Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Continuing Operations [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	$ 41,600	$ 26,363	$ 20,035
Deferred income taxes	6,725	10,669	8,308
Scheduled Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	(15,074)	$ (8,666)	(7,100)
Other Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	(9,189)		(25,770)
Common Class A [Member]
Cash flows from financing activities:
Excess tax benefit from share-based payment arrangements	5,012	$ 6,186	5,994
Net income	182,999	138,720	$ 106,000
Asset impairments	20,124	1,853
Stock-based compensation	11,871	7,436	$ 6,565
(Gain) loss on disposal of other assets	203	271	$ (2,339)
Gain from disposal activities	(5,919)	(5,744)
Deferred income taxes	12,341	13,355	$ 14,477
Excess tax benefit from share-based payment arrangements	(5,012)	(6,186)	(5,994)
Trade receivables, net	(13,047)	(59,474)	(37,370)
Inventories	(197,079)	(76,002)	(106,896)
Other assets	(31,620)	(31,182)	(5,655)
Floor plan notes payable	7,035	(647)	5,300
Trade payables	674	(3,105)	8,480
Accrued liabilities	16,273	(13,472)	12,304
Other long-term liabilities and deferred revenue	33,766	38,133	17,152
Net cash provided by operating activities	$ 74,209	30,319	32,059
Principal payments received on notes receivable		2,882	91
Capital expenditures	$ (83,244)	(85,983)	(50,025)
Proceeds from sales of assets	270	4,896	4,632
Cash paid for other investments	(28,110)	(9,110)	(3,915)
Cash paid for acquisitions, net of cash acquired	(71,615)	(659,634)	$ (81,105)
Proceeds from sales of stores	12,966	10,617
Net cash used in investing activities	(169,733)	(736,332)	$ (130,322)
Borrowings on floor plan notes payable: non-trade, net	136,201	440,341	128,636
Borrowings on lines of credit	1,261,597	1,435,144	800,000
Repayments on lines of credit	(1,298,120)	(1,251,375)	(814,355)
Proceeds from issuance of long-term debt	75,675	124,902	4,720
Proceeds from issuance of common stock	6,065	4,590	4,973
Repurchase of common stock	(31,548)	(22,968)	(7,903)
Dividends paid	(19,985)	(15,929)	(10,085)
Net cash provided by financing activities	110,634	712,225	79,110
Increase (decrease) in cash and cash equivalents	15,110	6,212	(19,153)
Cash and cash equivalents at beginning of year	29,898	23,686	42,839
Cash and cash equivalents at end of year	45,008	29,898	23,686
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	41,098	24,638	21,002
Cash paid during the period for income taxes, net	86,533	63,827	$ 42,682
Supplemental schedule of non-cash activities:
Debt issued or acquired in connection with acquisitions	2,160	$ 55,693
Debt forgiven in connection with acquisitions	$ 1,374
Floor plan debt acquired in connection with acquisitions		$ 24,686
Floor plan debt paid in connection with store disposals	$ 4,400	3,311
Issuance of Class A common stock in connection with acquisitions		$ 19,736