MDU Resources (MDU) 10-Q 2 Nov 23 2023 Q3 Quarterly report Financial data

Cover page

Cover page - shares	9 Months Ended
	Sep. 30, 2023	Oct. 26, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	1-03480
Entity Registrant Name	MDU RESOURCES GROUP INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	30-1133956
Entity Address, Address Line One	1200 West Century Avenue
Entity Address, Address Line Two	P.O. Box 5650
Entity Address, City or Town	Bismarck
Entity Address, State or Province	ND
Entity Address, Postal Zip Code	58506-5650
City Area Code	701
Local Phone Number	530-1000
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	MDU
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity common stock, shares outstanding		203,638,373
Entity Central Index Key	0000067716
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating revenues:
Operating revenues:	$ 1,000,795	$ 1,002,487	$ 3,522,020	$ 3,119,351
Operating expenses:
Operation and maintenance:	738,658	767,451	2,304,796	2,077,524
Purchased natural gas sold	55,967	61,863	542,848	444,527
Depreciation, depletion and amortization	53,146	51,843	158,877	158,622
Taxes, other than income	39,454	40,248	156,587	139,305
Electric fuel and purchased power	28,966	20,080	73,755	68,370
Total operating expenses	916,191	941,485	3,236,863	2,888,348
Operating income	84,604	61,002	285,157	231,003
Unrealized Gain (Loss) on investment in Knife River	30,150	0	170,170	0
Other income	8,918	5,774	29,251	2,521
Interest expense	32,129	20,196	82,541	58,275
Income before income taxes	91,543	46,580	402,037	175,249
Income taxes	13,325	4,211	92,311	28,352
Income from continuing operations	78,218	42,369	309,726	146,897
Discontinued operations, net of tax	(3,289)	105,602	(65,752)	103,504
Net income	$ 74,929	$ 147,971	$ 243,974	$ 250,401
Earnings per share - basic:
Income from continuing operations	$ 0.38	$ 0.21	$ 1.52	$ 0.72
Discontinued operations, net of tax	(0.01)	0.52	(0.32)	0.51
Earnings per share - basic	0.37	0.73	1.20	1.23
Earnings per share - diluted:
Income from continuing operations	0.38	0.21	1.52	0.72
Discontinued operations, net of tax	(0.01)	0.52	(0.32)	0.51
Earnings per share - diluted	$ 0.37	$ 0.73	$ 1.20	$ 1.23
Weighted average common shares outstanding - basic	203,638	203,351	203,633	203,351
Weighted average common shares outstanding - diluted	203,886	203,644	203,891	203,407
Regulated operation
Operating revenues:
Operating revenues:	$ 279,534	$ 263,774	$ 1,293,959	$ 1,141,007
Operating expenses:
Operation and maintenance:	99,295	89,662	296,818	281,909
Income from continuing operations	14,628	12,919	100,923	73,249
Nonregulated operation
Operating revenues:
Operating revenues:	721,261	738,713	2,228,061	1,978,344
Operating expenses:
Operation and maintenance:	639,363	677,789	2,007,978	1,795,615
Income from continuing operations	$ 63,590	$ 29,450	$ 208,803	$ 73,648

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net income	$ 74,929	$ 147,971	$ 243,974	$ 250,401
Other comprehensive income (loss):
Reclassification adjustment for loss on derivative instruments included in net income, tax	0	37	17	109
Reclassification adjustment for loss on derivative instruments included in net income, net of tax	0	111	81	334
Postretirement liability adjustment
Amortization of postretirement liability losses included in net periodic benefit credit, tax	98	148	263	460
Amortization of postretirement liability losses included in net periodic benefit credit, net of tax	(6)	461	481	1,367
other comprehensive (income) loss, reclassification adjustment to aoci, postretirement liabiltiy adjustment from regulatory asset, tax	0	0	0	(1,086)
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax	0	0	0	(3,265)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(6)	461	481	(1,898)
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	(17)	(88)	(21)	(207)
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax	(66)	(329)	(80)	(777)
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	3	12	9	27
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax	10	42	36	99
Net unrealized loss on available-for-sale investments	(56)	(287)	(44)	(678)
Other comprehensive income	(62)	285	518	(2,242)
Comprehensive income attributable to common stockholders	74,867	148,256	$ 244,492	$ 248,159
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Net unrealized gain (loss) on available-for-sale investments:
Other comprehensive income	$ 0	$ 111

Consolidated Balance Sheets

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	$ 1	$ 1
Common Stock, Shares, Issued	203,638,373	204,162,814	203,889,661
Treasury Stock, Common, Shares		538,921	538,921

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common stock	Other paid-in capital	Retained earnings	Accumulated other comprehensive loss	Treasury Stock, Common
Common stock balance (in shares) at Dec. 31, 2021		203,889,661
Balance at Dec. 31, 2021	$ 3,382,874	$ 203,889	$ 1,461,205	$ 1,762,410	$ (41,004)	$ (3,626)
Treasury Stock, Common, Shares at Dec. 31, 2021						(538,921)
Net income	31,763			31,763
Other comprehensive income	269				269
Dividends declared on common stock	(44,447)			(44,447)
Stock-based compensation	2,689		2,689
Repurchase of common stock						(266,821)
Repurchase of common stock	(7,399)					$ (7,399)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(12,303)
Treasury Stock, Shares, Retired						266,821
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings						$ 7,399
Tax withholding on stock-based compensation	(4,904)
Issuance of common stock	(127)		(127)
Common stock balance (in shares) at Mar. 31, 2022		203,889,661
Balance at Mar. 31, 2022	3,360,718	$ 203,889	1,451,464	1,749,726	(40,735)	$ (3,626)
Treasury Stock, Common, Shares at Mar. 31, 2022						(538,921)
Common stock balance (in shares) at Dec. 31, 2021		203,889,661
Balance at Dec. 31, 2021	3,382,874	$ 203,889	1,461,205	1,762,410	(41,004)	$ (3,626)
Treasury Stock, Common, Shares at Dec. 31, 2021						(538,921)
Net income	250,401
Other comprehensive income	(2,242)
Tax withholding on stock-based compensation	$ (4,904)
Common stock balance (in shares) at Sep. 30, 2022	203,889,661	203,889,661
Balance at Sep. 30, 2022	$ 3,491,858	$ 203,889	1,455,241	1,879,600	(43,246)	$ (3,626)
Treasury Stock, Common, Shares at Sep. 30, 2022	538,921					(538,921)
Common stock balance (in shares) at Mar. 31, 2022		203,889,661
Balance at Mar. 31, 2022	$ 3,360,718	$ 203,889	1,451,464	1,749,726	(40,735)	$ (3,626)
Treasury Stock, Common, Shares at Mar. 31, 2022						(538,921)
Net income	70,667			70,667
Other comprehensive income	(2,796)				(2,796)
Dividends declared on common stock	(44,446)			(44,446)
Stock-based compensation	2,689		2,689
Issuance of common stock	(22)		(22)
Common stock balance (in shares) at Jun. 30, 2022		203,889,661
Balance at Jun. 30, 2022	3,386,810	$ 203,889	1,454,131	1,775,947	(43,531)	$ (3,626)
Treasury Stock, Common, Shares at Jun. 30, 2022						(538,921)
Net income	147,971			147,971
Other comprehensive income	285				285
Dividends declared on common stock	(44,318)			(44,318)
Stock-based compensation	$ 1,110		1,110
Common stock balance (in shares) at Sep. 30, 2022	203,889,661	203,889,661
Balance at Sep. 30, 2022	$ 3,491,858	$ 203,889	1,455,241	1,879,600	(43,246)	$ (3,626)
Treasury Stock, Common, Shares at Sep. 30, 2022	538,921					(538,921)
Common stock balance (in shares) at Dec. 31, 2022	204,162,814	204,162,814
Balance at Dec. 31, 2022	$ 3,587,129	$ 204,163	1,466,037	1,951,138	(30,583)	$ (3,626)
Treasury Stock, Common, Shares at Dec. 31, 2022	538,921					(538,921)
Net income	$ 38,353			38,353
Other comprehensive income	217				217
Dividends declared on common stock	(45,574)			(45,574)
Stock-based compensation	3,108		3,108
Repurchase of common stock						(153,622)
Repurchase of common stock	(4,811)					$ (4,811)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(7,851)
Treasury Stock, Shares, Retired						153,622
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings						$ 4,811
Tax withholding on stock-based compensation	(3,040)
Common stock balance (in shares) at Mar. 31, 2023		204,162,814
Balance at Mar. 31, 2023	$ 3,575,382	$ 204,163	1,461,294	1,943,917	(30,366)	$ (3,626)
Treasury Stock, Common, Shares at Mar. 31, 2023						(538,921)
Common stock balance (in shares) at Dec. 31, 2022	204,162,814	204,162,814
Balance at Dec. 31, 2022	$ 3,587,129	$ 204,163	1,466,037	1,951,138	(30,583)	$ (3,626)
Treasury Stock, Common, Shares at Dec. 31, 2022	538,921					(538,921)
Net income	$ 243,974
Other comprehensive income	$ 518
Treasury Stock, Shares, Retired	538,921
Tax withholding on stock-based compensation	$ (3,040)
Common stock balance (in shares) at Sep. 30, 2023	203,638,373	203,638,373
Balance at Sep. 30, 2023	$ 2,757,434	$ 203,638	1,462,939	1,108,616	(17,759)	$ 0
Treasury Stock, Common, Shares at Sep. 30, 2023						0
Common stock balance (in shares) at Mar. 31, 2023		204,162,814
Balance at Mar. 31, 2023	3,575,382	$ 204,163	1,461,294	1,943,917	(30,366)	$ (3,626)
Treasury Stock, Common, Shares at Mar. 31, 2023						(538,921)
Net income	130,692			130,692
Other comprehensive income	363				363
Dividends declared on common stock	(45,158)			(45,158)
Stock-based compensation	(927)		(927)
Separation of Knife River, Treasury Stock Retirement						538,921
Separation of Knife River	$ (954,541)	(539)		969,934	12,306	$ 3,626
Issuance of common stock (shares)	14,480
Stock Issued		$ 14
Issuance of common stock	$ 382		368
Common stock balance (in shares) at Jun. 30, 2023		203,638,373
Balance at Jun. 30, 2023	2,706,193	$ 203,638	1,460,735	1,059,517	(17,697)	$ 0
Treasury Stock, Common, Shares at Jun. 30, 2023						0
Net income	74,929			74,929
Other comprehensive income	(62)				(62)
Dividends declared on common stock	(25,645)			(25,645)
Stock-based compensation	$ 2,204		2,204
Treasury Stock, Shares, Retired	538,921
Separation of Knife River	$ (185)			185
Common stock balance (in shares) at Sep. 30, 2023	203,638,373	203,638,373
Balance at Sep. 30, 2023	$ 2,757,434	$ 203,638	$ 1,462,939	$ 1,108,616	$ (17,759)	$ 0
Treasury Stock, Common, Shares at Sep. 30, 2023						0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating activities:
Net income	$ 243,974	$ 250,401
Discontinued operations, net of tax	(65,752)	103,504
Income from continuing operations	309,726	146,897
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	158,877	158,622
Deferred income taxes	63,745	13,697
Provision for credit losses	9,769	3,554
Amortization of debt issuance costs	991	725
Employee stock-based compensation costs	3,943	5,689
Pension and postretirement benefit plan net periodic benefit credit	(4,086)	(5,494)
Unrealized Gain (Loss) on investment in Knife River	(170,170)	0
Unrealized (gains) losses on investments	(3,501)	12,357
Gains on sales of assets	(6,761)	(4,925)
Changes in current assets and liabilities, net of acquisitions:
Receivables	161,366	(107,314)
Inventories	(19,694)	(43,649)
Other current assets	(68,161)	(32,241)
Accounts payable	(132,323)	89,876
Other current liabilities	42,310	40,931
Pension and postretirement benefit plan contributions	(7,541)	(62)
Other noncurrent changes	(3,362)	(24,981)
Net cash provided by continuing operations	335,128	253,682
Net cash provided by (used in) discontinued operations	(160,214)	31,251
Net cash provided by operating activities	174,914	284,933
Investing activities:
Capital expenditures	(370,585)	(341,162)
Net proceeds from sale or disposition of property and other	13,238	(4,101)
Investments	(3,339)	(2,185)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations	(360,686)	(347,448)
Cash Provided by (Used in) Investing Activities, Discontinued Operations	(55,012)	(117,900)
Net cash used in investing activities	(415,698)	(465,348)
Financing activities:
Issuance of short-term borrowings	461,400	0
Repayment of short-term borrowings	(193,500)	0
Issuance of long-term debt	411,900	220,429
Repayment of long-term debt	(434,994)	0
Debt issuance costs	(1,844)	(334)
Net proceeds from issuance of common stock	0	(149)
Dividends paid	(135,861)	(132,687)
Repurchase of common stock	(4,811)	(7,399)
Tax withholding on stock-based compensation	(3,040)	(4,904)
Net Cash Provided by (Used in) Financing Activities, Continuing Operations	99,250	74,956
Cash Provided by (Used in) Financing Activities, Discontinued Operations	93,509	125,918
Net Cash Provided by (Used in) Financing Activities, Total	192,759	200,874
Increase (decrease) in cash and cash equivalents	(48,025)	20,459
Cash and cash equivalents -- beginning of year	80,518	54,161
Cash and cash equivalents -- end of period	$ 32,493	$ 74,620

Basis of presentation

Basis of presentation	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2022 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses. The Company announced strategic initiatives in 2022 as part of the Company's continuous review of its business. On May 31, 2023, the Company completed the separation of Knife River, formerly the construction materials and contracting segment, which resulted in two independent, publicly traded companies, MDU Resources Group, Inc. and Knife River. The Company's board of directors approved the distribution of approximately 90 percent of the issued and outstanding shares of Knife River to the Company's stockholders. Stockholders of the Company received one share of Knife River common stock for every four shares of the Company's common stock held on May 22, 2023, the record date for the distribution. The Company retained approximately 10 percent or 5.7 million shares of Knife River common stock immediately following the separation with the intent to dispose of such shares within twelve months after the separation. The separation of Knife River was a tax-free spinoff transaction to the Company’s stockholders for U.S. federal income tax purposes. The Company's consolidated financial statements and accompanying notes for the current and prior periods have been restated to present the results of operations and the assets and liabilities of Knife River as discontinued operations, other than certain corporate overhead costs of the Company historically allocated to Knife River, which are reflected in Other. Also included in discontinued operations in the Consolidated Statements of Income are the supporting activities of Fidelity and certain interest expense related to financing activity associated with the Knife River separation. Unless otherwise indicated, the amounts presented in the accompanying notes to the consolidated financial statements relate to the Company's continuing operations. For more information on discontinued operations, see Note 3. On November 2, 2023, the Company announced its intent to pursue a tax-free spinoff of its wholly owned construction services business, MDU Construction Services. The Company's board of directors believes a tax-free spinoff of the construction services business supports the Company's goal of enhancing value for stockholders by becoming a pure-play regulated energy delivery company.

New accounting standards

New accounting standards	9 Months Ended
	Sep. 30, 2023
Accounting Standards Update and Change in Accounting Principle [Abstract]
New accounting standards	New accounting standards The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its Consolidated Financial Statements and/or disclosures: Standard Description Effective date Impact on financial statements/disclosures Recently adopted accounting standards ASU 2020-04 - Reference Rate Reform In March 2020, the FASB issued optional guidance to ease the facilitation of the effects of reference rate reform on financial reporting. The guidance applies to certain contract modifications, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. Beginning January 1, 2022, LIBOR or other discontinued reference rates cannot be applied to new contracts. New contracts will incorporate a new reference rate, which includes SOFR. LIBOR or other discontinued reference rates cannot be applied to contract modifications or hedging relationships entered into or evaluated after December 31, 2022. Existing contracts referencing LIBOR or other reference rates expected to be discontinued must have identified a replacement rate by June 30, 2023. Effective as of March 12, 2020 through December 31, 2022 For more information, see ASU 2022-06 - Reference Rate Reform: Deferral of Sunset Date below. ASU 2022-06 - Reference Rate Reform: Deferral of Sunset Date In December 2022, the FASB included a sunset provision within ASC 848 based on expectations of when LIBOR would cease being published. At the time ASU 2020-04 was issued, the UK Financial Conduct Authority had established its intent to cease overnight tenors of LIBOR after December 31, 2021. In March 2021, the UK Financial Conduct Authority announced that the intended cessation date of the overnight tenors of LIBOR would be June 30, 2023 which is beyond the current sunset date of ASC 848. The amendments in this Update defer the sunset date of ASC 848 from December 31, 2022 to December 31, 2024, after which entities will no longer be permitted to apply the relief in ASC 848. December 31, 2024 The Company has updated its credit agreements to include language regarding the successor or alternate rate to LIBOR. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures.

