CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
REVENUE:
Finance and insurance, net	$ 676.2	$ 797.0	$ 405.1
TOTAL REVENUE	14,802.7	15,433.8	9,837.7
COST OF SALES:
New vehicle	6,927.8	6,521.6
Used vehicle	4,150.2	4,843.8
Parts and service	931.0	921.6
Finance and insurance	37.9	46.3	3.6
TOTAL COST OF SALES	12,046.9	12,333.3	7,935.5
GROSS PROFIT	2,755.8	3,100.6	1,902.2
OPERATING EXPENSES:
Selling, general, and administrative	1,617.4	1,763.4	1,073.9
Depreciation and amortization	67.7	69.0	41.9
Asset impairments	117.2	0.0	0.0
Other operating income, net	0.0	(4.4)	(5.4)
INCOME FROM OPERATIONS	953.5	1,272.6	791.8
OTHER EXPENSES (INCOME):
Floor plan interest expense	9.6	8.4	8.2
Other interest expense, net	156.1	152.2	93.9
Gain on dealership divestitures, net	(13.5)	(207.1)	(8.0)
Total other expenses (income), net	152.2	(46.5)	94.1
INCOME BEFORE INCOME TAXES	801.3	1,319.1	697.7
Income tax expense	198.8	321.8	165.3
NET INCOME	$ 602.5	$ 997.3	$ 532.4
Basic—
Net income (in dollars per share)	$ 28.87	$ 44.78	$ 26.75
Diluted—
Net income (in dollars per share)	$ 28.74	$ 44.61	$ 26.49
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Basic (in shares)	20.9	22.3	19.9
Diluted (in shares)	21.0	22.4	20.1
Restricted Stock Awards
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Performance share units (in shares)	0.0	0.1	0.1
Performance Share Units
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Performance share units (in shares)	0.1	0.0	0.1
New vehicle
REVENUE:
REVENUE:	$ 7,630.7	$ 7,365.6	$ 4,934.1
COST OF SALES:
New vehicle			4,443.6
Used vehicle
REVENUE:
REVENUE:	4,414.3	5,197.1	3,315.6
COST OF SALES:
Used vehicle			3,027.3
Parts and services
REVENUE:
REVENUE:	$ 2,081.5	$ 2,074.2	1,182.9
COST OF SALES:
Parts and service			$ 461.0