Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019
Revenue from External Customer [Line Items]
Revenue	$ 1,786	$ 1,584	$ 4,868		$ 4,586
Companion animal
Revenue from External Customer [Line Items]
Revenue	768	731	2,134		2,162
Companion animal | U.S.
Revenue from External Customer [Line Items]
Revenue	332	294	848		847
Companion animal | International
Revenue from External Customer [Line Items]
Revenue	436	437	1,286		1,315
Livestock
Revenue from External Customer [Line Items]
Revenue	995	834	2,674		2,361
Livestock | U.S.
Revenue from External Customer [Line Items]
Revenue	664	550	1,757		1,495
Livestock | International
Revenue from External Customer [Line Items]
Revenue	331	284	917		866
Operating Segments | U.S.
Revenue from External Customer [Line Items]
Revenue	996	844	2,605		2,342
Operating Segments | International
Revenue from External Customer [Line Items]
Revenue	$ 767	$ 721	$ 2,203	[1]	$ 2,181	[1]

[1] Revenue denominated in euros was $517 million and $541 million for the nine months ended September 30, 2020 and September 30, 2019, respectively.