Discontinued Operations and Dis

Discontinued Operations and Disposal Groups	9 Months Ended
	Sep. 30, 2023
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure	Discontinued operations On May 31, 2023, the Company completed the previously announced separation of Knife River, its former construction materials and contracting segment, into a new publicly traded company. The separation was achieved through the Company's pro-rata distribution of approximately 90 percent of the outstanding shares of Knife River to the Company's common stockholders. To effect the separation, the Company distributed to its stockholders one share of Knife River common stock for every four shares of the Company's common stock held on May 22, 2023, the record date for the distribution, with the Company retaining approximately 10 percent, or 5.7 million shares of Knife River common stock immediately following the separation. The Company intends to dispose of the retained shares within twelve months after the separation. As a result of the separation, the historical assets and liabilities for Knife River have been classified as assets and liabilities of discontinued operations and the historical results of operations are shown in Discontinued operations, net of tax, other than allocated general corporate overhead costs of the Company, which do not meet the criteria for income (loss) from discontinued operations. The Company’s consolidated financial statements and accompanying notes for prior periods have been restated. For the comparative periods, Knife River's operations are only reflected through May 2023, whereas 2022 includes the full three and nine months from Knife River's operations. On April 25, 2023, Knife River issued $425 million of senior notes, pursuant to an indenture, due 2031 to qualified institutional buyers. Knife River also entered into a new credit agreement which provided a revolving credit facility in an initial amount of up to $350 million and a senior secured term loan facility in an amount up to $275 million. The net proceeds from the notes offering, revolving credit facility and the term loan were used to repay $825 million of Knife River's intercompany obligations owed to Centennial. Centennial used the entirety of these proceeds from Knife River to repay a portion of its existing third-party indebtedness. As a result of the separation, the Company retained legal ownership of 538,921 shares of the Company's common stock that were historically owned by a subsidiary of Knife River and recorded in Treasury stock at cost. Following the separation, the 538,921 treasury shares were retired. The Company will provide to Knife River and Knife River will provide to the Company transition services in accordance with the TSA entered into on May 31, 2023. For the three and nine months ended September 30, 2023, the Company received $1.3 million and $1.9 million; and paid $407,000 and $684,000, respectively, for these related activities. The majority of the transition services are expected to be provided for a period of one year, however, no longer than two years after the separation. Separation related costs of $1.0 million and $47.1 million, net of tax, were incurred during the three and nine months ended September 30, 2023, respectively. Separation costs incurred are presented in income (loss) from discontinued operations in the Consolidated Statements of Income. These charges primarily relate to transaction and third-party support costs, one-time business separation fees and related tax charges. The Company had no assets or liabilities related to the discontinued operations of Knife River on its balance sheet as of September 30, 2023. The carrying amounts of the major classes of assets and liabilities of discontinued operations included in the Company’s Consolidated Balance Sheets were as follows: September 30, 2022 December 31, 2022 Assets (In Thousands) Current assets: Cash and cash equivalents $ 16,761 $ 10,090 Receivables, net 447,882 241,302 Inventories 308,829 323,277 Prepayments and other current assets 16,949 17,848 Total current assets of discontinued operations 790,421 592,517 Noncurrent assets: Net property, plant and equipment 1,275,649 1,315,213 Goodwill 274,302 274,540 Other intangible assets, net 14,097 13,430 Investments 32,326 33,086 Operating lease right-of-use assets 43,431 45,872 Other 3,233 3,610 Total noncurrent assets of discontinued operations 1,643,038 1,685,751 Total assets of discontinued operations $ 2,433,459 $ 2,278,268 Liabilities Current liabilities: Short-term borrowings $ 100,000 $ 208,000 Long-term debt due within one year 128,133 30,211 Accounts payable 178,320 131,608 Taxes payable 12,874 8,502 Accrued compensation 27,383 29,192 Operating lease liabilities due within one year 13,000 13,210 Other accrued liabilities 73,852 76,200 Total current liabilities of discontinued operations 533,562 496,923 Noncurrent liabilities: Long-term debt 581,588 445,546 Deferred income taxes 175,529 175,804 Asset retirement obligations 27,964 33,015 Operating lease liabilities 30,431 32,663 Other 87,159 78,876 Total noncurrent liabilities of discontinued operations 902,671 765,904 Total liabilities of discontinued operations $ 1,436,233 $ 1,262,827 The reconciliation of the major classes of income and expense constituting pretax income (loss) from discontinued operations to the after-tax income (loss) from discontinued operations on the Consolidated Statements of Income were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Operating revenues $ — $ 974,774 $ 735,259 $ 1,995,500 Operating expenses 1,447 825,874 769,407 1,828,602 Operating income (loss) (1,447) 148,900 (34,148) 166,898 Other income (expense) — (1,005) 2,382 (4,399) Interest expense (66) 11,173 37,545 26,466 Income (loss) from discontinued operations before income taxes (1,381) 136,722 (69,311) 136,033 Income taxes 1,908 31,120 (3,559) 32,529 Discontinued operations, net of tax $ (3,289) $ 105,602 $ (65,752) $ 103,504

Seasonality of operations

Seasonality of operations	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Seasonality of operations	Seasonality of operationsSome of the Company's operations are highly seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Accordingly, the interim results for particular businesses, and for the Company as a whole, may not be indicative of results for the full fiscal year.

Receivables and allowance for e

Receivables and allowance for expected credit losses	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Receivables and allowance for expected credit loss	Receivables and allowance for expected credit losses Receivables consist primarily of trade receivables from the sale of goods and services, which are recorded at the invoiced amount, and contract assets, net of expected credit losses. For more information on contract assets, see Note 9. The Company's trade receivables are all due in 12 months or less. The total balance of receivables past due 90 days or more was $51.1 million, $30.8 million and $34.3 million at September 30, 2023 and 2022, and December 31, 2022, respectively. The Company's expected credit losses are determined through a review using historical credit loss experience; changes in asset specific characteristics; current conditions; and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. The Company develops and documents its methodology to determine its allowance for expected credit losses at each of its reportable business segments. Risk characteristics used by the business segments may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible. Management has reviewed the balance reserved through the allowance for expected credit losses and believes it is reasonable. Details of the Company's expected credit losses were as follows: Electric Natural gas Pipeline Construction Total (In thousands) At December 31, 2022 $ 375 $ 1,615 $ 2 $ 2,162 $ 4,154 Current expected credit loss provision 615 2,324 — 826 3,765 Less write-offs charged against the allowance 667 1,225 — 51 1,943 Credit loss recoveries collected 145 229 — 1 375 At March 31, 2023 $ 468 $ 2,943 $ 2 $ 2,938 $ 6,351 Current expected credit loss provision 182 90 — 1,825 2,097 Less write-offs charged against the allowance 316 1,454 — 103 1,873 Credit loss recoveries collected 79 161 — 58 298 At June 30, 2023 $ 413 $ 1,740 $ 2 $ 4,718 $ 6,873 Current expected credit loss provision 513 1,661 — 1,733 3,907 Less write-offs charged against the allowance 572 2,758 — 27 3,357 Credit loss recoveries collected 75 233 — — 308 At September 30, 2023 $ 429 $ 876 $ 2 $ 6,424 $ 7,731 Electric Natural gas Pipeline Construction Total (In thousands) At December 31, 2021 $ 269 $ 1,506 $ 2 $ 2,533 $ 4,310 Current expected credit loss provision 565 1,369 — 54 1,988 Less write-offs charged against the allowance 597 932 — 71 1,600 Credit loss recoveries collected 124 180 — 28 332 At March 31, 2022 $ 361 $ 2,123 $ 2 $ 2,544 $ 5,030 Current expected credit loss provision 113 92 — 292 497 Less write-offs charged against the allowance 234 939 — 104 1,277 Credit loss recoveries collected 108 177 — — 285 At June 30, 2022 $ 348 $ 1,453 $ 2 $ 2,732 $ 4,535 Current expected credit loss provision 300 881 — (111) 1,070 Less write-offs charged against the allowance 399 1,822 — 152 2,373 Credit loss recoveries collected 85 169 — 40 294 At September 30, 2022 $ 334 $ 681 $ 2 $ 2,509 $ 3,526

Inventories and natural gas in

Inventories and natural gas in storage	9 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories and natural gas in storage	Inventories and natural gas in storage Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method. The portion of the cost of natural gas in storage expected to be used within 12 months was included in inventories. Inventories on the Consolidated Balance Sheets were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Merchandise for resale 36,815 26,538 27,910 Natural gas in storage (current) 29,821 48,532 22,533 Materials and supplies $ 7,824 $ 9,917 $ 6,846 Other 5,775 4,827 6,959 Total $ 80,235 $ 89,814 $ 64,248

Earnings per share

Earnings per share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings per share	Earnings per share Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury. As a result of the separation, the Company retained legal ownership of 538,921 shares of the Company's common stock that were historically owned by a subsidiary of Knife River and recorded in Treasury stock at cost. Following the separation, the 538,921 treasury shares were retired. The 538,921 shares of treasury stock did not have an impact on weighted-average shares outstanding, as they were not outstanding prior to being retired. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 203,638 203,351 203,633 203,351 Effect of dilutive performance share awards and restricted stock units 248 293 258 56 Weighted average common shares outstanding - diluted 203,886 203,644 203,891 203,407 Earnings per share - basic: Income from continuing operations $ .38 $ .21 $ 1.52 $ .72 Discontinued operations, net of tax (.01) .52 (.32) .51 Earnings per share - basic $ .37 $ .73 $ 1.20 $ 1.23 Earnings per share - diluted: Income from continuing operations $ .38 $ .21 $ 1.52 $ .72 Discontinued operations, net of tax (.01) .52 (.32) .51 Earnings per share - diluted $ .37 $ .73 $ 1.20 $ 1.23 Shares excluded from the calculation of diluted earnings per share — — — 77 Dividends declared per common share $ .1250 $ .2175 $ .5700 $ .6525

Accumulated other comprehensive

Accumulated other comprehensive loss	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Accumulated other comprehensive loss	Accumulated other comprehensive loss The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2022 $ (125) $ (29,900) $ (558) $ (30,583) Other comprehensive income before reclassifications — — 70 70 Amounts reclassified from accumulated other comprehensive loss 34 100 13 147 Net current-period other comprehensive income 34 100 83 217 At March 31, 2023 $ (91) $ (29,800) $ (475) $ (30,366) Other comprehensive income before reclassifications — — (84) (84) Amounts reclassified from accumulated other comprehensive loss 47 387 13 447 Net current-period other comprehensive income (loss) 47 387 (71) 363 Amounts reclassified related to the separation of Knife River 44 12,262 — 12,306 At June 30, 2023 $ — $ (17,151) $ (546) $ (17,697) Other comprehensive loss before reclassifications — — (66) (66) Amounts reclassified from accumulated other comprehensive loss — (6) 10 4 Net current-period other comprehensive income (loss) — (6) (56) (62) At September 30, 2023 $ — $ (17,157) $ (602) $ (17,759) Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2021 $ (538) $ (40,461) $ (5) $ (41,004) Other comprehensive loss before reclassifications — — (320) (320) Amounts reclassified from accumulated other comprehensive loss 112 445 32 589 Net current-period other comprehensive income (loss) 112 445 (288) 269 At March 31, 2022 $ (426) $ (40,016) $ (293) $ (40,735) Other comprehensive loss before reclassifications — — (128) (128) Amounts reclassified to accumulated other comprehensive loss from a regulatory asset — (3,265) — (3,265) Amounts reclassified from accumulated other comprehensive loss 111 461 25 597 Net current-period other comprehensive income (loss) 111 (2,804) (103) (2,796) At June 30, 2022 $ (315) $ (42,820) $ (396) $ (43,531) Other comprehensive loss before reclassifications — — (329) (329) Amounts reclassified from accumulated other comprehensive loss 111 461 42 614 Net current-period other comprehensive income (loss) 111 461 (287) 285 At September 30, 2022 $ (204) $ (42,359) $ (683) $ (43,246) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated September 30, September 30, 2023 2022 2023 2022 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ — $ (148) $ (98) $ (443) Interest expense — 37 17 109 Income taxes — (111) (81) (334) Amortization of postretirement liability losses included in net periodic benefit credit (92) (609) (744) (1,827) Other income 98 148 263 460 Income taxes 6 (461) (481) (1,367) Reclassification adjustment on available-for-sale investments included in net income (13) (54) (45) (126) Other income 3 12 9 27 Income taxes (10) (42) (36) (99) Total reclassifications $ (4) $ (614) $ (598) $ (1,800)

Revenue from contracts with cus

Revenue from contracts with customers	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue from contracts with customers Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. The Company recognizes revenue from the sale of emissions allowances allocated under the environmental programs in certain states. The Company has the right to payment when the allowances are sold at auction. Revenue is recognized on a point in time basis within the quarter that the auction is held. The revenues associated with the sale of these allowances are deferred as a component of the respective jurisdiction’s regulatory asset or liability for environmental compliance. For more information on the Company’s regulatory assets and liabilities, see Note 12. Changes in cost estimates on certain contracts may result in the issuance of change orders, which can be approved or unapproved by the customer, or the assertion of contract claims. The Company recognizes amounts associated with change orders and claims as revenue if it is probable that the contract price will be adjusted and the amount of any such adjustment can be reasonably estimated. Change orders and claims are negotiated in the normal course of business and represent management’s estimates of additional contract revenues that have been earned and are probable of collection. The Company received notification from a customer on a large project with a contract that was billed on a time and materials basis with no stated maximum price, that it is withholding payment of approximately $30.0 million on remaining outstanding billings, including retention. The Company believes it has substantial defenses against these claims based upon the terms of the contract and the Company's belief that it has performed under the terms of the contract. The Company believes collection of the remaining outstanding billings, including retention is probable and, as a result, the Company has recognized the revenue from this project in its results. However, there is uncertainty surrounding this matter, including the potential long-term nature of dispute resolution, the Company filing a lien on the property and the broad range of possible consideration amounts as a result of negotiations and potential litigation to resolve the dispute. Disaggregation In the following tables, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 18. Three Months Ended September 30, 2023 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 34,303 $ 68,733 $ — $ — $ — $ 103,036 Commercial utility sales 49,754 40,360 — — — 90,114 Industrial utility sales 10,747 7,272 — — — 18,019 Other utility sales 1,865 — — — — 1,865 Natural gas transportation — 13,050 35,338 — — 48,388 Natural gas storage — — 4,808 — — 4,808 Electrical & mechanical specialty contracting — — — 514,378 — 514,378 Transmission & distribution specialty contracting — — — 192,056 — 192,056 Other 14,701 3,881 3,916 (89) 1,689 24,098 Intersegment eliminations (27) (69) (3,701) — (1,689) (5,486) Revenues from contracts with customers 111,343 133,227 40,361 706,345 — 991,276 Revenues out of scope (3,254) 1,669 43 11,061 — 9,519 Total external operating revenues $ 108,089 $ 134,896 $ 40,404 $ 717,406 $ — $ 1,000,795 Three Months Ended September 30, 2022 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 36,981 $ 64,074 $ — $ — $ — $ 101,055 Commercial utility sales 38,785 43,734 — — — 82,519 Industrial utility sales 10,838 7,209 — — — 18,047 Other utility sales 2,002 — — — — 2,002 Natural gas transportation — 11,910 32,144 — — 44,054 Natural gas storage — — 3,595 — — 3,595 Electrical & mechanical specialty contracting — — — 543,717 — 543,717 Transmission & distribution specialty contracting — — — 181,550 — 181,550 Other 10,758 3,495 3,814 200 1,472 19,739 Intersegment eliminations (34) (69) (3,581) (2,037) (1,472) (7,193) Revenues from contracts with customers 99,330 130,353 35,972 723,430 — 989,085 Revenues out of scope (47) 1,792 86 11,571 — 13,402 Total external operating revenues $ 99,283 $ 132,145 $ 36,058 $ 735,001 $ — $ 1,002,487 Nine Months Ended September 30, 2023 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 102,953 $ 517,351 $ — $ — $ — $ 620,304 Commercial utility sales 124,363 316,483 — — — 440,846 Industrial utility sales 31,880 33,293 — — — 65,173 Other utility sales 5,349 — — — — 5,349 Natural gas transportation — 38,225 104,716 — — 142,941 Natural gas storage — — 12,427 — — 12,427 Electrical & mechanical specialty contracting — — — 1,672,948 — 1,672,948 Transmission & distribution specialty contracting — — — 511,563 — 511,563 Other 38,111 11,874 9,713 121 6,412 66,231 Intersegment eliminations (82) (208) (37,889) — (6,412) (44,591) Revenues from contracts with customers 302,574 917,018 88,967 2,184,632 — 3,493,191 Revenues out of scope (7,799) 2,469 119 34,040 — 28,829 Total external operating revenues $ 294,775 $ 919,487 $ 89,086 $ 2,218,672 $ — $ 3,522,020 Nine Months Ended September 30, 2022 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 103,648 $ 439,639 $ — $ — $ — $ 543,287 Commercial utility sales 108,400 279,697 — — — 388,097 Industrial utility sales 32,067 29,242 — — — 61,309 Other utility sales 5,632 — — — — 5,632 Natural gas transportation — 35,747 95,685 — — 131,432 Natural gas storage — — 10,210 — — 10,210 Electrical & mechanical specialty contracting — — — 1,443,758 — 1,443,758 Transmission & distribution specialty contracting — — — 496,190 — 496,190 Other 33,727 9,854 8,201 357 4,368 56,507 Intersegment eliminations (102) (206) (37,309) (4,391) (4,368) (46,376) Revenues from contracts with customers 283,372 793,973 76,787 1,935,914 — 3,090,046 Revenues out of scope (4,854) (831) 210 34,780 — 29,305 Total external operating revenues $ 278,518 $ 793,142 $ 76,997 $ 1,970,694 $ — $ 3,119,351 Contract balances The timing of revenue recognition may differ from the timing of invoicing to customers. The timing of invoicing to customers does not necessarily correlate with the timing of revenues being recognized under the cost-to-cost method of accounting. Contracts from construction work are billed as work progresses in accordance with agreed upon contractual terms. Generally, billing to the customer occurs contemporaneous to revenue recognition. A variance in timing of the billings may result in a contract asset or a contract liability. A contract asset occurs when revenues are recognized under the cost-to-cost measure of progress, which exceeds amounts billed on uncompleted contracts. Such amounts will be billed as standard contract terms allow, usually based on various measures of performance or achievement. A contract liability occurs when there are billings in excess of revenues recognized under the cost-to-cost measure of progress on uncompleted contracts. Contract liabilities decrease as revenue is recognized from the satisfaction of the related performance obligation. The changes in contract assets and liabilities were as follows: September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 199,370 $ 154,144 $ 45,226 Receivables, net Contract liabilities - current (183,705) (168,361) (15,344) Accounts payable Contract liabilities - noncurrent (435) (6) (429) Noncurrent liabilities - other Net contract assets (liabilities) $ 15,230 $ (14,223) $ 29,453 The Company recognized $6.3 million and $164.3 million in revenue for the three and nine months ended September 30, 2023, respectively, which was previously included in contract liabilities at December 31, 2022. The Company recognized $8.2 million and $118.7 million in revenue for the three and nine months ended September 30, 2022, respectively, which was previously included in contract liabilities at December 31, 2021. The Company recognized a net increase in revenues of $20.2 million and $41.7 million for the three and nine months ended September 30, 2023, respectively, from performance obligations satisfied in prior periods. The Company recognized a net increase in revenues of $9.6 million and $43.7 million for the three and nine months ended September 30, 2022, respectively, from performance obligations satisfied in prior periods. Remaining performance obligations The remaining performance obligations, also referred to as backlog, at the construction services segment includes unrecognized revenues that the Company reasonably expects to be realized. These unrecognized revenues can include: projects that have a written award, a letter of intent, a notice to proceed, an agreed upon work order to perform work on mutually accepted terms and conditions and change orders or claims to the extent management believes additional contract revenues will be earned and are deemed probable of collection. Excluded from remaining performance obligations are potential orders under master service agreements. The majority of the Company's contracting services contracts have an original duration of less than two years. The remaining performance obligations at the pipeline segment include firm transportation and storage contracts with fixed pricing and fixed volumes. The Company has applied the practical expedient, which does not require additional disclosures for contracts with an original duration of less than 12 months, to certain firm transportation and non-regulated contracts. The Company's firm transportation and firm storage contracts included in the remaining performance obligations have weighted average remaining durations of approximately less than five years and two years, respectively. At September 30, 2023, the Company's remaining performance obligations were $2.5 billion. The Company expects to recognize the following revenue amounts in future periods related to these remaining performance obligations: $1.6 billion within the next 12 months or less; $371.0 million within the next 13 to 24 months; and $519.5 million in 25 months or more.

