Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 465,237	$ 431,612	$ 284,849
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	321,177	297,952	257,059
Deferred income taxes	(23,045)	(8,514)	(17,782)
Provision for doubtful accounts	27,631	27,336	32,325
Stock-based compensation	12,206	10,078	8,160
Gain on sale of utility system and other assets	(991)	(1,589)	(642)
Net change in receivables, deferred purchased gas costs, inventory and prepayments	(223,335)	(109,605)	(35,348)
Net change in payables, accrued interest, accrued taxes and other accrued liabilities	53,761	5,190	(1,819)
Pension and other postretirement benefits contributions	(22,027)	(15,135)	(20,282)
Other	(10,308)	7,354	1,504
Net cash flows from operating activities	600,306	644,679	508,024
Cash flows from investing activities:
Property, plant and equipment additions, including the debt component of allowance for funds used during construction of $6,047, $4,510 and $4,434	(1,062,763)	(1,020,519)	(835,642)
Acquisitions of utility systems and other, net	(116,891)	(36,326)	(3,501,835)
Net proceeds from the sale of utility systems and other assets	1,081	1,819	2,115
Other	271	(1,032)	1,696
Net cash flows used in investing activities	(1,178,302)	(1,056,058)	(4,333,666)
Cash flows from financing activities:
Customers' advances and contributions in aid of construction	11,714	15,264	9,585
Repayments of customers' advances	(5,006)	(7,725)	(8,337)
Net proceeds (repayments) of short-term debt	163,500	(13,350)	(129,407)
Proceeds from long-term debt	1,646,742	1,095,171	3,366,838
Repayments of long-term debt	(977,175)	(769,546)	(1,820,571)
Change in cash overdraft position	(53,028)	37,719	33,059
Proceeds from issuance of common stock under dividend reinvestment plan	16,619	16,799	16,522
Proceeds from issuance of common stock from private placement			729,301
Proceeds from issuance of common stock from forward equity sale agreement		299,739
Proceeds from tangible equity unit issuance	63,040
Proceeds from exercised stock options	2,475	4,172	1,589
Repurchase of common stock	(1,192)	(3,291)	(4,365)
Dividends paid on common stock	(288,632)	(258,650)	(232,571)
Other	(230)	817	(96)
Net cash flows from financing activities	578,827	417,119	1,961,547
Net increase (decrease) in cash and cash equivalents	831	5,740	(1,864,095)
Cash and cash equivalents at beginning of year	10,567	4,827	1,868,922
Cash and cash equivalents at end of year	11,398	10,567	4,827
Cash paid during the year for:
Interest, net of amounts capitalized	225,820	201,792	169,048
Income taxes	11,269	5,692	4,853
Non-cash investing activities:
Property, plant and equipment additions purchased at the period end, but not yet paid	102,129	95,945	98,569
Non-cash utility property contributions	$ 35,698	$ 36,882	$ 36,181