MDU Resources (MDU) 10-K 23 Feb 22 2021 FY Annual report Financial data

Cover page

Cover page - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 15, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 6,339,561,129
Entity Common Stock, Shares Outstanding		203,350,740
Entity Central Index Key	0000067716
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Minneapolis, Minnesota

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues:
Operating revenues	$ 5,680,733	$ 5,532,750	$ 5,336,776
Operating expenses:
Operation and maintenance:	4,078,623	4,028,262	3,895,294
Purchased natural gas sold	483,118	390,269	421,545
Depreciation, depletion and amortization	299,214	285,100	256,017
Taxes, other than income	211,454	217,253	196,143
Electric fuel and purchased power	74,105	66,941	86,557
Total operating expenses	5,146,514	4,987,825	4,855,556
Operating income	534,219	544,925	481,220
Other income	26,416	26,711	15,812
Interest expense	93,984	96,519	98,587
Income before income taxes	466,651	475,117	398,445
Income taxes	88,920	84,590	63,279
Income from continuing operations	377,731	390,527	335,166
Income (loss) from discontinued operations, net of tax	400	(322)	287
Net income	$ 378,131	$ 390,205	$ 335,453
Earnings per share - basic:
Income from continuing operations	$ 1.87	$ 1.95	$ 1.69
Discontinued operations, net of tax	0	0	0
Earnings per share - basic	1.87	1.95	1.69
Earnings per share - diluted:
Income from continuing operations	1.87	1.95	1.69
Discontinued operations, net of tax	0	0	0
Earnings per share - diluted	$ 1.87	$ 1.95	$ 1.69
Weighted average common shares outstanding - basic	202,076	200,502	198,612
Weighted Average Number of Shares Outstanding, Diluted	202,383	200,571	198,626
Regulated Operation
Operating revenues:
Operating revenues	$ 1,390,343	$ 1,249,146	$ 1,279,304
Operating expenses:
Operation and maintenance:	366,586	353,184	356,132
Income from continuing operations	143,085	135,103	122,535
Nonregulated Operation
Operating revenues:
Operating revenues	4,290,390	4,283,604	4,057,472
Operating expenses:
Operation and maintenance:	3,712,037	3,675,078	3,539,162
Income from continuing operations	$ 234,646	$ 255,424	$ 212,631

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net income	$ 378,131	$ 390,205	$ 335,453
Other comprehensive income (loss):
Reclassification adjustment for loss on derivative instruments included in net income, tax	145	145	(140)
Reclassification adjustment for loss on derivative instruments included in net income, net of tax	446	446	731
Postretirement liability adjustment:
Postretirement liability gains (losses) arising during the period, tax	1,626	(2,606)	(2,012)
Postretirment liability gains (losses) arising during the period, net of tax	4,876	(8,395)	(6,151)
Amortization of postretirement liability losses in net periodic benefit cost, tax	615	630	476
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	1,870	1,922	1,486
Postretirement liability adjustment	6,746	(6,473)	(4,665)
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	(67)	0	35
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax	(252)	(1)	134
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	36	14	10
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax	134	52	40
Net unrealized gain (loss) on available-for-sale investments	(118)	51	174
Other comprehensive income (loss)	7,074	(5,976)	(3,760)
Comprehensive income attributable to common stockholders	$ 385,205	$ 384,229	$ 331,693

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 54,161	$ 59,547
Receivables, net	946,741	873,986
Inventories	335,609	291,167
Current regulatory assets	118,691	68,527
Prepayments and other current assets	95,741	44,120
Total current assets	1,550,943	1,337,347
Noncurrent assets:
Property, plant and equipment	8,972,849	8,300,770
Less accumulated depreciation, depletion and amortization	3,216,461	3,133,831
Net property, plant and equipment	5,756,388	5,166,939
Goodwill	765,386	714,963
Other intangible assets, net	22,578	25,496
Regulatory assets	357,851	379,381
Investments	175,476	165,022
Operating lease right-of-use assets	124,138	120,113
Other	157,675	144,111
Total noncurrent assets	7,359,492	6,716,025
Total assets	8,910,435	8,053,372
Current liabilities:
Short-term borrowings	0	50,000
Long-term debt due within one year	148,053	1,555
Accounts payable	478,933	426,264
Taxes payable	80,372	88,844
Dividends payable	44,229	42,611
Accrued compensation	81,904	90,629
Operating lease liabilities due within one year	35,368	33,655
Regulatory liabilities due within one year	16,303	31,450
Other accrued liabilities	207,078	198,514
Total current liabilities	1,092,240	963,522
Noncurrent liabilities:
Long-term debt	2,593,847	2,211,575
Deferred income taxes	591,962	516,098
Asset retirement obligations	458,061	440,356
Regulatory liabilities	428,790	428,075
Operating lease liabilities	89,253	86,868
Other	273,408	327,773
Total noncurrent liabilities	4,435,321	4,010,745
Commitments and contingencies
Stockholders' equity:
Common stock	203,889	201,061
Other paid-in capital	1,461,205	1,371,385
Retained earnings	1,762,410	1,558,363
Accumulated other comprehensive loss	(41,004)	(48,078)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total stockholders' equity	3,382,874	3,079,105