Leases

Leases	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Lessee, Operating Leases	Leases The Company's leases primarily include operating leases for equipment, buildings, easements and vehicles. The Company leases certain equipment to third parties through its utility and construction services segments, which are considered short-term operating leases with terms of less than 12 months. The Company recognized revenue from operating leases of $11.2 million and $34.5 million for the three and nine months ended September 30, 2023, respectively. The Company recognized revenue from operating leases of $11.7 million and $35.1 million for the three and nine months ended September 30, 2022, respectively. At September 30, 2023, the Company had $9.1 million of lease receivables with a majority due within 12 months.

Goodwill and other intangible a

Goodwill and other intangible assets	9 Months Ended
	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets	Goodwill and other intangible assets The carrying amount of goodwill, which is related to the natural gas distribution and construction services segments, remained unchanged at $489.0 million at September 30, 2023 and 2022, and December 31, 2022. No impairments of goodwill have been recorded in these periods. Other amortizable intangible assets were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Customer relationships $ 10,450 $ 10,450 $ 10,450 Less accumulated amortization 7,924 5,834 6,356 2,526 4,616 4,094 Noncompete agreements 292 552 552 Less accumulated amortization 292 520 544 — 32 8 Total $ 2,526 $ 4,648 $ 4,102 Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2023, was $522,000 and $1.6 million, respectively. Amortization expense for amortizable intangible assets for the three and nine months ended September 30, 2022, was $565,000 and $1.7 million, respectively. Amortization expense for identifiable intangible assets as of September 30, 2023 is estimated to be as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Amortization expense $ 522 $ 1,888 $ 116 $ — $ — $ —

Regulatory assets and liabiliti

Regulatory assets and liabilities	9 Months Ended
	Sep. 30, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Regulatory assets and liabilities The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery or Refund Period as of September 30, 2023 * September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 107,101 $ 112,079 $ 141,306 Electric fuel and purchased power deferral Up to 1 year 17,775 2,328 2,656 Conservation programs Up to 1 year 14,411 9,363 8,544 Cost recovery mechanisms Up to 1 year 9,461 3,354 4,019 Other Up to 1 year 20,500 21,036 8,567 169,248 148,160 165,092 Noncurrent: Pension and postretirement benefits ** 144,448 137,582 143,349 Cost recovery mechanisms Up to 10 years 68,539 67,094 67,171 Natural gas costs recoverable through rate adjustments Up to 2 years 64,914 462 — Plant costs/asset retirement obligations Over plant lives 43,520 61,941 44,462 Environmental compliance programs - 36,605 — — Manufactured gas plant site remediation - 24,577 25,963 26,624 Plant to be retired - 19,947 24,740 21,525 Taxes recoverable from customers Over plant lives 12,266 12,394 12,330 Long-term debt refinancing costs Up to 37 years 2,747 3,335 3,188 Other Up to 16 years 11,406 10,931 11,010 428,969 344,442 329,659 Total regulatory assets $ 598,217 $ 492,602 $ 494,751 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year 20,445 873 955 Electric fuel and purchased power deferral Up to 1 year — 3,763 4,929 Cost recovery mechanisms Up to 1 year 5,754 2,674 1,977 Conservation programs Up to 1 year 1,976 325 4,126 Taxes refundable to customers Up to 1 year 1,513 4,264 3,937 Refundable fuel and electric costs Up to 1 year 18 1,812 3,253 Other Up to 1 year 15,307 4,888 7,263 45,013 18,599 26,440 Noncurrent: Plant removal and decommissioning costs Over plant lives 220,499 174,481 208,650 Taxes refundable to customers Over plant lives 194,804 205,517 203,222 Environmental compliance programs - 36,126 — — Cost recovery mechanisms Up to 19 years 20,012 12,535 14,025 Accumulated deferred investment tax credit Up to 19 years 14,800 14,665 13,594 Pension and postretirement benefits ** 7,120 19,687 7,376 Other Up to 15 years 1,751 6,327 1,587 495,112 433,212 448,454 Total regulatory liabilities $ 540,125 $ 451,811 $ 474,894 Net regulatory position $ 58,092 $ 40,791 $ 19,857 * Estimated recovery or refund period for amounts currently being recovered or refunded in rates to customers. ** Recovered as expense is incurred or cash contributions are made. At September 30, 2023 and 2022, and December 31, 2022, approximately $211.8 million, $264.4 million and $242.5 million, respectively, of regulatory assets were not earning a rate of return; however, these regulatory assets are expected to be recovered from customers in future rates. These assets are largely comprised of the unfunded portion of pension and postretirement benefits, the estimated future cost of manufactured gas plant site remediation, accelerated depreciation on plant retirement, certain pipeline integrity costs and the costs associated with environmental compliance. The Company is subject to environmental compliance regulations in certain states which require natural gas distribution companies to reduce overall GHG emissions to certain thresholds as established by each applicable state. Compliance with these standards may be achieved through increased energy efficiency and conservation measures, purchased emission allowances and offsets, purchases of community climate investment credits and purchases of low carbon fuels. Emission allowances are allocated by the respective states to the Company at no cost, of which a portion is required to be sold at auction. The Company expects the compliance costs for these regulations and the revenues from the sale of the allocated emissions allowances will be passed through to customers in rates and has, accordingly, deferred the environmental compliance obligation as a regulatory asset and proceeds from the sale of allowances as a regulatory liability. In the last half of 2021 through 2022, the Company experienced high natural gas costs due to increase in demand outpacing the supply along with the impact of global events. Additionally, in December 2022 and January 2023, natural gas prices significantly increased across the Pacific Northwest from multiple price-pressuring events including wide-spread below-normal temperatures and higher natural gas consumption; reduced natural gas flows due to pipeline constraints, including maintenance in West Texas; and historically low regional natural gas storage levels. For a discussion of the Company's most recent cases by jurisdiction, see Note 21. In February 2019, the Company announced the retirement of three aging coal-fired electric generating units. The Company accelerated the depreciation related to these facilities in property, plant and equipment and recorded the difference between the accelerated depreciation, in accordance with GAAP, and the depreciation approved for rate-making purposes as regulatory assets. Requests were filed with the NDPSC and SDPUC, and subsequently approved, to offset the savings associated with the cessation of operations of these units with the amortization of the deferred regulatory assets. The Company ceased operations of Lewis & Clark Station in March 2021 and Units 1 and 2 at Heskett Station in February 2022. The Company subsequently reclassified the costs being recovered for these facilities from plant retirement to cost recovery mechanisms in the previous table and began amortizing the associated plant retirement and closure costs in the jurisdictions where requests were filed. The Company expects to recover the regulatory assets related to the plant retirements in future rates. If, for any reason, the Company's regulated businesses cease to meet the criteria for application of regulatory accounting for all or part of their operations, the regulatory assets and liabilities relating to those portions ceasing to meet such criteria would be written off and included in the statement of income or accumulated other comprehensive loss in the period in which the discontinuance of regulatory accounting occurs.

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The fair value ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The estimated fair values of the Company's assets and liabilities measured on a recurring basis are determined using the market approach. The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of insurance contracts, to satisfy its obligations under its unfunded, nonqualified defined benefit and defined contribution plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $62.7 million, $75.7 million and $78.0 million, at September 30, 2023 and 2022, and December 31, 2022, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized loss on these investments was $1.4 million for the three months ended and an unrealized gain of $3.5 million for the nine months ended September 30, 2023, respectively. The net unrealized loss on these investments was $1.3 million and $12.4 million for the three and nine months ended September 30, 2022, respectively. The change in fair value, which is considered part of the cost of the plan, is classified in other income on the Consolidated Statements of Income. The Company did not elect the fair value option, which records gains and losses in income, for its available-for-sale securities, which include mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as investments on the Consolidated Balance Sheets. Unrealized gains or losses are recorded in accumulated other comprehensive loss. Details of available-for-sale securities were as follows: September 30, 2023 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,386 $ — $ 750 $ 7,636 U.S. Treasury securities 3,307 11 23 3,295 Total $ 11,693 $ 11 $ 773 $ 10,931 September 30, 2022 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,486 $ — $ 783 $ 7,703 U.S. Treasury securities 2,468 — 82 2,386 Total $ 10,954 $ — $ 865 $ 10,089 December 31, 2022 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,928 $ 2 $ 636 $ 8,294 U.S. Treasury securities 2,608 — 72 2,536 Total $ 11,536 $ 2 $ 708 $ 10,830 On May 31, 2023, the Company completed the Knife River separation and retained approximately 10 percent, or 5.7 million shares of Knife River common stock immediately following the separation. The Company did not retain a controlling interest in Knife River and therefore the fair value of its retained shares and subsequent fair value changes are included in assets of and results from continuing operations, respectively. At September 30, 2023, the fair value of the Company’s investment in Knife River common stock of $276.2 million was reflected in Investment in Knife River on the Consolidated Balance Sheets and was remeasured at fair value based on Knife River’s closing stock price on September 30, 2023, with an unrealized gain of $30.2 million and $170.2 million for the three and nine months ended September, 30, 2023, respectively, which is recorded in Unrealized gain on investment in Knife River on the Consolidated Statements of Income. The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at September 30, 2023 (In thousands) Assets: Investment in Knife River 276,213 $ — $ — $ 276,213 Money market funds — 25,818 — 25,818 Insurance contracts* — 62,736 — 62,736 Available-for-sale securities: Mortgage-backed securities — 7,637 — 7,637 U.S. Treasury securities — 3,295 — 3,295 Total assets measured at fair value $ 276,213 $ 99,486 $ — $ 375,699 * The insurance contracts invest approximately 50 percent in fixed-income investments, 19 percent in common stock of large-cap companies, 10 percent in target date investments, 10 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 3 percent in cash equivalents, 1 percent in international investments, and 1 percent in high-yield investments. Fair Value Measurements at September 30, 2022, Using Quoted Prices in Significant Significant Balance at September 30, 2022 (In thousands) Assets: Money market funds $ — $ 4,878 $ — $ 4,878 Insurance contracts* — 75,723 — 75,723 Available-for-sale securities: Mortgage-backed securities — 7,703 — 7,703 U.S. Treasury securities — 2,386 — 2,386 Total assets measured at fair value $ — $ 90,690 $ — $ 90,690 * The insurance contracts invest approximately 65 percent in fixed-income investments, 14 percent in common stock of large-cap companies, 7 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant Significant Balance at December 31, 2022 (In thousands) Assets: Money market funds $ — $ 4,913 $ — $ 4,913 Insurance contracts* — 77,958 — 77,958 Available-for-sale securities: Mortgage-backed securities — 8,294 — 8,294 U.S. Treasury securities — 2,536 — 2,536 Total assets measured at fair value $ — $ 93,701 $ — $ 93,701 * The insurance contracts invest approximately 63 percent in fixed-income investments, 15 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents. The Company's money market funds are valued at the net asset value of shares held at the end of the period, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the Company's mortgage-backed securities and U.S. Treasury securities are based on comparable market transactions, other observable inputs or other sources, including pricing from outside sources. The estimated fair value of the Company's insurance contracts are based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data. Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. The Company applies the provisions of the fair value measurement standard to its nonrecurring, non-financial measurements, including long-lived asset impairments. These assets are not measured at fair value on an ongoing basis but are subject to fair value adjustments only in certain circumstances. The Company reviews the carrying value of its long-lived assets, excluding goodwill, whenever events or changes in circumstances indicate that such carrying amounts may not be recoverable. The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was categorized as Level 2 in the fair value hierarchy and was based on discounted future cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Carrying amount $ 2,341,147 $ 2,278,730 $ 2,365,667 Fair value $ 1,960,926 $ 1,989,362 $ 2,053,396 The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values .

Debt

Debt	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Debt	Debt Due to the Knife River separation, Centennial repaid all of its outstanding debt in the second quarter of 2023, which was funded by the Knife River repayment and the Company entering into various new debt instruments. Refer to Note 3 for additional information related to the repayment of debt associated with the Knife River separation. Certain debt instruments of the Company and its subsidiaries contain restrictive and financial covenants and cross-default provisions. In order to borrow under the debt agreements, the Company and its subsidiaries must be in compliance with the applicable covenants and certain other conditions, all of which the Company and its subsidiaries, as applicable, were in compliance with at September 30, 2023. In the event the Company or its subsidiaries do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. Montana-Dakota's commercial paper program is supported by a revolving credit agreement. While the amount of commercial paper outstanding does not reduce available capacity under the respective revolving credit agreement, Montana-Dakota does not issue commercial paper in an aggregate amount exceeding the available capacity under the credit agreement. The commercial paper and revolving credit agreement borrowings may vary during the period, largely the result of fluctuations in working capital requirements due to the seasonality of certain operations of the Company and its subsidiaries. Short-term debt Cascade On January 20, 2023, Cascade entered into a $150.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of January 19, 2024. The agreement contains customary covenants and provisions, including a covenant of Cascade not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans and investments. Intermountain On January 20, 2023, Intermountain entered into a $125.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of January 19, 2024. In March, April, and May 2023, Intermountain paid down $20.0 million, $30.0 million, and $30.0 million, respectively, of the outstanding balance. The agreement contains customary covenants and provisions, including a covenant of Intermountain not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans and investments. Centennial On March 18, 2022, Centennial entered into a $100.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of March 17, 2023. On March 17, 2023, Centennial amended this agreement to extend the maturity date to September 15, 2023. On May 31, 2023, Centennial repaid the full balance outstanding under the term loan agreement. O n December 19, 2022, Centennial entered into a $135.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of December 18, 2023. On May 31, 2023, Centennial repaid the full balance outstanding under the term loan agreement. MDU Resources Group, Inc. On May 1, 2023, the Company entered into a $75.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of November 1, 2023. On May 31, 2023, the Company repaid the full balance outstanding under the term loan agreement. On May 31, 2023, the Company entered into a $150.0 million revolving credit agreement with a SOFR-based variable interest rate and a maturity date of May 29, 2024. At September 30, 2023, the amount outstanding was $111.4 million. The agreement contains customary covenants and provisions, including a covenant of the Company not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans and investments. Long-term debt Centennial On June 9, 2023, Centennial repaid the full balances outstanding on all its long-term senior note debt, which aggregated $455.0 million. MDU Resources Group, Inc . On May 31, 2023, the Company entered into a $200.0 million revolving credit agreement with a SOFR-based variable interest rate and a maturity date of May 31, 2028. Any borrowings under the revolving credit agreement are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued borrowings. The credit agreement contains customary covenants and provisions, including a covenant of the Company not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans and investments. On May 31, 2023, the Company entered into a $375.0 million term loan agreement with a SOFR-based variable interest rate and a maturity date of May 31, 2025. The term loan agreement contains customary covenants and provisions, including a covenant of the Company not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. The covenants also include certain restrictions on the sale of certain assets, loans and investments. Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2023 September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Senior Notes due on dates ranging from July 15, 2024 to June 15, 2062 4.33 % $ 1,757,000 $ 1,847,000 $ 1,848,500 Term Loan Agreements due on dates ranging from May 31, 2025 to September 3, 2032 6.52 % 381,300 7,000 7,000 Commercial paper supported by revolving credit agreement 5.80 % 97,700 268,272 349,050 Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029 7.32 % 35,000 35,000 35,000 Credit agreements due on dates ranging from October 13, 2027 to November 30, 2027 8.50 % 38,900 125,580 130,000 Other notes due on dates ranging from January 1, 2024 to November 30, 2038 8.41 % 37,884 1,617 1,614 Less unamortized debt issuance costs 6,637 5,295 5,211 Less discount — 444 286 Total long-term debt 2,341,147 2,278,730 2,365,667 Less current maturities 61,319 86,319 47,819 Net long-term debt $ 2,279,828 $ 2,192,411 $ 2,317,848 Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at September 30, 2023, were as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Long-term debt maturities $ 619 $ 158,400 $ 532,700 $ 140,700 $ 59,600 $ 1,455,765

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Tax Disclosure	Income taxes During the three and nine months ended September 30, 2023, Income before income taxes was $91.5 million and $402.0 million respectively, while income tax expense was $13.3 million and $92.3 million, respectively. The effective tax rate was 14.6 percent and 23.0 percent for the three and nine months ended September 30, 2023, respectively. The effective tax rate for the current three and nine month periods differed from the 2023 statutory rate of 24.8 percent primarily due to tax credits and other permanent tax benefits, partially offset by tax expense recorded related to basis differences in the Company's retained Knife River shares. During the three and nine months ended September 30, 2022, Income before income taxes was $46.6 million and $175.2 million respectively, and income tax expense was $4.2 million and $28.4 million, respectively. The effective tax rate was 9.0 percent and 16.2 percent for the three and nine months ended September 30, 2022, respectively. The effective tax rate differed from the 2022 statutory rate of 24.8 percent due to tax credits and other permanent tax benefits.

Cash flow information

Cash flow information	9 Months Ended
	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Cash flow information	Cash flow information Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Interest, net* $ 84,352 $ 55,954 Income taxes paid (refunded), net** $ 40,290 $ (5,499) * AFUDC - borrowed was $7.4 million and $2.4 million for the nine months ended September 30, 2023 and 2022, respectively. ** Income taxes paid, including discontinued operations, were $39.4 million and $17.7 million for the nine months ended September 30, 2023 and 2022, respectively. Noncash investing and financing transactions were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 36,307 $ 30,641 $ 39,158 Property, plant and equipment additions in accounts payable $ 37,598 $ 39,393 $ 35,637 Restricted Cash Restricted cash represents deposits held by the Company’s captive insurance company that is required by state insurance regulations to remain in the captive insurance company as cash. The Company had restricted cash of $24.7 million, $33.8 million and $35.6 million at September 30, 2023 and 2022 and December 31, 2022, respectively.

