CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Net Income	$ 98,168	$ 96,740
Adjustments to reconcile net income to cash provided by operations:
Depreciation and depletion	124,779	113,676
Amortization of debt issuance costs, discount and deferred hedge gain	2,343	2,337
Stock-based compensation costs	4,168	3,797
Equity portion of allowance for funds used during construction	(4,066)	(9,397)
Loss on disposition of assets	151	21
Other Noncash Expense	0	4,659
Deferred income taxes	16,746	12,953
Changes in current assets and liabilities:
Accounts receivable	32,841	62,757
Inventories	(2,458)	(417)
Other current assets	9,907	(1,130)
Accounts payable	(27,688)	(20,693)
Accrued expenses and other	(2,861)	(2,157)
Regulatory assets	(27,653)	(12,398)
Regulatory liabilities	(4,200)	(24,939)
Other noncurrent assets and liabilities	(8,576)	(1,866)
Cash Provided by Operating Activities	211,601	223,943
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Property, plant, and equipment additions	(220,978)	(247,361)
Investment in debt & equity securities	(5,778)	(917)
Cash Used in Investing Activities	(226,756)	(248,278)
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Dividends on common stock	(80,654)	(79,275)
Issuance of long-term debt	500,000	215,000
Proceeds from (Repayments of) Short-Term Debt, Maturing in More than Three Months	0	100,000
Repayments on long-term debt	(300,000)	(100,000)
Line of credit repayments, net	(103,000)	(105,000)
Other financing activities, net	(3,660)	(539)
Cash Provided by Financing Activities	12,686	30,186
(Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(2,469)	5,851
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance	29,017	25,187
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance	26,548	31,038
Cash Paid [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activity	67,166	59,995
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital expenditures included in accounts payable	$ 32,015	$ 27,144