Note 9 - Equity Method Investment (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Proceeds from Sale of Property, Plant, and Equipment, Total			$ 15,569	$ 38,127
Reversal of Deferred Gains of Sale of Property			(7)	(171)
Income (Loss) from Equity Method Investments, Total	$ 2,375	$ 1,775	5,410	3,265
Transport Enterprise Leasing LLC [Member]
Proceeds from Sale of Property, Plant, and Equipment, Total			0	100
Revenue from Related Parties			4,600	3,900
Reversal of Deferred Gains of Sale of Property			$ 100	$ 200
Equity Method Investment, Ownership Percentage	49.00%	49.00%	49.00%	49.00%
Due from Related Parties, Total	$ 5,600		$ 5,600		$ 5,100
Income (Loss) from Equity Method Investments, Total			5,400
Equity Method Investments	31,500		31,500		$ 26,100
Transport Enterprise Leasing LLC [Member] \| Reduction in TEL Investment [Member]
Deferred Gain on Sale of Property	$ 200		$ 200

Amounts reversed from the deferred gains on sale of property.

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