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Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Sales	$ 46,840	$ 42,294	$ 40,122
Proceeds from sale of intangible assets	80	95	85
Operating Segments
Segment Reporting Information [Line Items]
Sales	46,319	42,151	39,662
Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	41,751	37,689	35,390
Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	11,084	7,171	3,809
Operating Segments | Pharmaceutical segment | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	444	187	20
Operating Segments | Pharmaceutical segment | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	404	149	0
Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	388	522	556
Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	3,737	3,151	2,308
Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	2,275	1,798	1,676
Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	926	907	821
Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	791	728	686
Operating Segments | Pharmaceutical segment | Vaqta
Segment Reporting Information [Line Items]
Sales	238	239	218
Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	1,131	917	704
Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	662	742	636
Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	273	265	280
Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	263	496	602
Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	257	367	382
Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	249	326	422
Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	830	893	819
Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	411	582	837
Operating Segments | Pharmaceutical segment | Belsomra
Segment Reporting Information [Line Items]
Sales	306	260	210
Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	975	1,140	1,204
Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	370	455	1,660
Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	590	857	1,344
Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	285	497	751
Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	391	347	225
Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	419	329	300
Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	3,482	3,686	3,737
Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	2,041	2,228	2,158
Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	879	902	761
Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	787	703	686
Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	698	708	732
Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	442	453	484
Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	293	376	387
Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	288	335	363
Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	241	268	298
Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	4,901	4,705	5,314
Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Sales	4,393	4,212	3,875
Operating Segments | Animal Health | Livestock
Segment Reporting Information [Line Items]
Sales	2,784	2,630	2,484
Operating Segments | Animal Health | Companion Animals
Segment Reporting Information [Line Items]
Sales	1,609	1,582	1,391
Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	175	250	397
Other
Segment Reporting Information [Line Items]
Sales	521	143	460
United States
Segment Reporting Information [Line Items]
Sales	20,325	18,212	17,424
United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	20,239	18,094	17,340
United States | Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	18,759	16,608	15,854
United States | Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	6,305	4,150	2,309
United States | Operating Segments | Pharmaceutical segment | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	269	127	0
United States | Operating Segments | Pharmaceutical segment | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	239	95	0
United States | Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	183	312	342
United States | Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,831	1,873	1,565
United States | Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	1,683	1,430	1,374
United States | Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	679	627	581
United States | Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	506	496	481
United States | Operating Segments | Pharmaceutical segment | Vaqta
Segment Reporting Information [Line Items]
Sales	130	127	94
United States | Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	533	386	239
United States | Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	282	353	309
United States | Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	2	7	10
United States | Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	30	253	361
United States | Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	92	191	189
United States | Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	6	12	20
United States | Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Belsomra
Segment Reporting Information [Line Items]
Sales	92	96	98
United States | Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	398	513	565
United States | Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	118	8	771
United States | Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	14	45	352
United States | Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	16	10	124
United States | Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	1,724	1,969	2,153
United States | Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	589	811	863
United States | Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	742	722	564
United States | Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	568	495	496
United States | Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	29	20	40
United States | Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	24	23	18
United States | Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	9	23	54
