Condensed Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUES	$ 3,039.6	$ 3,118.3	$ 7,861.7	$ 8,932.4
COST OF SALES	2,527.7	2,652.7	6,574.4	7,581.0
GROSS PROFIT	512.0	465.6	1,287.2	1,351.4
Selling, general and administrative expenses	305.8	353.9	870.9	1,020.3
Depreciation and amortization expense	19.1	18.2	56.5	53.0
Asset impairments	0.0	10.3	23.8	10.8
INCOME (LOSS) FROM OPERATIONS	187.1	83.3	336.0	267.2
Floorplan interest expense	8.1	15.3	31.1	47.0
Other interest expense, net	14.6	18.9	49.0	55.8
(Gain) loss on extinguishment of debt	3.3	0.0	13.7	0.0
INCOME (LOSS) BEFORE INCOME TAXES	161.0	49.0	242.2	164.4
(Benefit) provision for income taxes	34.6	10.9	55.8	38.5
NET INCOME (LOSS)	$ 126.4	$ 38.0	$ 186.4	$ 125.9
BASIC EARNINGS (LOSS) PER SHARE (in dollars per share)	$ 6.86	$ 2.04	$ 10.11	$ 6.78
Weighted average common shares outstanding (in shares)	17,776,888	17,961,555	17,770,619	17,889,572
DILUTED EARNINGS (LOSS) PER SHARE (in dollars per share)	$ 6.83	$ 2.04	$ 10.08	$ 6.77
Weighted average dilutive common shares outstanding (in shares)	17,835,549	17,978,700	17,818,538	17,900,000
New vehicle retail sales
REVENUES	$ 1,580.7	$ 1,652.3	$ 3,985.5	$ 4,632.2
COST OF SALES	1,481.5	1,577.0	3,759.7	4,415.7
Used vehicle retail sales
REVENUES	867.2	869.7	2,287.4	2,527.8
COST OF SALES	796.1	815.5	2,127.9	2,372.5
Used vehicle wholesale sales
REVENUES	86.7	85.2	221.9	273.4
COST OF SALES	80.7	84.9	212.9	272.7
Parts and service sales
REVENUES	375.6	383.5	1,028.2	1,130.8
COST OF SALES	169.4	175.4	473.9	520.1
Finance, insurance and other, net
REVENUES	$ 129.5	$ 127.5	$ 338.7	$ 368.2