Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 29, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	$ 1,253	$ 1,452	$ 1,215
Other comprehensive income (loss) attributable to Covetrus before reclassifications	13	(5)	(40)
Reclassified from Accumulated other comprehensive loss to earnings	7	1
Period change	20	(4)	(40)
Common stock, shares ending balance	1,537	1,253	1,452
Derivative Gain (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	0	0	0
Other comprehensive income (loss) attributable to Covetrus before reclassifications	(8)	(1)	0
Reclassified from Accumulated other comprehensive loss to earnings	5	1
Period change	(3)	0	0
Common stock, shares ending balance	(3)	0	0
Gain (Loss) on Pension Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	0	0	(2)
Other comprehensive income (loss) attributable to Covetrus before reclassifications	0	0	2
Reclassified from Accumulated other comprehensive loss to earnings	0	0
Period change	0	0	2
Common stock, shares ending balance	0	0	0
Foreign Currency Translation Gain (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	(86)	(82)	(41)
Other comprehensive income (loss) attributable to Covetrus before reclassifications	21	(4)	(41)
Reclassified from Accumulated other comprehensive loss to earnings	2	0
Period change	23	(4)	(41)
Common stock, shares ending balance	(63)	(86)	(82)
Unrealized Gain (Loss) from Foreign Currency Hedging
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	0	0	1
Other comprehensive income (loss) attributable to Covetrus before reclassifications	0	0	(1)
Reclassified from Accumulated other comprehensive loss to earnings	0	0
Period change	0	0	(1)
Common stock, shares ending balance	0	0	0
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Common stock, shares beginning balance	(86)	(82)	(42)
Common stock, shares ending balance	$ (66)	$ (86)	$ (82)