Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 172,129,000	$ 40,582,000	$ 66,053,000
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	157,951,000	157,627,000	144,935,000
Loss (gain) on sale of property and equipment, net	105,000	(1,755,000)	544,000
Loss on impairment of assets		8,247,000
Stock-based compensation expense related to employee stock options and employee stock purchases	15,606,000	12,875,000	12,384,000
(Benefit) provision for deferred income tax expense	(62,203,000)	8,331,000	31,645,000
Excess tax expense from stock-based compensation		294,000	337,000
Change in accounts receivable, net	(29,424,000)	1,673,000	11,921,000
Change in inventories	(147,453,000)	291,773,000	18,664,000
Change in prepaid expenses and other, net	(3,383,000)	24,155,000	(3,690,000)
Change in trade accounts payable	8,964,000	(22,411,000)	(4,154,000)
Draws (payments) on floor plan notes payable – trade, net	19,355,000	3,989,000	(17,005,000)
Change in customer deposits	8,932,000	(4,020,000)	(22,371,000)
Change in accrued expenses	12,158,000	(190,000)	(12,013,000)
Net cash provided by operating activities	152,737,000	521,170,000	227,250,000
Cash flows from investing activities:
Acquisition of property and equipment	(209,917,000)	(196,965,000)	(367,790,000)
Proceeds from the sale of property and equipment	3,968,000	12,494,000	3,319,000
Business acquisitions	(2,180,000)	(681,000)	(69,013,000)
Proceeds from the sale of available for sale securities	325,000	450,000	275,000
Other	1,241,000	(4,708,000)	(3,025,000)
Net cash used in investing activities	(206,563,000)	(189,410,000)	(436,234,000)
Cash flows from financing activities:
Draws (payments) on floor plan notes payable – non-trade, net	112,261,000	(211,802,000)	31,568,000
Proceeds from long-term debt	152,563,000	121,188,000	218,026,000
Principal payments on long-term debt	(145,038,000)	(164,940,000)	(154,685,000)
Principal payments on capital lease obligations	(12,449,000)	(23,479,000)	(14,506,000)
Proceeds from issuance of shares relating to employee stock options and employee stock purchases	23,327,000	8,260,000	3,766,000
Excess tax expense from stock-based compensation		(294,000)	(337,000)
Common stock repurchased	(33,800,000)	(43,514,000)	(1,464,000)
Debt issuance costs	(523,000)
Net cash provided by (used in) financing activities	96,341,000	(314,581,000)	82,368,000
Net increase (decrease) in cash and cash equivalents	42,515,000	17,179,000	(126,616,000)
Cash and cash equivalents, beginning of year	82,026,000	64,847,000	191,463,000
Cash and cash equivalents, end of year	124,541,000	82,026,000	64,847,000
Supplemental disclosure of cash flow information:
Interest	34,149,000	37,904,000	35,356,000
Income taxes paid (refunded), net	31,323,000	(10,939,000)	16,126,000
Noncash investing and financing activities:
Assets acquired under capital leases	$ 15,205,000	$ 24,207,000	$ 41,021,000