Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 197,058	$ 182,999	$ 138,720
Adjustments to reconcile net income to net cash provided by operating activities:
Asset impairments	13,992	20,124	1,853
Depreciation and amortization	49,369	41,600	26,363
Stock-based compensation	11,047	11,871	7,436
(Gain) loss on disposal of other assets	(4,343)	203	270
Gain from disposal activities	(1,102)	(5,919)	(5,744)
Deferred income taxes	10,138	12,341	13,355
Excess tax benefit from share-based payment arrangements	(4,389)	(5,012)	(6,186)
(Increase) decrease (net of acquisitions and dispositions):
Trade receivables, net	(105,961)	(13,047)	(59,474)
Inventories	(168,847)	(197,079)	(76,002)
Other assets	(13,305)	(31,290)	(30,534)
Increase (decrease) (net of acquisitions and dispositions):
Floor plan notes payable	16,385	7,035	(647)
Trade payables	16,449	674	(3,105)
Accrued liabilities	42,852	16,273	(13,471)
Other long-term liabilities and deferred revenue	27,173	33,766	38,133
Net cash provided by operating activities	86,516	74,539	30,967
Cash flows from investing activities:
Principal payments received on notes receivable			2,882
Capital expenditures	(100,761)	(83,244)	(85,983)
Proceeds from sales of assets	2,211	270	4,896
Cash paid for other investments	(30,280)	(28,110)	(9,110)
Cash paid for acquisitions, net of cash acquired	(234,700)	(71,615)	(659,634)
Proceeds from sales of stores	11,837	12,966	10,617
Net cash used in investing activities	(351,693)	(169,733)	(736,332)
Cash flows from financing activities:
Borrowings on floor plan notes payable: non-trade, net	252,893	136,201	440,341
Borrowings on lines of credit	1,244,343	1,261,597	1,435,144
Repayments on lines of credit	(1,123,082)	(1,298,120)	(1,251,375)
Proceeds from issuance of long-term debt	66,466	75,675	124,902
Proceeds from issuance of common stock	6,932	6,065	4,590
Repurchase of common stock	(112,939)	(31,548)	(22,968)
Excess tax benefit from share-based payment arrangements	4,389	5,012	6,186
Dividends paid	(24,131)	(19,985)	(15,929)
Net cash provided by financing activities	270,451	110,304	711,577
Increase in cash and cash equivalents	5,274	15,110	6,212
Cash and cash equivalents at beginning of year	45,008	29,898	23,686
Cash and cash equivalents at end of year	50,282	45,008	29,898
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	49,730	41,098	24,610
Cash paid during the period for income taxes, net	57,236	86,533	63,827
Supplemental schedule of non-cash activities:
Debt issued in connection with acquisitions		2,160	55,693
Non-cash assets transferred in connection with acquisitions	2,637
Forgiven outstanding notes receivable		1,374
Debt assumed in connection with acquisitions	48,081
Acquisition of assets with capital leases	8,916
Floor plan debt paid in connection with store disposals	5,284	4,400	3,311
Scheduled Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	(16,717)	(15,404)	(9,314)
Other Payments [Member]
Cash flows from financing activities:
Principal payments on long-term debt, scheduled	$ (27,703)	$ (9,189)