Revenue - Revenue by Product (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Revenues	$ 1,674	$ 1,584	$ 1,547	$ 1,455	$ 1,564	$ 1,480	$ 1,415	$ 1,366	$ 6,260	$ 5,825	$ 5,307
Vaccines
Revenue from External Customer [Line Items]
Revenues									1,483	1,488	1,373
Other pharmaceuticals
Revenue from External Customer [Line Items]
Revenues									780	765	753
Dermatology [Member]
Revenue from External Customer [Line Items]
Revenues									770	607	428
Anti-infectives
Revenue from External Customer [Line Items]
Revenues									1,254	1,280	1,253
Parasiticides
Revenue from External Customer [Line Items]
Revenues									966	836	763
Other non-pharmaceuticals
Revenue from External Customer [Line Items]
Revenues									184	170	174
Medicated feed additives
Revenue from External Customer [Line Items]
Revenues									470	485	475
Animal health diagnostics
Revenue from External Customer [Line Items]
Revenues									268	136	44
Total Products and Services
Revenue from External Customer [Line Items]
Revenues									6,175	5,767	5,263
Contract Manufacturing and Human Health Diagnostics [Member]
Revenue from External Customer [Line Items]
Revenues									$ 85	$ 58	$ 44