CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Revenues	$ 3,352,246,000	$ 2,111,886,000	$ 6,139,043,000	$ 4,419,942,000
Cost of Sales:
Cost of Sales	(2,841,438,000)	(1,804,503,000)	(5,227,342,000)	(3,761,981,000)
Gross profit	510,808,000	307,383,000	911,701,000	657,961,000
Selling, general and administrative expenses	(320,620,000)	(230,359,000)	(609,976,000)	(512,515,000)
Impairment charges	0	(833,000)	0	(268,833,000)
Depreciation and amortization	(24,761,000)	(22,647,000)	(48,448,000)	(44,944,000)
Operating income (loss)	165,427,000	53,544,000	253,277,000	(168,331,000)
Other income (expense):
Interest expense, floor plan	(4,329,000)	(6,314,000)	(9,441,000)	(16,822,000)
Interest expense, other, net	(10,077,000)	(9,797,000)	(20,363,000)	(20,762,000)
Other income (expense), net	0	0	100,000	100,000
Total other income (expense)	(14,406,000)	(16,111,000)	(29,704,000)	(37,484,000)
Income (loss) from continuing operations before taxes	151,021,000	37,433,000	223,573,000	(205,815,000)
Provision for income taxes for continuing operations - benefit (expense)	(37,030,000)	(6,437,000)	(55,893,000)	37,680,000
Income (loss) from continuing operations	113,991,000	30,996,000	167,680,000	(168,135,000)
Discontinued operations:
Income (loss) from discontinued operations before taxes	(204,000)	(289,000)	516,000	(573,000)
Provision for income taxes for discontinued operations - benefit (expense)	58,000	84,000	(129,000)	166,000
Income (loss) from discontinued operations	(146,000)	(205,000)	387,000	(407,000)
Net income (loss)	$ 113,845,000	$ 30,791,000	$ 168,067,000	$ (168,542,000)
Basic earnings (loss) per common share:
Earnings (loss) per share from continuing operations (usd per share)	$ 2.74	$ 0.72	$ 4.03	$ (3.93)
Earnings (loss) per share from discontinued operations (usd per share)	0	0	0.01	(0.01)
Earnings (loss) per common share (usd per share)	$ 2.74	$ 0.72	$ 4.04	$ (3.94)
Weighted average common shares outstanding	41,581	42,940	41,561	42,779
Diluted earnings (loss) per common share:
Earnings (loss) per share from continuing operations (usd per share)	$ 2.63	$ 0.71	$ 3.86	$ (3.93)
Earnings (loss) per share from discontinued operations (usd per share)	0	0	0.01	(0.01)
Earnings (loss) per common share (usd per share)	$ 2.63	$ 0.71	$ 3.87	$ (3.94)
Weighted average common shares outstanding	43,424	43,575	43,483	42,779
Total vehicles
Revenues:
Revenues	$ 2,814,396,000	$ 1,742,055,000	$ 5,135,618,000	$ 3,600,140,000
Cost of Sales:
Cost of Sales	(2,656,690,000)	(1,669,724,000)	(4,876,730,000)	(3,450,421,000)
New vehicles
Revenues:
Revenues	1,462,893,000	900,003,000	2,619,210,000	1,859,492,000
Cost of Sales:
Cost of Sales	(1,344,467,000)	(854,617,000)	(2,431,319,000)	(1,768,690,000)
Used vehicles
Revenues:
Revenues	1,266,696,000	808,877,000	2,356,794,000	1,658,930,000
Cost of Sales:
Cost of Sales	(1,231,943,000)	(781,506,000)	(2,291,171,000)	(1,599,428,000)
Wholesale vehicles
Revenues:
Revenues	84,807,000	33,175,000	159,614,000	81,718,000
Cost of Sales:
Cost of Sales	(80,280,000)	(33,601,000)	(154,240,000)	(82,303,000)
Parts, service and collision repair
Revenues:
Revenues	360,596,000	259,058,000	681,509,000	593,738,000
Cost of Sales:
Cost of Sales	(184,748,000)	(134,779,000)	(350,612,000)	(311,560,000)
Finance, insurance and other, net
Revenues:
Revenues	$ 177,254,000	$ 110,773,000	$ 321,916,000	$ 226,064,000