CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Total revenues	$ 14,372,400,000	$ 14,001,100,000	$ 12,396,400,000
Cost of Sales:
Total cost of sales	(12,126,700,000)	(11,684,100,000)	(10,482,100,000)
Cost of Sales	12,126,700,000	11,684,100,000	10,482,100,000
Gross profit	2,245,700,000	2,317,000,000	1,914,300,000
Selling, general and administrative expenses	(1,600,500,000)	(1,555,100,000)	(1,274,700,000)
Impairment charges	79,300,000	320,400,000	100,000
Depreciation and amortization	(142,300,000)	(127,500,000)	(101,100,000)
Operating income	423,600,000	314,000,000.0	538,400,000
Other income (expense):
Interest expense, floor plan	(67,200,000)	(34,300,000)	(16,700,000)
Interest expense, other, net	(114,600,000)	(89,900,000)	(48,000,000.0)
Other income (expense), net	100,000	200,000	(15,500,000)
Total other income (expense)	(181,700,000)	(124,000,000.0)	(80,200,000)
Income (loss) before taxes	241,900,000	190,000,000.0	458,200,000
Provision for income taxes - benefit (expense)	(63,700,000)	(101,500,000)	(109,300,000)
Discontinued operations:
Net income (loss)	$ 178,200,000	$ 88,500,000	$ 348,900,000
Basic earnings (loss) per common share:
Earnings (loss) per common share (usd per share)	$ 5.09	$ 2.29	$ 8.43
Weighted average common shares outstanding (in shares)	35,000	38,700	41,400
Diluted earnings (loss) per common share:
Earnings (loss) per common share (usd per share)	$ 4.97	$ 2.23	$ 8.06
Weighted average common shares outstanding (in shares)	35,900	39,700	43,300
EchoPark Total Impairment [Member]
Cost of Sales:
Impairment charges	$ 78,300,000	$ 204,900,000
Franchised Dealership Impairment [Member]
Cost of Sales:
Impairment charges	1,000,000.0		$ 0
Powersport Total Impairment
Cost of Sales:
Impairment charges	0	0	0
Total vehicles
Revenues:
Total revenues		11,722,300,000	10,418,800,000
Cost of Sales:
Total cost of sales	(11,241,200,000)	(10,876,900,000)	(9,814,600,000)
Cost of Sales	11,241,200,000	10,876,900,000	9,814,600,000
Used vehicles
Revenues:
Total revenues	5,213,600,000	5,515,400,000	4,933,600,000
Cost of Sales:
Total cost of sales	(5,062,400,000)	(5,334,600,000)	(4,800,600,000)
Cost of Sales	5,062,400,000	5,334,600,000	4,800,600,000
Wholesale vehicles
Revenues:
Total revenues	318,800,000	484,900,000	367,200,000
Cost of Sales:
Total cost of sales	(321,400,000)	(488,000,000.0)	(357,300,000)
Cost of Sales	321,400,000	488,000,000.0	357,300,000
Total new vehicles
Revenues:
Total revenues	6,396,800,000	5,722,000,000	5,118,000,000
Cost of Sales:
Total cost of sales	(5,857,400,000)	(5,054,300,000)	(4,656,700,000)
Cost of Sales	5,857,400,000	5,054,300,000	4,656,700,000
Fleet new vehicles
Revenues:
Total revenues	92,200,000	99,400,000	124,600,000
Cost of Sales:
Total cost of sales	(88,200,000)	(94,500,000)	(123,000,000.0)
Cost of Sales	88,200,000	94,500,000	123,000,000.0
Retail new vehicles
Revenues:
Total revenues	6,304,600,000	5,622,600,000	4,993,400,000
Cost of Sales:
Total cost of sales	(5,769,200,000)	(4,959,800,000)	(4,533,700,000)
Cost of Sales	5,769,200,000	4,959,800,000	4,533,700,000
Parts, service and collision repair
Revenues:
Total revenues	1,759,500,000	1,599,700,000	1,340,400,000
Cost of Sales:
Total cost of sales	(885,500,000)	(807,200,000)	(667,500,000)
Cost of Sales	885,500,000	807,200,000	667,500,000
Finance, insurance and other, net
Revenues:
Total revenues	683,700,000	$ 679,100,000	$ 637,200,000
Total_Vehicles [Member]
Revenues:
Total revenues	$ 11,929,200,000