Goodwill and Intangible Assets, Net (Goodwill) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022		Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill, gross, beginning balance		$ 3,163.6		$ 3,113.3
Goodwill, Impaired, Accumulated Impairment Loss		(1,928.3)		(1,928.3)
Goodwill, beginning balance		1,235.3		1,185.0
Acquisitions, dispositions, and other adjustments, net	[1]	84.8		50.3
Goodwill, gross, ending balance		3,248.4		3,163.6
Goodwill, Impaired, Accumulated Impairment Loss		(1,928.3)		(1,928.3)
Goodwill, ending balance		1,320.1		1,235.3
Reporting Unit, Domestic [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance		368.7		367.2
Goodwill, Impaired, Accumulated Impairment Loss		(140.0)		(140.0)
Goodwill, beginning balance		228.7		227.2
Acquisitions, dispositions, and other adjustments, net	[1]	7.6		1.5
Goodwill, gross, ending balance		376.3		368.7
Goodwill, Impaired, Accumulated Impairment Loss		(140.0)		(140.0)
Goodwill, ending balance		236.3		228.7
Reporting Unit, Import [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance		517.9		500.6
Goodwill, Impaired, Accumulated Impairment Loss		0.0		0.0
Goodwill, beginning balance		517.9		500.6
Acquisitions, dispositions, and other adjustments, net	[1]	0.8		17.3
Goodwill, gross, ending balance		518.7		517.9
Goodwill, Impaired, Accumulated Impairment Loss		0.0		0.0
Goodwill, ending balance		518.7		517.9
Reporting Unit, Premium Luxury [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance		741.5		714.6
Goodwill, Impaired, Accumulated Impairment Loss		(257.4)		(257.4)
Goodwill, beginning balance		484.1		457.2
Acquisitions, dispositions, and other adjustments, net	[1]	(2.0)		26.9
Goodwill, gross, ending balance		739.5		741.5
Goodwill, Impaired, Accumulated Impairment Loss		(257.4)		(257.4)
Goodwill, ending balance		482.1		484.1
Reporting Unit, Other
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	[2]	1,535.5		1,530.9
Goodwill, Impaired, Accumulated Impairment Loss	[2]	(1,530.9)		(1,530.9)
Goodwill, beginning balance		4.6		0.0
Acquisitions, dispositions, and other adjustments, net	[1]	78.4		4.6
Goodwill, gross, ending balance	[2]	1,613.9	[3]	1,535.5
Goodwill, Impaired, Accumulated Impairment Loss	[2]	(1,530.9)		(1,530.9)
Goodwill, ending balance		83.0		4.6
Single Reporting Unit (before change in reporting units)
Goodwill [Roll Forward]
Goodwill, Impaired, Accumulated Impairment Loss		(1,470.0)		(1,470.0)
Goodwill, Impaired, Accumulated Impairment Loss		$ (1,470.0)		$ (1,470.0)

[1] Includes amounts reclassified to held for sale and related adjustments, which are presented in Other Current Assets in our Consolidated Balance Sheet as of period end.

[2] Gross goodwill balance and accumulated impairment losses reflected in “Other” include$1.47 billion associated with our single reporting unit (prior to September 30, 2008, our reporting unit reporting structure was comprised of a single reporting unit), as well as amounts associated with the Collision Center and Parts Center reporting units.

[3] Gross goodwill balance reflected in “Other” includes amounts associated with the AutoNation Finance reporting unit