Note 1 - General and Basis of Presentation - Customers as a Percentage of Total Revenues (Details) - Revenue Benchmark [Member] - Customer Concentration Risk [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Southern California Public Power Authority [Member]
Percent of revenues	21.00%	21.30%	23.80%	21.60%
Sierra Pacific Power Company And Nevada Power Company [Member]
Percent of revenues	15.90%	18.10%	17.90%	18.60%
Kenya Power and Lighting Co LTD [Member]
Percent of revenues	14.40%	15.50%	14.40%	14.80%