Total liabilities and stockholders' equity	$ 8,910,435	$ 8,053,372
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par Value Per Share	$ 1	$ 1
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921
MDU Resources Group, Inc. [Member]
Current assets:
Cash and cash equivalents	$ 6,159	$ 8,781
Receivables, net	6,120	4,865
Prepayments and other current assets	2,528	1,612
Total current assets	64,503	65,797
Noncurrent assets:
Investments	55,686	52,000
Operating lease right-of-use assets	114	56
Other	26,558	28,866
Total noncurrent assets	3,458,259	3,160,569
Total assets	3,522,762	3,226,366
Current liabilities:
Accounts payable	2,546	2,135
Taxes payable	1,672	4,056
Dividends payable	44,229	42,611
Accrued compensation	4,098	7,825
Operating lease liabilities due within one year	52	40
Other accrued liabilities	7,309	6,881
Total current liabilities	66,039	68,960
Noncurrent liabilities:
Operating lease liabilities	62	16
Other	73,787	78,285
Total noncurrent liabilities	73,849	78,301
Commitments and contingencies
Stockholders' equity:
Common stock	203,889	201,061
Other paid-in capital	1,461,205	1,371,385
Retained earnings	1,762,410	1,558,363
Accumulated other comprehensive loss	(41,004)	(48,078)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)
Total stockholders' equity	3,382,874	3,079,105
Total liabilities and stockholders' equity	$ 3,522,762	$ 3,226,366
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par Value Per Share	$ 1	$ 1
Common Stock, Shares, Issued	203,889,661	201,061,198
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	Total accumulated other comprehensive loss	Treasury stock
Balance (in shares) at Dec. 31, 2018		196,564,907
Treasury stock (in shares) at Dec. 31, 2018						(538,921)
Balance at Dec. 31, 2018	$ 2,566,775	$ 196,565	$ 1,248,576	$ 1,163,602	$ (38,342)	$ (3,626)
Net income	335,453			335,453
Other comprehensive income (loss)	(3,760)				(3,760)
Dividends declared on common stock	(162,408)			(162,408)
Employee stock-based compensation	7,353		7,353
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(3,261)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(3,015)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)		246,214
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings		$ 246
Issuance of common stock (in shares)		4,111,669
Issuance of common stock	106,848	$ 4,112	102,736
Balance at Dec. 31, 2019	2,847,246	$ 200,923	1,355,404	1,336,647	(42,102)	$ (3,626)
Balance (in shares) at Dec. 31, 2019		200,922,790
Treasury stock (in shares) at Dec. 31, 2019						(538,921)
Net income	390,205			390,205
Other comprehensive income (loss)	(5,976)				(5,976)
Dividends declared on common stock	(168,489)			(168,489)
Employee stock-based compensation	13,096		13,096
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(388)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(362)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)		26,406
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings		$ 26
Issuance of common stock (in shares)		112,002
Issuance of common stock	3,385	$ 112	3,273
Balance at Dec. 31, 2020	$ 3,079,105	$ 201,061	1,371,385	1,558,363	(48,078)	$ (3,626)
Balance (in shares) at Dec. 31, 2020	201,061,198	201,061,198
Treasury stock (in shares) at Dec. 31, 2020						(538,921)
Net income	$ 378,131			378,131
Other comprehensive income (loss)	7,074				7,074
Dividends declared on common stock	(174,084)			(174,084)
Employee stock-based compensation	14,709		14,709
Repurchase of common stock (in shares)						(392,294)
Repurchase of common stock	(6,701)					$ (6,701)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(10,828)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)						392,294
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings						$ 6,701
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(4,127)
Issuance of common stock (in shares)		2,828,463
Issuance of common stock	88,767	$ 2,828	85,939
Balance at Dec. 31, 2021	$ 3,382,874	$ 203,889	$ 1,461,205	$ 1,762,410	$ (41,004)	$ (3,626)
Balance (in shares) at Dec. 31, 2021	203,889,661	203,889,661
Treasury stock (in shares) at Dec. 31, 2021						(538,921)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income	$ 378,131	$ 390,205	$ 335,453
Income (loss) from discontinued operations, net of tax	400	(322)	287
Income from continuing operations	377,731	390,527	335,166
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	299,214	285,100	256,017
Deferred income taxes	60,250	(1,801)	63,415
Provision for credit losses	1,085	10,576	7,864
Amortization of debt issuance costs	1,333	2,162	1,330
Employee stock-based compensation costs	14,709	13,096	7,353
Pension & postretirement benefit plan net periodic benefit cost (credit)	(4,900)	(3,001)	703
Unrealized gains on investments	(7,728)	(14,563)	(11,445)
Gains on sales of assets	(13,056)	(15,350)	(15,479)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(60,024)	(2,780)	(112,238)
Inventories	(42,302)	(7,221)	9,331
Other current assets	(71,964)	31,601	(38,283)
Accounts payable	15,247	15,955	30,079
Other current liabilities	(17,650)	35,591	51,278
Pension & postretirement benefit plan contributions	(476)	(434)	(25,613)
Other noncurrent changes	(55,367)	30,291	(17,662)
Net cash provided by continuing operations	496,102	769,749	541,816
