Note 10 - Employee Benefit Plans - Asset Allocations at Measurement Date (Details) - Norwegian Pension Plan [Member]	Dec. 31, 2017	Dec. 31, 2016
Asset allocation measurement	100.00%
Predecessor [Member]
Asset allocation measurement		100.00%
Equity Securities [Member]
Asset allocation measurement	11.00%
Equity Securities [Member] | Predecessor [Member]
Asset allocation measurement		5.00%
Real Estate [Member]
Asset allocation measurement	10.00%
Real Estate [Member] | Predecessor [Member]
Asset allocation measurement		10.00%
Money Market Funds [Member]
Asset allocation measurement	14.00%
Money Market Funds [Member] | Predecessor [Member]
Asset allocation measurement		24.00%
Held to Maturity Bonds [Member]
Asset allocation measurement	27.00%
Held to Maturity Bonds [Member] | Predecessor [Member]
Asset allocation measurement		32.00%
Bonds [Member]
Asset allocation measurement	13.00%
Bonds [Member] | Predecessor [Member]
Asset allocation measurement		7.00%
Other Plan Assets [Member]
Asset allocation measurement	25.00%
Other Plan Assets [Member] | Predecessor [Member]
Asset allocation measurement		22.00%