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Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 10,794	$ 10,325	$ 31,296	$ 29,689
Proceeds from sale of marketing rights			81	60
Operating Segments
Segment Reporting Information [Line Items]
Sales	10,734	10,256	31,230	29,289
Other
Segment Reporting Information [Line Items]
Sales	60	69	66	400
United States
Segment Reporting Information [Line Items]
Sales	5,030	4,594	13,425	13,096
United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,010	4,587	13,324	13,023
United States | Other
Segment Reporting Information [Line Items]
Sales	20	7	101	73
International
Segment Reporting Information [Line Items]
Sales	5,764	5,732	17,871	16,593
International | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,725	5,669	17,906	16,266
International | Other
Segment Reporting Information [Line Items]
Sales	39	63	(35)	327
Total Pharmaceutical segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	9,658	9,156	27,859	26,101
Total Pharmaceutical segment sales | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	1,889	1,047	5,020	2,512
Total Pharmaceutical segment sales | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	123	137	396	413
Total Pharmaceutical segment sales | Operating Segments | Temodar
Segment Reporting Information [Line Items]
Sales	46	68	159	198
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	49	5	125	5
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	43	0	78	0
Total Pharmaceutical segment sales | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,048	675	2,317	1,675
Total Pharmaceutical segment sales | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	525	519	1,343	1,273
Total Pharmaceutical segment sales | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	214	229	586	558
Total Pharmaceutical segment sales | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	191	179	540	525
Total Pharmaceutical segment sales | Operating Segments | Zostavax
Segment Reporting Information [Line Items]
Sales	54	234	163	547
Total Pharmaceutical segment sales | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	217	185	661	495
Total Pharmaceutical segment sales | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	188	162	551	458
Total Pharmaceutical segment sales | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	137	159	437	445
Total Pharmaceutical segment sales | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	95	91	287	290
Total Pharmaceutical segment sales | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	79	94	257	327
Total Pharmaceutical segment sales | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	72	73	212	206
Total Pharmaceutical segment sales | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	210	219	673	602
Total Pharmaceutical segment sales | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	135	214	459	651
Total Pharmaceutical segment sales | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	66	56	191	150
Total Pharmaceutical segment sales | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	275	310	860	896
Total Pharmaceutical segment sales | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	104	468	347	1,363
Total Pharmaceutical segment sales | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	165	320	696	1,021
Total Pharmaceutical segment sales | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	92	142	414	565
Total Pharmaceutical segment sales | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	84	59	258	171
Total Pharmaceutical segment sales | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	94	70	238	221
Total Pharmaceutical segment sales | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	927	1,012	2,756	2,799
Total Pharmaceutical segment sales | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	563	513	1,693	1,572
Total Pharmaceutical segment sales | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	234	214	686	573
Total Pharmaceutical segment sales | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	186	155	535	503
Total Pharmaceutical segment sales | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	161	161	521	550
Total Pharmaceutical segment sales | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	103	128	348	360
Total Pharmaceutical segment sales | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	71	42	274	266
Total Pharmaceutical segment sales | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	83	80	249	272
Total Pharmaceutical segment sales | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	60	72	198	232
Total Pharmaceutical segment sales | Operating Segments | Fosamax
Segment Reporting Information [Line Items]
Sales	45	53	159	180
Total Pharmaceutical segment sales | Operating Segments | Dulera
Segment Reporting Information [Line Items]
Sales	50	59	149	210
Total Pharmaceutical segment sales | Operating Segments | Other Pharmaceutical
Segment Reporting Information [Line Items]
Sales	980	952	3,023	3,017
Total Pharmaceutical segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	4,649	4,197	12,206	11,887
Total Pharmaceutical segment sales | United States | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	1,109	604	2,906	1,522
Total Pharmaceutical segment sales | United States | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	71	88	239	257
Total Pharmaceutical segment sales | United States | Operating Segments | Temodar
Segment Reporting Information [Line Items]
Sales	0	0	3	4
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	33	0	88	0
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	30	0	49	0
Total Pharmaceutical segment sales | United States | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	740	484	1,422	1,195
Total Pharmaceutical segment sales | United States | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	429	419	1,097	1,058
Total Pharmaceutical segment sales | United States | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	160	174	394	392
Total Pharmaceutical segment sales | United States | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	134	127	384	377
Total Pharmaceutical segment sales | United States | Operating Segments | Zostavax
Segment Reporting Information [Line Items]
Sales	(1)	139	16	356
Total Pharmaceutical segment sales | United States | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	96	63	272	162
Total Pharmaceutical segment sales | United States | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	89	78	257	220
Total Pharmaceutical segment sales | United States | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	74	93	252	268
Total Pharmaceutical segment sales | United States | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	55	41	150	148
Total Pharmaceutical segment sales | United States | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	2	6	10	17
Total Pharmaceutical segment sales | United States | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	1	5	6	7
Total Pharmaceutical segment sales | United States | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	23	27	76	72
Total Pharmaceutical segment sales | United States | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	123	143	383	422
Total Pharmaceutical segment sales | United States | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	18	228	8	683
Total Pharmaceutical segment sales | United States | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	9	65	34	298
Total Pharmaceutical segment sales | United States | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	0	(6)	11	114
