Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 66,262,000	$ 28,092,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	117,054,000	118,149,000
Gain on sale of property and equipment	(76,000)	(1,571,000)
Loss on impairment of assets		8,247,000
Stock-based compensation expense related to stock options and employee stock purchases	12,036,000	9,426,000
Deferred income tax expense	8,609,000	3,355,000
Excess tax expense from stock-based compensation		808,000
Change in accounts receivable, net	(1,481,000)	8,560,000
Change in inventories, net	(87,799,000)	199,228,000
Change in prepaid expenses and other, net	1,156,000	24,163,000
Change in trade accounts payable	12,469,000	(10,298,000)
Draws (payments) on floor plan notes payable – trade, net	26,439,000	(623,000)
Change in customer deposits	4,558,000	(6,560,000)
Change in accrued expenses	11,048,000	5,783,000
Net cash provided by operating activities	170,275,000	386,759,000
Cash flows from investing activities:
Acquisition of property and equipment	(138,756,000)	(159,546,000)
Proceeds from the sale of property and equipment	3,905,000	9,427,000
Business acquisitions		(681,000)
Proceeds from the sale of available for sale securities	325,000	450,000
Change in other assets	4,831,000	(4,520,000)
Net cash used in investing activities	(129,695,000)	(154,870,000)
Cash flows from financing activities:
Draws (payments) on floor plan notes payable – non-trade, net	33,611,000	(142,229,000)
Proceeds from long-term debt	97,319,000	103,248,000
Principal payments on long-term debt	(108,526,000)	(122,619,000)
Principal payments on capital lease obligations	(9,280,000)	(14,174,000)
Proceeds from issuance of shares relating to employee stock options and employee stock purchases	20,096,000	4,826,000
Excess tax expense from stock-based compensation		(808,000)
Common stock repurchased	(27,388,000)	(33,282,000)
Debt issuance costs	(523,000)
Net cash provided by (used in) financing activities	5,309,000	(205,038,000)
Net increase in cash and cash equivalents	45,889,000	26,851,000
Cash and cash equivalents, beginning of period	82,026,000	64,847,000
Cash and cash equivalents, end of period	127,915,000	91,698,000
Supplemental disclosure of cash flow information:
Interest	24,952,000	29,172,000
Income taxes, net of refunds	30,487,000	(12,993,000)
Noncash investing activities:
Assets acquired under capital leases	$ 8,243,000	$ 16,797,000