Business Acquisitions - Unaudited Pro Forma Financial Information (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 29, 2018	Dec. 30, 2017
Business Acquisition [Line Items]
Goodwill impairment	$ (1)	$ 939	$ 0	$ 0	$ 938	$ 0	$ 0
Vets First Choice
Business Acquisition [Line Items]
Net sales					4,000	3,981
Goodwill impairment					938	0
Net loss					(1,032)	(63)
Net loss attributable to Covetrus					$ (1,029)	$ (63)