Unaudited Condensed Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
TOTAL REVENUE		$ 6,890.1	$ 6,869.2	$ 13,288.8	$ 13,622.0
TOTAL COST OF SALES		5,554.8	5,507.5	10,667.1	10,951.4
TOTAL GROSS PROFIT		1,335.3	1,361.7	2,621.7	2,670.6
Selling, general, and administrative expenses		842.9	754.8	1,625.6	1,496.2
Depreciation and amortization		54.6	48.8	107.4	98.8
Other (income) expense, net		(1.4)	0.0	6.2	(1.5)
OPERATING INCOME		439.2	558.1	882.5	1,077.1
Non-operating income (expense) items:
Floorplan interest expense		(32.8)	(5.8)	(59.9)	(11.0)
Other interest expense		(46.0)	(34.1)	(87.1)	(63.7)
Other income (loss), net		4.4	(13.7)	9.6	(20.1)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES		364.8	504.5	745.1	982.3
Income tax provision		92.3	128.0	184.8	243.7
NET INCOME FROM CONTINUING OPERATIONS		272.5	376.5	560.3	738.6
Income (loss) from discontinued operations, net of income taxes		0.0	(0.2)	0.9	(0.2)
NET INCOME		$ 272.5	$ 376.3	$ 561.2	$ 738.4
BASIC EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	[1]	$ 6.06	$ 6.51	$ 12.15	$ 12.33
Discontinued operations (in dollars per share)	[1]	0	0	0.02	0
Net income (in dollars per share)	[1]	$ 6.06	$ 6.51	$ 12.17	$ 12.33
Weighted average common shares outstanding (in shares)		45.0	57.8	46.1	59.9
DILUTED EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	[1]	$ 6.02	$ 6.48	$ 12.08	$ 12.25
Discontinued operations (in dollars per share)	[1]	0	0	0.02	0
Net income (in dollars per share)	[1]	$ 6.02	$ 6.48	$ 12.09	$ 12.25
Weighted average common shares outstanding (in shares)		45.3	58.1	46.4	60.3
COMMON SHARES OUTSTANDING, net of treasury stock, at period end (in shares)		44.0	56.0	44.0	56.0
New vehicle
TOTAL REVENUE		$ 3,281.0	$ 2,935.8	$ 6,212.9	$ 5,743.0
TOTAL COST OF SALES		2,993.3	2,582.3	5,638.3	5,044.5
TOTAL GROSS PROFIT		287.7	353.5	574.6	698.5
Used vehicle
TOTAL REVENUE		2,088.0	2,520.4	4,120.6	5,092.8
TOTAL COST OF SALES		1,953.7	2,363.9	3,831.9	4,799.7
TOTAL GROSS PROFIT		134.3	156.5	288.7	293.1
Parts and service
TOTAL REVENUE		1,145.3	1,036.3	2,235.1	2,040.2
TOTAL COST OF SALES		602.8	554.6	1,181.5	1,097.4
TOTAL GROSS PROFIT		542.5	481.7	1,053.6	942.8
Finance and insurance, net
TOTAL REVENUE		369.5	367.6	701.9	731.5
TOTAL GROSS PROFIT		369.5	367.6	701.9	731.5
Other
TOTAL REVENUE		6.3	9.1	18.3	14.5
TOTAL COST OF SALES		5.0	6.7	15.4	9.8
TOTAL GROSS PROFIT		$ 1.3	$ 2.4	$ 2.9	$ 4.7

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