Note 16 - Segment Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)		Dec. 31, 2013 USD ($)
Operating Segments [Member] | Truckload [Member]
Revenues	$ 655,918		$ 663,001		$ 644,403
Operating income (loss)	74,107		54,151		27,746
Depreciation and amortization (1)	60,138	[1]	45,669	[1]	42,848	[1]
Total assets	581,212		463,900		402,637
Capital expenditures, net (2)	147,896	[2]	87,871	[2]	90,336	[2]
Operating Segments [Member] | Other Segments [Member]
Revenues	71,057		59,796		51,702
Operating income (loss)	5,768		3,894		1,271
Depreciation and amortization (1)	13	[1]	59	[1]	72	[1]
Total assets	26,315		27,338		20,883
Capital expenditures, net (2)	$ 29	[2]	$ 14	[2]	$ 10	[2]
Operating Segments [Member] | Corporate Segment [Member]
Revenues
Operating income (loss)	$ (12,093)		$ (18,399)		$ (8,623)
Depreciation and amortization (1)	1,233	[1]	656	[1]	775	[1]
Total assets	39,896		48,066		37,668
Capital expenditures, net (2)	1,069	[2]	1,570	[2]	1,630	[2]
Operating Segments [Member]
Revenues	726,975		722,797		690,327
Operating income (loss)	67,782		39,646		20,394
Depreciation and amortization (1)	61,384	[1]	46,384	[1]	43,694	[1]
Total assets	647,423		539,304		461,188
Capital expenditures, net (2)	$ 148,994	[2]	$ 89,455	[2]	$ 91,976	[2]
Intersegment Eliminations [Member] | Truckload [Member]
Revenues
Intersegment Eliminations [Member] | Other Segments [Member]
Revenues	$ (2,735)		$ (3,817)		$ (5,778)
Intersegment Eliminations [Member] | Corporate Segment [Member]
Revenues
Intersegment Eliminations [Member]
Revenues	$ (2,735)		$ (3,817)		$ (5,778)
Revenues	724,240		718,980		684,549
Operating income (loss)	67,782		39,646		$ 20,394
Total assets	$ 647,423		$ 539,304

[1] Includes gains and losses on disposition of equipment .

[2] Includes equipment purchased under capital leases.