Revenue - Revenue by Product (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
Vaccines
Revenue from External Customer [Line Items]
Revenue	417	336	830	685
Parasiticides
Revenue from External Customer [Line Items]
Revenue	460	307	850	562
Anti-infectives
Revenue from External Customer [Line Items]
Revenue	259	241	580	521
Dermatology
Revenue from External Customer [Line Items]
Revenue	285	227	533	424
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	248	192	474	389
Medicated feed additives
Revenue from External Customer [Line Items]
Revenue	103	109	215	234
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenue	99	69	188	129
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	57	50	113	101
Total products and services
Revenue from External Customer [Line Items]
Revenue	$ 1,928	$ 1,531	$ 3,783	$ 3,045