United States | Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	0	0	0
United States | Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	103	115	123
United States | Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	1,563	1,319	1,759
United States | Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Sales	1,306	1,238	1,090
United States | Operating Segments | Animal Health | Livestock
Segment Reporting Information [Line Items]
Sales	582	528	471
United States | Operating Segments | Animal Health | Companion Animals
Segment Reporting Information [Line Items]
Sales	724	710	619
United States | Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	174	248	396
United States | Other
Segment Reporting Information [Line Items]
Sales	86	118	84
Int’l
Segment Reporting Information [Line Items]
Sales	26,515	24,083	22,698
Int’l | Operating Segments
Segment Reporting Information [Line Items]
Sales	26,079	24,057	22,322
Int’l | Operating Segments | Pharmaceutical segment
Segment Reporting Information [Line Items]
Sales	22,992	21,081	19,536
Int’l | Operating Segments | Pharmaceutical segment | Keytruda
Segment Reporting Information [Line Items]
Sales	4,779	3,021	1,500
Int’l | Operating Segments | Pharmaceutical segment | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	176	61	20
Int’l | Operating Segments | Pharmaceutical segment | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	165	54	0
Int’l | Operating Segments | Pharmaceutical segment | Emend
Segment Reporting Information [Line Items]
Sales	205	210	213
Int’l | Operating Segments | Pharmaceutical segment | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,905	1,279	743
Int’l | Operating Segments | Pharmaceutical segment | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	592	368	303
Int’l | Operating Segments | Pharmaceutical segment | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	247	281	240
Int’l | Operating Segments | Pharmaceutical segment | RotaTeq
Segment Reporting Information [Line Items]
Sales	284	232	204
Int’l | Operating Segments | Pharmaceutical segment | Vaqta
Segment Reporting Information [Line Items]
Sales	108	112	124
Int’l | Operating Segments | Pharmaceutical segment | Bridion
Segment Reporting Information [Line Items]
Sales	598	531	465
Int’l | Operating Segments | Pharmaceutical segment | Noxafil
Segment Reporting Information [Line Items]
Sales	380	389	327
Int’l | Operating Segments | Pharmaceutical segment | Primaxin
Segment Reporting Information [Line Items]
Sales	271	258	270
Int’l | Operating Segments | Pharmaceutical segment | Invanz
Segment Reporting Information [Line Items]
Sales	233	243	241
Int’l | Operating Segments | Pharmaceutical segment | Cubicin
Segment Reporting Information [Line Items]
Sales	165	176	193
Int’l | Operating Segments | Pharmaceutical segment | Cancidas
Segment Reporting Information [Line Items]
Sales	242	314	402
Int’l | Operating Segments | Pharmaceutical segment | Simponi
Segment Reporting Information [Line Items]
Sales	830	893	819
Int’l | Operating Segments | Pharmaceutical segment | Remicade
Segment Reporting Information [Line Items]
Sales	411	582	837
Int’l | Operating Segments | Pharmaceutical segment | Belsomra
Segment Reporting Information [Line Items]
Sales	214	164	112
Int’l | Operating Segments | Pharmaceutical segment | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	576	627	639
Int’l | Operating Segments | Pharmaceutical segment | Zepatier
Segment Reporting Information [Line Items]
Sales	252	447	888
Int’l | Operating Segments | Pharmaceutical segment | Zetia
Segment Reporting Information [Line Items]
Sales	575	813	992
Int’l | Operating Segments | Pharmaceutical segment | Vytorin
Segment Reporting Information [Line Items]
Sales	269	487	627
Int’l | Operating Segments | Pharmaceutical segment | Atozet
Segment Reporting Information [Line Items]
Sales	391	347	225
Int’l | Operating Segments | Pharmaceutical segment | Adempas
Segment Reporting Information [Line Items]
Sales	419	329	300
Int’l | Operating Segments | Pharmaceutical segment | Januvia
Segment Reporting Information [Line Items]
Sales	1,758	1,718	1,584
Int’l | Operating Segments | Pharmaceutical segment | Janumet
Segment Reporting Information [Line Items]
Sales	1,452	1,417	1,296
Int’l | Operating Segments | Pharmaceutical segment | NuvaRing
Segment Reporting Information [Line Items]
Sales	136	180	197
Int’l | Operating Segments | Pharmaceutical segment | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	219	208	191
Int’l | Operating Segments | Pharmaceutical segment | Singulair
Segment Reporting Information [Line Items]
Sales	669	688	692
Int’l | Operating Segments | Pharmaceutical segment | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	418	431	466
Int’l | Operating Segments | Pharmaceutical segment | Nasonex
Segment Reporting Information [Line Items]
Sales	284	353	333
Int’l | Operating Segments | Pharmaceutical segment | Arcoxia
Segment Reporting Information [Line Items]
Sales	288	335	363
Int’l | Operating Segments | Pharmaceutical segment | Follistim AQ
Segment Reporting Information [Line Items]
Sales	138	153	174
Int’l | Operating Segments | Pharmaceutical segment | Other pharmaceutical
Segment Reporting Information [Line Items]
Sales	3,343	3,380	3,556
Int’l | Operating Segments | Animal Health
Segment Reporting Information [Line Items]
Sales	3,086	2,974	2,785
Int’l | Operating Segments | Animal Health | Livestock
Segment Reporting Information [Line Items]
Sales	2,201	2,102	2,013
Int’l | Operating Segments | Animal Health | Companion Animals
Segment Reporting Information [Line Items]
Sales	885	872	772
Int’l | Operating Segments | Other segments
Segment Reporting Information [Line Items]
Sales	1	2	1
Int’l | Other
Segment Reporting Information [Line Items]
Sales	$ 436	$ 26	$ 376

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The cash inflow from disposal of asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

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