Note 5 - Fair Value of Financial Instruments - Amounts of Gain (Loss) Recognized in Condensed Consolidated Statements on Derivative Instruments Not Designated as Hedges (Details) - Derivatives and Foreign Currency Transaction Gains (Losses) [Member] - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Currency Forward and Price Swap Transaction on Responsive Reserve System ("RRS") Prices [Member]
Amount of gain (loss) recognized		$ 0	$ 0	$ 0	$ (14,540)
Currency Forward Contracts [Member]
Amount of gain (loss) recognized	[1]	(4,498)	1,200	(4,706)	(269)
Cross Currency Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Cross currency swap (2)	[2]	$ (28,733)	$ 6,808	$ (35,415)	$ (4,294)

[1] The foregoing currency forward and price swap transactions were not designated as hedge transactions and were marked to market with the corresponding gains or losses recognized within “Derivatives and foreign currency transaction gains (losses)” in the condensed consolidated statements of operations and comprehensive income. The price swap transaction was related to a hedging agreement with a third party that was effective January 1, 2021 under which the Company fixed the price per MWh on a portion of RRS provided by its Rabbit Hill storage facility. The price swap transaction was terminated effective April 1, 2021.

[2] The foregoing cross currency swap transactions were designated as a cash flow hedge as further described under Note 1 to the condensed consolidated financial statements. The changes in the cross currency swap fair value are initially recorded in "Other comprehensive income (loss)" and a corresponding amount is reclassified out of "Accumulated other comprehensive income (loss)" to "Derivatives and foreign currency transaction gains (losses)" to offset the remeasurement of the underlying hedged transaction which also impacts the same line item in the condensed consolidated statements of operations and comprehensive income.