REVENUES: Electric utility operating revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues [Abstract]
Revenue from contracts with customers	$ 318,182	$ 291,327
Alternative revenue programs and other revenues	25,739	24,241
Electric utility revenues	$ 343,921	$ 315,568