Total Pharmaceutical segment sales | United States | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	498	598	1,466	1,646
Total Pharmaceutical segment sales | United States | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	225	197	625	640
Total Pharmaceutical segment sales | United States | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	193	160	550	425
Total Pharmaceutical segment sales | United States | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	133	110	375	367
Total Pharmaceutical segment sales | United States | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	5	16	16	28
Total Pharmaceutical segment sales | United States | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	4	9	18	15
Total Pharmaceutical segment sales | United States | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	7	(23)	8	16
Total Pharmaceutical segment sales | United States | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	26	30	83	104
Total Pharmaceutical segment sales | United States | Operating Segments | Fosamax
Segment Reporting Information [Line Items]
Sales	2	4	3	7
Total Pharmaceutical segment sales | United States | Operating Segments | Dulera
Segment Reporting Information [Line Items]
Sales	44	52	128	191
Total Pharmaceutical segment sales | United States | Operating Segments | Other Pharmaceutical
Segment Reporting Information [Line Items]
Sales	317	266	877	876
Total Pharmaceutical segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,010	4,959	15,653	14,214
Total Pharmaceutical segment sales | International | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	780	442	2,114	990
Total Pharmaceutical segment sales | International | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	52	49	157	156
Total Pharmaceutical segment sales | International | Operating Segments | Temodar
Segment Reporting Information [Line Items]
Sales	46	68	156	194
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lynparza
Segment Reporting Information [Line Items]
Sales	15	5	37	5
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lenvima
Segment Reporting Information [Line Items]
Sales	13	0	29	0
Total Pharmaceutical segment sales | International | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	308	191	894	481
Total Pharmaceutical segment sales | International | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	96	100	246	215
Total Pharmaceutical segment sales | International | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	54	56	192	166
Total Pharmaceutical segment sales | International | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	57	52	156	148
Total Pharmaceutical segment sales | International | Operating Segments | Zostavax
Segment Reporting Information [Line Items]
Sales	56	94	147	191
Total Pharmaceutical segment sales | International | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	120	122	389	333
Total Pharmaceutical segment sales | International | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	99	83	294	237
Total Pharmaceutical segment sales | International | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	62	66	185	177
Total Pharmaceutical segment sales | International | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	40	50	137	141
Total Pharmaceutical segment sales | International | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	77	88	247	310
Total Pharmaceutical segment sales | International | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	71	68	206	199
Total Pharmaceutical segment sales | International | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	210	219	673	602
Total Pharmaceutical segment sales | International | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	135	214	459	651
Total Pharmaceutical segment sales | International | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	43	30	115	78
Total Pharmaceutical segment sales | International | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	151	167	477	474
Total Pharmaceutical segment sales | International | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	86	241	339	680
Total Pharmaceutical segment sales | International | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	157	255	662	723
Total Pharmaceutical segment sales | International | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	92	148	402	451
Total Pharmaceutical segment sales | International | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	84	59	258	171
Total Pharmaceutical segment sales | International | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	94	70	238	221
Total Pharmaceutical segment sales | International | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	429	414	1,291	1,153
Total Pharmaceutical segment sales | International | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	339	316	1,067	933
Total Pharmaceutical segment sales | International | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	41	54	135	148
Total Pharmaceutical segment sales | International | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	53	45	160	137
Total Pharmaceutical segment sales | International | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	156	145	505	522
Total Pharmaceutical segment sales | International | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	99	119	330	345
Total Pharmaceutical segment sales | International | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	64	65	266	250
Total Pharmaceutical segment sales | International | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	83	80	249	272
Total Pharmaceutical segment sales | International | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	34	41	115	128
Total Pharmaceutical segment sales | International | Operating Segments | Fosamax
Segment Reporting Information [Line Items]
Sales	42	48	155	173
Total Pharmaceutical segment sales | International | Operating Segments | Dulera
Segment Reporting Information [Line Items]
Sales	6	7	21	19
Total Pharmaceutical segment sales | International | Operating Segments | Other Pharmaceutical
Segment Reporting Information [Line Items]
Sales	666	688	2,150	2,140
Total Animal Health segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	1,021	1,000	3,176	2,894
Total Animal Health segment sales | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	660	655	1,946	1,816
Total Animal Health segment sales | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	361	345	1,230	1,078
Total Animal Health segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	306	290	924	842
Total Animal Health segment sales | United States | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	153	137	383	359
Total Animal Health segment sales | United States | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	153	153	541	483
Total Animal Health segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	715	710	2,252	2,052
Total Animal Health segment sales | International | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	508	518	1,563	1,457
Total Animal Health segment sales | International | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	207	192	689	595
Other segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	55	100	195	294
Other segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	55	100	194	294
Other segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	$ 0	$ 0	$ 1	$ 0

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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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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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