Note 16 - Commitments and Contingencies (Details Textual)	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due	$ 738,000
Capital Addition Purchase Commitments [Member] \| Revenue Equipment [Member]
Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year	121,900,000
Capital Addition Purchase Commitments [Member] \| Building [Member]
Purchase Obligation, Future Minimum Payments, Remainder of Fiscal Year	$ 4,000,000

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant