Revenue - Revenue by Product (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
Vaccines
Revenue from External Customer [Line Items]
Revenue	413	349
Parasiticides
Revenue from External Customer [Line Items]
Revenue	390	255
Anti-infectives
Revenue from External Customer [Line Items]
Revenue	321	280
Dermatology
Revenue from External Customer [Line Items]
Revenue	248	197
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	226	197
Medicated feed additives
Revenue from External Customer [Line Items]
Revenue	112	125
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenue	89	60
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	56	51
Total products and services
Revenue from External Customer [Line Items]
Revenue	$ 1,855	$ 1,514