Revenue - Revenue by Species (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue from External Customer [Line Items]
Revenue	$ 1,948	$ 1,548	$ 3,819	$ 3,082
Contract manufacturing & human health
Revenue from External Customer [Line Items]
Revenue	20	17	36	37
Dogs and Cats
Revenue from External Customer [Line Items]
Revenue	1,161	831	2,177	1,577
Horses
Revenue from External Customer [Line Items]
Revenue	68	51	128	102
Cattle
Revenue from External Customer [Line Items]
Revenue	342	320	741	690
Swine
Revenue from External Customer [Line Items]
Revenue	161	146	351	303
Poultry
Revenue from External Customer [Line Items]
Revenue	134	135	265	283
Fish
Revenue from External Customer [Line Items]
Revenue	39	30	76	56
Sheep and other
Revenue from External Customer [Line Items]
Revenue	23	18	45	34
Livestock
Revenue from External Customer [Line Items]
Revenue	699	649	1,478	1,366
Companion animal
Revenue from External Customer [Line Items]
Revenue	1,229	882	2,305	1,679
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	$ 248	$ 192	$ 474	$ 389