Business segment data

Business segment data	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Business segment data	Business segment data The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these operating segments is defined based on the reporting and review process used by the Company's chief executive officer. The Company's operations are located within the United States. The electric segment generates, transmits and distributes electricity in Montana, North Dakota, South Dakota and Wyoming. The natural gas distribution segment distributes natural gas in those states, as well as in Idaho, Minnesota, Oregon and Washington. These operations also supply related value-added services. The pipeline segment provides natural gas transportation and underground storage services through a regulated pipeline system primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment also provides non-regulated cathodic protection services. The construction services segment provides a full spectrum of construction services through its electrical and mechanical and transmission and distribution specialty contracting services across the United States. These specialty contracting services are provided to utilities, manufacturing, transportation, commercial, industrial, institutional, renewable and governmental customers. Its electrical and mechanical contracting services include construction and maintenance of electrical and communication wiring and infrastructure, fire suppression systems, and mechanical piping and services. Its transmission and distribution contracting services include construction and maintenance of overhead and underground electrical, gas and communication infrastructure, as well as manufacturing and supplying transmission and distribution line construction equipment and tools. The Other category includes the activities of Centennial Capital, which, through its subsidiary InterSource Insurance Company, insures various types of risks as a captive insurer for certain of the Company's subsidiaries. The function of the captive insurer is to fund the self-insured layers of the insured Company's general liability, automobile liability, pollution liability and other coverages. Centennial Capital also owns certain real and personal property. In addition, the Other category includes certain assets, liabilities and tax adjustments of the holding company primarily associated with corporate functions, as well as costs associated with the announced strategic initiatives. Also included are certain general and administrative costs (reflected in operation and maintenance expense) and interest expense, which were previously allocated to the refining business, Fidelity and Knife River which do not meet the criteria for income (loss) from discontinued operations. Discontinued operations includes Knife River's operations, strategic initiative costs and interest on debt facilities repaid in connection with the Knife River separation. For the comparative periods below, Knife River's operations are only reflected through May 2023, whereas 2022 includes the full three and nine months from Knife River's operations. Discontinued operations also includes the supporting activities of Fidelity other than certain general and administrative costs and interest expense as described above. The information below follows the same accounting policies as described in Note 2 of the Notes to Consolidated Financial Statements in the 2022 Annual Report. Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) External operating revenues: Regulated operations: Electric $ 108,089 $ 99,283 $ 294,775 $ 278,518 Natural gas distribution 134,896 132,145 919,487 793,142 Pipeline 36,549 32,346 79,697 69,347 279,534 263,774 1,293,959 1,141,007 Non-regulated operations: Pipeline 3,855 3,712 9,389 7,650 Construction services 717,406 735,001 2,218,672 1,970,694 Other — — — — 721,261 738,713 2,228,061 1,978,344 Total external operating revenues $ 1,000,795 $ 1,002,487 $ 3,522,020 $ 3,119,351 Intersegment operating revenues: Regulated operations: Electric $ 27 $ 34 $ 82 $ 102 Natural gas distribution 69 69 208 206 Pipeline 3,666 3,508 37,624 36,845 3,762 3,611 37,914 37,153 Non-regulated operations: Pipeline 35 73 265 464 Construction services — 2,037 — 4,391 Other 1,689 1,472 6,412 4,368 1,724 3,582 6,677 9,223 Total intersegment operating revenues $ 5,486 $ 7,193 $ 44,591 $ 46,376 Operating income (loss): Electric $ 28,718 $ 30,395 $ 71,372 $ 53,764 Natural gas distribution (15,258) (16,688) 45,674 38,929 Pipeline 17,767 14,963 44,693 39,448 Construction services 50,091 34,949 139,619 110,588 Other 3,286 (2,617) (16,201) (11,726) Total operating income $ 84,604 $ 61,002 $ 285,157 $ 231,003 Income (loss) from continuing operations: Regulated operations: Electric $ 20,942 $ 21,596 $ 53,887 $ 37,476 Natural gas distribution (17,764) (18,058) 18,007 10,758 Pipeline 11,450 9,381 29,029 25,015 14,628 12,919 100,923 73,249 Non-regulated operations: Pipeline 508 779 337 (179) Construction services 35,975 29,248 105,951 86,596 Other 27,107 (577) 102,515 (12,769) 63,590 29,450 208,803 73,648 Income from continuing operations 78,218 42,369 309,726 146,897 Discontinued operations, net of tax (3,289) 105,602 (65,752) 103,504 Net income $ 74,929 $ 147,971 $ 243,974 $ 250,401 A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Operating revenues reconciliation: Total reportable segment operating revenues $ 1,004,592 $ 1,008,208 $ 3,560,199 $ 3,161,359 Other revenue 1,689 1,472 6,412 4,368 Elimination of intersegment operating revenues (5,486) (7,193) (44,591) (46,376) Total consolidated operating revenues $ 1,000,795 $ 1,002,487 $ 3,522,020 $ 3,119,351

Employee benefit plans

Employee benefit plans	9 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Employee benefit plans	Employee benefit plans Pension and other postretirement plans The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. In connection with the previously discussed separation of Knife River on May 31, 2023, Knife River's pension plan, including the associated assets and liabilities, was transferred to Knife River and therefore is no longer reflected as part of the Company. Also in connection with the separation, a remeasurement of the Company's postretirement plan and the Company's unfunded, non-qualified defined benefit plan were performed and the applicable liabilities from the plans relating to transferring employees were transferred to Knife River. Components of net periodic benefit credit for the Company's pension benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit credit: Interest cost $ 3,380 $ 2,349 $ 10,140 $ 7,047 Expected return on assets (4,299) (4,370) (12,897) (13,112) Amortization of net actuarial loss 773 1,456 2,319 4,370 Net periodic benefit credit $ (146) $ (565) $ (438) $ (1,695) Components of net periodic benefit credit for the Company's other postretirement benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit credit: Service cost $ 131 $ 223 $ 405 $ 669 Interest cost 489 346 1,467 1,038 Expected return on assets (1,334) (1,319) (4,026) (3,957) Amortization of prior service credit (330) (330) (989) (989) Amortization of net actuarial gain (96) (142) (408) (425) Net periodic benefit credit, including amount capitalized (1,140) (1,222) (3,551) (3,664) Less amount capitalized 23 47 76 131 Net periodic benefit credit $ (1,163) $ (1,269) $ (3,627) $ (3,795) The components of net periodic benefit credit, other than the service cost component, are included in other income on the Consolidated Statements of Income. The service cost component is included in operation and maintenance expense on the Consolidated Statements of Income. Nonqualified defined benefit plans In addition to the qualified defined benefit pension plans reflected in the table at the beginning of this note, the Company also has unfunded, nonqualified defined benefit plans for executive officers and certain key management employees. The Company's net periodic benefit cost for these plans was $759,000 and $648,000 for the three months ended September 30, 2023 and 2022, respectively, and $2.3 million and $1.9 million for the nine months ended September 30, 2023 and 2022 respectively. The components of net periodic benefit cost for these plans are included in other income on the Consolidated Statements of Income.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock Based Compensation	Stock-based compensationIn connection with the completed separation of Knife River through the spinoff, the provisions of the existing compensation plans required adjustments to the number and terms of outstanding employee time-vested restricted stock units and performance share awards to preserve the intrinsic value of the awards immediately prior to the separation. The outstanding awards will continue to vest over the original vesting period, which is generally three years from the grant date. However, the performance share awards will no longer be subject to performance-based vesting conditions. The number of performance share awards were first adjusted for performance. The combined performance factors were determined based on the performance of the Company as of December 31, 2022. Outstanding awards at the time of the spinoff were converted into awards of the holder’s employer following separation. The Company recorded $204,000 of incremental compensation expense related to the conversion of the restricted stock units, which is being recognized over the remaining service period of one to three years. There was no incremental compensation expense related to the conversion of the performance share awards.

Regulatory matters

Regulatory matters	9 Months Ended
	Sep. 30, 2023
Regulated Operations [Abstract]
Regulatory Matters	Regulatory matters The Company regularly reviews the need for electric and natural gas rate changes in each of the jurisdictions in which service is provided. The Company files for rate adjustments to seek recovery of operating costs and capital investments, as well as reasonable returns as allowed by regulators. Certain regulatory proceedings and cases may also contain recurring mechanisms that can have an annual true-up. Examples of these recurring mechanisms include: infrastructure riders, transmission trackers, renewable resource cost adjustment riders, as well as weather normalization and decoupling mechanisms. The following paragraphs summarize the Company's significant open regulatory proceedings and cases by jurisdiction including updates to those reported in the 2022 Annual Report and should be read in conjunction with previous filings. The Company is unable to predict the ultimate outcome of these matters, the timing of final decisions of the various regulators and courts, or the effect on the Company's results of operations, financial position or cash flows. MTPSC On November 4, 2022, Montana-Dakota filed an application with the MTPSC for an electric general rate increase of approximately $10.5 million annually or 15.2 percent above current rates, which was revised on March 15, 2023, to $11.5 million annually or 17.0 percent above current rates to reflect the loss of a large industrial customer. The requested increase is primarily to recover investments made since the last rate case, including Heskett Unit 4, increases in operation and maintenance expenses, and increases in property taxes. On January 24, 2023, the MTPSC approved Montana-Dakota's request for an interim increase of approximately $1.7 million or 2.7 percent above current rates, subject to refund, effective February 1, 2023. On June 12, 2023, an all-party settlement agreement was filed reflecting an annual revenue increase of $6.1 million or 9.1 percent overall. The reduction from the original filing includes a return on equity of 9.65 percent and removal of Heskett Unit 4 due to not being in service until the second half of 2023. The MTPSC issued a final order approving the settlement on September 21, 2023, with rates effective October 1, 2023. NDPSC On July 14, 2023, Montana-Dakota filed an application with the NDPSC to request an update to its transmission cost adjustment rider requesting to recover revenues of $2.2 million, which includes a true-up of a prior period adjustment, resulting in a decrease of $10.7 million from current rates. The request is to recover transmission-related expenses and the revenue requirement for transmission facilities not currently recovered through electric service rates. The request also reflects the inclusion of the proposed net benefit of a large customer now taking service under Rate 45, as discussed in Part I, Item 2, which accounted for approximately $7.6 million of the decrease. A revised filing was submitted on August 25, 2023, reducing the request to $1.3 million. The NDPSC approved the transmission cost adjustment on September 27, 2023, with rates effective November 1, 2023. On November 1, 2023, Montana-Dakota filed a request with the NDPSC for a natural gas general rate increase of approximately $11.6 million annually or 7.5 percent above current rates. The requested increase is primarily to recover investments in system upgrades and pipeline replacement projects enhancing the reliability, safety and integrity of the natural gas system, as well as increased costs to operate and maintain that system. The filing also includes a request for interim revenue of $10.1 million, subject to refund, to be effective early January 2024. The NDPSC has up to seven months to issue a final decision on this general rate increase request. This matter is pending before the NDPSC. Montana-Dakota has a renewable resource cost adjustment rate tariff that allows for annual adjustments for recent projected capital costs and related expenses for projects determined to be recoverable under the tariff. On October 31, 2023, Montana-Dakota filed an annual update to its renewable resource cost adjustment requesting to recover a revenue requirement of approximately $21.0 million annually. The update reflects an increase of approximately $5.7 million from the revenues currently included in rates. The request proposes the rates be effective for service rendered on and after February 1, 2024. This matter is pending before the NDPSC. SDPUC On August 15, 2023, Montana-Dakota filed a request with the SDPUC for an electric general rate increase of approximately $3.0 million annually or 17.3 percent above current rates. The requested increase is primarily to recover investments in production, transmission and distribution facilities and the associated depreciation, operation and maintenance expenses and taxes associated with the increased investment. The SDPUC has up to six months to issue a decision on this request. This matter is pending before the SDPUC. On August 15, 2023, Montana-Dakota filed a request with the SDPUC for a natural gas general rate increase of approximately $7.4 million annually or 11.2 percent above current rates. The requested increase is primarily to recover investments and the associated depreciation, operation and maintenance expenses and taxes associated with the increased investment. The SDPUC has up to six months to issue a decision on this request. This matter is pending before the SDPUC. WUTC On June 1, 2023, Cascade filed its annual pipeline cost recovery mechanism requesting an increase in annual revenue of approximately $3.1 million or 0.9 percent, which was revised on October 13, 2023, to $2.4 million or 0.7 percent. The filing was effective November 1, 2023. FERC On January 27, 2023, WBI Energy Transmission filed a general rate case with the FERC for increases in its transportation and storage services rates that also included a Greenhouse Gas Cost Recovery Mechanism for anticipated future costs. In August 2023, the Company reached a rate case settlement agreement with its customers and FERC staff and the agreed-upon rates were placed into effect as of August 1, 2023. The settlement agreement did not include a Greenhouse Gas Cost Recovery Mechanism. On October 17, 2023, the Administrative Law Judge certified the Company's rate case settlement agreement to the FERC for final approval. On August 31, 2023, Montana-Dakota filed an update to its transmission formula rate under the MISO tariff for its multi-value project and network upgrade changes for $15.2 million to be effective January 1, 2024.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries, which may include, but are not limited to, matters involving property damage, personal injury, and environmental, contractual, statutory and regulatory obligations. The Company accrues a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. The Company does not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, the Company discloses the nature of the contingency and, in some circumstances, an estimate of the possible loss. Accruals are based on the best information available, but in certain situations management is unable to estimate an amount or range of a reasonably possible loss including, but not limited to when: (1) the damages are unsubstantiated or indeterminate, (2) the proceedings are in the early stages, (3) numerous parties are involved, or (4) the matter involves novel or unsettled legal theories. At September 30, 2023 and 2022, and December 31, 2022, the Company accrued contingent liabilities, which have not been discounted, of $21.0 million, $33.5 million and $31.9 million, respectively. At September 30, 2023 and 2022, and December 31, 2022, the Company also recorded corresponding insurance receivables of $98,000, $11.9 million and $10.0 million, respectively, and regulatory assets of $20.1 million, $20.5 million and $20.9 million, respectively, related to the accrued liabilities. The accruals are for contingencies resulting from litigation and environmental matters. This includes amounts that have been accrued for matters discussed in Environmental matters within this note. The Company will continue to monitor each matter and adjust accruals as might be warranted based on new information and further developments. Management believes that the outcomes with respect to probable and reasonably possible losses in excess of the amounts accrued, net of insurance recoveries, while uncertain, either cannot be estimated or will not have a material effect upon the Company's financial position, results of operations or cash flows. Unless otherwise required by GAAP, legal costs are expensed as they are incurred. Environmental matters The Company is a party to claims for the cleanup of environmental contamination at certain manufactured gas plant sites. There were no material changes to the Company's environmental matters that were previously reported in the 2022 Annual Report other than the removal of the Portland Harbor Site, which relates to Knife River and any potential associated liability was included in the distribution of Knife River. Guarantees Certain subsidiaries of the Company have outstanding guarantees to third parties that guarantee the performance of other subsidiaries of the Company. These guarantees are related to construction contracts, insurance deductibles and loss limits, and certain other guarantees. At September 30, 2023, the fixed maximum amounts guaranteed under these agreements aggregate $330.8 million. Certain of the guarantees also have no fixed maximum amounts specified. At September 30, 2023, the amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $9.5 million in 2023; $67.4 million in 2024; $251.1 million in 2025; $1.5 million in 2026; $1.0 million in 2027; and $300,000 thereafter. There were no amounts outstanding under the previously mentioned guarantees at September 30, 2023. In the event of default under these guarantee obligations, the subsidiary issuing the guarantee for that particular obligation would be required to make payments under its guarantee. Certain subsidiaries have outstanding letters of credit to third parties related to insurance policies and other agreements, some of which are guaranteed by other subsidiaries of the Company. At September 30, 2023, the fixed maximum amounts guaranteed under these letters of credit aggregated $11.1 million, with the scheduled expiration of the maximum amounts guaranteed under these letters aggregate $8.9 million in 2023 and $2.2 million in 2024. There were no amounts outstanding under the previously mentioned letters of credit at September 30, 2023. In the event of default under these letter of credit obligations, the subsidiary guaranteeing the letter of credit would be obligated for reimbursement of payments made under the letter of credit. In addition, Centennial and MDU Construction Services have issued guarantees to third parties related to the routine purchase of maintenance items, materials and lease obligations for which no fixed maximum amounts have been specified. These guarantees have no scheduled maturity date. In the event a subsidiary of the Company defaults under these obligations, Centennial or MDU Construction Services would be required to make payments under these guarantees. Any amounts outstanding by subsidiaries of the Company were reflected on the Consolidated Balance Sheet at September 30, 2023. In the normal course of business, Centennial has surety bonds related to construction contracts and reclamation obligations of its subsidiaries. In the event a subsidiary of Centennial does not fulfill a bonded obligation, Centennial would be responsible to the surety bond company for completion of the bonded contract or obligation. A large portion of the surety bonds is expected to expire within the next 12 months; however, Centennial will likely continue to enter into surety bonds for its subsidiaries in the future. At September 30, 2023, approximately $330.8 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet. Variable interest entities The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary. Fuel Contract Coyote Station entered into a coal supply agreement with Coyote Creek that provides for the purchase of coal necessary to supply the coal requirements of the Coyote Station for the period May 2016 through December 2040. Coal purchased under the coal supply agreement is reflected in inventories on the Consolidated Balance Sheets and is recovered from customers as a component of electric fuel and purchased power. The coal supply agreement creates a variable interest in Coyote Creek due to the transfer of all operating and economic risk to the Coyote Station owners, as the agreement is structured so that the price of the coal will cover all costs of operations, as well as future reclamation costs. The Coyote Station owners are also providing a guarantee of the value of the assets of Coyote Creek as they would be required to buy the assets at book value should they terminate the contract prior to the end of the contract term and are providing a guarantee of the value of the equity of Coyote Creek in that they are required to buy the entity at the end of the contract term at equity value. Although the Company has determined that Coyote Creek is a VIE, the Company has concluded that it is not the primary beneficiary of Coyote Creek because the authority to direct the activities of the entity is shared by the four unrelated owners of the Coyote Station, with no primary beneficiary existing. As a result, Coyote Creek is not required to be consolidated in the Company's financial statements. At September 30, 2023, the Company's exposure to loss as a result of the Company's involvement with the VIE, based on the Company's ownership percentage, was $28.1 million.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net income	$ 74,929	$ 130,692	$ 38,353	$ 147,971	$ 70,667	$ 31,763	$ 243,974	$ 250,401

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the three months ended September 30, 2023, no director or officer of the Company adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K.
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Basis of presentation (Policies

Basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2022 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses.

