporting Information [Line Items]
Sales	371	212	166
Operating Segments \| Pharmaceutical \| Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	8,583	8,886	6,897
Operating Segments \| Pharmaceutical \| ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	2,485	2,368	2,241
Operating Segments \| Pharmaceutical \| Vaxneuvance
Segment Reporting Information [Line Items]
Sales	808	665	170
Operating Segments \| Pharmaceutical \| RotaTeq
Segment Reporting Information [Line Items]
Sales	711	769	783
Operating Segments \| Pharmaceutical \| Pneumovax 23
Segment Reporting Information [Line Items]
Sales	263	412	602
Operating Segments \| Pharmaceutical \| Bridion
Segment Reporting Information [Line Items]
Sales	1,764	1,842	1,685
Operating Segments \| Pharmaceutical \| Prevymis
Segment Reporting Information [Line Items]
Sales	785	605	428
Operating Segments \| Pharmaceutical \| Dificid
Segment Reporting Information [Line Items]
Sales	340	302	263
Operating Segments \| Pharmaceutical \| Zerbaxa
Segment Reporting Information [Line Items]
Sales	252	218	169
Operating Segments \| Pharmaceutical \| Noxafil
Segment Reporting Information [Line Items]
Sales	177	213	238
Operating Segments \| Pharmaceutical \| Winrevair
Segment Reporting Information [Line Items]
Sales	419	0	0
Operating Segments \| Pharmaceutical \| Alliance revenue - Adempas/Verquvo
Segment Reporting Information [Line Items]
Sales	415	367	341
Operating Segments \| Pharmaceutical \| Adempas
Segment Reporting Information [Line Items]
Sales	287	255	238
Operating Segments \| Pharmaceutical \| Lagevrio
Segment Reporting Information [Line Items]
Sales	964	1,428	5,684
Operating Segments \| Pharmaceutical \| Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	394	483	633
Operating Segments \| Pharmaceutical \| Delstrigo
Segment Reporting Information [Line Items]
Sales	249	201	151
Operating Segments \| Pharmaceutical \| Pifeltro
Segment Reporting Information [Line Items]
Sales	163	142	118
Operating Segments \| Pharmaceutical \| Belsomra
Segment Reporting Information [Line Items]
Sales	222	231	258
Operating Segments \| Pharmaceutical \| Simponi
Segment Reporting Information [Line Items]
Sales	543	710	706
Operating Segments \| Pharmaceutical \| Remicade
Segment Reporting Information [Line Items]
Sales	114	187	207
Operating Segments \| Pharmaceutical \| Januvia
Segment Reporting Information [Line Items]
Sales	1,334	2,189	2,813
Operating Segments \| Pharmaceutical \| Janumet
Segment Reporting Information [Line Items]
Sales	935	1,177	1,700
Operating Segments \| Pharmaceutical \| Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	2,510	2,333	2,462
Operating Segments \| Animal Health
Segment Reporting Information [Line Items]
Sales	5,877	5,625	5,550
Operating Segments \| Animal Health \| Livestock
Segment Reporting Information [Line Items]
Sales	3,462	3,337	3,300
Operating Segments \| Animal Health \| Companion Animal
Segment Reporting Information [Line Items]
Sales	2,415	2,288	2,250
Other
Segment Reporting Information [Line Items]
Sales	891	907	1,728
United States
Segment Reporting Information [Line Items]
Sales	32,277	28,480	27,206
United States \| Operating Segments
Segment Reporting Information [Line Items]
Sales	32,151	28,343	26,811
United States \| Operating Segments \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	30,290	26,539	24,989
United States \| Operating Segments \| Pharmaceutical \| Keytruda
Segment Reporting Information [Line Items]
Sales	17,872	15,114	12,686
United States \| Operating Segments \| Pharmaceutical \| Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	626	607	584
United States \| Operating Segments \| Pharmaceutical \| Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	705	657	579
United States \| Operating Segments \| Pharmaceutical \| Welireg
Segment Reporting Information [Line Items]
