Segment Information (Details) $ in Millions		12 Months Ended
		Dec. 31, 2023 USD ($) segments	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segments		3
Revenues		$ 26,948.9	$ 26,985.0	$ 25,844.0
Floorplan interest expense		144.7	41.4	25.7
Depreciation and amortization		220.5	200.3	193.3
Segment assets		11,980.0	10,059.7	8,943.6
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		1,507.2	1,983.1	1,877.1
Segment, Expenditure, Addition to Long-Lived Assets	[1]	416.0	336.2	231.9
Other interest expense		(181.4)	(134.9)	(93.0)
Other income, net		24.4	(14.7)	24.3
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		1,350.2	1,833.5	1,808.4
AN Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenues		25,720.5	25,955.9	24,988.3
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		1,886.9	2,268.6	2,147.9
AN Reportable Segment, Domestic [Member]
Segment Reporting Information [Line Items]
Revenues		7,573.2	7,987.5	7,959.9
Floorplan interest expense		57.3	14.4	7.9
Depreciation and amortization		43.6	39.1	39.3
Segment assets		2,507.7	1,974.3	1,758.5
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		415.4	565.3	595.8
Segment, Expenditure, Addition to Long-Lived Assets	[1]	102.0	32.8	15.5
AN Reportable Segment, Import [Member]
Segment Reporting Information [Line Items]
Revenues		7,880.9	7,690.3	7,798.5
Floorplan interest expense		21.5	4.8	5.1
Depreciation and amortization		39.2	35.6	33.9
Segment assets		2,034.6	1,555.6	1,424.2
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		635.0	734.2	714.7
Segment, Expenditure, Addition to Long-Lived Assets	[1]	106.6	70.1	27.1
AN Reportable Segment, Premium Luxury [Member]
Segment Reporting Information [Line Items]
Revenues		10,266.4	10,278.1	9,229.9
Floorplan interest expense		53.9	15.0	8.8
Depreciation and amortization		76.9	74.9	64.8
Segment assets		3,506.8	2,996.8	2,668.6
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		836.5	969.1	837.4
Segment, Expenditure, Addition to Long-Lived Assets	[1]	69.4	126.5	80.0
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	1,228.4	1,029.1	855.7
Floorplan interest expense		12.0	7.2	3.9
Depreciation and amortization		60.8	50.7	55.3
Segment assets		3,930.9	3,533.0	3,092.3
Segment Reporting Information, Income (Loss) before Income Taxes [Abstract]
Segment income (loss)		(379.7)	(285.5)	(270.8)
Segment, Expenditure, Addition to Long-Lived Assets	[1]	$ 138.0	$ 106.8	$ 109.3

[1] (2) Includes accrued construction in progress and excludes property associated with leases entered during the year.

[2] (1) “Corporate and other” is comprised of our other businesses, including AutoNation USA used vehicle stores, collision centers, parts distribution centers, auction operations, and AutoNation Mobile Service.