Net cash provided by (used in) discontinued operations	(325)	(1,375)	464
Net cash provided by operating activities	495,777	768,374	542,280
Investing activities:
Capital expenditures	(659,425)	(558,007)	(576,065)
Acquisitions, net of cash acquired	(237,718)	(105,979)	(55,597)
Net proceeds from sale or disposition of property and other	15,238	35,557	29,812
Investments	(3,973)	(1,814)	(2,011)
Net cash used in investing activities	(885,878)	(630,243)	(603,861)
Financing activities:
Issuance of short-term borrowings	50,000	75,000	170,000
Repayment of short-term borrowings	(100,000)	(25,000)	(170,000)
Issuance of long-term debt	554,027	117,450	603,969
Repayment of long-term debt	(24,979)	(148,634)	(468,917)
Debt issuance costs	(918)	(477)	(4,537)
Proceeds from issuance of common stock	88,767	3,385	106,848
Dividends paid	(171,354)	(166,405)	(160,256)
Repurchase of common stock	(6,701)	0	0
Tax withholding on stock-based compensation	(4,127)	(362)	(3,015)
Net cash provided by (used in) financing activities	384,715	(145,043)	74,092
Increase (decrease) in cash and cash equivalents	(5,386)	(6,912)	12,511
Cash and cash equivalents - beginning of year	59,547	66,459	53,948
Cash and cash equivalents - end of year	$ 54,161	$ 59,547	$ 66,459

Basis of Presentation

Basis of Presentation	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure	Basis of Presentation The abbreviations and acronyms used throughout are defined following the Notes to Consolidated Financial Statements. The consolidated financial statements of the Company include the accounts of the following businesses: electric, natural gas distribution, pipeline, construction materials and contracting, construction services and other. The electric and natural gas distribution businesses, as well as a portion of the pipeline business, are regulated. Construction materials and contracting, construction services and the other businesses, as well as a portion of the pipeline business, are non-regulated. For further descriptions of the Company's businesses, see Note 17. Beginning in March 2020, governmental restrictions and guidelines implemented to control the spread of COVID-19 reduced commercial and interpersonal activity throughout the Company's areas of operation. Most of the Company's products and services are considered essential to America and its communities and, as a result, operations have generally continued through the COVID-19 pandemic and reopening of the country's economy. The Company has assessed the impacts of the COVID-19 pandemic on its results of operations for the years ended December 31, 2021 and 2020, and determined there were no material adverse impacts. The assets and liabilities of the Company's discontinued operations have been classified as held for sale and are included in prepayments and other current assets, noncurrent assets - other and other accrued liabilities on the Consolidated Balance Sheets and are not material to the financial statements for any period presented. The results and supporting activities are shown in income (loss) from discontinued operations on the Consolidated Statements of Income. Unless otherwise indicated, the amounts presented in the accompanying notes to the consolidated financial statements relate to the Company's continuing operations. In 2021, the Company made changes to the presentation of the Consolidated Statements of Cash Flows to provide further clarity on the sources and uses of net cash provided by operating activities and net cash provided by (used in) financing activities. Certain prior year amounts have been reclassified to conform to the current year presentation. These reclassifications did not impact total net cash provided by operating activities or net cash provided by (used in) financing activities for the years ended December 31, 2020 and 2019. Management has also evaluated the impact of events occurring after December 31, 2021, up to the date of issuance of these consolidated financial statements on February 23, 2022, that would require recognition or disclosure in the financial statements. Principles of consolidation The consolidated financial statements were prepared in accordance with GAAP and include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation, except for certain transactions related to the Company's regulated operations in accordance with GAAP. For more information on intercompany revenues, see Note 17. The statements also include the Company's ownership interests in the assets, liabilities and expenses of jointly owned electric transmission and generating facilities. See Note 19 for additional information. Use of estimates The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Estimates are used for items such as long-lived assets and goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; aggregate reserves; property depreciable lives; tax provisions; revenue recognized using the cost-to-cost measure of progress for contracts; expected credit losses; environmental and other loss contingencies; regulatory assets expected to be recovered in rates charged to customers; costs on construction contracts; unbilled revenues; actuarially determined benefit costs; asset retirement