Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Current assets:
Cash, cash equivalents and restricted cash	$ 32,493	$ 70,428	$ 57,859
Receivables, net	893,019	1,064,340	850,137
Current regulatory assets	169,248	165,092	148,160
Inventories	80,235	64,248	89,814
Prepayments and other current assets	63,805	55,123	87,901
Investment in Knife River	276,213	0	0
Current assets of discontinued operations	0	592,517	790,421
Total current assets	1,515,013	2,011,748	2,024,292
Noncurrent assets:
Property, plant and equipment	7,211,680	6,874,630	6,814,651
Less accumulated depreciation, depletion and amortization	2,191,514	2,098,298	2,096,450
Net property, plant and equipment	5,020,166	4,776,332	4,718,201
Goodwill	488,960	488,960	488,960
Other intangible assets, net	2,526	4,102	4,648
Regulatory assets	428,969	329,659	344,442
Investments	139,327	128,827	125,534
Operating lease right-of-use assets	75,729	73,502	76,155
Other	198,459	161,900	181,860
Noncurrent assets of discontinued operations	0	1,685,751	1,643,038
Total noncurrent assets	6,354,136	7,649,033	7,582,838
Total assets	7,869,149	9,660,781	9,607,130
Current liabilities:
Short-term borrowings	306,400	38,500	0
Long-term debt due within one year	61,319	47,819	86,319
Accounts payable	414,479	525,560	452,379
Taxes payable	49,500	62,308	80,691
Dividends payable	25,455	45,245	44,229
Accrued compensation	94,230	59,470	72,441
Operating lease liabilities due within one year	23,112	21,307	21,568
Regulatory liabilities due within one year	45,013	26,440	18,599
Other accrued liabilities	154,147	156,031	158,514
Current liabilities of discontinued operations	0	496,923	533,562
Total current liabilities	1,173,655	1,479,603	1,468,302
Noncurrent liabilities:
Long-term debt	2,279,828	2,317,848	2,192,411
Deferred income taxes	526,654	455,499	442,468
Asset retirement obligations	384,083	372,870	444,967
Regulatory liabilities	495,112	448,454	433,212
Operating lease liabilities	52,908	52,871	55,453
Other	199,475	180,603	175,788
Noncurrent liabilities of discontinued operations	0	765,904	902,671
Total noncurrent liabilities	3,938,060	4,594,049	4,646,970
Commitments and contingencies
Stockholders' equity:
Common stock	203,638	204,163	203,889
Other paid-in capital	1,462,939	1,466,037	1,455,241
Retained earnings	1,108,616	1,951,138	1,879,600
Accumulated other comprehensive loss	(17,759)	(30,583)	(43,246)
Treasury Stock, Common, Value	0	3,626	3,626
Total stockholders' equity	2,757,434	3,587,129	3,491,858
Total liabilities and stockholders' equity	$ 7,869,149	$ 9,660,781	$ 9,607,130
Common Stock, Shares Authorized	500,000,000	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00	$ 1.00
Common Stock, Shares, Issued	203,638,373	204,162,814	203,889,661
Treasury Stock, Common, Shares		538,921	538,921