Revenue - Revenue by Product (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
Vaccines
Revenue from External Customer [Line Items]
Revenue	421	401	1,251	1,086
Parasiticides
Revenue from External Customer [Line Items]
Revenue	396	305	1,246	867
Anti-infectives
Revenue from External Customer [Line Items]
Revenue	329	349	909	870
Dermatology
Revenue from External Customer [Line Items]
Revenue	326	257	859	681
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	243	208	717	597
Medicated feed additives
Revenue from External Customer [Line Items]
Revenue	99	102	314	336
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenue	95	87	283	216
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	60	54	173	155
Total products and services
Revenue from External Customer [Line Items]
Revenue	$ 1,969	$ 1,763	$ 5,752	$ 4,808