Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities
Net income	$ 55,194	$ 69,640
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	66,508	62,990
Other amortization	10,362	9,425
Provision for credit losses	1,175	(3,263)
Loans originated, held for sale	(5,450)	(73,931)
Proceeds from sale of loans, held for sale	5,662	75,629
Gain on sales of investment securities, net and equity-method investment	0	(8,123)
Gain on sale of loans, net	(130)	(1,077)
Deferred income taxes	(1,076)	(5,255)
Share-based compensation expense	2,031	2,117
Allowance for equity funds used during construction	(3,301)	(2,409)
Other	(988)	(2,552)
Changes in assets and liabilities
Decrease in accounts receivable and unbilled revenues, net	82,423	4,454
Decrease (increase) in fuel oil stock	33,429	(35,333)
Decrease (increase) in regulatory assets	(8,898)	(5,089)
Increase in regulatory liabilities	11,551	5,520
Increase in accounts, interest and dividends payable	24,748	71,490
Change in prepaid and accrued income taxes, tax credits and utility revenue taxes	(47,305)	(14,928)
Decrease in defined benefit pension and other postretirement benefit plans liability	(1,950)	(1,309)
Change in other assets and liabilities	(43,033)	(55,411)
Net cash provided by operating activities	180,952	92,585
Cash flows from investing activities
Available-for-sale investment securities purchased	0	(291,168)
Principal repayments on available-for-sale investment securities	32,484	104,654
Proceeds from repayments or maturities of held-to-maturity investment securities	17,938	4,547
Purchase of stock from Federal Home Loan Bank	(35,960)	0
Redemption of stock from Federal Home Loan Bank	52,520	0
Net decrease (increase) in loans held for investment	(68,871)	28,076
Purchase of loans held for investment	(13,012)	0
Capital expenditures	(124,297)	(79,163)
Contributions to low income housing investments	(418)	0
Other	2,148	5,340
Net cash used in investing activities	(137,468)	(227,714)
Cash flows from financing activities
Net increase in deposit liabilities	60,905	117,060
Net increase (decrease) in short-term borrowings with original maturities of three months or less	(88,666)	17,493
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(564,430)	49,080
Proceeds from issuance of short-term debt	65,000	0
Proceeds from issuance of other bank borrowings	550,000	0
Proceeds from issuance of long-term debt	150,000	7,312
Repayment of long-term debt	(53,878)	(13,446)
Withheld shares for employee taxes on vested share-based compensation	(2,338)	(3,065)
Common stock dividends	(39,446)	(38,301)
Preferred stock dividends of subsidiaries	(473)	(473)
Other	(5,535)	(4,377)
Net cash provided by financing activities	71,139	131,283
Net increase (decrease) in cash, cash equivalents and restricted cash	114,623	(3,846)
Cash, cash equivalents and restricted cash, beginning of period	204,927	311,462
Cash, cash equivalents and restricted cash, end of period	319,550	307,616
Less: Restricted cash	(4,216)	(5,912)
Cash and cash equivalents, end of period	$ 315,334	$ 301,704