Business Segment Information: Information Relating to Segments Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information
Revenue	$ 411,283	$ 474,195	$ 1,332,442	$ 1,297,765
Operating income (loss)	63,516	72,389	238,399	245,742
Electric Utilities
Segment Reporting Information
Revenue	193,073	204,379	411,782	410,917
Operating income (loss)	46,619	45,226	107,679	95,972
Gas Utilities
Segment Reporting Information
Revenue	222,720	274,169	929,636	895,561
Operating income (loss)	17,725	28,195	132,350	151,735
Corporate, Non-Segment
Segment Reporting Information
Operating income (loss)	(828)	(1,032)	(1,630)	(1,965)
Inter-segment Revenues
Segment Reporting Information
Revenue	(4,510)	(4,353)	(8,976)	(8,713)
External Customers | Electric Utilities
Segment Reporting Information
Revenue	190,212	201,450	406,105	405,059
External Customers | Gas Utilities
Segment Reporting Information
Revenue	221,071	272,745	926,337	892,706
Intercompany Customers | Electric Utilities
Segment Reporting Information
Revenue	2,861	2,929	5,677	5,858
Intercompany Customers | Gas Utilities
Segment Reporting Information
Revenue	$ 1,649	$ 1,424	$ 3,299	$ 2,855