Revenue - Revenue by Species (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue from External Customer [Line Items]
Revenue	$ 1,534	$ 1,455
Cattle
Revenue from External Customer [Line Items]
Revenue	370	380
Swine
Revenue from External Customer [Line Items]
Revenue	157	149
Poultry
Revenue from External Customer [Line Items]
Revenue	148	139
Fish
Revenue from External Customer [Line Items]
Revenue	26	23
Sheep and other
Revenue from External Customer [Line Items]
Revenue	16	16
Companion animal
Revenue from External Customer [Line Items]
Revenue	717	707
Dogs and Cats [Member]
Revenue from External Customer [Line Items]
Revenue	746	688
Livestock
Revenue from External Customer [Line Items]
Revenue	797	729
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	197	190
Horses
Revenue from External Customer [Line Items]
Revenue	$ 51	$ 41