Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenue:
TOTAL REVENUE		$ 27,631.4	$ 26,765.4	$ 26,948.9
Cost of Sales:
TOTAL COST OF SALES		22,682.9	21,980.0	21,817.4
Gross Profit:
TOTAL GROSS PROFIT		4,948.5	4,785.4	5,131.5
AutoNation finance income (loss)		9.8	(9.3)	(13.9)
Selling, general, and administrative expenses		3,362.2	3,263.9	3,253.2
Depreciation and amortization		251.4	240.7	220.5
Goodwill impairment		65.3	0.0	0.0
Franchise rights impairment		93.7	12.5	0.0
Other income, net		(54.2)	(46.5)	(8.0)
OPERATING INCOME		1,239.9	1,305.5	1,651.9
Non-operating income (expense) items:
Floorplan interest expense		(188.8)	(218.9)	(144.7)
Other interest expense		(180.0)	(179.7)	(181.4)
Other income, net		13.4	9.8	24.4
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		884.5	916.7	1,350.2
Income tax provision		235.4	224.5	330.0
NET INCOME FROM CONTINUING OPERATIONS		649.1	692.2	1,020.2
Income from discontinued operations, net of income taxes		0.0	0.0	0.9
NET INCOME		$ 649.1	$ 692.2	$ 1,021.1
BASIC EARNINGS PER SHARE:
Continuing operations (in dollars per share)	[1]	$ 17.26	$ 17.09	$ 22.87
Discontinued operations (in dollars per share)	[1]	0	0	0.02
Net income (in dollars per share)	[1]	$ 17.26	$ 17.09	$ 22.89
Weighted average common shares outstanding, basic (in shares)		37.6	40.5	44.6
DILUTED EARNINGS PER SHARE:
Continuing operations (in dollars per share)	[1]	$ 17.04	$ 16.92	$ 22.72
Discontinued operations (in dollars per share)	[1]	0	0	0.02
Net income (in dollars per share)	[1]	$ 17.04	$ 16.92	$ 22.74
Weighted average common shares outstanding (in shares)		38.1	40.9	44.9
COMMON SHARES OUTSTANDING, net of treasury stock, at period end (in shares)		35.2	39.0	41.6
AN Reportable Segment, AN Finance
Gross Profit:
AutoNation finance income (loss)		$ 9.8	$ (9.3)	$ (13.9)
New Vehicle [Member]
Revenue:
TOTAL REVENUE		13,501.3	13,048.2	12,767.4
Cost of Sales:
TOTAL COST OF SALES		12,836.5	12,272.7	11,705.6
Gross Profit:
TOTAL GROSS PROFIT		664.8	775.5	1,061.8
Used Vehicle [Member]
Revenue:
TOTAL REVENUE		7,814.0	7,719.9	8,198.5
Cost of Sales:
TOTAL COST OF SALES		7,351.4	7,281.4	7,690.5
Gross Profit:
TOTAL GROSS PROFIT		462.6	438.5	508.0
Parts and Service [Member]
Revenue:
TOTAL REVENUE		4,835.4	4,614.6	4,533.7
Cost of Sales:
TOTAL COST OF SALES		2,480.3	2,405.6	2,394.4
Gross Profit:
TOTAL GROSS PROFIT		2,355.1	2,209.0	2,139.3
Finance and Insurance, Net [Member]
Revenue:
TOTAL REVENUE		1,464.4	1,360.1	1,418.8
Gross Profit:
TOTAL GROSS PROFIT		1,464.4	1,360.1	1,418.8
Product and Service, Other [Member]
Revenue:
TOTAL REVENUE		16.3	22.6	30.5
Cost of Sales:
TOTAL COST OF SALES		14.7	20.3	26.9
Gross Profit:
TOTAL GROSS PROFIT		$ 1.6	$ 2.3	$ 3.6

[1] (1) EPS amounts are calculated discretely and, therefore, may not add up to the total due to rounding.