Segment and Other Revenue Information - Revenue by Species (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Revenue from External Customer [Line Items]
Revenue	$ 1,269	$ 1,208	$ 2,500	$ 2,370
Livestock:
Revenue from External Customer [Line Items]
Revenue	689	673	1,392	1,356
Cattle
Revenue from External Customer [Line Items]
Revenue	382	366	768	743
Swine
Revenue from External Customer [Line Items]
Revenue	148	150	308	296
Poultry
Revenue from External Customer [Line Items]
Revenue	122	118	238	240
Fish
Revenue from External Customer [Line Items]
Revenue	19	22	40	39
Other
Revenue from External Customer [Line Items]
Revenue	18	17	38	38
Companion Animal:
Revenue from External Customer [Line Items]
Revenue	568	523	1,085	989
Horses
Revenue from External Customer [Line Items]
Revenue	35	36	70	75
Dogs and Cats
Revenue from External Customer [Line Items]
Revenue	533	487	1,015	914
Contract Manufacturing
Revenue from External Customer [Line Items]
Revenue	$ 12	$ 12	$ 23	$ 25