CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
REVENUE:
TOTAL REVENUE	$ 4,373.1	$ 4,246.2	$ 8,521.6	$ 8,447.4
COST OF SALES:
TOTAL COST OF SALES	3,621.2	3,515.5	7,045.5	6,966.7
GROSS PROFIT	751.9	730.7	1,476.1	1,480.7
OPERATING EXPENSES:
Selling, general, and administrative	475.5	476.5	931.8	945.1
Depreciation and amortization	19.0	18.2	38.2	36.9
Asset impairments	0.0	135.4	14.3	135.4
INCOME FROM OPERATIONS	257.4	100.5	491.7	363.3
OTHER EXPENSES (INCOME):
Floor plan interest expense	18.1	21.0	38.8	43.8
Other interest expense, net	41.4	45.1	83.7	89.2
Gain on dealership divestitures, net	(5.9)	(3.6)	(10.1)	(3.6)
Total other expenses, net	53.6	62.5	112.5	129.4
INCOME BEFORE INCOME TAXES	203.8	38.0	379.2	233.9
Income tax expense	51.0	9.9	94.4	58.7
NET INCOME	$ 152.8	$ 28.1	$ 284.9	$ 175.2
Basic—
Net income (in dollars per share)	$ 7.77	$ 1.40	$ 14.50	$ 8.66
Diluted—
Net income (in dollars per share)	$ 7.76	$ 1.39	$ 14.46	$ 8.64
WEIGHTED AVERAGE SHARES OUTSTANDING:
Basic (in shares)	19.7	20.1	19.6	20.2
Diluted (in shares)	19.7	20.2	19.7	20.3
New vehicle
REVENUE:
TOTAL REVENUE	$ 2,303.9	$ 2,164.9	$ 4,442.0	$ 4,229.1
COST OF SALES:
TOTAL COST OF SALES	2,143.9	2,009.8	4,138.9	3,911.2
Used vehicle
REVENUE:
TOTAL REVENUE	1,285.8	1,308.0	2,521.6	2,664.9
COST OF SALES:
TOTAL COST OF SALES	1,216.8	1,247.0	2,388.1	2,532.0
Parts and service
REVENUE:
TOTAL REVENUE	601.5	580.9	1,189.1	1,171.2
COST OF SALES:
TOTAL COST OF SALES	246.7	241.0	491.6	497.2
Finance and insurance, net
REVENUE:
TOTAL REVENUE	182.0	192.4	368.9	382.1
COST OF SALES:
TOTAL COST OF SALES	$ 13.8	$ 17.7	$ 26.9	$ 26.3
Performance share units
WEIGHTED AVERAGE SHARES OUTSTANDING:
Incremental common shares (in shares)	0.0	0.0	0.1	0.1
Restricted stock
WEIGHTED AVERAGE SHARES OUTSTANDING:
Incremental common shares (in shares)	0.0	0.1	0.0	0.0