STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net income	$ 231,232	$ 221,742	$ 206,434
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	279,830	228,479	207,233
Deferred income taxes	24,773	(22,034)	43,449
Share-based compensation expense	12,184	10,741	10,498
Provision for doubtful accounts	9,698	6,003	9,131
Proceeds from Securitization Bonds, Operating Activities	197,366	1,330,582	0
Changes in assets and liabilities:
Accounts receivable	196,272	(213,656)	(57,902)
Materials and supplies	(6,776)	(15,981)	(2,126)
Natural gas in storage	82,108	(89,559)	(85,700)
Payments for Removal Costs	(62,023)	(47,032)	(49,029)
Accounts payable	(90,046)	85,915	107,207
Accrued taxes other than income	(9,559)	11,317	3,235
Customer deposits	4,333	(4,600)	(5,574)
Increase (Decrease) In Regulatory Assets And Liabilities Current, net	7,249	52,417	(1,562,574)
Increase (Decrease) In Regulatory Assets And Liabilities Noncurrent, net	38,869	53,992	(367,210)
Increase (Decrease) in Other Current Assets and Liabilities, Net	26,070	(23,377)	18,461
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net	(2,048)	(14,107)	(11,190)
Cash provided by operating activities	939,532	1,570,842	(1,535,657)
Investing activities
Capital expenditures	(666,634)	(609,486)	(495,246)
Payments for Other Investing Activities	(8,508)	(8,632)	(7,554)
Proceeds from Sale of Other Assets, Investing Activities	5,499	4,008	1,717
Cash used in investing activities	(669,643)	(614,110)	(501,083)
Financing activities
Borrowings (repayments) of short-term debt, net	(463,500)	58,000	75,775
Proceeds from Issuance of Senior Long-term Debt	299,583	297,591	2,498,895
Issuance of securitized utility tariff bonds, net of discounts	0	335,931	0
Payments of Debt Issuance Costs	(2,508)	(8,567)	(35,110)
Proceeds from Issuance of Common Stock	85,259	133,711	26,662
Repayments of Other Long-Term Debt	0	(1,627,000)	(400,000)
Repayment of securitized utility tariff bonds	20,716	0
Dividends paid	(144,094)	(133,954)	(123,912)
Payment, Tax Withholding, Share-based Payment Arrangement	(2,653)	(3,169)	(4,711)
Cash used in financing activities	(248,629)	(947,457)	2,037,599
Change in cash and cash equivalents	21,260	9,275	859
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance	18,127	8,852	7,993
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	39,387	18,127	8,852
Interest Paid, Excluding Capitalized Interest, Operating Activities	80,726	84,871	70,066
Income Taxes Paid, Net	$ 20,844	$ 67,421	$ (10,809)