Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Current assets:
Cash and cash equivalents	$ 50,780	$ 70,428	$ 53,663
Receivables, net	934,173	1,064,340	760,696
Current regulatory assets	193,162	165,092	102,535
Inventories	60,154	64,248	50,977
Prepayments and other current assets	60,502	55,123	82,533
Investment in Knife River	246,063	0	0
Current assets of discontinued operations	0	583,218	798,665
Total current assets	1,544,834	2,002,449	1,849,069
Noncurrent assets:
Property, plant and equipment	7,083,229	6,874,630	6,692,019
Less accumulated depreciation, depletion and amortization	2,160,439	2,098,298	2,067,811
Net property, plant and equipment	4,922,790	4,776,332	4,624,208
Goodwill	488,960	488,960	488,960
Other intangible assets, net	3,049	4,102	5,213
Regulatory assets	345,185	329,659	347,061
Investments	139,569	128,827	127,847
Operating lease right-of-use assets	74,553	73,502	69,869
Other	165,910	161,900	170,709
Noncurrent assets of discontinued operations	0	1,685,751	1,636,027
Total noncurrent assets	6,140,016	7,649,033	7,469,894
Total assets	7,684,850	9,651,482	9,318,963
Current liabilities:
Short-term borrowings	345,000	38,500	0
Long-term debt due within one year	1,319	47,819	86,319
Accounts payable	399,339	525,560	394,317
Taxes payable	60,284	62,308	97,471
Dividends payable	45,310	45,245	44,229
Accrued compensation	66,555	59,470	69,538
Operating lease liabilities due within one year	22,666	21,307	19,960
Regulatory liabilities due within one year	48,057	26,440	17,884
Other accrued liabilities	143,235	156,031	138,479
Current liabilities of discontinued operations	0	487,624	502,317
Total current liabilities	1,131,765	1,470,304	1,370,514
Noncurrent liabilities:
Long-term debt	2,246,103	2,317,848	2,003,881
Deferred income taxes	515,661	455,499	428,249
Asset retirement obligations	380,058	372,870	440,216
Regulatory liabilities	455,877	448,454	433,019
Operating lease liabilities	52,328	52,871	50,625
Other	196,865	180,603	178,204
Noncurrent liabilities of discontinued operations	0	765,904	1,027,445
Total noncurrent liabilities	3,846,892	4,594,049	4,561,639
Commitments and contingencies
Stockholders' equity:
Common stock	203,638	204,163	203,889
Other paid-in capital	1,460,735	1,466,037	1,454,131
Retained earnings	1,059,517	1,951,138	1,775,947
Accumulated other comprehensive loss	(17,697)	(30,583)	(43,531)
Treasury Stock, Common, Value	0	3,626	3,626
Total stockholders' equity	2,706,193	3,587,129	3,386,810
Total liabilities and stockholders' equity	$ 7,684,850	$ 9,651,482	$ 9,318,963
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