Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Apr. 02, 2017
Revenue from External Customer [Line Items]
Revenue	$ 1,366	$ 1,231
U.S.
Revenue from External Customer [Line Items]
Revenue	634	605
International
Revenue from External Customer [Line Items]
Revenue		615
Companion Animal [Member]
Revenue from External Customer [Line Items]
Revenue	590	517
Companion Animal [Member] | U.S.
Revenue from External Customer [Line Items]
Revenue	342	323
Companion Animal [Member] | International
Revenue from External Customer [Line Items]
Revenue	248	194
Livestock [Member]
Revenue from External Customer [Line Items]
Revenue	770	703
Livestock [Member] | U.S.
Revenue from External Customer [Line Items]
Revenue	292	282
Livestock [Member] | International
Revenue from External Customer [Line Items]
Revenue	478	421
Contract Manufacturing
Revenue from External Customer [Line Items]
Revenue	$ 6	$ 11