Note 9 - Equity Method Investment (Details Textual) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	May. 31, 2011	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	May. 31, 2016	Dec. 31, 2014
Earnout [Member]
Accrued Liabilities, Current		$ 0		$ 0
Transport Enterprise Leasing LLC [Member] | Based on 2011 Results [Member]
Business Combination, Contingent Consideration, Liability	$ 1,000,000
Transport Enterprise Leasing LLC [Member] | Based on 2012 Results [Member]
Income (Loss) from Equity Method Investments	$ 2,400,000
Transport Enterprise Leasing LLC [Member] | Services Provided [Member]
Revenue from Related Parties				600,000
Transport Enterprise Leasing LLC [Member] | Reduction in TEL Investment [Member]
Deferred Gain on Sale of Property		900,000		900,000
Transport Enterprise Leasing LLC [Member]
Equity Method Investment, Ownership Percentage	49.00%
Payments to Acquire Equity Method Investments	$ 1,500,000			1,500,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 4,500,000
Income (Loss) from Equity Method Investments				2,700,000
Proceeds from Sale of Property, Plant, and Equipment				5,800,000
Deferred Gain on Sale of Property		100,000		100,000
Due from Related Parties		2,300,000		2,300,000			$ 2,200,000
Equity Method Investments		14,800,000		14,800,000			12,200,000
Scenario, Forecast [Member]
Option to Acquire Interest in Equity Method Investment, Percentage of Ownership						100.00%
Accrued Liabilities, Current		32,942,000		32,942,000			$ 39,470,000
Income (Loss) from Equity Method Investments		$ 1,335,000	$ 850,000	2,720,000	$ 1,650,000
Proceeds from Sale of Property, Plant, and Equipment				$ 21,620,000	$ 48,540,000