Revenue - Revenue by Species (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue from External Customer [Line Items]
Revenue	$ 1,990	$ 1,786	$ 5,809	$ 4,868
Contract manufacturing & human health
Revenue from External Customer [Line Items]
Revenue	21	23	57	60
Dogs and Cats
Revenue from External Customer [Line Items]
Revenue	1,142	947	3,319	2,524
Horses
Revenue from External Customer [Line Items]
Revenue	60	48	188	150
Cattle
Revenue from External Customer [Line Items]
Revenue	403	417	1,144	1,107
Swine
Revenue from External Customer [Line Items]
Revenue	153	151	504	454
Poultry
Revenue from External Customer [Line Items]
Revenue	124	129	389	412
Fish
Revenue from External Customer [Line Items]
Revenue	56	45	132	101
Sheep and other
Revenue from External Customer [Line Items]
Revenue	31	26	76	60
Livestock
Revenue from External Customer [Line Items]
Revenue	767	768	2,245	2,134
Companion animal
Revenue from External Customer [Line Items]
Revenue	1,202	995	3,507	2,674
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	$ 243	$ 208	$ 717	$ 597