Note 10 - Employee Benefit Plans - Asset Allocations at Measurement Date (Details) - Norwegian Pension Plan [Member]	Dec. 31, 2016	Dec. 31, 2015
Asset allocation measurement	100.00%	100.00%
Equity Securities [Member]
Asset allocation measurement	5.00%	7.00%
Real Estate [Member]
Asset allocation measurement	10.00%	14.00%
Money Market Funds [Member]
Asset allocation measurement	24.00%	22.00%
Held to Maturity Bonds [Member]
Asset allocation measurement	32.00%	35.00%
Bonds [Member]
Asset allocation measurement	7.00%	17.00%
Other Plan Assets [Member]
Asset allocation measurement	22.00%	5.00%