STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Regulated Operating Revenue	$ 2,427,428	$ 2,083,558	$ 2,371,990
Cost of natural gas	998,913	778,333	1,134,510
Operating expenses
Operations and maintenance	558,497	530,256	508,399
Depreciation and amortization	317,256	296,699	279,830
General taxes	95,295	79,371	71,661
Total operating expenses	971,048	906,326	859,890
Operating income	457,467	398,899	377,590
Other Nonoperating Income (Expense)	6,801	7,572	9,476
Interest expense, net	(142,809)	(147,235)	(115,339)
Income before income taxes	321,459	259,236	271,727
Income taxes	(57,235)	(36,386)	(40,495)
Net income	$ 264,224	$ 222,850	$ 231,232
Earnings per share
Basic	$ 4.39	$ 3.92	$ 4.16
Diluted	$ 4.37	$ 3.91	$ 4.14
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Basic	60,161	56,826	55,600
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Diluted	60,513	57,033	55,860
Common Stock, Dividends, Per Share, Declared	$ 2.68	$ 2.64	$ 2.60