Note 9 - Equity Method Investment (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Proceeds from Sale of Property, Plant, and Equipment, Total			$ 38,127	$ 26,060
Income (Loss) from Equity Method Investments, Total	$ 1,775	$ 800	3,265	1,825
Transport Enterprise Leasing LLC [Member]
Proceeds from Sale of Property, Plant, and Equipment, Total			100	100
Revenue from Related Parties			3,900	2,200
Deferred Gain on Sale of Property	$ 200	$ 100	$ 200	$ 100
Equity Method Investment, Ownership Percentage	49.00%		49.00%
Due from Related Parties, Total	$ 5,100		$ 5,100		$ 8,600
Income (Loss) from Equity Method Investments, Total			3,300
Equity Method Investments	23,600		23,600		$ 20,100
Transport Enterprise Leasing LLC [Member] \| Reduction in TEL Investment [Member]
Deferred Gain on Sale of Property	$ 200		$ 200

Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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