obligations; lease classification; present value of right-of-use assets and lease liabilities; and the valuation of stock-based compensation. As additional information becomes available, or actual amounts are determinable, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Significant Accounting Policies New accounting standards The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its financial statements and or disclosures: Standard Description Effective date Impact on financial statements/disclosures Recently adopted accounting standards ASU 2018-14 - Changes to the Disclosure Requirements for Defined Benefit Plans In August 2018, the FASB issued guidance on modifying the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans as part of the disclosure framework project. The guidance removed disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and added disclosure requirements identified as relevant. The guidance added, among other things, the requirement to include an explanation for significant gains and losses related to changes in benefit obligations for the period. The guidance removed, among other things, the disclosure requirement to disclose the amount of net periodic benefit costs to be amortized over the next fiscal year from accumulated other comprehensive income (loss) and the effects a one percentage point change in assumed health care cost trend rates will have on certain benefit components. January 1, 2021 The Company determined the guidance did not materially impact its consolidated financial statement disclosures. ASU 2019-12 - Simplifying the Accounting for Income Taxes In December 2019, the FASB issued guidance on simplifying the accounting for income taxes by removing certain exceptions in ASC 740 and providing simplification amendments. The guidance removed exceptions on intraperiod tax allocations and reporting and provided simplification on accounting for franchise taxes, tax basis goodwill and tax law changes. January 1, 2021 The Company determined the guidance did not materially impact its results of operations, financial position, cash flows or disclosures. Recently issued accounting standards not yet adopted 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 identify a replacement rate by June 30, 2023. Effective as of March 12, 2020 and will continue through December 31, 2022 The Company has updated its credit agreements to include language regarding the successor or alternate rate to LIBOR, and a review of other contracts and agreements is on-going. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures. ASU 2021-10 - Government Assistance In November 2021, the FASB issued guidance on modifying the disclosure requirements to increase the transparency of government assistance including disclosure of the types of assistance, an entity's accounting for the assistance and the effect of the assistance on an entity's financial statements. January 1, 2022 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2022. Cash and cash equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Revenue recognition 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 electric and natural gas distribution segments generate revenue from the sales of electric and natural gas products and services, which includes retail and transportation services. These segments establish a customer's retail or transportation service account based on the customer's application/ contract for service, which indicates approval of a contract for service. The contract identifies an obligation to provide service in exchange for delivering or standing ready to deliver the identified commodity; and the customer is obligated to pay for the service as provided in the applicable tariff. The product sales are based on a fixed rate that includes a base and per-unit rate, which are included in approved tariffs as determined by state or federal regulatory agencies. The quantity of the commodity consumed or transported determines the total per-unit revenue. The service provided, along with the product consumed or transported, are a single performance obligation because both are required in combination to successfully transfer the contracted product or service to the customer. Revenues are recognized over time as customers receive and consume the products and services. The method of measuring progress toward the completion of the single performance obligation is on a per-unit output method basis, with revenue recognized based on the direct measurement of the value to the customer of the goods or services transferred to date. For contracts governed by the Company’s utility tariffs, amounts are billed monthly with the amount due between 15 and 22 days of receipt of the invoice depending on the applicable state’s tariff. For other contracts not governed by tariff, payment terms are net 30 days. At this time, the segment has no material obligations for returns, refunds or other similar obligations. The pipeline segment generates revenue from providing natural gas transportation and underground storage services, as well as other energy-related services to both third parties and internal customers, largely the natural gas distribution segment. The pipeline segment establishes