New accounting standards (Polic

New accounting standards (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Standards Update and Change in Accounting Principle [Abstract]
New accounting standards	The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its Consolidated Financial Statements and/or disclosures: Standard Description Effective date Impact on financial statements/disclosures Recently adopted accounting standards ASU 2020-04 - Reference Rate Reform In March 2020, the FASB issued optional guidance to ease the facilitation of the effects of reference rate reform on financial reporting. The guidance applies to certain contract modifications, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. Beginning January 1, 2022, LIBOR or other discontinued reference rates cannot be applied to new contracts. New contracts will incorporate a new reference rate, which includes SOFR. LIBOR or other discontinued reference rates cannot be applied to contract modifications or hedging relationships entered into or evaluated after December 31, 2022. Existing contracts referencing LIBOR or other reference rates expected to be discontinued must have identified a replacement rate by June 30, 2023. Effective as of March 12, 2020 through December 31, 2022 For more information, see ASU 2022-06 - Reference Rate Reform: Deferral of Sunset Date below. ASU 2022-06 - Reference Rate Reform: Deferral of Sunset Date In December 2022, the FASB included a sunset provision within ASC 848 based on expectations of when LIBOR would cease being published. At the time ASU 2020-04 was issued, the UK Financial Conduct Authority had established its intent to cease overnight tenors of LIBOR after December 31, 2021. In March 2021, the UK Financial Conduct Authority announced that the intended cessation date of the overnight tenors of LIBOR would be June 30, 2023 which is beyond the current sunset date of ASC 848. The amendments in this Update defer the sunset date of ASC 848 from December 31, 2022 to December 31, 2024, after which entities will no longer be permitted to apply the relief in ASC 848. December 31, 2024 The Company has updated its credit agreements to include language regarding the successor or alternate rate to LIBOR. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures.

Discontinued Operations and D_2

Discontinued Operations and Disposal Groups (Policies)	9 Months Ended
	Sep. 30, 2023
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations, Policy	As a result of the separation, the historical assets and liabilities for Knife River have been classified as assets and liabilities of discontinued operations and the historical results of operations are shown in Discontinued operations, net of tax, other than allocated general corporate overhead costs of the Company, which do not meet the criteria for income (loss) from discontinued operations. The Company’s consolidated financial statements and accompanying notes for prior periods have been restated. For the comparative periods, Knife River's operations are only reflected through May 2023, whereas 2022 includes the full three and nine months from Knife River's operations.

Receivables and allowance for_2

Receivables and allowance for expected credit losses (Policies)	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Accounts receivable and allowance for doubtful accounts	Receivables consist primarily of trade receivables from the sale of goods and services, which are recorded at the invoiced amount, and contract assets, net of expected credit losses. For more information on contract assets, see Note 9. The Company's trade receivables are all due in 12 months or less.
Expected credit loss	The Company's expected credit losses are determined through a review using historical credit loss experience; changes in asset specific characteristics; current conditions; and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. The Company develops and documents its methodology to determine its allowance for expected credit losses at each of its reportable business segments. Risk characteristics used by the business segments may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible.

Inventories and natural gas i_2

Inventories and natural gas in storage (Policies)	9 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories and natural gas in storage	Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method.

Earnings per share (Policies)

Earnings per share (Policies)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings per share	Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury.

Revenue from contracts with c_2

Revenue from contracts with customers (Policies)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes. The Company recognizes revenue from the sale of emissions allowances allocated under the environmental programs in certain states. The Company has the right to payment when the allowances are sold at auction. Revenue is recognized on a point in time basis within the quarter that the auction is held. The revenues associated with the sale of these allowances are deferred as a component of the respective jurisdiction’s regulatory asset or liability for environmental compliance. For more information on the Company’s regulatory assets and liabilities, see Note 12.

Environmental allowances and ob

Environmental allowances and obligations (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Emission Credits or Allowances, Policy	Environmental allowances and obligations The Company's natural gas distribution segment acquires environmental allowances as part of its requirement to comply with environmental regulations in certain states. Allowances are allocated by the respective states to the Company at no cost and additional allowances are required to be purchased as needed based on the requirements in the respective states. The segment records purchased and allocated environmental allowances at weighted average cost under the inventory method of accounting. Environmental allowances are included in noncurrent assets - other on the Consolidated Balance Sheets. Environmental compliance obligations, which are based on GHG emissions, are measured at the carrying value of environmental allowances held plus the estimated value of additional allowances necessary to satisfy the compliance obligation. Environmental compliance obligations are included in noncurrent liabilities - other on the Consolidated Balance Sheets. At September 30, 2023, the Company accrued $36.6 million in compliance obligations. The Company recognizes revenue from the sale of emissions allowances allocated under the environmental programs when the allowances are sold at auction. The revenues associated with the sale of these allowances are deferred as a component of the respective jurisdiction’s regulatory asset or liability for environmental compliance. As environmental allowances are surrendered, the segment reduces the associated environmental compliance assets and liabilities from the Consolidated Balance Sheets. The expenses and revenues associated with the Company’s environmental allowances and obligations are deferred as regulatory assets and liabilities. For more information on the Company’s regulatory assets and liabilities, see Note 12.

Fair value disclosures (Policie

Fair value disclosures (Policies)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair value measurements	The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income.
Investments	The Company did not elect the fair value option, which records gains and losses in income, for its available-for-sale securities, which include mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as investments on the Consolidated Balance Sheets.

Business segment data (Policies

Business segment data (Policies)	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Business segment data	The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these operating segments is defined based on the reporting and review process used by the Company's chief executive officer.

Stock-Based Compensation (Polic

Stock-Based Compensation (Policies)	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Share-Based Payment Arrangement	In connection with the completed separation of Knife River through the spinoff, the provisions of the existing compensation plans required adjustments to the number and terms of outstanding employee time-vested restricted stock units and performance share awards to preserve the intrinsic value of the awards immediately prior to the separation. The outstanding awards will continue to vest over the original vesting period, which is generally three years from the grant date. However, the performance share awards will no longer be subject to performance-based vesting conditions. The number of performance share awards were first adjusted for performance.

Contingencies (Policies)

Contingencies (Policies)	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Contingencies	The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries, which may include, but are not limited to, matters involving property damage, personal injury, and environmental, contractual, statutory and regulatory obligations. The Company accrues a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. The Company does not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, the Company discloses the nature of the contingency and, in some circumstances, an estimate of the possible loss. Accruals are based on the best information available, but in certain situations management is unable to estimate an amount or range of a reasonably possible loss including, but not limited to when: (1) the damages are unsubstantiated or indeterminate, (2) the proceedings are in the early stages, (3) numerous parties are involved, or (4) the matter involves novel or unsettled legal theories.
Variable interest entity	The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary.

Discontinued Operations and D_3

Discontinued Operations and Disposal Groups (Tables)	9 Months Ended
	Sep. 30, 2023
Discontinued Operations and Disposal Groups [Abstract]
Schedule of discontinued operations, including balance sheet and income statement	The carrying amounts of the major classes of assets and liabilities of discontinued operations included in the Company’s Consolidated Balance Sheets were as follows: September 30, 2022 December 31, 2022 Assets (In Thousands) Current assets: Cash and cash equivalents $ 16,761 $ 10,090 Receivables, net 447,882 241,302 Inventories 308,829 323,277 Prepayments and other current assets 16,949 17,848 Total current assets of discontinued operations 790,421 592,517 Noncurrent assets: Net property, plant and equipment 1,275,649 1,315,213 Goodwill 274,302 274,540 Other intangible assets, net 14,097 13,430 Investments 32,326 33,086 Operating lease right-of-use assets 43,431 45,872 Other 3,233 3,610 Total noncurrent assets of discontinued operations 1,643,038 1,685,751 Total assets of discontinued operations $ 2,433,459 $ 2,278,268 Liabilities Current liabilities: Short-term borrowings $ 100,000 $ 208,000 Long-term debt due within one year 128,133 30,211 Accounts payable 178,320 131,608 Taxes payable 12,874 8,502 Accrued compensation 27,383 29,192 Operating lease liabilities due within one year 13,000 13,210 Other accrued liabilities 73,852 76,200 Total current liabilities of discontinued operations 533,562 496,923 Noncurrent liabilities: Long-term debt 581,588 445,546 Deferred income taxes 175,529 175,804 Asset retirement obligations 27,964 33,015 Operating lease liabilities 30,431 32,663 Other 87,159 78,876 Total noncurrent liabilities of discontinued operations 902,671 765,904 Total liabilities of discontinued operations $ 1,436,233 $ 1,262,827 The reconciliation of the major classes of income and expense constituting pretax income (loss) from discontinued operations to the after-tax income (loss) from discontinued operations on the Consolidated Statements of Income were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Operating revenues $ — $ 974,774 $ 735,259 $ 1,995,500 Operating expenses 1,447 825,874 769,407 1,828,602 Operating income (loss) (1,447) 148,900 (34,148) 166,898 Other income (expense) — (1,005) 2,382 (4,399) Interest expense (66) 11,173 37,545 26,466 Income (loss) from discontinued operations before income taxes (1,381) 136,722 (69,311) 136,033 Income taxes 1,908 31,120 (3,559) 32,529 Discontinued operations, net of tax $ (3,289) $ 105,602 $ (65,752) $ 103,504

Receivables and allowance for_3

Receivables and allowance for expected credit losses (Tables)	9 Months Ended
	Sep. 30, 2023
Credit Loss [Abstract]
Accounts Receivable, Allowance for Credit Loss	Details of the Company's expected credit losses were as follows: Electric Natural gas Pipeline Construction Total (In thousands) At December 31, 2022 $ 375 $ 1,615 $ 2 $ 2,162 $ 4,154 Current expected credit loss provision 615 2,324 — 826 3,765 Less write-offs charged against the allowance 667 1,225 — 51 1,943 Credit loss recoveries collected 145 229 — 1 375 At March 31, 2023 $ 468 $ 2,943 $ 2 $ 2,938 $ 6,351 Current expected credit loss provision 182 90 — 1,825 2,097 Less write-offs charged against the allowance 316 1,454 — 103 1,873 Credit loss recoveries collected 79 161 — 58 298 At June 30, 2023 $ 413 $ 1,740 $ 2 $ 4,718 $ 6,873 Current expected credit loss provision 513 1,661 — 1,733 3,907 Less write-offs charged against the allowance 572 2,758 — 27 3,357 Credit loss recoveries collected 75 233 — — 308 At September 30, 2023 $ 429 $ 876 $ 2 $ 6,424 $ 7,731 Electric Natural gas Pipeline Construction Total (In thousands) At December 31, 2021 $ 269 $ 1,506 $ 2 $ 2,533 $ 4,310 Current expected credit loss provision 565 1,369 — 54 1,988 Less write-offs charged against the allowance 597 932 — 71 1,600 Credit loss recoveries collected 124 180 — 28 332 At March 31, 2022 $ 361 $ 2,123 $ 2 $ 2,544 $ 5,030 Current expected credit loss provision 113 92 — 292 497 Less write-offs charged against the allowance 234 939 — 104 1,277 Credit loss recoveries collected 108 177 — — 285 At June 30, 2022 $ 348 $ 1,453 $ 2 $ 2,732 $ 4,535 Current expected credit loss provision 300 881 — (111) 1,070 Less write-offs charged against the allowance 399 1,822 — 152 2,373 Credit loss recoveries collected 85 169 — 40 294 At September 30, 2022 $ 334 $ 681 $ 2 $ 2,509 $ 3,526

Inventories and natural gas i_3

Inventories and natural gas in storage (Tables)	9 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories	Inventories on the Consolidated Balance Sheets were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Merchandise for resale 36,815 26,538 27,910 Natural gas in storage (current) 29,821 48,532 22,533 Materials and supplies $ 7,824 $ 9,917 $ 6,846 Other 5,775 4,827 6,959 Total $ 80,235 $ 89,814 $ 64,248

Earnings per share (Tables)

Earnings per share (Tables)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Weighted average common shares outstanding	A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 203,638 203,351 203,633 203,351 Effect of dilutive performance share awards and restricted stock units 248 293 258 56 Weighted average common shares outstanding - diluted 203,886 203,644 203,891 203,407 Earnings per share - basic: Income from continuing operations $ .38 $ .21 $ 1.52 $ .72 Discontinued operations, net of tax (.01) .52 (.32) .51 Earnings per share - basic $ .37 $ .73 $ 1.20 $ 1.23 Earnings per share - diluted: Income from continuing operations $ .38 $ .21 $ 1.52 $ .72 Discontinued operations, net of tax (.01) .52 (.32) .51 Earnings per share - diluted $ .37 $ .73 $ 1.20 $ 1.23 Shares excluded from the calculation of diluted earnings per share — — — 77 Dividends declared per common share $ .1250 $ .2175 $ .5700 $ .6525

Accumulated other comprehensi_2

Accumulated other comprehensive loss (Tables)	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Accumulated comprehensive loss	Accumulated other comprehensive loss The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2022 $ (125) $ (29,900) $ (558) $ (30,583) Other comprehensive income before reclassifications — — 70 70 Amounts reclassified from accumulated other comprehensive loss 34 100 13 147 Net current-period other comprehensive income 34 100 83 217 At March 31, 2023 $ (91) $ (29,800) $ (475) $ (30,366) Other comprehensive income before reclassifications — — (84) (84) Amounts reclassified from accumulated other comprehensive loss 47 387 13 447 Net current-period other comprehensive income (loss) 47 387 (71) 363 Amounts reclassified related to the separation of Knife River 44 12,262 — 12,306 At June 30, 2023 $ — $ (17,151) $ (546) $ (17,697) Other comprehensive loss before reclassifications — — (66) (66) Amounts reclassified from accumulated other comprehensive loss — (6) 10 4 Net current-period other comprehensive income (loss) — (6) (56) (62) At September 30, 2023 $ — $ (17,157) $ (602) $ (17,759) Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2021 $ (538) $ (40,461) $ (5) $ (41,004) Other comprehensive loss before reclassifications — — (320) (320) Amounts reclassified from accumulated other comprehensive loss 112 445 32 589 Net current-period other comprehensive income (loss) 112 445 (288) 269 At March 31, 2022 $ (426) $ (40,016) $ (293) $ (40,735) Other comprehensive loss before reclassifications — — (128) (128) Amounts reclassified to accumulated other comprehensive loss from a regulatory asset — (3,265) — (3,265) Amounts reclassified from accumulated other comprehensive loss 111 461 25 597 Net current-period other comprehensive income (loss) 111 (2,804) (103) (2,796) At June 30, 2022 $ (315) $ (42,820) $ (396) $ (43,531) Other comprehensive loss before reclassifications — — (329) (329) Amounts reclassified from accumulated other comprehensive loss 111 461 42 614 Net current-period other comprehensive income (loss) 111 461 (287) 285 At September 30, 2022 $ (204) $ (42,359) $ (683) $ (43,246) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated September 30, September 30, 2023 2022 2023 2022 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ — $ (148) $ (98) $ (443) Interest expense — 37 17 109 Income taxes — (111) (81) (334) Amortization of postretirement liability losses included in net periodic benefit credit (92) (609) (744) (1,827) Other income 98 148 263 460 Income taxes 6 (461) (481) (1,367) Reclassification adjustment on available-for-sale investments included in net income (13) (54) (45) (126) Other income 3 12 9 27 Income taxes (10) (42) (36) (99) Total reclassifications $ (4) $ (614) $ (598) $ (1,800)
Reclassification out of accumulated other comprehensive loss	The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows: Three Months Ended Nine Months Ended Location on Consolidated September 30, September 30, 2023 2022 2023 2022 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ — $ (148) $ (98) $ (443) Interest expense — 37 17 109 Income taxes — (111) (81) (334) Amortization of postretirement liability losses included in net periodic benefit credit (92) (609) (744) (1,827) Other income 98 148 263 460 Income taxes 6 (461) (481) (1,367) Reclassification adjustment on available-for-sale investments included in net income (13) (54) (45) (126) Other income 3 12 9 27 Income taxes (10) (42) (36) (99) Total reclassifications $ (4) $ (614) $ (598) $ (1,800)

Revenue from contracts with c_3

Revenue from contracts with customers (Tables)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	In the following tables, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 18. Three Months Ended September 30, 2023 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 34,303 $ 68,733 $ — $ — $ — $ 103,036 Commercial utility sales 49,754 40,360 — — — 90,114 Industrial utility sales 10,747 7,272 — — — 18,019 Other utility sales 1,865 — — — — 1,865 Natural gas transportation — 13,050 35,338 — — 48,388 Natural gas storage — — 4,808 — — 4,808 Electrical & mechanical specialty contracting — — — 514,378 — 514,378 Transmission & distribution specialty contracting — — — 192,056 — 192,056 Other 14,701 3,881 3,916 (89) 1,689 24,098 Intersegment eliminations (27) (69) (3,701) — (1,689) (5,486) Revenues from contracts with customers 111,343 133,227 40,361 706,345 — 991,276 Revenues out of scope (3,254) 1,669 43 11,061 — 9,519 Total external operating revenues $ 108,089 $ 134,896 $ 40,404 $ 717,406 $ — $ 1,000,795 Three Months Ended September 30, 2022 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 36,981 $ 64,074 $ — $ — $ — $ 101,055 Commercial utility sales 38,785 43,734 — — — 82,519 Industrial utility sales 10,838 7,209 — — — 18,047 Other utility sales 2,002 — — — — 2,002 Natural gas transportation — 11,910 32,144 — — 44,054 Natural gas storage — — 3,595 — — 3,595 Electrical & mechanical specialty contracting — — — 543,717 — 543,717 Transmission & distribution specialty contracting — — — 181,550 — 181,550 Other 10,758 3,495 3,814 200 1,472 19,739 Intersegment eliminations (34) (69) (3,581) (2,037) (1,472) (7,193) Revenues from contracts with customers 99,330 130,353 35,972 723,430 — 989,085 Revenues out of scope (47) 1,792 86 11,571 — 13,402 Total external operating revenues $ 99,283 $ 132,145 $ 36,058 $ 735,001 $ — $ 1,002,487 Nine Months Ended September 30, 2023 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 102,953 $ 517,351 $ — $ — $ — $ 620,304 Commercial utility sales 124,363 316,483 — — — 440,846 Industrial utility sales 31,880 33,293 — — — 65,173 Other utility sales 5,349 — — — — 5,349 Natural gas transportation — 38,225 104,716 — — 142,941 Natural gas storage — — 12,427 — — 12,427 Electrical & mechanical specialty contracting — — — 1,672,948 — 1,672,948 Transmission & distribution specialty contracting — — — 511,563 — 511,563 Other 38,111 11,874 9,713 121 6,412 66,231 Intersegment eliminations (82) (208) (37,889) — (6,412) (44,591) Revenues from contracts with customers 302,574 917,018 88,967 2,184,632 — 3,493,191 Revenues out of scope (7,799) 2,469 119 34,040 — 28,829 Total external operating revenues $ 294,775 $ 919,487 $ 89,086 $ 2,218,672 $ — $ 3,522,020 Nine Months Ended September 30, 2022 Electric Natural gas Pipeline Construction Other Total (In thousands) Residential utility sales $ 103,648 $ 439,639 $ — $ — $ — $ 543,287 Commercial utility sales 108,400 279,697 — — — 388,097 Industrial utility sales 32,067 29,242 — — — 61,309 Other utility sales 5,632 — — — — 5,632 Natural gas transportation — 35,747 95,685 — — 131,432 Natural gas storage — — 10,210 — — 10,210 Electrical & mechanical specialty contracting — — — 1,443,758 — 1,443,758 Transmission & distribution specialty contracting — — — 496,190 — 496,190 Other 33,727 9,854 8,201 357 4,368 56,507 Intersegment eliminations (102) (206) (37,309) (4,391) (4,368) (46,376) Revenues from contracts with customers 283,372 793,973 76,787 1,935,914 — 3,090,046 Revenues out of scope (4,854) (831) 210 34,780 — 29,305 Total external operating revenues $ 278,518 $ 793,142 $ 76,997 $ 1,970,694 $ — $ 3,119,351
Contract balances	The changes in contract assets and liabilities were as follows: September 30, 2023 December 31, 2022 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 199,370 $ 154,144 $ 45,226 Receivables, net Contract liabilities - current (183,705) (168,361) (15,344) Accounts payable Contract liabilities - noncurrent (435) (6) (429) Noncurrent liabilities - other Net contract assets (liabilities) $ 15,230 $ (14,223) $ 29,453

