Unaudited Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
TOTAL REVENUE	$ 7,037.4	$ 6,586.1	$ 20,702.2	$ 19,552.2
TOTAL COST OF SALES	5,799.0	5,403.3	16,968.5	16,008.4
TOTAL GROSS PROFIT	1,238.4	1,182.8	3,733.7	3,543.8
AUTONATION FINANCE INCOME (LOSS)	1.5	(6.2)	3.6	(10.5)
Selling, general, and administrative expenses	850.1	811.3	2,526.7	2,430.2
Depreciation and amortization	64.2	61.3	189.9	179.5
Goodwill impairment	0.0	0.0	65.3	0.0
Franchise rights impairment	0.0	0.0	71.7	0.0
Other income, net	(46.8)	(46.7)	(42.3)	(42.4)
OPERATING INCOME	372.4	350.7	926.0	966.0
Non-operating income (expense) items:
Floorplan interest expense	(47.5)	(60.5)	(139.3)	(163.8)
Other interest expense	(45.1)	(44.9)	(133.6)	(136.3)
Other income, net	7.8	2.1	6.9	9.0
INCOME BEFORE INCOME TAXES	287.6	247.4	660.0	674.9
Income tax provision	72.5	61.6	183.0	168.8
NET INCOME	$ 215.1	$ 185.8	$ 477.0	$ 506.1
BASIC EARNINGS PER SHARE:
Earnings per share, basic (in dollars per share)	$ 5.72	$ 4.66	$ 12.49	$ 12.40
Weighted average common shares outstanding (in shares)	37.6	39.9	38.2	40.8
DILUTED EARNINGS PER SHARE:
Earnings per share, diluted (in dollars per share)	$ 5.65	$ 4.61	$ 12.36	$ 12.31
Weighted average common shares outstanding (in shares)	38.1	40.3	38.6	41.1
COMMON SHARES OUTSTANDING, net of treasury stock, at period end (in shares)	36.9	39.6	36.9	39.6
New vehicle
TOTAL REVENUE	$ 3,415.6	$ 3,171.2	$ 10,060.0	$ 9,273.0
TOTAL COST OF SALES	3,264.6	2,994.1	9,550.7	8,709.6
TOTAL GROSS PROFIT	151.0	177.1	509.3	563.4
Used vehicle
TOTAL REVENUE	2,015.7	1,901.4	5,923.1	5,808.6
TOTAL COST OF SALES	1,900.8	1,790.2	5,558.3	5,474.5
TOTAL GROSS PROFIT	114.9	111.2	364.8	334.1
Parts and service
TOTAL REVENUE	1,226.2	1,170.9	3,611.3	3,460.4
TOTAL COST OF SALES	629.2	612.7	1,848.0	1,809.8
TOTAL GROSS PROFIT	597.0	558.2	1,763.3	1,650.6
Finance and insurance, net
TOTAL REVENUE	374.8	335.4	1,095.0	994.1
TOTAL GROSS PROFIT	374.8	335.4	1,095.0	994.1
Other
TOTAL REVENUE	5.1	7.2	12.8	16.1
TOTAL COST OF SALES	4.4	6.3	11.5	14.5
TOTAL GROSS PROFIT	$ 0.7	$ 0.9	$ 1.3	$ 1.6