Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities
Net income	$ 185,207	$ 193,062
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	190,075	184,389
Other amortization	28,916	24,511
Provision for credit losses	(692)	(22,367)
Loans originated, held for sale	(120,195)	(281,744)
Proceeds from sale of loans, held for sale	126,357	304,820
Gain on sales of investment securities, net and equity-method investment	(8,123)	(528)
Gain on sale of loans, net	(1,630)	(7,497)
Deferred income taxes	(21,631)	(13,473)
Share-based compensation expense	7,337	6,727
Allowance for equity funds used during construction	(7,431)	(6,995)
Other	(5,392)	(7,046)
Changes in assets and liabilities
Increase in accounts receivable and unbilled revenues, net	(159,619)	(58,758)
Increase in fuel oil stock	(127,413)	(42,612)
Decrease (increase) in regulatory assets	34,278	(4,952)
Increase in regulatory liabilities	29,294	8,806
Increase in accounts, interest and dividends payable	39,009	36,850
Change in prepaid and accrued income taxes, tax credits and utility revenue taxes	73,279	11,133
Decrease in defined benefit pension and other postretirement benefit plans liability	(4,228)	(5,288)
Change in other assets and liabilities	(44,411)	(51,833)
Net cash provided by operating activities	212,987	267,205
Cash flows from investing activities
Available-for-sale investment securities purchased	(366,177)	(1,318,520)
Principal repayments on available-for-sale investment securities	285,519	449,459
Proceeds from sale of available-for-sale investment securities	0	197,354
Purchases of held-to-maturity investment securities	0	(314,327)
Proceeds from repayments or maturities of held-to-maturity investment securities	10,433	49,074
Purchase of stock from Federal Home Loan Bank	(93,000)	(32,980)
Redemption of stock from Federal Home Loan Bank	88,000	31,660
Net decrease (increase) in loans held for investment	(395,185)	157,619
Proceeds from sale of residential loans	0	17,398
Purchase of loans held for investment	(77,274)	0
Capital expenditures	(236,278)	(219,252)
Contributions to low income housing investments	(740)	(12,402)
Acquisition of business	(25,706)	0
Other	15,646	10,078
Net cash used in investing activities	(794,762)	(984,839)
Cash flows from financing activities
Net increase in deposit liabilities	86,673	589,581
Net increase in short-term borrowings with original maturities of three months or less	117,127	27,755
Net increase in other bank borrowings with original maturities of three months or less	320,735	39,635
Repayment of short-term debt	0	(65,000)
Proceeds from issuance of long-term debt	67,312	206,988
Repayment of long-term debt	(16,752)	(80,607)
Withheld shares for employee taxes on vested share-based compensation	(3,158)	(2,006)
Common stock dividends	(114,917)	(111,477)
Preferred stock dividends of subsidiaries	(1,417)	(1,417)
Other	(6,112)	(7,462)
Net cash provided by financing activities	449,491	595,990
Net decrease in cash, cash equivalents and restricted cash	(132,284)	(121,644)
Cash, cash equivalents and restricted cash, beginning of period	311,462	358,979
Cash, cash equivalents and restricted cash, end of period	179,178	237,335
Less: Restricted cash	(3,898)	(9,412)
Cash and cash equivalents, end of period	$ 175,280	$ 227,923