STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Regulated Operating Revenue	$ 2,371,990	$ 2,578,005	$ 1,808,597
Cost of natural gas	1,134,510	1,459,087	775,006
Operating expenses
Operations and maintenance	508,399	472,265	449,676
Depreciation and amortization	279,830	228,479	207,233
General taxes	71,661	68,217	66,424
Total operating expenses	859,890	768,961	723,333
Operating income	377,590	349,957	310,258
Other Nonoperating Income (Expense)	9,476	(4,183)	(3,207)
Interest expense, net	(115,339)	(77,506)	(60,301)
Income before income taxes	271,727	268,268	246,750
Income taxes	(40,495)	(46,526)	(40,316)
Net income	$ 231,232	$ 221,742	$ 206,434
Earnings per share
Basic	$ 4.16	$ 4.09	$ 3.85
Diluted	$ 4.14	$ 4.08	$ 3.85
Weighted Average Number of Shares Outstanding, Basic [Abstract]
Basic	55,600	54,207	53,575
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Diluted	55,860	54,338	53,674
Common Stock, Dividends, Per Share, Declared	$ 2.60	$ 2.48	$ 2.32