Note 13 - Subsequent Event (Details Textual) - Second Export Credit Agreement [Member]			6 Months Ended
	Aug. 07, 2020	Apr. 08, 2019	Jun. 30, 2020
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate		3.00%	3.00%
Subsequent Event [Member]
Debt Instrument, Increase (Decrease) in Stated Rate	1.25%
Subsequent Event [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	0.75%