Revenue - Revenue by 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
Cattle [Member]
Revenue from External Customer [Line Items]
Revenue	416	386
Swine [Member]
Revenue from External Customer [Line Items]
Revenue	175	160
Poultry [Member]
Revenue from External Customer [Line Items]
Revenue	136	116
Fish [Member]
Revenue from External Customer [Line Items]
Revenue	22	21
Sheep and Other [Member]
Revenue from External Customer [Line Items]
Revenue	21	20
Livestock [Member]
Revenue from External Customer [Line Items]
Revenue	770	703
Horses
Revenue from External Customer [Line Items]
Revenue	41	35
Dogs and Cats [Member]
Revenue from External Customer [Line Items]
Revenue	549	482
Companion Animal [Member]
Revenue from External Customer [Line Items]
Revenue	590	517
Contract manufacturing [Member]
Revenue from External Customer [Line Items]
Revenue	$ 6	$ 11