Sales	466	209	123
United States \| Operating Segments \| Pharmaceutical \| Alliance revenue - Reblozyl
Segment Reporting Information [Line Items]
Sales	303	168	123
United States \| Operating Segments \| Pharmaceutical \| Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	2,425	2,083	2,065
United States \| Operating Segments \| Pharmaceutical \| ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	1,919	1,837	1,724
United States \| Operating Segments \| Pharmaceutical \| Vaxneuvance
Segment Reporting Information [Line Items]
Sales	461	561	163
United States \| Operating Segments \| Pharmaceutical \| RotaTeq
Segment Reporting Information [Line Items]
Sales	472	493	508
United States \| Operating Segments \| Pharmaceutical \| Pneumovax 23
Segment Reporting Information [Line Items]
Sales	56	127	346
United States \| Operating Segments \| Pharmaceutical \| Bridion
Segment Reporting Information [Line Items]
Sales	1,401	1,156	922
United States \| Operating Segments \| Pharmaceutical \| Prevymis
Segment Reporting Information [Line Items]
Sales	371	264	188
United States \| Operating Segments \| Pharmaceutical \| Dificid
Segment Reporting Information [Line Items]
Sales	303	274	241
United States \| Operating Segments \| Pharmaceutical \| Zerbaxa
Segment Reporting Information [Line Items]
Sales	146	119	89
United States \| Operating Segments \| Pharmaceutical \| Noxafil
Segment Reporting Information [Line Items]
Sales	7	32	51
United States \| Operating Segments \| Pharmaceutical \| Winrevair
Segment Reporting Information [Line Items]
Sales	408	0	0
United States \| Operating Segments \| Pharmaceutical \| Alliance revenue - Adempas/Verquvo
Segment Reporting Information [Line Items]
Sales	388	350	329
United States \| Operating Segments \| Pharmaceutical \| Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0
United States \| Operating Segments \| Pharmaceutical \| Lagevrio
Segment Reporting Information [Line Items]
Sales	176	10	1,523
United States \| Operating Segments \| Pharmaceutical \| Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	185	215	274
United States \| Operating Segments \| Pharmaceutical \| Delstrigo
Segment Reporting Information [Line Items]
Sales	56	49	39
United States \| Operating Segments \| Pharmaceutical \| Pifeltro
Segment Reporting Information [Line Items]
Sales	113	101	87
United States \| Operating Segments \| Pharmaceutical \| Belsomra
Segment Reporting Information [Line Items]
Sales	72	81	79
United States \| Operating Segments \| Pharmaceutical \| Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0
United States \| Operating Segments \| Pharmaceutical \| Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0
United States \| Operating Segments \| Pharmaceutical \| Januvia
Segment Reporting Information [Line Items]
Sales	469	1,151	1,248
United States \| Operating Segments \| Pharmaceutical \| Janumet
Segment Reporting Information [Line Items]
Sales	161	223	355
United States \| Operating Segments \| Pharmaceutical \| Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	729	658	663
United States \| Operating Segments \| Animal Health
Segment Reporting Information [Line Items]
Sales	1,861	1,804	1,822
United States \| Operating Segments \| Animal Health \| Livestock
Segment Reporting Information [Line Items]
Sales	732	700	710
United States \| Operating Segments \| Animal Health \| Companion Animal
Segment Reporting Information [Line Items]
Sales	1,129	1,104	1,112
United States \| Other
Segment Reporting Information [Line Items]
Sales	126	137	395
Int’l
Segment Reporting Information [Line Items]
Sales	31,891	31,635	32,077
Int’l \| Operating Segments
Segment Reporting Information [Line Items]
Sales	31,126	30,865	30,744
Int’l \| Operating Segments \| Pharmaceutical
Segment Reporting Information [Line Items]
Sales	27,110	27,044	27,016
