Note 18 - Business Segments - Revenue From Major Customers (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue	[1]	$ 734,159	$ 663,084	$ 705,342
Southern California Public Power Authority [Member]
Revenue	[2]	$ 157,663	$ 157,318	$ 145,450
Percentage of revenues	[2]	21.50%	23.70%	20.60%
Sierra Pacific Power Company And Nevada Power Company [Member]
Revenue	[2],[3]	$ 124,116	$ 120,206	$ 123,734
Percentage of revenues	[2],[3]	16.90%	18.10%	17.50%
Kenya Power and Lighting Co LTD [Member]
Revenue	[2]	$ 105,837	$ 102,844	$ 115,474
Percentage of revenues	[2]	14.40%	15.50%	16.40%

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

[2] Revenues reported in Electricity segment.

[3] Subsidiaries of NV Energy, Inc.