Goodwill And Intangible Assets, Net (Goodwill Allocated to Reporting Units and Changes in Fair Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, beginning balance			$ 1,501.9
Acquisitions, dispositions, and other adjustments, net			2.9
Impairment	$ 0.0	$ 0.0	(318.3)	$ 0.0
Goodwill, ending balance	1,186.5		1,186.5
Accumulated impairment loss	1,470.0		1,470.0		$ 1,470.0
Reporting Unit, Domestic [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance			227.3
Acquisitions, dispositions, and other adjustments, net			(0.1)
Impairment			0.0
Goodwill, ending balance	227.2		227.2
Accumulated impairment loss	140.0		140.0		$ 140.0
Reporting Unit, Import [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance			498.9
Acquisitions, dispositions, and other adjustments, net			3.2
Impairment			0.0
Goodwill, ending balance	502.1		502.1
Reporting Unit, Premium Luxury [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance			714.9
Acquisitions, dispositions, and other adjustments, net			(0.3)
Impairment			(257.4)
Goodwill, ending balance	457.2		457.2
Accumulated impairment loss	257.4		257.4
Reporting Unit, Collision Centers [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance			41.7
Acquisitions, dispositions, and other adjustments, net			(0.1)
Impairment			(41.6)
Goodwill, ending balance	0.0		0.0
Accumulated impairment loss	41.6		41.6
Reporting Unit, Parts Centers [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance			19.1
Acquisitions, dispositions, and other adjustments, net			0.2
Impairment			(19.3)
Goodwill, ending balance	0.0		0.0
Accumulated impairment loss	$ 19.3		$ 19.3