Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Scheduled Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	$ (8,062,000)	$ (7,324,000)
Other Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	(2,303,000)	(9,189,000)
Common Class A [Member]
Cash flows from financing activities:
Excess tax benefit from share-based payment arrangements	4,384,000	4,865,000
Net income	91,698,000	91,876,000
Asset impairments	6,996,000	10,260,000
Depreciation and amortization	24,166,000	20,013,000
Stock-based compensation	6,018,000	5,822,000
(Gain) loss on disposal of other assets	(4,512,000)	44,000
Gain on disposal of franchise	(1,102,000)	(5,919,000)
Deferred income taxes	5,704,000	(1,145,000)
Excess tax benefit from share-based payment arrangements	(4,384,000)	(4,865,000)
Trade receivables, net	6,564,000	7,570,000
Inventories	(114,052,000)	(122,660,000)
Other assets	5,688,000	(3,815,000)
Floor plan notes payable	8,685,000	4,417,000
Trade payables	6,678,000	8,854,000
Accrued liabilities	17,595,000	7,717,000
Other long-term liabilities and deferred revenue	10,668,000	11,161,000
Net cash provided by operating activities	66,410,000	29,330,000
Capital expenditures	(43,247,000)	(48,008,000)
Proceeds from sales of assets	197,000	145,000
Cash paid for other investments	(16,690,000)	(15,222,000)
Cash paid for acquisitions, net of cash acquired	(18,807,000)	(87,000)
Proceeds from sales of stores	11,837,000	12,966,000
Net cash used in investing activities	(66,710,000)	(50,206,000)
Borrowings on floor plan notes payable, net: non-trade	58,622,000	35,685,000
Borrowings on lines of credit	487,623,000	557,394,000
Repayments on lines of credit	(468,955,000)	(602,818,000)
Proceeds from issuance of long-term debt	12,080,000	59,425,000
Proceeds from issuance of common stock	3,329,000	2,589,000
Repurchase of common stock	(104,858,000)	(16,773,000)
Dividends paid	(11,524,000)	(9,482,000)
Net cash used in (provided by) financing activities	(29,664,000)	14,372,000
Decrease in cash and cash equivalents	(29,964,000)	(6,504,000)
Cash and cash equivalents at beginning of period	45,008,000	29,898,000
Cash and cash equivalents at end of period	15,044,000	23,394,000
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	24,960,000	22,262,000
Cash paid during the period for income taxes, net	9,684,000	28,699,000
Supplemental schedule of non-cash activities:
Floor plan debt paid in connection with store disposals	5,284,000	4,400,000
Non-cash consideration given in connection with acquisitions	$ 2,637,000