Earnings Per Share - Reconciliation of Basic Shares to Diluted Shares (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Feb. 06, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 29, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 29, 2018	Dec. 30, 2017
Earnings Per Share [Abstract]
Net (loss) income attributable to Covetrus		$ (37)	$ (959)	$ (10)	$ (13)	$ 33	$ 16	$ 29	$ 23	$ (1,019)	[1]	$ 101	$ 64
Basic (in shares)										107		71	71
Effect of dilutive shares (in shares)	1									0		1	1
Diluted shares (in shares)										107		72	72
Basic (in usd per share)		$ (0.33)	$ (8.56)	$ (0.09)	$ (0.14)	$ 0.47	$ 0.22	$ 0.40	$ 0.32	$ (9.50)		$ 1.41	$ 0.90
Diluted (in usd per share)		$ (0.33)	$ (8.56)	$ (0.09)	$ (0.14)	$ 0.46	$ 0.22	$ 0.40	$ 0.31	$ (9.50)		$ 1.40	$ 0.89

[1] Net income earned from January 1, 2019 through February 7, 2019 is attributed to the former parent as it was the sole shareholder prior to February 7, 2019