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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Sierra Pacific Power Company And Nevada Power Company [Member]
Percent of revenues	17.70%	19.50%	18.60%	20.30%
Southern California Public Power Authority [Member]
Percent of revenues	21.30%	25.50%	21.60%	25.20%
Kenya Power and Lighting Co LTD [Member]
Percent of revenues	15.50%	17.30%	14.80%	16.40%