Revenue - Revenue by Species (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from External Customer [Line Items]
Revenue	$ 1,871	$ 1,534
Contract manufacturing & human health
Revenue from External Customer [Line Items]
Revenue	16	20
Dogs and Cats
Revenue from External Customer [Line Items]
Revenue	1,016	746
Horses
Revenue from External Customer [Line Items]
Revenue	60	51
Cattle
Revenue from External Customer [Line Items]
Revenue	399	370
Swine
Revenue from External Customer [Line Items]
Revenue	190	157
Poultry
Revenue from External Customer [Line Items]
Revenue	131	148
Fish
Revenue from External Customer [Line Items]
Revenue	37	26
Sheep and other
Revenue from External Customer [Line Items]
Revenue	22	16
Livestock
Revenue from External Customer [Line Items]
Revenue	779	717
Companion animal
Revenue from External Customer [Line Items]
Revenue	1,076	797
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	$ 226	$ 197