Revenue - Revenue by Major 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
Companion animal
Revenue from External Customer [Line Items]
Revenue		717	707
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue		287	273
Companion animal | International
Revenue from External Customer [Line Items]
Revenue		430	434
Livestock
Revenue from External Customer [Line Items]
Revenue		797	729
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue		499	445
Livestock | International
Revenue from External Customer [Line Items]
Revenue		298	284
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue		786	718
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	[1]	$ 728	$ 718

[1] Revenue denominated in euros was $170 million and $181 million for the three months ended March 31, 2020 and March 31, 2019, respectively.