Note 8 - Business Segments (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Number of Reportable Segments	3
Revenue from Contract with Customer, Including Assessed Tax	$ 185,232	$ 183,710
Goodwill	90,446		$ 90,325
Electricity Segment [Member]
Revenue from Contract with Customer, Including Assessed Tax	170,310	162,525
Goodwill	85,800	86,000
Electricity Segment [Member] | Accounted for Under ASC 606 [Member]
Revenue from Contract with Customer, Including Assessed Tax	32,700	22,800
Energy Storage and Management Services [Member]
Goodwill	4,600	4,600
Product Segment [Member]
Revenue from Contract with Customer, Including Assessed Tax	10,042	14,628
Goodwill	$ 0	$ 0