Note 10 - Certain Segment Financial Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating Segments [Member] | Domestic [Member]
Revenues:
Revenues		$ 826,709	$ 768,170	$ 1,595,611	$ 1,458,853
Segment income*:
Segment income	[1]	27,614	31,320	49,344	58,613
Floor plan interest expense:
Floor plan interest expense		6,183	4,920	12,615	9,642
Operating Segments [Member] | Import [Member]
Revenues:
Revenues		934,018	855,305	1,799,761	1,615,385
Segment income*:
Segment income	[1]	28,228	28,149	50,861	45,212
Floor plan interest expense:
Floor plan interest expense		4,443	3,736	8,742	7,448
Operating Segments [Member] | Luxury [Member]
Revenues:
Revenues		371,866	372,500	718,679	709,493
Segment income*:
Segment income	[1]	9,398	10,801	13,633	17,446
Floor plan interest expense:
Floor plan interest expense		2,650	2,308	5,308	4,370
Operating Segments [Member]
Revenues:
Revenues		2,132,593	1,995,975	4,114,051	3,783,731
Segment income*:
Segment income	[1]	65,240	70,270	113,838	121,271
Floor plan interest expense:
Floor plan interest expense		13,276	10,964	26,665	21,460
Corporate, Non-Segment [Member]
Revenues:
Revenues		746	972	2,149	2,394
Segment income*:
Segment income	[1]	31,563	20,984	61,634	42,961
Corporate and Other [Member]
Floor plan interest expense:
Floor plan interest expense		(7,067)	(6,309)	(14,547)	(12,156)
Revenues		2,133,339	1,996,947	4,116,200	3,786,125
Segment income		77,303	75,639	137,324	133,695
Depreciation and amortization		(12,503)	(10,287)	(24,166)	(20,013)
Other interest expense		(5,502)	(4,972)	(10,961)	(9,800)
Other expense, net		(1,495)	(356)	(3,021)	(724)
Floor plan interest expense		$ 6,209	$ 4,655	$ 12,118	$ 9,304

[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.