CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net Income	$ 135,504	$ 101,664
Items not affecting cash:
Depreciation and depletion	140,896	134,336
Amortization of debt issuance costs, discount and deferred hedge gain	3,951	3,604
Stock-based compensation costs	5,850	5,347
Equity portion of allowance for funds used during construction	(7,829)	(4,503)
Loss (gain) on disposition of assets	6,536	(26)
Deferred income taxes	(681)	(3,759)
Changes in current assets and liabilities:
Accounts receivable	28,901	34,290
Inventories	(23,400)	(15,130)
Other current assets	(8,442)	(4,194)
Accounts payable	(12,472)	(4,181)
Accrued expenses	85,015	67,553
Regulatory assets	(67,672)	7,372
Regulatory liabilities	(32,941)	13,433
Other noncurrent assets	610	(1,825)
Other noncurrent liabilities	(32,216)	(11,466)
Cash Provided by Operating Activities	221,610	322,515
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(311,160)	(282,987)
Investment in equity securities	(655)	(42)
Cash Used in Investing Activities	(311,815)	(283,029)
FINANCING ACTIVITIES:
Treasury stock activity	359	(1,723)
Proceeds from issuance of common stock, net	121,066	0
Dividends on common stock	(95,148)	(90,260)
Issuance of long-term debt, net	99,915	150,000
Payment for Debt Extinguishment or Debt Prepayment Cost	(955)	0
Line of credit borrowings (repayments), net	73,000	(193,000)
(Repayments) issuance of short-term borrowings	(100,000)	100,000
Financing costs	(909)	(2,564)
Cash Provided by (Used in) Financing Activities	97,328	(37,547)
Increase in Cash, Cash Equivalents, and Restricted Cash	7,123	1,939
Cash, Cash Equivalents, and Restricted Cash, beginning of period	17,096	12,070
Cash, Cash Equivalents, and Restricted Cash, end of period	24,219	14,009
Cash paid during the period for:
Income taxes	3,630	100
Interest	57,473	55,220
Significant non-cash transactions:
Capital expenditures included in accounts payable	$ 23,500	$ 15,986