Consolidated Statements of Income (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
New and used commercial vehicle sales	$ 2,149,335,000	$ 1,801,964,000	$ 926,584,000
Parts and service sales	817,280,000	675,277,000	489,259,000
Lease and rental	100,247,000	83,426,000	67,423,000
Finance and insurance	13,638,000	10,867,000	7,922,000
Other	10,067,000	9,077,000	6,739,000
Total revenue	3,090,567,000	2,580,611,000	1,497,927,000
Cost of products sold:
New and used commercial vehicle sales	2,005,776,000	1,679,170,000	854,879,000
Parts and service sales	499,850,000	408,544,000	300,783,000
Lease and rental	84,174,000	69,620,000	57,375,000
Total cost of products sold	2,589,800,000	2,157,334,000	1,213,037,000
Gross profit	500,767,000	423,277,000	284,890,000
Selling, general and administrative	361,727,000	306,273,000	227,467,000
Depreciation and amortization	25,016,000	20,084,000	15,720,000
Gain (loss) on sale of assets	176,000	418,000	(36,000)
Operating income	114,200,000	97,338,000	41,667,000
Interest income (expense):
Interest income	21,000	20,000	127,000
Interest expense	(13,038,000)	(7,181,000)	(5,490,000)
Total interest expense, net	13,017,000	7,161,000	5,363,000
Income from continuing operations before taxes	101,183,000	90,177,000	36,304,000
Provision for income taxes	38,728,000	34,964,000	11,737,000
Income from continuing operations	62,455,000	55,213,000	24,567,000
Income from discontinued operations, net of tax			6,715,000
Net income	$ 62,455,000	$ 55,213,000	$ 31,282,000
Earnings per common share - Basic:
Income from continuing operations (in Dollars per share)	$ 1.62	$ 1.46	$ 0.66
Net income (in Dollars per share)	$ 1.62	$ 1.46	$ 0.84
Earnings per common share - Diluted:
Income from continuing operations (in Dollars per share)	$ 1.57	$ 1.42	$ 0.64
Net income (in Dollars per share)	$ 1.57	$ 1.42	$ 0.82