Note 10 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended
	Dec. 31, 2016	Oct. 31, 2016	Oct. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Defined Benefit Plan, Benefit Obligation	$ 1,100			$ 1,100
Defined Benefit Plan, Expected Return on Plan Assets				182	$ 185
Plan 401K [Member]
Deferred Compensation Arrangement with Individual, Employer Contribution					1,000	$ 2,100
Merchant Navy Officers Pension Fund [Member]
Other Employee-related Liabilities	2,600			2,600
Defined Benefit Plan, Funded Status of Plan							$ (7,500)
Defined Benefit Plan, Contributions by Employer				$ 400	400	700
Defined Benefit Plan, Benefit Obligation						2,200
Defined Benefit Plan, Benefits Paid		$ 300	$ 1,900
Merchant Navy Officers Pension Fund [Member] | Minimum [Member]
Defined Contribution Plan, Hedging Interest Rate and Inflation Risk Percentage				65.00%
Merchant Navy Officers Pension Fund [Member] | Maximum [Member]
Defined Contribution Plan, Hedging Interest Rate and Inflation Risk Percentage				80.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match				5.00%
Norwegian Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation	5,600			$ 5,600	6,400	8,200
Defined Contribution Plan, Number of Employees Covered				3
Defined Benefit Plan, Fair Value of Plan Assets	5,500			$ 5,500	$ 5,500	$ 6,100
Defined Benefit Plan, Expected Contributions in Current Fiscal Year				$ 600
Defined Benefit Plan, Expected Return on Plan Assets	$ 0
Norwegian Pension Plan [Member] | Seamen [Member]
Defined Contribution Plan, Number of Employees Covered				137