Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) shares in Millions, $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Net Parent Investment	Net Parent Investment Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Balance at Dec. 30, 2018	$ 563.2	$ 1.1	$ 0.0	$ 0.0	$ 0.0	$ 576.2	$ 1.1	$ (13.0)
Balance (in shares) at Dec. 30, 2018			0.0
Increase (Decrease) in Stockholders' Equity
Net income	105.8					105.8
Foreign currency translation adjustments, net of tax	(2.7)							(2.7)
Stock-based compensation expense	1.9					1.9
Reclassification of net parent investment to common stock and additional paid-in capital	0.0		$ 1.3		(214.5)	213.2
Reclassification of net parent investment to common stock and additional paid-in capital (in shares)			133.4
Dividend paid to KAR	(1,278.0)					(1,278.0)
Net transfer to parent and affiliates	379.8					379.8
Balance at Jun. 30, 2019	(228.9)		$ 1.3	0.0	(214.5)	0.0		(15.7)
Balance (in shares) at Jun. 30, 2019			133.4
Balance at Mar. 31, 2019	618.9		$ 0.0	0.0	0.0	629.4		(10.5)
Balance (in shares) at Mar. 31, 2019			0.0
Increase (Decrease) in Stockholders' Equity
Net income	51.3					51.3
Foreign currency translation adjustments, net of tax	(5.2)							(5.2)
Stock-based compensation expense	0.9					0.9
Reclassification of net parent investment to common stock and additional paid-in capital	0.0		$ 1.3		(214.5)	213.2
Reclassification of net parent investment to common stock and additional paid-in capital (in shares)			133.4
Dividend paid to KAR	(1,278.0)					(1,278.0)
Net transfer to parent and affiliates	383.2					383.2
Balance at Jun. 30, 2019	(228.9)		$ 1.3	0.0	(214.5)	$ 0.0		(15.7)
Balance (in shares) at Jun. 30, 2019			133.4
Balance at Dec. 29, 2019	$ (137.2)		$ 1.3	3.5	(127.1)			(14.9)
Balance (in shares) at Dec. 29, 2019	133.6		133.6
Increase (Decrease) in Stockholders' Equity
Net income	$ 77.9				77.9
Foreign currency translation adjustments, net of tax	(5.7)							(5.7)
Stock-based compensation expense	4.5			4.5
Common stock issued for the exercise and vesting of stock-based awards	1.1			1.1
Common stock issued for the exercise and vesting of stock-based awards (in shares)			0.6
Withholding taxes withheld on share based awards	(8.0)			(8.0)
Withholding taxes on stock-based awards (in shares)			(0.2)
Balance at Jun. 28, 2020	$ (67.4)		$ 1.3	1.1	(49.2)			(20.6)
Balance (in shares) at Jun. 28, 2020	134.0		134.0
Balance at Mar. 29, 2020	$ (103.6)		$ 1.3	0.0	(82.4)			(22.5)
Balance (in shares) at Mar. 29, 2020			133.9
Increase (Decrease) in Stockholders' Equity
Net income	33.2				33.2
Foreign currency translation adjustments, net of tax	1.9							1.9
Stock-based compensation expense	2.4			2.4
Common stock issued for the exercise and vesting of stock-based awards	0.3			0.3
Common stock issued for the exercise and vesting of stock-based awards (in shares)			0.1
Withholding taxes withheld on share based awards	(1.6)			(1.6)
Balance at Jun. 28, 2020	$ (67.4)		$ 1.3	$ 1.1	$ (49.2)			$ (20.6)
Balance (in shares) at Jun. 28, 2020	134.0		134.0