Note 10 - Segments - Certain Segment Financial Information (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating Segments [Member] | Domestic [Member]
Revenues:
Total revenues		$ 888,026	$ 814,216	$ 2,483,637	$ 2,273,068
Segment income*:
Segment income	[1]	32,394	33,240	84,913	91,853
Floor plan interest expense:
Floor plan interest expense		6,255	5,441	18,869	15,083
Operating Segments [Member] | Import [Member]
Revenues:
Total revenues		989,077	894,371	2,788,838	2,509,756
Segment income*:
Segment income	[1]	32,832	31,453	86,385	76,665
Floor plan interest expense:
Floor plan interest expense		4,661	3,779	13,403	11,227
Operating Segments [Member] | Luxury [Member]
Revenues:
Total revenues		392,537	374,558	1,111,215	1,084,051
Segment income*:
Segment income	[1]	7,423	8,318	21,736	25,764
Floor plan interest expense:
Floor plan interest expense		2,720	2,345	8,027	6,715
Operating Segments [Member]
Revenues:
Total revenues		2,269,640	2,083,145	6,383,690	5,866,875
Segment income*:
Segment income	[1]	72,649	73,011	193,034	194,282
Floor plan interest expense:
Floor plan interest expense		13,636	11,565	40,299	33,025
Corporate, Non-Segment [Member]
Revenues:
Total revenues		327	1,700	2,477	4,095
Segment income*:
Segment income	[1]	26,794	5,366	81,881	48,327
Corporate and Other [Member]
Floor plan interest expense:
Floor plan interest expense		(7,450)	(6,614)	(21,995)	(18,770)
Total revenues		2,269,967	2,084,845	6,386,167	5,870,970
Segment income		80,077	62,639	217,401	196,334
Depreciation and amortization		(12,206)	(10,531)	(36,372)	(30,544)
Other interest expense, net		(5,647)	(4,900)	(16,608)	(14,700)
Other expense, net		(1,513)	(307)	(4,534)	(1,031)
Floor plan interest expense		$ 6,186	$ 4,951	$ 18,304	$ 14,255

[1] Segment income for each of the segments is defined as Income before income taxes, depreciation and amortization, other interest expense and other expense, net.