Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020
Revenue from External Customer [Line Items]
Revenue	$ 1,990	$ 1,786	$ 5,809		$ 4,868
Contract manufacturing & human health
Revenue from External Customer [Line Items]
Revenue	21	23	57		60
Companion animal
Revenue from External Customer [Line Items]
Revenue	1,202	995	3,507		2,674
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue	775	664	2,227		1,757
Companion animal | International
Revenue from External Customer [Line Items]
Revenue	427	331	1,280		917
Livestock
Revenue from External Customer [Line Items]
Revenue	767	768	2,245		2,134
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue	290	332	775		848
Livestock | International
Revenue from External Customer [Line Items]
Revenue	477	436	1,470		1,286
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue	1,065	996	3,002		2,605
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	$ 904	$ 767	$ 2,750	[1]	$ 2,203	[1]

[1] Revenue denominated in euros was $605 million and $517 million for the nine months ended September 30, 2021 and 2020, respectively.