Note 10 - Intangible Assets and Goodwill (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net, Ending Balance	$ 363,314
Finite-Lived Intangible Assets, Accumulated Amortization	110,138	$ 89,363
Amortization of Intangible Assets, Total	21,700	14,400	$ 13,300
Increase (Decrease) in Intangible Assets, Current	192,500	20,400	0
Finite Lived Intangible Assets, Write off	0	0	0
Goodwill, Ending Balance	89,954	24,566	20,140
Goodwill, Impairment Loss	0	0	$ 0
Power Purchase Agreements and Intangible Assets Related to Storage Activities [Member]
Finite-Lived Intangible Assets, Net, Ending Balance	363,300	194,400
Finite-Lived Intangible Assets, Accumulated Amortization	$ 110,100	$ 89,400