Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021		Jun. 30, 2020
Revenue from External Customer [Line Items]
Revenue	$ 1,948	$ 1,548	$ 3,819		$ 3,082
Contract manufacturing & human health
Revenue from External Customer [Line Items]
Revenue	20	17	36		37
Companion animal
Revenue from External Customer [Line Items]
Revenue	1,229	882	2,305		1,679
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue	794	594	1,452		1,093
Companion animal | International
Revenue from External Customer [Line Items]
Revenue	435	288	853		586
Livestock
Revenue from External Customer [Line Items]
Revenue	699	649	1,478		1,366
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue	210	229	485		516
Livestock | International
Revenue from External Customer [Line Items]
Revenue	489	420	993		850
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue	1,004	823	1,937		1,609
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	$ 924	$ 708	$ 1,846	[1]	$ 1,436	[1]

[1] Revenue denominated in euros was $401 million and $331 million for the six months ended June 30, 2021 and 2020, respectively.