CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Total revenues	$ 6,009.4	$ 2,758.6	$ 10,352.4	$ 5,562.3
Cost of sales:
Total cost of sales	4,898.8	2,294.2	8,526.3	4,637.0
Gross profit	1,110.6	464.4	1,826.1	925.3
Asset impairments	0.0	7.9	0.0	7.9
Selling, general and administrative	634.0	304.5	1,084.2	650.5
Depreciation and amortization	30.3	22.3	57.2	44.3
Operating income	446.3	129.7	684.7	222.6
Floor plan interest expense	(6.4)	(8.1)	(13.3)	(22.1)
Other interest expense, net	(28.1)	(16.8)	(51.6)	(33.8)
Other income, net	7.6	3.5	11.1	5.8
Income before income taxes	419.4	108.3	630.9	172.5
Income tax provision	(114.5)	(30.6)	(169.8)	(48.6)
Net income	$ 304.9	$ 77.7	$ 461.1	$ 123.9
Basic net income per share (in dollars per share)	$ 10.83	$ 3.40	$ 16.83	$ 5.37
Shares used in basic per share calculations (in shares)	28.1	22.8	27.4	23.1
Diluted net income per share (in dollars per share)	$ 10.75	$ 3.38	$ 16.69	$ 5.32
Shares used in diluted per share calculations (in shares)	28.4	23.0	27.6	23.3
Cash dividends paid per Class A and Class B share (in dollars per share)	$ 0.35	$ 0.30	$ 0.66	$ 0.60
New vehicle retail
Revenues:
Total revenues	$ 3,146.2	$ 1,367.8	$ 5,339.5	$ 2,741.3
Cost of sales:
Total cost of sales	2,832.5	1,275.6	4,869.0	2,570.9
Used vehicle retail
Revenues:
Total revenues	1,804.9	922.2	3,157.0	1,796.5
Cost of sales:
Total cost of sales	1,572.3	823.9	2,788.3	1,608.3
Used vehicle wholesale
Revenues:
Total revenues	217.4	51.3	352.6	118.0
Cost of sales:
Total cost of sales	201.0	49.2	331.6	115.3
Finance and insurance
Revenues:
Total revenues	269.6	124.9	467.9	246.7
Service, body and parts
Revenues:
Total revenues	521.0	275.5	925.0	605.4
Cost of sales:
Total cost of sales	242.9	131.1	428.6	292.8
Fleet and other
Revenues:
Total revenues	50.3	16.9	110.4	54.4
Cost of sales:
Total cost of sales	$ 50.1	$ 14.4	$ 108.8	$ 49.7