Revenue - Revenue by Major 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
Companion animal
Revenue from External Customer [Line Items]
Revenue		1,076	797
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue		658	499
Companion animal | International
Revenue from External Customer [Line Items]
Revenue		418	298
Livestock
Revenue from External Customer [Line Items]
Revenue		779	717
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue		275	287
Livestock | International
Revenue from External Customer [Line Items]
Revenue		504	430
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue		933	786
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	[1]	$ 922	$ 728

[1] Revenue denominated in euros was $192 million and $170 million for the three months ended March 31, 2021 and 2020, respectively.