Note 8 - Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Derivative assets	$ 0	$ 19,920
Derivative liabilities	3,006	480
Fair Value, Recurring [Member]
Derivative assets	0	19,920
Derivative liabilities	3,006	480
Fair Value, Recurring [Member] | Fixed Price Derivative Contracts [Member]
Derivative assets	0	19,920
Derivative liabilities	3,006	480
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Price Derivative Contracts [Member]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative assets	0	19,920
Derivative liabilities	3,006	480
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Price Derivative Contracts [Member]
Derivative assets	0	19,920
Derivative liabilities	3,006	480
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Price Derivative Contracts [Member]
Derivative assets	0	0
Derivative liabilities	$ 0	$ 0