Segment Reporting - Profits to Income Before Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Profits	$ 3,519	$ 3,259	$ 7,357	$ 6,326
Interest income	14	75	39	164
Interest expense	(209)	(233)	(421)	(442)
Depreciation and amortization			(1,869)	(1,871)
Research and development	(2,123)	(2,189)	(4,331)	(4,119)
Restructuring costs	(83)	(59)	(155)	(212)
Total segment profits
Segment Reporting Information [Line Items]
Profits	6,967	7,518	14,923	14,510
Total segment profits | Pharmaceutical segment
Segment Reporting Information [Line Items]
Profits	6,560	7,115	14,036	13,690
Total segment profits | Animal Health segment
Segment Reporting Information [Line Items]
Profits	407	405	885	820
Total segment profits | Other segment
Segment Reporting Information [Line Items]
Profits	0	(2)	2	0
Other profits
Segment Reporting Information [Line Items]
Profits	61	94	200	124
Unallocated
Segment Reporting Information [Line Items]
Interest income	14	75	39	164
Interest expense	(209)	(233)	(421)	(442)
Depreciation and amortization	(390)	(427)	(772)	(786)
Research and development	(1,994)	(2,093)	(4,092)	(3,935)
Amortization of purchase accounting adjustments	(299)	(378)	(594)	(775)
Restructuring costs	(83)	(59)	(155)	(212)
Other unallocated, net	$ (548)	$ (1,238)	$ (1,771)	$ (2,322)