Note 3 - Vessel Acquisitions and Dispositions (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended		1 Months Ended	3 Months Ended				1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jun. 30, 2014	Feb. 28, 2014 Vessel [Member] North Sea [Member]	Sep. 30, 2014 Large Platform Supply Vessel [Member] Subsequent Event [Member] Southeast Asia [Member]	Sep. 30, 2011 Large Platform Supply Vessel [Member] North Sea [Member]	Jun. 30, 2012 Large Platform Supply Vessel [Member] Thoma Sea [Member]	Sep. 30, 2012 Large Platform Supply Vessel [Member] BAE Systems [Member]	Apr. 30, 2014 Additional PSV [Member] North Sea [Member]	Sep. 30, 2011 Additional PSV [Member] North Sea [Member]	Sep. 30, 2011 North Sea [Member]	Jun. 30, 2012 Thoma Sea [Member]	Sep. 30, 2012 Thoma Sea [Member]	Sep. 30, 2014 Americas [Member]	Sep. 30, 2013 Americas [Member]	Sep. 30, 2012 Americas [Member]	Sep. 30, 2014 Americas [Member]	Sep. 30, 2013 Americas [Member]
Note 3 - Vessel Acquisitions and Dispositions (Details) [Line Items]
Property, Plant and Equipment, Additions							$ 30,900,000
Number of Vessel Sold								2
Gain (Loss) on Disposition of Assets	6,877,000	6,001,000	6,877,000	5,875,000				5,500,000									1,357,000	(102,000)		1,357,000	(110,000)
Interest Costs Capitalized	1,700,000	4,200,000	6,600,000	10,700,000
Number of Shipyards Use in Agreements													1	3
Number of Vessels Under Construction									6	2	2				2
Estimated Cost of Building Vessels												60,000,000		288,000,000					168,000,000
Number of Vessels Expected to Operate														7					4
Number of Vessels Delivered					5
Number of Vessels, Expected To Be Delivered			3
Increase (Decrease) in Restricted Cash																52,400,000
Escrow Deposit	$ 3,683,000		$ 3,683,000		$ 8,742,000	$ 3,700,000