REVENUES: Electric utility operating revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenues [Abstract]
Revenue from contracts with customers	$ 417,897	$ 385,666
Alternative revenue programs and other revenues	30,402	43,672
Electric utility revenues	$ 448,299	$ 429,338