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	9 Months Ended
	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Other amortizable intangible assets	Other amortizable intangible assets were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Customer relationships $ 10,450 $ 10,450 $ 10,450 Less accumulated amortization 7,924 5,834 6,356 2,526 4,616 4,094 Noncompete agreements 292 552 552 Less accumulated amortization 292 520 544 — 32 8 Total $ 2,526 $ 4,648 $ 4,102
Estimated amortization expense	Amortization expense for identifiable intangible assets as of September 30, 2023 is estimated to be as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Amortization expense $ 522 $ 1,888 $ 116 $ — $ — $ —

Regulatory assets and liabili_2

Regulatory assets and liabilities (Tables)	9 Months Ended
	Sep. 30, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery or Refund Period as of September 30, 2023 * September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 107,101 $ 112,079 $ 141,306 Electric fuel and purchased power deferral Up to 1 year 17,775 2,328 2,656 Conservation programs Up to 1 year 14,411 9,363 8,544 Cost recovery mechanisms Up to 1 year 9,461 3,354 4,019 Other Up to 1 year 20,500 21,036 8,567 169,248 148,160 165,092 Noncurrent: Pension and postretirement benefits ** 144,448 137,582 143,349 Cost recovery mechanisms Up to 10 years 68,539 67,094 67,171 Natural gas costs recoverable through rate adjustments Up to 2 years 64,914 462 — Plant costs/asset retirement obligations Over plant lives 43,520 61,941 44,462 Environmental compliance programs - 36,605 — — Manufactured gas plant site remediation - 24,577 25,963 26,624 Plant to be retired - 19,947 24,740 21,525 Taxes recoverable from customers Over plant lives 12,266 12,394 12,330 Long-term debt refinancing costs Up to 37 years 2,747 3,335 3,188 Other Up to 16 years 11,406 10,931 11,010 428,969 344,442 329,659 Total regulatory assets $ 598,217 $ 492,602 $ 494,751 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year 20,445 873 955 Electric fuel and purchased power deferral Up to 1 year — 3,763 4,929 Cost recovery mechanisms Up to 1 year 5,754 2,674 1,977 Conservation programs Up to 1 year 1,976 325 4,126 Taxes refundable to customers Up to 1 year 1,513 4,264 3,937 Refundable fuel and electric costs Up to 1 year 18 1,812 3,253 Other Up to 1 year 15,307 4,888 7,263 45,013 18,599 26,440 Noncurrent: Plant removal and decommissioning costs Over plant lives 220,499 174,481 208,650 Taxes refundable to customers Over plant lives 194,804 205,517 203,222 Environmental compliance programs - 36,126 — — Cost recovery mechanisms Up to 19 years 20,012 12,535 14,025 Accumulated deferred investment tax credit Up to 19 years 14,800 14,665 13,594 Pension and postretirement benefits ** 7,120 19,687 7,376 Other Up to 15 years 1,751 6,327 1,587 495,112 433,212 448,454 Total regulatory liabilities $ 540,125 $ 451,811 $ 474,894 Net regulatory position $ 58,092 $ 40,791 $ 19,857 * Estimated recovery or refund period for amounts currently being recovered or refunded in rates to customers. ** Recovered as expense is incurred or cash contributions are made.
Regulatory Liabilities	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery or Refund Period as of September 30, 2023 * September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 107,101 $ 112,079 $ 141,306 Electric fuel and purchased power deferral Up to 1 year 17,775 2,328 2,656 Conservation programs Up to 1 year 14,411 9,363 8,544 Cost recovery mechanisms Up to 1 year 9,461 3,354 4,019 Other Up to 1 year 20,500 21,036 8,567 169,248 148,160 165,092 Noncurrent: Pension and postretirement benefits ** 144,448 137,582 143,349 Cost recovery mechanisms Up to 10 years 68,539 67,094 67,171 Natural gas costs recoverable through rate adjustments Up to 2 years 64,914 462 — Plant costs/asset retirement obligations Over plant lives 43,520 61,941 44,462 Environmental compliance programs - 36,605 — — Manufactured gas plant site remediation - 24,577 25,963 26,624 Plant to be retired - 19,947 24,740 21,525 Taxes recoverable from customers Over plant lives 12,266 12,394 12,330 Long-term debt refinancing costs Up to 37 years 2,747 3,335 3,188 Other Up to 16 years 11,406 10,931 11,010 428,969 344,442 329,659 Total regulatory assets $ 598,217 $ 492,602 $ 494,751 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year 20,445 873 955 Electric fuel and purchased power deferral Up to 1 year — 3,763 4,929 Cost recovery mechanisms Up to 1 year 5,754 2,674 1,977 Conservation programs Up to 1 year 1,976 325 4,126 Taxes refundable to customers Up to 1 year 1,513 4,264 3,937 Refundable fuel and electric costs Up to 1 year 18 1,812 3,253 Other Up to 1 year 15,307 4,888 7,263 45,013 18,599 26,440 Noncurrent: Plant removal and decommissioning costs Over plant lives 220,499 174,481 208,650 Taxes refundable to customers Over plant lives 194,804 205,517 203,222 Environmental compliance programs - 36,126 — — Cost recovery mechanisms Up to 19 years 20,012 12,535 14,025 Accumulated deferred investment tax credit Up to 19 years 14,800 14,665 13,594 Pension and postretirement benefits ** 7,120 19,687 7,376 Other Up to 15 years 1,751 6,327 1,587 495,112 433,212 448,454 Total regulatory liabilities $ 540,125 $ 451,811 $ 474,894 Net regulatory position $ 58,092 $ 40,791 $ 19,857 * Estimated recovery or refund period for amounts currently being recovered or refunded in rates to customers. ** Recovered as expense is incurred or cash contributions are made.

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Available-for-sale securities	Details of available-for-sale securities were as follows: September 30, 2023 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,386 $ — $ 750 $ 7,636 U.S. Treasury securities 3,307 11 23 3,295 Total $ 11,693 $ 11 $ 773 $ 10,931 September 30, 2022 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,486 $ — $ 783 $ 7,703 U.S. Treasury securities 2,468 — 82 2,386 Total $ 10,954 $ — $ 865 $ 10,089 December 31, 2022 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,928 $ 2 $ 636 $ 8,294 U.S. Treasury securities 2,608 — 72 2,536 Total $ 11,536 $ 2 $ 708 $ 10,830
Assets and liabilities measured at fair value on a recurring basis	The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at September 30, 2023, Using Quoted Prices in Significant Significant Balance at September 30, 2023 (In thousands) Assets: Investment in Knife River 276,213 $ — $ — $ 276,213 Money market funds — 25,818 — 25,818 Insurance contracts* — 62,736 — 62,736 Available-for-sale securities: Mortgage-backed securities — 7,637 — 7,637 U.S. Treasury securities — 3,295 — 3,295 Total assets measured at fair value $ 276,213 $ 99,486 $ — $ 375,699 * The insurance contracts invest approximately 50 percent in fixed-income investments, 19 percent in common stock of large-cap companies, 10 percent in target date investments, 10 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 3 percent in cash equivalents, 1 percent in international investments, and 1 percent in high-yield investments. Fair Value Measurements at September 30, 2022, Using Quoted Prices in Significant Significant Balance at September 30, 2022 (In thousands) Assets: Money market funds $ — $ 4,878 $ — $ 4,878 Insurance contracts* — 75,723 — 75,723 Available-for-sale securities: Mortgage-backed securities — 7,703 — 7,703 U.S. Treasury securities — 2,386 — 2,386 Total assets measured at fair value $ — $ 90,690 $ — $ 90,690 * The insurance contracts invest approximately 65 percent in fixed-income investments, 14 percent in common stock of large-cap companies, 7 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements at December 31, 2022, Using Quoted Prices in Significant Significant Balance at December 31, 2022 (In thousands) Assets: Money market funds $ — $ 4,913 $ — $ 4,913 Insurance contracts* — 77,958 — 77,958 Available-for-sale securities: Mortgage-backed securities — 8,294 — 8,294 U.S. Treasury securities — 2,536 — 2,536 Total assets measured at fair value $ — $ 93,701 $ — $ 93,701 * The insurance contracts invest approximately 63 percent in fixed-income investments, 15 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 6 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents.
Fair value of long term debt outstanding	The estimated fair value of the Company's Level 2 long-term debt was as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Carrying amount $ 2,341,147 $ 2,278,730 $ 2,365,667 Fair value $ 1,960,926 $ 1,989,362 $ 2,053,396

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Long-term debt outstanding	Long-term debt outstanding was as follows: Weighted Average Interest Rate at September 30, 2023 September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Senior Notes due on dates ranging from July 15, 2024 to June 15, 2062 4.33 % $ 1,757,000 $ 1,847,000 $ 1,848,500 Term Loan Agreements due on dates ranging from May 31, 2025 to September 3, 2032 6.52 % 381,300 7,000 7,000 Commercial paper supported by revolving credit agreement 5.80 % 97,700 268,272 349,050 Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029 7.32 % 35,000 35,000 35,000 Credit agreements due on dates ranging from October 13, 2027 to November 30, 2027 8.50 % 38,900 125,580 130,000 Other notes due on dates ranging from January 1, 2024 to November 30, 2038 8.41 % 37,884 1,617 1,614 Less unamortized debt issuance costs 6,637 5,295 5,211 Less discount — 444 286 Total long-term debt 2,341,147 2,278,730 2,365,667 Less current maturities 61,319 86,319 47,819 Net long-term debt $ 2,279,828 $ 2,192,411 $ 2,317,848
Schedule of debt maturities	Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at September 30, 2023, were as follows: Remainder of 2023 2024 2025 2026 2027 Thereafter (In thousands) Long-term debt maturities $ 619 $ 158,400 $ 532,700 $ 140,700 $ 59,600 $ 1,455,765

Cash flow information (Tables)

Cash flow information (Tables)	9 Months Ended
	Sep. 30, 2023
Supplemental Cash Flow Information [Abstract]
Cash expenditures for interest and income taxes and noncash investing and financing transactions	Cash expenditures for interest and income taxes were as follows: Nine Months Ended September 30, 2023 2022 (In thousands) Interest, net* $ 84,352 $ 55,954 Income taxes paid (refunded), net** $ 40,290 $ (5,499) * AFUDC - borrowed was $7.4 million and $2.4 million for the nine months ended September 30, 2023 and 2022, respectively. ** Income taxes paid, including discontinued operations, were $39.4 million and $17.7 million for the nine months ended September 30, 2023 and 2022, respectively. Noncash investing and financing transactions were as follows: September 30, 2023 September 30, 2022 December 31, 2022 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 36,307 $ 30,641 $ 39,158 Property, plant and equipment additions in accounts payable $ 37,598 $ 39,393 $ 35,637

Business segment data (Tables)

Business segment data (Tables)	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Information on the Company's businesses	Information on the Company's segments was as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) External operating revenues: Regulated operations: Electric $ 108,089 $ 99,283 $ 294,775 $ 278,518 Natural gas distribution 134,896 132,145 919,487 793,142 Pipeline 36,549 32,346 79,697 69,347 279,534 263,774 1,293,959 1,141,007 Non-regulated operations: Pipeline 3,855 3,712 9,389 7,650 Construction services 717,406 735,001 2,218,672 1,970,694 Other — — — — 721,261 738,713 2,228,061 1,978,344 Total external operating revenues $ 1,000,795 $ 1,002,487 $ 3,522,020 $ 3,119,351 Intersegment operating revenues: Regulated operations: Electric $ 27 $ 34 $ 82 $ 102 Natural gas distribution 69 69 208 206 Pipeline 3,666 3,508 37,624 36,845 3,762 3,611 37,914 37,153 Non-regulated operations: Pipeline 35 73 265 464 Construction services — 2,037 — 4,391 Other 1,689 1,472 6,412 4,368 1,724 3,582 6,677 9,223 Total intersegment operating revenues $ 5,486 $ 7,193 $ 44,591 $ 46,376 Operating income (loss): Electric $ 28,718 $ 30,395 $ 71,372 $ 53,764 Natural gas distribution (15,258) (16,688) 45,674 38,929 Pipeline 17,767 14,963 44,693 39,448 Construction services 50,091 34,949 139,619 110,588 Other 3,286 (2,617) (16,201) (11,726) Total operating income $ 84,604 $ 61,002 $ 285,157 $ 231,003 Income (loss) from continuing operations: Regulated operations: Electric $ 20,942 $ 21,596 $ 53,887 $ 37,476 Natural gas distribution (17,764) (18,058) 18,007 10,758 Pipeline 11,450 9,381 29,029 25,015 14,628 12,919 100,923 73,249 Non-regulated operations: Pipeline 508 779 337 (179) Construction services 35,975 29,248 105,951 86,596 Other 27,107 (577) 102,515 (12,769) 63,590 29,450 208,803 73,648 Income from continuing operations 78,218 42,369 309,726 146,897 Discontinued operations, net of tax (3,289) 105,602 (65,752) 103,504 Net income $ 74,929 $ 147,971 $ 243,974 $ 250,401
Reconciliation of Revenue from Segments to Consolidated	A reconciliation of reportable segment operating revenues to consolidated operating revenues is as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Operating revenues reconciliation: Total reportable segment operating revenues $ 1,004,592 $ 1,008,208 $ 3,560,199 $ 3,161,359 Other revenue 1,689 1,472 6,412 4,368 Elimination of intersegment operating revenues (5,486) (7,193) (44,591) (46,376) Total consolidated operating revenues $ 1,000,795 $ 1,002,487 $ 3,522,020 $ 3,119,351

Employee benefit plans (Tables)

Employee benefit plans (Tables)	9 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Schedule of net benefit costs	Components of net periodic benefit credit for the Company's pension benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit credit: Interest cost $ 3,380 $ 2,349 $ 10,140 $ 7,047 Expected return on assets (4,299) (4,370) (12,897) (13,112) Amortization of net actuarial loss 773 1,456 2,319 4,370 Net periodic benefit credit $ (146) $ (565) $ (438) $ (1,695) Components of net periodic benefit credit for the Company's other postretirement benefit plans were as follows: Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 (In thousands) Components of net periodic benefit credit: Service cost $ 131 $ 223 $ 405 $ 669 Interest cost 489 346 1,467 1,038 Expected return on assets (1,334) (1,319) (4,026) (3,957) Amortization of prior service credit (330) (330) (989) (989) Amortization of net actuarial gain (96) (142) (408) (425) Net periodic benefit credit, including amount capitalized (1,140) (1,222) (3,551) (3,664) Less amount capitalized 23 47 76 131 Net periodic benefit credit $ (1,163) $ (1,269) $ (3,627) $ (3,795)

Discontinued Operations and D_4

Discontinued Operations and Disposal Groups (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Apr. 25, 2023	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	May 31, 2023	Dec. 31, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operations Pro Rata Distribution					90%
Retained Shares Ownership Percentage					10%
Long-term debt		$ 2,341,147	$ 2,341,147	$ 2,278,730		$ 2,365,667
Repayments of Long-term Debt			$ 434,994	0
Treasury Stock, Shares, Retired		538,921	538,921
Restructuring and Related Cost, Incurred Cost		$ 1,000	$ 47,100
Retained Shares [Abstract]					5,700,000
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation | Cash Received, TSA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Continuing Cash Flows after Disposal		1,300	1,900
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation | Cash Paid, TSA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Amount of Continuing Cash Flows after Disposal		407	684
Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of Long-term Debt	$ 825,000
Senior Notes
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt		$ 1,757,000	$ 1,757,000	$ 1,847,000		$ 1,848,500
Senior Notes | Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt	425,000
Revolving Credit Facility | Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt	350,000
Term Loan Agreement | Knife River Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term debt	$ 275,000