a contract with a customer based upon the customer’s request for firm or interruptible natural gas transportation or storage service(s). The contract identifies an obligation for the segment to provide the requested service(s) in exchange for consideration from the customer over a specified term. Depending on the type of service(s) requested and contracted, the service provided may include transporting or storing an identified quantity of natural gas and/or standing ready to deliver or store an identified quantity of natural gas. Natural gas transportation and storage revenues are based on fixed rates, which may include reservation fees and/or per-unit commodity rates. The services provided by the segment are generally treated as single performance obligations satisfied over time simultaneous to when the service is provided and revenue is recognized. Rates for the segment’s regulated services are based on its FERC approved tariff or customer negotiated rates, and rates for its non-regulated services are negotiated with its customers and set forth in the contract. For contracts governed by the company’s tariff, amounts are billed on or before the ninth business day of the following month and the amount is due within 12 days of receipt of the invoice. For other contracts not governed by the tariff, payment terms are net 30 days. At this time, the segment has no material obligations for returns, refunds or other similar obligations. The construction materials and contracting segment generates revenue from contracting services and construction materials sales. This segment focuses on the vertical integration of its contracting services with its construction materials to support the aggregate-based product lines. This segment provides contracting services to a customer when a contract has been signed by both the customer and a representative of the segment obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services this segment provides generally includes integrating a set of services and related construction materials into a single project to create a distinct bundle of goods and services, which the Company evaluates to determine whether a separate performance obligation exists. The transaction price is the original contract price plus any subsequent change orders and variable consideration. Examples of variable consideration that exist in this segment's contracts include liquidated damages; performance bonuses or incentives and penalties; claims; unapproved/unpriced change orders; and index pricing. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using estimation methods that best predict the most likely amount of consideration the Company expects to be entitled to or expects to incur. The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management's estimates made in determining the value of variable consideration recorded. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. This is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. This segment also sells construction materials to third parties and internal customers. The contract for material sales is the use of a sales order or an invoice, which includes the pricing and payment terms. All material contracts contain a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations. The construction services segment generates revenue from specialty contracting services which also includes the sale of construction equipment and other supplies. This segment provides specialty contracting services to a customer when a contract has been signed by both the customer and a representative of the segment obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services this segment provides generally includes multiple promised goods and services in a single project to create a distinct bundle of goods and services, which the Company evaluates to determine whether a separate performance obligation exists. The transaction price is the original contract price plus any subsequent change orders and variable consideration. Examples of variable consideration that exist in this segment's contracts include claims, unapproved/unpriced change orders, bonuses, incentives, penalties and liquidated damages. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using estimation methods that best predict the most likely amount of consideration the Company expects to be entitled to or expects to incur. The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management's estimates made in determining the value of variable consideration recorded. