Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
REVENUES	$ 2,889,058	$ 3,012,292	$ 8,692,546	$ 8,203,316
COST OF SALES	2,453,957	2,580,872	7,399,519	6,983,482
GROSS PROFIT	435,101	431,420	1,293,027	1,219,834
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	316,771	328,327	949,210	916,674
DEPRECIATION AND AMORTIZATION EXPENSE	16,981	15,059	49,961	42,758
ASSET IMPAIRMENTS	23,159	9,526	27,427	9,526
INCOME FROM OPERATIONS	78,190	78,508	266,429	250,876
OTHER EXPENSE:
Floorplan interest expense	(14,685)	(13,491)	(43,335)	(38,659)
Other interest expense, net	(19,140)	(17,874)	(57,374)	(52,188)
INCOME BEFORE INCOME TAXES	44,365	47,143	165,720	160,029
PROVISION FOR INCOME TAXES	(9,587)	(17,262)	(38,666)	(57,076)
NET INCOME	$ 34,778	$ 29,881	$ 127,054	$ 102,953
BASIC EARNINGS PER SHARE (in dollars per share)	$ 1.74	$ 1.43	$ 6.18	$ 4.85
Weighted average common shares outstanding (in shares)	19,253	20,222	19,859	20,475
DILUTED EARNINGS PER SHARE (in dollars per share)	$ 1.74	$ 1.43	$ 6.18	$ 4.85
Weighted average common shares outstanding (in shares)	19,261	20,225	19,868	20,480
CASH DIVIDENDS PER COMMON SHARE (in dollars per share)	$ 0.26	$ 0.24	$ 0.78	$ 0.72
New vehicle retail sales
REVENUES	$ 1,539,498	$ 1,710,241	$ 4,608,658	$ 4,496,222
COST OF SALES	1,461,896	1,621,909	4,379,047	4,263,752
Used vehicle retail sales
REVENUES	792,405	743,038	2,394,828	2,089,914
COST OF SALES	742,250	695,915	2,249,964	1,952,873
Used vehicle wholesale sales
REVENUES	86,570	104,827	283,453	308,361
COST OF SALES	86,884	105,012	281,871	308,713
Parts and service sales
REVENUES	354,501	343,193	1,062,145	994,522
COST OF SALES	162,927	158,036	488,637	458,144
Finance, insurance and other, net
REVENUES	$ 116,084	$ 110,993	$ 343,462	$ 314,297