Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Sales revenue	$ 1,069,290	$ 878,526	$ 2,980,875	$ 2,439,114
Cost of revenue	903,901	736,016	2,509,215	2,038,174
Gross profit	165,389	142,510	471,660	400,940
Asset impairments				115
Selling, general and administrative	108,570	95,132	318,984	276,561
Operating income	51,720	43,027	137,957	111,577
Floor plan interest expense	(2,909)	(3,370)	(9,394)	(9,326)
Other interest expense	(1,933)	(2,125)	(6,235)	(7,382)
Other income, net	835	453	2,220	1,770
Income from continuing operations before income taxes	47,713	37,985	124,548	96,639
Income tax provision	(16,822)	(14,893)	(46,494)	(36,908)
Income from continuing operations, net of income tax	30,891	23,092	78,054	59,731
Income from discontinued operations, net of income tax	127	151	574	799
Net income	31,018	23,243	78,628	60,530
Basic income per share from continuing operations (in Dollars per share)	$ 1.19	$ 0.91	$ 3.03	$ 2.32
Basic income per share from discontinued operations (in Dollars per share)	$ 0.01	$ 0.00	$ 0.02	$ 0.03
Basic net income per share (in Dollars per share)	$ 1.20	$ 0.91	$ 3.05	$ 2.35
Shares used in basic per share calculations (in Shares)	25,866	25,469	25,776	25,730
Diluted income per share from continuing operations (in Dollars per share)	$ 1.18	$ 0.89	$ 2.98	$ 2.28
Diluted income per share from discontinued operations (in Dollars per share)		$ 0.01	$ 0.03	$ 0.03
Diluted net income per share (in Dollars per share)	$ 1.18	$ 0.90	$ 3.01	$ 2.31
Shares used in diluted per share calculations (in Shares)	26,237	25,947	26,159	26,203
New Vehicle [Member]
Sales revenue	604,135	491,846	1,667,063	1,340,731
Cost of revenue	565,549	456,753	1,555,042	1,241,820
Used Retail Vehicle [Member]
Sales revenue	280,734	227,157	778,427	625,117
Cost of revenue	239,093	193,885	662,920	532,577
Used Wholesale Vehicle [Member]
Sales revenue	43,396	35,006	120,593	103,469
Cost of revenue	42,686	35,042	118,214	102,812
Finance and Insurance [Member]
Sales revenue	37,132	30,929	103,013	82,989
Service, Body and Parts [Member]
Sales revenue	97,784	89,038	282,686	258,038
Cost of revenue	50,793	46,033	145,223	133,224
Fleet and Other [Member]
Sales revenue	6,109	4,550	29,093	28,770
Cost of revenue	5,780	4,303	27,816	27,741
Continuing Operations [Member]
Depreciation and amortization	$ 5,099	$ 4,351	$ 14,719	$ 12,687