Discontinued Operations (Detail

Discontinued Operations (Details - Balance Sheet) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Cash and Cash Equivalents			$ 10,090	$ 16,761
Discontinued Operation, Receivables, Net			241,302	447,882
Discontinued Operation, Inventory, Current			323,277	308,829
Discontinued Operation, Prepaid and Other Assets, Current			17,848	16,949
Discontinued Operation, Assets, Current			592,517	790,421
Discontinued Operation, Property, Plant and Equipment, Net			1,315,213	1,275,649
Discontinued Operation, Goodwill			274,540	274,302
Discontinued Operation, Intangible Assets, Net			13,430	14,097
Discontinued Operation, Long-Term Investments			33,086	32,326
Discontinued Operation, Operating Lease, Right-of-Use Asset			45,872	43,431
Discontinued Operation, Other Assets, Noncurrent			3,610	3,233
Noncurrent assets of discontinued operations	$ 0		1,685,751	1,643,038
Discontinued Operation, Total Assets			2,278,268	2,433,459
Discontinued Operation, Short-Term Debt			208,000	100,000
Discontinued Operation, Long-Term Debt, Current Maturities			30,211	128,133
Discontinued Operation, Accounts Payable			131,608	178,320
Discontinued Operation, Taxes Payable, Current			8,502	12,874
Discontinued Operation, Employee-related Liabilities, Current			29,192	27,383
Discontinued Operation, Operating Lease, Liability, Current			13,210	13,000
Discontinued Operation, Accrued Liabilities, Current			76,200	73,852
Current liabilities of discontinued operations	0		496,923	533,562
Discontinued Operation, Long-Term Debt, Excluding Current Maturities			445,546	581,588
Discontinued Operation, Deferred Income Tax Liabilities, Net			175,804	175,529
Discontinued Operation, Asset Retirement Obligations, Noncurrent			33,015	27,964
Discontinued Operation, Operating Lease Liability, Noncurrent			32,663	30,431
Discontinued Operation, Other Liabilities, Noncurrent			78,876	87,159
Noncurrent liabilities of discontinued operations	0		765,904	902,671
Discontinued Operation, Total Liabilities			$ 1,262,827	$ 1,436,233
Separation of Knife River	$ (185)	$ (954,541)

Discontinued Operations (Deta_2

Discontinued Operations (Details Income Stmt) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Revenue	$ 0	$ 974,774	$ 735,259	$ 1,995,500
Discontinued Operation, Operating Expense	1,447	825,874	769,407	1,828,602
Discontinued Operation, Operating Income (Loss)	(1,447)	148,900	(34,148)	166,898
Discontinued Operation, Other Income (Expense)	0	(1,005)	2,382	(4,399)
Discontinued Operation, Interest Expense	(66)	11,173	37,545	26,466
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(1,381)	136,722	(69,311)	136,033
Discontinued Operations, Income Tax Expense (Benefit)	1,908	31,120	(3,559)	32,529
Discontinued Operation, Income (Loss) from Discontinued Operation During Phase-out Period, Net of Tax	$ (3,289)	$ 105,602	$ (65,752)	$ 103,504

Receivables and allowance for_4

Receivables and allowance for expected credit losses (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Credit Loss [Abstract]
Accounts Receivable, Noncurrent, 90 Days or More Past Due, Still Accruing	$ 51.1	$ 34.3	$ 30.8

Receivables and allowance for_5

Receivables and allowance for expected credit losses (Details 2) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses							$ 9,769	$ 3,554
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	$ 6,873	$ 6,351	$ 4,154	$ 4,535	$ 5,030	$ 4,310	4,154	4,310
Provision for credit losses	3,907	2,097	3,765	1,070	497	1,988
Less write-offs charged against the allowance	3,357	1,873	1,943	2,373	1,277	1,600
Credit loss recoveries collected	308	298	375	294	285	332
Balance	7,731	6,873	6,351	3,526	4,535	5,030	7,731	3,526
Electric | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	413	468	375	348	361	269	375	269
Provision for credit losses	513	182	615	300	113	565
Less write-offs charged against the allowance	572	316	667	399	234	597
Credit loss recoveries collected	75	79	145	85	108	124
Balance	429	413	468	334	348	361	429	334
Natural gas distribution | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	1,740	2,943	1,615	1,453	2,123	1,506	1,615	1,506
Provision for credit losses	1,661	90	2,324	881	92	1,369
Less write-offs charged against the allowance	2,758	1,454	1,225	1,822	939	932
Credit loss recoveries collected	233	161	229	169	177	180
Balance	876	1,740	2,943	681	1,453	2,123	876	681
Pipeline | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2	2	2	2	2	2	2	2
Provision for credit losses	0	0	0	0	0	0
Less write-offs charged against the allowance	0	0	0	0	0	0
Credit loss recoveries collected	0	0	0	0	0	0
Balance	2	2	2	2	2	2	2	2
Construction services | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	4,718	2,938	2,162	2,732	2,544	2,533	2,162	2,533
Provision for credit losses	1,733	1,825	826	(111)	292	54
Less write-offs charged against the allowance	27	103	51	152	104	71
Credit loss recoveries collected	0	58	1	40	0	28
Balance	$ 6,424	$ 4,718	$ 2,938	$ 2,509	$ 2,732	$ 2,544	$ 6,424	$ 2,509

Inventories and natural gas i_4

Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Inventory Disclosure [Abstract]
Merchandise for resale	$ 36,815	$ 27,910	$ 26,538
Natural gas in storage (current)	29,821	22,533	48,532
Materials and supplies	7,824	6,846	9,917
Other	5,775	6,959	4,827
Total	80,235	64,248	89,814
Natural gas in storage noncurrent	$ 47,400	$ 47,500	$ 47,200

Treasury Stock (Details)

Treasury Stock (Details) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Earnings Per Share [Abstract]
Treasury Stock, Shares, Retired	538,921	538,921

Earnings per share (Details 2)

Earnings per share (Details 2) - $ / shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Weighted average common shares outstanding - basic	203,638	203,351	203,633	203,351
Effect of dilutive performance share awards and restricted stock units	248	293	258	56
Weighted average common shares outstanding - diluted	203,886	203,644	203,891	203,407
Income from continuing operations	$ 0.38	$ 0.21	$ 1.52	$ 0.72
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	(0.01)	0.52	(0.32)	0.51
Earnings Per Share, Basic	0.37	0.73	1.20	1.23
Income (Loss) from Continuing Operations, Per Diluted Share	0.38	0.21	1.52	0.72
Discontinued operations, net of tax	(0.01)	0.52	(0.32)	0.51
Earnings Per Share, Diluted	$ 0.37	$ 0.73	$ 1.20	$ 1.23
Shares excluded from the calculation of diluted earnings per share	0	0	0	77
Dividends declared per common share	$ 0.1250	$ 0.2175	$ 0.5700	$ 0.6525

Accumulated other comprehensi_3

Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated other comprehensive loss [Roll Forward]
Balance	$ 2,706,193	$ 3,575,382	$ 3,587,129	$ 3,386,810	$ 3,360,718	$ 3,382,874	$ 3,587,129	$ 3,382,874
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax	0			0			0	(3,265)
Other comprehensive income (loss)	(62)	363	217	285	(2,796)	269	518	(2,242)
Balance	2,757,434	2,706,193	3,575,382	3,491,858	3,386,810	3,360,718	2,757,434	3,491,858
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive loss [Roll Forward]
Balance	0	(91)	(125)	(315)	(426)	(538)	(125)	(538)
Other comprehensive loss before reclassifications	0	0	0	0	0	0
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax					0
Amounts reclassified from accumulated other comprehensive loss	0	47	34	111	111	112
Other comprehensive income (loss)	0	47	34	111	111	112
Amounts reclassified related to the separation of Knife River		44
Balance	0	0	(91)	(204)	(315)	(426)	0	(204)
Postretirement liability adjustment
Accumulated other comprehensive loss [Roll Forward]
Balance	(17,151)	(29,800)	(29,900)	(42,820)	(40,016)	(40,461)	(29,900)	(40,461)
Other comprehensive loss before reclassifications	0	0	0	0	0	0
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax					(3,265)
Amounts reclassified from accumulated other comprehensive loss	(6)	387	100	461	461	445
Other comprehensive income (loss)	(6)	387	100	461	(2,804)	445
Amounts reclassified related to the separation of Knife River		12,262
Balance	(17,157)	(17,151)	(29,800)	(42,359)	(42,820)	(40,016)	(17,157)	(42,359)
Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive loss [Roll Forward]
Balance	(546)	(475)	(558)	(396)	(293)	(5)	(558)	(5)
Other comprehensive loss before reclassifications	(66)	(84)	70	329	(128)	(320)
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax	269				0
Amounts reclassified from accumulated other comprehensive loss	10	13	13	42	25	32
Other comprehensive income (loss)	(56)	(71)	83	(287)	(103)	(288)
Amounts reclassified related to the separation of Knife River		0
Balance	(602)	(546)	(475)	(683)	(396)	(293)	(602)	(683)
Total accumulated other comprehensive loss
Accumulated other comprehensive loss [Roll Forward]
Balance	(17,697)	(30,366)	(30,583)	(43,531)	(40,735)	(41,004)	(30,583)	(41,004)
Other comprehensive loss before reclassifications	(66)	(84)	70	329	(128)	(320)
Other Comprehensive (Income) Loss, Reclassification Adjustment to AOCI, Postretirement Liability Adjustment From Regulatory Asset , Net of Tax					(3,265)
Amounts reclassified from accumulated other comprehensive loss	4	447	147	614	597	589
Other comprehensive income (loss)	(62)	363	217	285	(2,796)	269
Amounts reclassified related to the separation of Knife River		12,306
Balance	$ (17,759)	$ (17,697)	$ (30,366)	$ (43,246)	$ (43,531)	$ (40,735)	$ (17,759)	$ (43,246)

Reclassification out of accumul

Reclassification out of accumulated other comprehensive loss (Details 2) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	$ (32,129)			$ (20,196)			$ (82,541)	$ (58,275)
Other income	8,918			5,774			29,251	2,521
Income taxes	(13,325)			(4,211)			(92,311)	(28,352)
Net income	74,929	$ 130,692	$ 38,353	147,971	$ 70,667	$ 31,763	243,974	250,401
Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Net income	(4)			(614)			(598)	(1,800)
Reclassification adjustment for loss on derivative instruments included in net income | Reclassification out of accumulated other comprehensive loss | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	0			(148)			(98)	(443)
Income taxes	0			37			17	109
Net income	0			(111)			(81)	(334)
Amortization of postretirement liability losses included in net periodic benefit credit | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Other income	(92)			(609)			(744)	(1,827)
Income taxes	98			148			263	460
Net income	6			(461)			(481)	(1,367)
Reclassification adjustment on available-for-sale investments included in net income | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Other income	(13)			(54)			(45)	(126)
Income taxes	3			12			9	27
Net income	$ (10)			$ (42)			$ (36)	$ (99)

Disaggregation of revenue (Deta

Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Operating revenues:	$ 1,000,795	$ 1,002,487	$ 3,522,020	$ 3,119,351
Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	48,388	44,054	142,941	131,432
Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues:	4,808	3,595	12,427	10,210
Electrical & mechanical specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	514,378	543,717	1,672,948	1,443,758
Transmission & distribution specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	192,056	181,550	511,563	496,190
Other
Disaggregation of Revenue [Line Items]
Operating revenues:	24,098	19,739	66,231	56,507
Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	991,276	989,085	3,493,191	3,090,046
Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	9,519	13,402	28,829	29,305
Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	103,036	101,055	620,304	543,287
Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	90,114	82,519	440,846	388,097
Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	18,019	18,047	65,173	61,309
Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	1,865	2,002	5,349	5,632
Electric
Disaggregation of Revenue [Line Items]
Operating revenues:	108,089	99,283	294,775	278,518
Electric | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(27)	(34)	(82)	(102)
Electric | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	14,701	10,758	38,111	33,727
Electric | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	111,343	99,330	302,574	283,372
Electric | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	(3,254)	(47)	(7,799)	(4,854)
Electric | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	34,303	36,981	102,953	103,648
Electric | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	49,754	38,785	124,363	108,400
Electric | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	10,747	10,838	31,880	32,067
Electric | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	1,865	2,002	5,349	5,632
Natural gas distribution
Disaggregation of Revenue [Line Items]
Operating revenues:	134,896	132,145	919,487	793,142
Natural gas distribution | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(69)	(69)	(208)	(206)
Natural gas distribution | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	13,050	11,910	38,225	35,747
Natural gas distribution | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	3,881	3,495	11,874	9,854
Natural gas distribution | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	133,227	130,353	917,018	793,973
Natural gas distribution | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	1,669	1,792	2,469	(831)
Natural gas distribution | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	68,733	64,074	517,351	439,639
Natural gas distribution | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	40,360	43,734	316,483	279,697
Natural gas distribution | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	7,272	7,209	33,293	29,242
Natural gas distribution | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Pipeline
Disaggregation of Revenue [Line Items]
Operating revenues:	40,404	36,058	89,086	76,997
Pipeline | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(3,701)	(3,581)	(37,889)	(37,309)
Pipeline | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	35,338	32,144	104,716	95,685
Pipeline | Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues:	4,808	3,595	12,427	10,210
Pipeline | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	3,916	3,814	9,713	8,201
Pipeline | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	40,361	35,972	88,967	76,787
Pipeline | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	43	86	119	210
Construction services
Disaggregation of Revenue [Line Items]
Operating revenues:	717,406	735,001	2,218,672	1,970,694
Construction services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	0	(2,037)	0	(4,391)
Construction services | Electrical & mechanical specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	514,378	543,717	1,672,948	1,443,758
Construction services | Transmission & distribution specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	192,056	181,550	511,563	496,190
Construction services | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	(89)	200	121	357
Construction services | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	706,345	723,430	2,184,632	1,935,914
Construction services | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	11,061	11,571	34,040	34,780
Other
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Other | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(1,689)	(1,472)	(6,412)	(4,368)
Other | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	1,689	1,472	6,412	4,368
Other | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Other | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Consolidated Operations | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	$ (5,486)	$ (7,193)	$ (44,591)	$ (46,376)

Contract balances (Details 2)

Contract balances (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Construction Contractor, Contract Cost, Subject to Uncertainty, Amount	$ 30,000		$ 30,000
Contract assets	199,370		199,370		$ 154,144
Change in contract assets			45,226
Contract liabilities - current	(183,705)		(183,705)		(168,361)
Change in contract liabilities - current			(15,344)
Contract liabilities - noncurrent	(435)		(435)		(6)
Change in contract liabilities - noncurrent			(429)
Net contract assets (liabilities)	15,230		15,230		$ (14,223)
Change in net contract assets (liabilities)			29,453
Amounts included in contract liability at the beginning of the period	6,300	$ 8,200	164,300	$ 118,700
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 20,200	$ 9,600	$ 41,700	$ 43,700

Revenue from contracts with c_4

Revenue from contracts with customers Remaining performance obligations (Details 3) $ in Millions	Sep. 30, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1,600
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 371
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	13 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 519.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	25 months

Lessor accounting (Details)

Lessor accounting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Leases [Abstract]
Operating Lease, Lease Income	$ 11.2	$ 11.7	$ 34.5	$ 35.1
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	$ 9.1		$ 9.1

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 488,960	$ 488,960	$ 488,960

Other intangible assets (Detail

Other intangible assets (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 2,526	$ 4,648	$ 2,526	$ 4,648	$ 4,102
Amortization of intangible assets	522	565	1,600	1,700
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	10,450	10,450	10,450	10,450	10,450
Intangible assets, less accumulated amortization	7,924	5,834	7,924	5,834	6,356
Intangible assets, net (excluding goodwill)	2,526	4,616	2,526	4,616	4,094
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	292	552	292	552	552
Intangible assets, less accumulated amortization	292	520	292	520	544
Intangible assets, net (excluding goodwill)	$ 0	$ 32	$ 0	$ 32	$ 8

Future amortization expense (De

Future amortization expense (Details 3) $ in Thousands	Sep. 30, 2023 USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2023	$ 522
2024	1,888
2025	116
2026	0
2027	0
Thereafter	$ 0

Regulatory assets (Details)

Regulatory assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Regulatory Assets
Regulatory Assets, Current	$ 169,248	$ 165,092	$ 148,160
Regulatory Assets, Noncurrent	428,969	329,659	344,442
Total regulatory assets	598,217	494,751	492,602
Regulatory assets not earning a rate of return	$ 211,800	242,500	264,400
Natural gas costs recoverable through rate adjustments
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory Assets, Current	$ 107,101	141,306	112,079
Regulatory Assets, Noncurrent	$ 64,914	0	462
Natural gas costs recoverable through rate adjustments | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 2 years
Conservation programs
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory Assets, Current	$ 14,411	8,544	9,363
Cost recovery mechanisms
Regulatory Assets
Regulatory Assets, Current	9,461	4,019	3,354
Regulatory Assets, Noncurrent	$ 68,539	67,171	67,094
Cost recovery mechanisms | Minimum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Cost recovery mechanisms | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 10 years
Other regulatory assets
Regulatory Assets
Regulatory Assets, Current	$ 20,500	8,567	21,036
Regulatory Assets, Noncurrent	$ 11,406	11,010	10,931
Other regulatory assets | Minimum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Other regulatory assets | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 16 years
Pension and postretirement benefits
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	**
Regulatory Assets, Noncurrent	$ 144,448	143,349	137,582
Plant costs/asset retirement obligations
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Over plant lives
Regulatory Assets, Noncurrent	$ 43,520	44,462	61,941
Manufactured gas plant site remediation
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	-
Regulatory Assets, Noncurrent	$ 24,577	26,624	25,963
Plant to be retired
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	-
Regulatory Assets, Noncurrent	$ 19,947	21,525	24,740
Environmental compliance programs
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	-
Regulatory Assets, Noncurrent	$ 36,605	0	0
Taxes recoverable from customers
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Over plant lives
Regulatory Assets, Noncurrent	$ 12,266	12,330	12,394
Long-term debt refinancing costs
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 37 years
Regulatory Assets, Noncurrent	$ 2,747	3,188	3,335
Regulatory Asset, Electric Fuel & Purchased Power Deferral
Regulatory Assets
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory Assets, Current	$ 17,775	$ 2,656	$ 2,328

