Represents the operating income or loss before the gain or loss on the disposition of the facility.

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- Definition

Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Note 17 - Business Segments - Operating Revenue and Operating Income by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating revenue	$ 182,771	$ 170,679	$ 171,511	$ 173,159	$ 172,661	$ 170,464	$ 166,090	$ 161,929	$ 698,120	$ 671,144	$ 664,994
Operating income	$ 14,333	$ 13,022	$ 15,569	$ 13,938	$ 14,533	$ 14,869	$ 14,776	$ 14,125	56,862	58,303	61,063
Facility [Member]
Total operating income before gain on disposition of facilities									56,862	58,303	56,959
Gain on disposition of facilities											4,104
Truckload [Member]
Operating revenue									380,210	375,851	398,361
Operating income									26,326	27,438	35,517
Truckload [Member] \| Revenue, Net of Fuel Surcharge [Member]
Operating revenue									336,596	339,967	348,101
Truckload [Member] \| Fuel Surcharge Revenue [Member]
Operating revenue									43,614	35,884	50,260
Dedicated [Member]
Operating revenue									166,881	157,370	118,272
Operating income									17,074	19,550	12,818
Dedicated [Member] \| Revenue, Net of Fuel Surcharge [Member]
Operating revenue									153,691	147,007	107,264
Dedicated [Member] \| Fuel Surcharge Revenue [Member]
Operating revenue									13,190	10,363	11,008
Intermodal [Member]
Operating revenue									80,621	71,490	76,958
Operating income									8,303	7,131	4,832
Intermodal [Member] \| Revenue, Net of Fuel Surcharge [Member]
Operating revenue									70,282	64,508	65,877
Intermodal [Member] \| Fuel Surcharge Revenue [Member]
Operating revenue									10,339	6,982	11,081
Brokerage [Member]
Operating revenue									70,408	66,433	71,403
Operating income									$ 5,159	$ 4,184	$ 3,792