Revenue - Revenue by Product (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
Contract Manufacturing and Human Health Diagnostics [Member]
Revenue from External Customer [Line Items]
Revenue	23	19	60	63
Vaccines
Revenue from External Customer [Line Items]
Revenue	401	364	1,086	1,092
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	208	196	597	573
Anti-infectives
Revenue from External Customer [Line Items]
Revenue	349	312	870	891
Parasiticides
Revenue from External Customer [Line Items]
Revenue	305	243	867	740
Medicated feed additives
Revenue from External Customer [Line Items]
Revenue	102	112	336	339
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenue	87	69	216	194
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenue	54	47	155	128
Total products and services
Revenue from External Customer [Line Items]
Revenue	1,763	1,565	4,808	4,523
Dermatology
Revenue from External Customer [Line Items]
Revenue	257	222	681	566
Cattle
Revenue from External Customer [Line Items]
Revenue	$ 417	$ 389	$ 1,107	$ 1,148