Regulatory liabilities (Details

Regulatory liabilities (Details 2) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	$ 45,013	$ 26,440	$ 18,599
Regulatory liabilities	495,112	448,454	433,212
Total regulatory liabilities	540,125	474,894	451,811
Net regulatory position	$ 58,092	19,857	40,791
Natural gas costs refundable through rate adjustments
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory liabilities due within one year	$ 20,445	955	873
Electric fuel and purchased power deferral
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory liabilities due within one year	$ 0	4,929	3,763
Cost Recovery Mechanisms
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	5,754	1,977	2,674
Regulatory liabilities	$ 20,012	14,025	12,535
Cost Recovery Mechanisms | Minimum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Cost Recovery Mechanisms | Maximum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 19 years
Conservation programs
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory liabilities due within one year	$ 1,976	4,126	325
Taxes refundable to customers
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	1,513	3,937	4,264
Regulatory liabilities	$ 194,804	203,222	205,517
Taxes refundable to customers | Minimum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Taxes refundable to customers | Maximum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Over plant lives
Refundable Fuel and Electric Costs
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Regulatory liabilities due within one year	$ 18	3,253	1,812
Other regulatory liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	15,307	7,263	4,888
Regulatory liabilities	$ 1,751	1,587	6,327
Other regulatory liabilities | Minimum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 1 year
Other regulatory liabilities | Maximum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 15 years
Plant removal and decommissioning costs
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Over plant lives
Regulatory liabilities	$ 220,499	208,650	174,481
Accumulated Deferred ITC
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	Up to 19 years
Regulatory liabilities	$ 14,800	13,594	14,665
Pension and postretirement benefits
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of September 30, 2023	**
Regulatory liabilities	$ 7,120	7,376	19,687
Environmental compliance programs
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 36,126	$ 0	$ 0

Environmental allowances and _2

Environmental allowances and obligations (Details) $ in Millions	Sep. 30, 2023 USD ($)
Accounting Policies [Abstract]
Environmental Compliance Obligations	$ 36.6

Fair value measurements Insuran

Fair value measurements Insurance contracts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 62.7	$ 75.7	$ 62.7	$ 75.7	$ 78
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	$ (1.4)	$ (1.3)	$ 3.5	$ (12.4)

Available-for-sale securities (

Available-for-sale securities (Details 2) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Available-for-sale securities [Abstract]
Cost	$ 11,693	$ 11,536	$ 10,954
Gross Unrealized Gains	11	2	0
Gross Unrealized Losses	773	708	865
Fair Value	10,931	10,830	10,089
Mortgage-backed securities
Available-for-sale securities [Abstract]
Cost	8,386	8,928	8,486
Gross Unrealized Gains	0	2	0
Gross Unrealized Losses	750	636	783
Fair Value	7,636	8,294	7,703
U.S. Treasury securities
Available-for-sale securities [Abstract]
Cost	3,307	2,608	2,468
Gross Unrealized Gains	11	0	0
Gross Unrealized Losses	23	72	82
Fair Value	$ 3,295	$ 2,536	$ 2,386

Investment in Knife River (Deta

Investment in Knife River (Details 3) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	May 31, 2023
Fair value, balance sheet grouping [Line Items]
Retained Shares Ownership Percentage				10%
Retained Shares				5.7
Unrealized Gain (Loss) on Investments		$ 3,501	$ (12,357)
Investment in Knife River
Fair value, balance sheet grouping [Line Items]
Investments, Fair Value Disclosure	$ 276,200	276,200
Unrealized Gain (Loss) on Investments	$ 30,200	$ 170,200

Fair value measurements Assets

Fair value measurements Assets (Details 4) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	50%	63%	65%
Percentage investment in common stock of large-cap companies	19%	15%	14%
Percentage investment in target date investments	10%	6%	6%
Percentage investment in common stock of mid-cap companies	10%	8%	7%
Percentage investment in common stock of small-cap companies	6%	6%	6%
Percentage investment in cash and cash equivalents	3%	2%	2%
Percentage investment in international investments	1%
Percentage Investment in High-Yield Investments	1%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 375,699	$ 93,701	$ 90,690
Fair Value, Inputs, Level 1 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	276,213
Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	99,486	93,701	90,690
Investment in Knife River | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	276,213
Investment in Knife River | Fair Value, Inputs, Level 1 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	276,213
Money market funds | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	25,818	4,913	4,878
Money market funds | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	25,818	4,913	4,878
Insurance contracts* | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	62,736	77,958	75,723
Insurance contracts* | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	62,736	77,958	75,723
Mortgage-backed securities | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	7,637	8,294	7,703
Mortgage-backed securities | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	7,637	8,294	7,703
U.S. Treasury securities | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	3,295	2,536	2,386
U.S. Treasury securities | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 3,295	$ 2,536	$ 2,386

Fair value measurements Debt (D

Fair value measurements Debt (Details 5) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,341,147	$ 2,365,667	$ 2,278,730
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,341,147	2,365,667	2,278,730
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 1,960,926	$ 2,053,396	$ 1,989,362

Short-term Debt (Details 1)

Short-term Debt (Details 1) - USD ($) $ in Thousands				9 Months Ended
	May 31, 2023	Apr. 30, 2023	Mar. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	May 01, 2023	Mar. 17, 2023	Jan. 20, 2023	Dec. 31, 2022	Dec. 19, 2022
Short-Term Debt [Line Items]
Short-term borrowings				$ 306,400	$ 0				$ 38,500
Repayment of short-term borrowings				193,500	$ 0
Term Loan Agreement | Cascade Natural Gas [Member]
Short-Term Debt [Line Items]
Short-term borrowings								$ 150,000
Ratio of total debt to total capitalization as specified in debt covenants								65%
Term Loan Agreement | Intermountain Gas Company
Short-Term Debt [Line Items]
Short-term borrowings								$ 125,000
Ratio of total debt to total capitalization as specified in debt covenants								65%
Repayment of short-term borrowings	$ 30,000	$ 30,000	$ 20,000
Term Loan Agreement | Centennial Energy Holdings, Inc.
Short-Term Debt [Line Items]
Short-term borrowings							$ 100,000			$ 135,000
Term Loan Agreement | Centennial Energy Holdings, Inc. | Maximum [Member]
Short-Term Debt [Line Items]
Repayment of short-term borrowings	135,000
Term Loan Agreement | Centennial Energy Holdings, Inc. | Minimum [Member]
Short-Term Debt [Line Items]
Repayment of short-term borrowings	100,000
Term Loan Agreement | MDU Resources Group, Inc.
Short-Term Debt [Line Items]
Short-term borrowings						$ 75,000
Repayment of short-term borrowings	75,000
Revolving Credit Facility | MDU Resources Group, Inc.
Short-Term Debt [Line Items]
Short-term borrowings	$ 150,000
Ratio of total debt to total capitalization as specified in debt covenants	65%
Revolving Credit Agreement, Amount Outstanding | MDU Resources Group, Inc.
Short-Term Debt [Line Items]
Short-term borrowings				$ 111,400

Long-term debt outstanding (Det

Long-term debt outstanding (Details 2) - USD ($) $ in Thousands		9 Months Ended
	Jun. 09, 2023	Sep. 30, 2023	Sep. 30, 2022	May 31, 2023	Dec. 31, 2022
Long-term debt outstanding [Line Items]
Repayments of Long-term Debt		$ 434,994	$ 0
Long-term debt		2,341,147	2,278,730		$ 2,365,667
Long-term debt due within one year		61,319	86,319		47,819
Long-term debt		2,279,828	2,192,411		2,317,848
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs		6,637	5,295		5,211
Discount		0	444		286
Long-term Debt | Centennial Energy Holdings, Inc.
Long-term debt outstanding [Line Items]
Repayments of Long-term Debt	$ 455,000
Revolving Credit Facility | MDU Resources Group, Inc.
Long-term debt outstanding [Line Items]
Long-term debt				$ 200,000
Ratio of total debt to total capitalization as specified in debt covenants				65%
Term Loan Agreement | MDU Resources Group, Inc.
Long-term debt outstanding [Line Items]
Long-term debt				$ 375,000
Ratio of total debt to total capitalization as specified in debt covenants				65%
Senior Notes
Long-term debt outstanding [Line Items]
Long-term debt		$ 1,757,000	1,847,000		1,848,500
Weighted Average Interest Rate		4.33%
Term Loan Agreements
Long-term debt outstanding [Line Items]
Long-term debt		$ 381,300	7,000		7,000
Weighted Average Interest Rate		6.52%
Commercial Paper
Long-term debt outstanding [Line Items]
Long-term debt		$ 97,700	268,272		349,050
Weighted Average Interest Rate		5.80%
Medium-term Notes
Long-term debt outstanding [Line Items]
Long-term debt		$ 35,000	35,000		35,000
Weighted Average Interest Rate		7.32%
Credit Agreements
Long-term debt outstanding [Line Items]
Long-term debt		$ 38,900	125,580		130,000
Weighted Average Interest Rate		8.50%
Other Notes
Long-term debt outstanding [Line Items]
Long-term debt		$ 37,884	$ 1,617		$ 1,614
Weighted Average Interest Rate		8.41%

Schedule of debt maturities (De

Schedule of debt maturities (Details 3) $ in Thousands	Sep. 30, 2023 USD ($)
Long-term debt maturities [Line Items]
Remainder of 2023	$ 619
2024	158,400
2025	532,700
2026	140,700
2027	59,600
Thereafter	$ 1,455,765

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 91,543	$ 46,580	$ 402,037	$ 175,249
Income taxes	$ 13,325	$ 4,211	$ 92,311	$ 28,352
Effective Income Tax Rate Reconciliation, Percent	14.60%	9%	23%	16.20%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			24.80%	24.80%

Cash flow information (Details)

Cash flow information (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Interest, net*	$ 84,352	$ 55,954
Income taxes paid (refunded), net**	40,290	(5,499)
AFUDC borrowed	7,400	2,400
Right-of-use assets obtained in exchange for new operating lease liabilities	36,307	30,641	$ 39,158
Property, plant and equipment additions in accounts payable	37,598	39,393	$ 35,637
Continuing and discontinued operations
Income taxes paid (refunded), net**	$ 39,400	$ 17,700

Restricted Cash (Details 2)

Restricted Cash (Details 2) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	$ 32,493	$ 80,518	$ 74,620	$ 54,161
Restricted Cash-Captive Insurance
Restricted Cash and Cash Equivalents Items [Line Items]
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	$ 24,700	$ 35,600	$ 33,800

Business segment data (Details)

Business segment data (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenues	$ 1,000,795			$ 1,002,487			$ 3,522,020	$ 3,119,351
Operating income	84,604			61,002			285,157	231,003
Income from continuing operations	78,218			42,369			309,726	146,897
Discontinued operations, net of tax	(3,289)			105,602			(65,752)	103,504
Net income	74,929	$ 130,692	$ 38,353	147,971	$ 70,667	$ 31,763	243,974	250,401
Electric
Segment Reporting Information [Line Items]
Revenues	108,089			99,283			294,775	278,518
Operating income	28,718			30,395			71,372	53,764
Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	134,896			132,145			919,487	793,142
Operating income	(15,258)			(16,688)			45,674	38,929
Pipeline
Segment Reporting Information [Line Items]
Revenues	40,404			36,058			89,086	76,997
Operating income	17,767			14,963			44,693	39,448
Construction services
Segment Reporting Information [Line Items]
Revenues	717,406			735,001			2,218,672	1,970,694
Operating income	50,091			34,949			139,619	110,588
Other
Segment Reporting Information [Line Items]
Revenues	0			0			0	0
Operating income	3,286			(2,617)			(16,201)	(11,726)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	(27)			(34)			(82)	(102)
Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	(69)			(69)			(208)	(206)
Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	(3,701)			(3,581)			(37,889)	(37,309)
Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	0			(2,037)			0	(4,391)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	(1,689)			(1,472)			(6,412)	(4,368)
Intersegment eliminations | Consolidated Operations
Segment Reporting Information [Line Items]
Revenues	(5,486)			(7,193)			(44,591)	(46,376)
Total intersegment operating revenues | Consolidated Operations
Segment Reporting Information [Line Items]
Revenues	5,486			7,193			44,591	46,376
Regulated operation
Segment Reporting Information [Line Items]
Revenues	279,534			263,774			1,293,959	1,141,007
Income from continuing operations	14,628			12,919			100,923	73,249
Regulated operation | Electric
Segment Reporting Information [Line Items]
Revenues	108,089			99,283			294,775	278,518
Income from continuing operations	20,942			21,596			53,887	37,476
Regulated operation | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	134,896			132,145			919,487	793,142
Income from continuing operations	(17,764)			(18,058)			18,007	10,758
Regulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	36,549			32,346			79,697	69,347
Income from continuing operations	11,450			9,381			29,029	25,015
Regulated operation | Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	27			34			82	102
Regulated operation | Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	69			69			208	206
Regulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	3,666			3,508			37,624	36,845
Regulated operation | Intersegment eliminations | Regulated Operations
Segment Reporting Information [Line Items]
Revenues	3,762			3,611			37,914	37,153
Nonregulated operation
Segment Reporting Information [Line Items]
Revenues	721,261			738,713			2,228,061	1,978,344
Income from continuing operations	63,590			29,450			208,803	73,648
Nonregulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	3,855			3,712			9,389	7,650
Income from continuing operations	508			779			337	(179)
Nonregulated operation | Construction services
Segment Reporting Information [Line Items]
Revenues	717,406			735,001			2,218,672	1,970,694
Income from continuing operations	35,975			29,248			105,951	86,596
Nonregulated operation | Other
Segment Reporting Information [Line Items]
Revenues	0			0			0	0
Income from continuing operations	27,107			(577)			102,515	(12,769)
Nonregulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	35			73			265	464
Nonregulated operation | Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	0			2,037			0	4,391
Nonregulated operation | Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	1,689			1,472			6,412	4,368
Nonregulated operation | Intersegment eliminations | Non-regulated Operations
Segment Reporting Information [Line Items]
Revenues	$ 1,724			$ 3,582			$ 6,677	$ 9,223

Business segment data operating

Business segment data operating revenues reconciliation (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,000,795	$ 1,002,487	$ 3,522,020	$ 3,119,351
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,004,592	1,008,208	3,560,199	3,161,359
Corporate, Non-Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,689	1,472	6,412	4,368
Intersegment Eliminations [Member] | Consolidated Operations
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ (5,486)	$ (7,193)	$ (44,591)	$ (46,376)

Employee benefit plans (Details

Employee benefit plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Qualified plan | Underfunded plan | Pension benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Interest cost	$ 3,380	$ 2,349	$ 10,140	$ 7,047
Expected return on assets	(4,299)	(4,370)	(12,897)	(13,112)
Amortization of net actuarial (gain) loss	773	1,456	2,319	4,370
Net periodic benefit cost (credit)	(146)	(565)	(438)	(1,695)
Qualified plan | Overfunded Plan | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	131	223	405	669
Interest cost	489	346	1,467	1,038
Expected return on assets	(1,334)	(1,319)	(4,026)	(3,957)
Amortization of prior service credit	(330)	(330)	(989)	(989)
Amortization of net actuarial (gain) loss	(96)	(142)	(408)	(425)
Net periodic benefit credit, including amount capitalized	(1,140)	(1,222)	(3,551)	(3,664)
Less amount capitalized	23	47	76	131
Net periodic benefit cost (credit)	(1,163)	(1,269)	(3,627)	(3,795)
Nonqualified plan | Unfunded plan | Supplemental employee retirement plans
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Net periodic benefit cost (credit)	$ 759	$ 648	$ 2,300	$ 1,900

Stock-Based Compensation (Detai

Stock-Based Compensation (Details)	9 Months Ended
	Sep. 30, 2023 USD ($)
Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Payment Arrangement, Plan Modification, Incremental Cost	$ 204,000

MTPSC (Details)

MTPSC (Details) - MTPSC - Montana-Dakota Utilities Co. [Member] - Electric - USD ($) $ in Millions	Jun. 12, 2023	Mar. 15, 2023	Feb. 01, 2023	Nov. 04, 2022
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 10.5
Public Utilities, Requested Rate Increase (Decrease), Percentage				15.20%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 6.1	$ 11.5
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage	9.10%	17%
Public Utilities, Interim Rate Increase (Decrease), Amount			$ 1.7
Public Utilities, Interim Rate Increase (Decrease), Percentage			2.70%
Public Utilities, Requested Return on Equity, Percentage	9.65%

NDPSC (Details 2)

NDPSC (Details 2) - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($) $ in Millions	Nov. 01, 2023	Aug. 25, 2023	Jul. 14, 2023
Electric
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ (10.7)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 1.3
Total Transmission Cost Adjustment Rider			2.2
Public Utilities, Requested Rate (Decrease), Net Benefit Amount			$ (7.6)
Electric | Subsequent Event [Member] | Pending Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 5.7
Renewable Resource Cost Adjustment Rate Tariff	21
Natural gas distribution | Subsequent Event [Member] | Pending Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 11.6
Public Utilities, Requested Rate Increase (Decrease), Percentage	7.50%
Public Utilities, Interim Rate Increase (Decrease), Amount	$ 10.1

SDPUC (Details 3)

SDPUC (Details 3) - Pending Rate Case [Member] - SDPUC - Montana-Dakota Utilities Co. [Member] $ in Millions	Aug. 15, 2023 USD ($)
Electric
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 3
Public Utilities, Requested Rate Increase (Decrease), Percentage	17.30%
Natural gas distribution
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 7.4
Public Utilities, Requested Rate Increase (Decrease), Percentage	11.20%

WUTC (Details 4)

WUTC (Details 4) - Pipeline Cost Recovery Mechanism - WUTC [Member] - Cascade Natural Gas [Member] - USD ($) $ in Millions	Oct. 13, 2023	Jun. 01, 2023
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 3.1
Public Utilities, Requested Rate Increase (Decrease), Percentage		0.90%
Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 2.4
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage	0.70%

FERC (Details 5)

FERC (Details 5) $ in Millions	Jan. 01, 2024 USD ($)
Electric | FERC [Member] | Montana-Dakota Utilities Co. [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Transmission Formula Revenue Requirement	$ 15.2

Litigation (Details)

Litigation (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 21,000	$ 31,900	$ 33,500
Insurance Receivable	98	10,000	11,900
Regulatory Assets	$ 20,100	$ 20,900	$ 20,500

Guarantees (Details 2)

Guarantees (Details 2)	Sep. 30, 2023 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 330,800,000
Fixed maximum amounts guaranteed by year 2023	9,500,000
Fixed maximum amounts guaranteed by year 2024	67,400,000
Fixed maximum amounts guaranteed by year 2025	251,100,000
Fixed maximum amounts guaranteed by year 2026	1,500,000
Fixed maximum amounts guaranteed by year 2027	1,000,000
Fixed maximum amounts guaranteed, thereafter	300,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	11,100,000
Outstanding letters of credit	0
Letters of credit set to expire - 2023	8,900,000
Letters of credit set to expire - 2024	2,200,000
Amount of surety bonds outstanding	$ 330,800,000

Variable interest entities (Det

Variable interest entities (Details 3) $ in Millions	Sep. 30, 2023 USD ($)
Fuel contract
Variable Interest Entities [Line Items]
Variable interest entity, reporting entity involvement, maximum loss exposure, amount	$ 28.1