Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Revenue from External Customer [Line Items]
Revenue	$ 1,548	$ 1,547	$ 3,082		$ 3,002
Companion animal
Revenue from External Customer [Line Items]
Revenue	649	724	1,366		1,431
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue	229	280	516		553
Companion animal | International
Revenue from External Customer [Line Items]
Revenue	420	444	850		878
Livestock
Revenue from External Customer [Line Items]
Revenue	882	798	1,679		1,527
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue	594	500	1,093		945
Livestock | International
Revenue from External Customer [Line Items]
Revenue	288	298	586		582
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue	823	780	1,609		1,498
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	$ 708	$ 742	$ 1,436	[1]	$ 1,460	[1]

[1] Revenue denominated in euros was $331 million and $365 million for the six months ended June 30, 2020 and June 30, 2019, respectively.