Basis of Presentation and Nature of Operations - Narrative (Details) $ in Millions		6 Months Ended
	Jun. 28, 2019 USD ($) shares	Jun. 28, 2020 USD ($) segment facility	Jun. 30, 2019 USD ($)	Dec. 29, 2019 USD ($)	Dec. 30, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of facilities | facility		200
Number of reportable segments | segment		2
Issued and outstanding shares distributed to holders of record, percentage	100.00%
Subsidiary common stock, conversion rate | shares	1
Parent common stock, conversion rate | shares	1
Dividend paid to KAR		$ 0.0	$ 1,278.0
Payments for certain fixed assets	$ 40.9
Accrued income taxes		19.6		$ 1.5
Reduction to cash and cash equivalents		(187.0)		(47.1)
Reduction to other accrued expenses		(67.5)		$ (49.3)
Reclassification Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction to cash and cash equivalents		$ 2.4			$ 11.7
Reduction to other accrued expenses			$ 2.4		$ 11.7
Affiliated Entity
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Dividend paid to KAR	1,278.0
Payments to settle intercompany debt	456.6
Payments to settle other intercompany accounts	$ 117.7