CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
OPERATING ACTIVITIES:
Net Income	$ 183,008	$ 186,840	$ 155,215
Items not affecting cash:
Depreciation and depletion	195,020	187,467	179,644
Amortization of debt issuance costs, discount and deferred hedge gain	5,321	5,250	4,911
Stock-based compensation costs	5,488	5,350	4,149
Equity portion of allowance for funds used during construction	(14,191)	(11,092)	(6,895)
Loss (gain) on disposition of assets	482	(47)	37
Deferred income taxes	(8,992)	525	(7,574)
Changes in current assets and liabilities:
Accounts receivable	(46,282)	(30,442)	(824)
Inventories	(26,744)	(19,604)	(7,085)
Other current assets	(3,833)	(6,835)	(3,477)
Accounts payable	50,537	7,494	16,043
Accrued expenses	16,846	26,055	5,909
Regulatory assets	(20,512)	(69,616)	14,749
Regulatory liabilities	(7,034)	(27,674)	22,773
Other noncurrent assets	3,994	2,313	(5,396)
Other noncurrent liabilities	(25,866)	(36,006)	(20,030)
Cash Provided by Operating Activities	307,242	219,978	352,149
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(515,140)	(434,328)	(405,762)
Investment in equity securities	(1,719)	(1,505)	(42)
Cash Used in Investing Activities	(516,859)	(435,833)	(405,804)
FINANCING ACTIVITIES:
Dividends on common stock	(140,062)	(128,483)	(120,350)
Proceeds from issuance of common stock, net	276,971	196,246	0
Issuance of long-term debt	0	99,915	150,000
Payment for Debt Extinguishment or Debt Prepayment Cost	0	(955)	0
Line of credit borrowings (repayments), net	77,000	151,000	(67,000)
(Repayments) issuances of short-term borrowings	0	(100,000)	100,000
Treasury stock activity	603	707	(1,391)
Financing costs	(1,194)	(909)	(2,578)
Cash Provided by Financing Activities	213,318	217,521	58,681
Net Increase in Cash, Cash Equivalents, and Restricted Cash	3,701	1,666	5,026
Cash, Cash Equivalents, and Restricted Cash, beginning of period	18,762	17,096	12,070
Cash, Cash Equivalents, and Restricted Cash, end of period	$ 22,463	$ 18,762	$ 17,096