CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues:
Total revenues	$ 12,396,400,000	$ 9,767,000,000	$ 10,454,300,000
Cost of Sales:
Total cost of sales	(10,482,100,000)	(8,343,400,000)	(8,933,300,000)
Gross profit	1,914,300,000	1,423,600,000	1,521,000,000
Selling, general and administrative expenses	(1,274,700,000)	(1,028,700,000)	(1,099,400,000)
Impairment charges	100,000	270,000,000.0	20,800,000
Depreciation and amortization	(101,100,000)	(91,000,000.0)	(93,100,000)
Operating income	538,400,000	33,900,000	307,700,000
Other income (expense):
Interest expense, floor plan	(16,700,000)	(27,200,000)	(48,500,000)
Interest expense, other, net	(48,000,000.0)	(41,600,000)	(53,000,000.0)
Other income (expense), net	(15,500,000)	100,000	(6,600,000)
Total other income (expense)	(80,200,000)	(68,700,000)	(108,100,000)
Income (loss) from continuing operations before taxes	458,200,000	(34,800,000)	199,600,000
Provision for income taxes for continuing operations - benefit (expense)	(109,300,000)	(15,900,000)	(55,100,000)
Income (loss) from continuing operations	348,900,000	(50,700,000)	144,500,000
Discontinued operations:
Income (loss) from discontinued operations before taxes	0	(1,000,000.0)	(600,000)
Provision for income taxes for discontinued operations - benefit (expense)	0	300,000	200,000
Income (loss) from discontinued operations	0	(700,000)	(400,000)
Net income (loss)	$ 348,900,000	$ (51,400,000)	$ 144,100,000
Basic earnings (loss) per common share:
Earnings (loss) per share from continuing operations (usd per share)	$ 8.43	$ (1.19)	$ 3.36
Earnings (loss) per share from discontinued operations (usd per share)	0	(0.02)	(0.01)
Earnings (loss) per common share (usd per share)	$ 8.43	$ (1.21)	$ 3.35
Weighted average common shares outstanding (in shares)	41,404	42,483	43,016
Diluted earnings (loss) per common share:
Earnings (loss) per share from continuing operations (usd per share)	$ 8.06	$ (1.19)	$ 3.31
Earnings (loss) per share from discontinued operations (usd per share)	0	(0.02)	(0.01)
Earnings (loss) per common share (usd per share)	$ 8.06	$ (1.21)	$ 3.30
Weighted average common shares outstanding (in shares)	43,280	42,483	43,710
EchoPark Total Impairment [Member]
Cost of Sales:
Impairment charges	$ 100,000	$ 0	$ 19,700,000
Franchised Dealership Impairment [Member]
Cost of Sales:
Impairment charges	0		1,100,000
New vehicles
Revenues:
Total revenues	5,118,000,000	4,281,200,000	4,889,200,000
Cost of Sales:
Total cost of sales	(4,656,700,000)	(4,047,100,000)	(4,656,100,000)
Used vehicles
Revenues:
Total revenues	4,877,200,000	3,564,800,000	3,490,000,000
Cost of Sales:
Total cost of sales	(4,745,300,000)	(3,458,800,000)	(3,342,600,000)
Wholesale vehicles
Revenues:
Total revenues	367,200,000	197,400,000	202,900,000
Cost of Sales:
Total cost of sales	(357,300,000)	(198,300,000)	(207,300,000)
Total vehicles
Revenues:
Total revenues	10,362,400,000	8,043,400,000	8,582,100,000
Cost of Sales:
Total cost of sales	(9,759,300,000)	(7,704,200,000)	(8,206,000,000)
Parts, service and collision repair
Revenues:
Total revenues	1,396,800,000	1,233,700,000	1,395,300,000
Cost of Sales:
Total cost of sales	(722,800,000)	(639,200,000)	(727,300,000)
Finance, insurance and other, net
Revenues:
Total revenues	$ 637,200,000	$ 489,900,000	$ 476,900,000