Int’l \| Operating Segments \| Pharmaceutical \| Keytruda
Segment Reporting Information [Line Items]
Sales	11,610	9,897	8,251
Int’l \| Operating Segments \| Pharmaceutical \| Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	685	592	532
Int’l \| Operating Segments \| Pharmaceutical \| Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	305	303	297
Int’l \| Operating Segments \| Pharmaceutical \| Welireg
Segment Reporting Information [Line Items]
Sales	43	10	0
Int’l \| Operating Segments \| Pharmaceutical \| Alliance revenue - Reblozyl
Segment Reporting Information [Line Items]
Sales	68	43	43
Int’l \| Operating Segments \| Pharmaceutical \| Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	6,158	6,803	4,832
Int’l \| Operating Segments \| Pharmaceutical \| ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	566	531	518
Int’l \| Operating Segments \| Pharmaceutical \| Vaxneuvance
Segment Reporting Information [Line Items]
Sales	347	103	7
Int’l \| Operating Segments \| Pharmaceutical \| RotaTeq
Segment Reporting Information [Line Items]
Sales	239	276	275
Int’l \| Operating Segments \| Pharmaceutical \| Pneumovax 23
Segment Reporting Information [Line Items]
Sales	207	285	256
Int’l \| Operating Segments \| Pharmaceutical \| Bridion
Segment Reporting Information [Line Items]
Sales	363	686	762
Int’l \| Operating Segments \| Pharmaceutical \| Prevymis
Segment Reporting Information [Line Items]
Sales	414	341	240
Int’l \| Operating Segments \| Pharmaceutical \| Dificid
Segment Reporting Information [Line Items]
Sales	37	28	22
Int’l \| Operating Segments \| Pharmaceutical \| Zerbaxa
Segment Reporting Information [Line Items]
Sales	106	100	79
Int’l \| Operating Segments \| Pharmaceutical \| Noxafil
Segment Reporting Information [Line Items]
Sales	170	181	187
Int’l \| Operating Segments \| Pharmaceutical \| Winrevair
Segment Reporting Information [Line Items]
Sales	11	0	0
Int’l \| Operating Segments \| Pharmaceutical \| Alliance revenue - Adempas/Verquvo
Segment Reporting Information [Line Items]
Sales	27	16	12
Int’l \| Operating Segments \| Pharmaceutical \| Adempas
Segment Reporting Information [Line Items]
Sales	287	255	238
Int’l \| Operating Segments \| Pharmaceutical \| Lagevrio
Segment Reporting Information [Line Items]
Sales	787	1,418	4,161
Int’l \| Operating Segments \| Pharmaceutical \| Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	209	268	359
Int’l \| Operating Segments \| Pharmaceutical \| Delstrigo
Segment Reporting Information [Line Items]
Sales	193	152	111
Int’l \| Operating Segments \| Pharmaceutical \| Pifeltro
Segment Reporting Information [Line Items]
Sales	50	41	30
Int’l \| Operating Segments \| Pharmaceutical \| Belsomra
Segment Reporting Information [Line Items]
Sales	150	150	179
Int’l \| Operating Segments \| Pharmaceutical \| Simponi
Segment Reporting Information [Line Items]
Sales	543	710	706
Int’l \| Operating Segments \| Pharmaceutical \| Remicade
Segment Reporting Information [Line Items]
Sales	114	187	207
Int’l \| Operating Segments \| Pharmaceutical \| Januvia
Segment Reporting Information [Line Items]
Sales	865	1,039	1,565
Int’l \| Operating Segments \| Pharmaceutical \| Janumet
Segment Reporting Information [Line Items]
Sales	774	954	1,344
Int’l \| Operating Segments \| Pharmaceutical \| Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	1,782	1,675	1,803
Int’l \| Operating Segments \| Animal Health
Segment Reporting Information [Line Items]
Sales	4,016	3,821	3,728
Int’l \| Operating Segments \| Animal Health \| Livestock
Segment Reporting Information [Line Items]
Sales	2,729	2,637	2,590
Int’l \| Operating Segments \| Animal Health \| Companion Animal
Segment Reporting Information [Line Items]
Sales	1,287	1,184	1,138
Int’l \| Other
Segment Reporting Information [Line Items]
Sales	$ 765	$ 770	$ 1,333