Revenue - Revenue by Product (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Revenues	$ 6,675	$ 6,260	$ 5,825
Vaccines
Revenue from External Customer [Line Items]
Revenues	1,476	1,483	1,488
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenues	821	780	765
Dermatology [Member]
Revenue from External Customer [Line Items]
Revenues	941	770	607
Anti-infectives
Revenue from External Customer [Line Items]
Revenues	1,206	1,254	1,280
Parasiticides
Revenue from External Customer [Line Items]
Revenues	1,173	966	836
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenues	210	184	170
Medicated feed additives
Revenue from External Customer [Line Items]
Revenues	460	470	485
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenues	305	268	136
Total Products and Services
Revenue from External Customer [Line Items]
Revenues	6,592	6,175	5,767
Contract Manufacturing and Human Health Diagnostics [Member]
Revenue from External Customer [Line Items]
Revenues	$ 83	$ 85	$ 58