Note 18 - Business Segments (Details Textual) $ in Thousands		12 Months Ended
		Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)
Number of Reportable Segments		3
Revenue from Contract with Customer, Including Assessed Tax	[1]	$ 734,159	$ 663,084	$ 705,342
Goodwill, Ending Balance		90,325	89,954	24,566
Electricity Segment [Member]
Revenue from Contract with Customer, Including Assessed Tax		631,727	585,771	541,393
Goodwill, Ending Balance		85,700	85,300	20,500
Electricity Segment [Member] | Accounting Standards Update 2014-09 [Member]
Revenue from Contract with Customer, Including Assessed Tax		102,500	83,400	68,100
Energy Storage and Management Services [Member]
Goodwill, Ending Balance		4,600	4,600	4,100	$ 66,200
Product Segment [Member]
Revenue from Contract with Customer, Including Assessed Tax		71,414	46,920	148,125
Goodwill, Ending Balance		$ 0	$ 0	$ 0

[1] Revenues as reported in the geographic area in which they originate.