Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues:
Sales revenue	$ 1,297,111	$ 1,069,290	$ 3,597,019	$ 2,980,875
Cost of sales:
Cost of revenue	1,099,271	903,901	3,034,818	2,509,215
Gross profit	197,840	165,389	562,201	471,660
Selling, general and administrative	131,627	108,570	378,919	318,984
Depreciation and amortization	6,067	5,099	17,399	14,719
Operating income	60,146	51,720	165,883	137,957
Floor plan interest expense	(3,127)	(2,909)	(9,326)	(9,394)
Other interest expense	(2,051)	(1,933)	(5,894)	(6,235)
Other income, net	1,027	835	3,110	2,220
Income from continuing operations before income taxes	55,995	47,713	153,773	124,548
Income tax provision	(21,458)	(16,822)	(59,372)	(46,494)
Income from continuing operations, net of income tax	34,537	30,891	94,401	78,054
Income from discontinued operations, net of income tax		127	3,179	574
Net income	34,537	31,018	97,580	78,628
Basic income per share from continuing operations (in Dollars per share)	$ 1.32	$ 1.19	$ 3.62	$ 3.03
Basic income per share from discontinued operations (in Dollars per share)		$ 0.01	$ 0.12	$ 0.02
Basic net income per share (in Dollars per share)	$ 1.32	$ 1.20	$ 3.74	$ 3.05
Shares used in basic per share calculations (in Shares)	26,118	25,866	26,071	25,776
Diluted income per share from continuing operations (in Dollars per share)	$ 1.31	$ 1.18	$ 3.58	$ 2.98
Diluted income per share from discontinued operations (in Dollars per share)			$ 0.13	$ 0.03
Diluted net income per share (in Dollars per share)	$ 1.31	$ 1.18	$ 3.71	$ 3.01
Shares used in diluted per share calculations (in Shares)	26,359	26,237	26,337	26,159
New Vehicle [Member]
Revenues:
Sales revenue	732,121	604,135	2,006,127	1,667,063
Cost of sales:
Cost of revenue	684,473	565,549	1,873,461	1,555,042
Used Retail Vehicle [Member]
Revenues:
Sales revenue	340,522	280,734	952,890	778,427
Cost of sales:
Cost of revenue	296,624	239,093	824,129	662,920
Used Wholesale Vehicle [Member]
Revenues:
Sales revenue	48,853	43,396	135,832	120,593
Cost of sales:
Cost of revenue	48,349	42,686	132,493	118,214
Finance and Insurance [Member]
Revenues:
Sales revenue	46,855	37,132	130,324	103,013
Service, Body and Parts [Member]
Revenues:
Sales revenue	120,772	97,784	339,726	282,686
Cost of sales:
Cost of revenue	62,351	50,793	174,291	145,223
Fleet and Other [Member]
Revenues:
Sales revenue	7,988	6,109	32,120	29,093
Cost of sales:
Cost of revenue	$ 7,474	$ 5,780	$ 30,444	$ 27,816