Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 40,582,000	$ 66,053,000	$ 79,957,000
Adjustments to reconcile net income to net cash provided by operating activities-
Depreciation and amortization	157,627,000	144,935,000	126,452,000
(Gain) loss on sale of property and equipment, net	(1,755,000)	544,000	(151,000)
Loss on impairment of assets	8,247,000
Stock-based compensation expense related to employee stock options and employee stock purchases	12,875,000	12,384,000	11,343,000
Provision for deferred income tax expense	8,331,000	31,645,000	25,229,000
Excess tax expense (benefit) from stock-based compensation	294,000	337,000	(5,207,000)
Acquired research and development			2,000,000
Change in accounts receivable, net	1,673,000	11,921,000	(67,664,000)
Change in inventories	291,773,000	18,664,000	(151,911,000)
Change in prepaid expenses and other, net	24,155,000	(3,690,000)	(13,215,000)
Change in trade accounts payable	(22,411,000)	(4,154,000)	24,180,000
(Payments) draws on floor plan notes payable – trade, net	3,989,000	(17,005,000)	44,870,000
Change in customer deposits	(4,020,000)	(22,371,000)	(13,802,000)
Change in accrued expenses	(190,000)	(12,013,000)	26,856,000
Net cash provided by operating activities	521,170,000	227,250,000	88,937,000
Cash flows from investing activities:
Acquisition of property and equipment	(196,965,000)	(367,790,000)	(260,820,000)
Proceeds from the sale of property and equipment	12,494,000	3,319,000	249,000
Business acquisitions	(681,000)	(69,013,000)	(157,626,000)
Proceeds from the sale of available for sale securities	450,000	275,000	150,000
Other	(4,708,000)	(3,025,000)	1,631,000
Net cash used in investing activities	(189,410,000)	(436,234,000)	(416,416,000)
Cash flows from financing activities:
(Payments) draws on floor plan notes payable – non-trade, net	(211,802,000)	31,568,000	207,458,000
Proceeds from long-term debt	121,188,000	218,026,000	214,622,000
Principal payments on long-term debt	(164,940,000)	(154,685,000)	(112,828,000)
Principal payments on capital lease obligations	(23,479,000)	(14,506,000)	(12,531,000)
Proceeds from issuance of shares relating to employee stock options and employee stock purchases	8,260,000	3,766,000	11,962,000
Excess tax (expense) benefit from stock-based compensation	(294,000)	(337,000)	5,207,000
Common stock repurchased	(43,514,000)	(1,464,000)	(12,253,000)
Net cash provided by financing activities	(314,581,000)	82,368,000	301,637,000
Net increase (decrease) in cash and cash equivalents	17,179,000	(126,616,000)	(25,842,000)
Cash and cash equivalents, beginning of year	64,847,000	191,463,000	217,305,000
Cash and cash equivalents, end of year	82,026,000	64,847,000	191,463,000
Cash paid during the year for:
Interest	37,904,000	35,356,000	29,539,000
Income taxes (refunded) paid, net	(10,939,000)	16,126,000	29,795,000
Noncash investing and financing activities:
Common stock issued related to business acquisition			2,000,000
Assets acquired under capital leases	$ 24,207,000	$ 41,021,000	$ 24,314,000