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Revenue is recognized over time using the input method based on the measurement of progress on a project. The input method is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. This segment also sells construction equipment and other supplies to third parties and internal customers. The contract for these sales is the use of a sales order or invoice, which includes the pricing and payment terms. All such contracts include a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations. The Company recognizes all other revenues when services are rendered or goods are delivered. Legal costs The Company expenses external legal fees as they are incurred. Business combinations For all business combinations, the Company preliminarily allocates the purchase price of the acquisitions to the assets acquired and liabilities assumed based on their estimated fair values as of the acquisition dates and are considered provisional until final fair values are determined or the measurement period has passed. The Company expects to record adjustments as it accumulates the information needed to estimate the fair value of assets acquired and liabilities assumed, including working capital balances, estimated fair value of identifiable intangible assets, property, plant and equipment, total consideration and goodwill. The excess of the purchase price over the aggregate fair values is recorded as goodwill. The Company calculated the fair value of the assets acquired in 2021 and 2020 using a market or cost approach (or a combination of both). Fair values for some of the assets were determined based on Level 3 inputs including estimated future cash flows, discount rates, growth rates, sales projections, retention rates and terminal values, all of which require significant management judgment and are susceptible to change. The final fair value of the net assets acquired may result in adjustments to the assets and liabilities, including goodwill, and will be made as soon as practical, but no later than 12 months from the respective acquisition dates. Any subsequent measurement period adjustments are not expected to have a material impact on the Company's results of operations. 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 3. 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 $44.8 million and $43.9 million at December 31, 2021 and 2020, 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. The Company conducted additional analysis of its receivables and allowance for expected credit losses due to the impacts of COVID-19. As more customer balances entered arrears, further analysis supported increasing the uncollectible factors used in determining the expected credit losses of certain segments during 2020. During 2021, certain segments continued to experience balances in arrears higher than historical levels, which supported the continued use of increased uncollectible factors, while other segments experienced balances in arrears returning to historical levels alleviating the need for certain associated credit loss estimates. 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 Construction Total (In thousands) At January 1, 2020 $ 328 $ 1,056 $ — $ 5,357 $ 1,756 $ 8,497 Current expected credit loss provision* 1,517 3,187 2 1,447 4,832 10,985 Less write-offs charged against the allowance 1,289 2,511 — 640 866 5,306 Credit loss recoveries collected 343 839 — — — 1,182 At December 31, 2020 899 2,571 2 6,164 5,722 15,358 Current expected credit loss provision* 1,099 2,188 — 68 (2,250) 1,105 Less write-offs charged against the allowance 2,139 4,072 — 826 1,032 8,069 Credit loss recoveries collected 410 819 — — 93 1,322 At December 31, 2021 $ 269 $ 1,506 $ 2 $ 5,406 $ 2,533 $ 9,716 * Includes impacts from businesses acquired. Receivables also consist of accrued unbilled revenue representing revenues recognized in excess of amounts billed. Accrued unbilled revenue at MDU Energy Capital was $144.9 million and $94.0 million at December 31, 2021 and 2020, respectively. Amounts representing balances billed but not paid by customers under retainage provisions in contracts at December 31 were as follows: 2021 2020 (In thousands) Short-term retainage* $ 70,600 $ 100,054 Long-term retainage** 10,742 2,761 Total retainage $ 81,342 $ 102,815 * Expected to be paid within 12 months or less and included in receivables, net. ** Included in noncurrent assets - other. 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 at December 31 consisted of: 2021 2020 (In thousands) Aggregates held for resale $ 184,363 $ 175,782 Asphalt oil 57,002 28,238 Materials and supplies 30,629 25,142 Merchandise for resale 28,501 21,087 Natural gas in storage (current) 18,867 21,919 Other 16,247 18,999 Total $ 335,609 $ 291,167 The remainder of natural gas in storage, which largely represents the cost of gas required to maintain pressure levels for normal operating purposes, was included in noncurrent assets - other and was $47.5 million at December 31, 2021 and 2020. Property, plant and equipment Additions to property, plant and equipment are recorded at cost. When regulated assets are retired, or otherwise disposed of in the ordinary course of business, the original cost of the asset is charged to accumulated depreciation. With respect to the retirement or disposal of all other assets, the resulting gains or losses are recognized as a component of income. The Company is permitted to capitalize AFUDC on regulated construction projects and to include such amounts in rate base when the related facilities are placed in service. In addition, the Company capitalizes interest, when applicable, on certain construction projects associated with its other operations. The amount of AFUDC for the years ended December 31 was as follows: 2021 2020 2019 (In thousands) AFUDC - borrowed $ 2,833 $ 2,640 $ 2,807 AFUDC - equity $ 6,961 $ 1,270 $ 698 Generally, property, plant and equipment are depreciated on a straight-line basis over the average useful lives of the assets, except for depletable aggregate reserves, which are depleted based on the units-of-production method. The Company collects removal costs for certain plant assets in regulated utility rates. These amounts are recorded as regulatory liabilities on the Consolidated Balance Sheets. Impairment of long-lived assets The Company reviews the carrying values of its long-lived assets, excluding goodwill, whenever events or changes in circumstances indicate that such carrying values may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted future cash flows attributable to the assets, compared to the carrying value of the assets. If impairment has occurred, the amount of the impairment recognized is determined by estimating the fair value of the assets and recording a loss if the carrying value is greater than the fair value. The impairments are recorded in operation and maintenance expense on the Consolidated Statements of Income. No significant impairment losses were recorded in 2021, 2020 or 2019. Unforeseen events and changes in circumstances could require the recognition of impairment losses at some future date. Regulatory assets and liabilities The Company's regulated businesses are subject to various state and federal agency regulations. The accounting policies followed by these businesses are generally subject to the Uniform System of Accounts of the FERC as well as the provisions of ASC 980 - Regulated Operations . These accounting policies differ in some respects from those used by the Company's non-regulated businesses. The Company's regulated businesses account for certain income and expense items under the provisions of regulatory accounting, which requires these businesses to defer as regulatory assets or liabilities certain items that would have otherwise been reflected as expense or income, respectively. The Company records regulatory assets or liabilities at the time the Company determines the amounts to be recoverable in current or future rates. Regulatory assets and liabilities are being amortized consistently with the regulatory treatment established by the FERC and the applicable state public service commission. See Note 6 for more information regarding the nature and amounts of these regulatory deferrals. Natural gas costs recoverable or refundable through rate adjustments Under the terms of certain orders of the applicable state public service commissions, the Company is deferring natural gas commodity, transportation and storage costs that are greater or less than amounts presently being recovered through its existing rate schedules. Such orders generally provide that these amounts are recoverable or refundable through rate adjustments. Natural gas costs refundable through rate adjustments were $6.7 million and $18.6 million at December 31, 2021 and 2020, respectively, which was included in regulatory liabilities due within one year on the Consolidated Balance Sheets. Natural gas costs recoverable through rate adjustments were $91.6 million and $64.0 million at December 31, 2021 and 2020, respectively, which was included in current regulatory assets and noncurrent assets - regulatory assets on the Consolidated Balance Sheets. Goodwill Goodwill represents the excess of the purchase price over the fair value of identifiable net tangible and intangible assets acquired in a business combination. Goodwill is required to be tested for impairment annually, which the Company completes in the fourth quarter, or more frequently if events or changes in circumstances indicate that goodwill may be impaired. The Company has determined that the reporting units for its goodwill impairment test are its operating segments, or components of an operating segment, that constitute a business for which discrete financial information is available and for which segment management regularly reviews the operating results. For more information on the Company's operating segments, see Note 17. Goodwill impairment, if any, is measured by comparing the fair value of each reporting unit to its carrying value. If the fair value of a reporting unit exceeds its carrying value, the goodwill of the reporting unit is not impaired. If the carrying value of a reporting unit exceeds its fair value, the Company must record an impairment loss for the amount that the carrying value of the reporting unit, including goodwill, exceeds the fair value of the reporting unit. For the years ended December 31, 2021, 2020 and 2019, there were no impairment losses recorded. The Company performed its annual goodwill impairment test in the fourth quarter of 2021 and determined the fair value substantially exceeded the carrying value at all reporting units at October 31, 2021. Investments The Company's investments include the cash surrender value of life insurance policies, an insurance contract, mortgage-backed securities and U.S. Treasury securities. The Company measures its investment in the insurance contract at fair value with any unrealized gains and losses recorded on the Consolidated Statements of Income. The Company has not elected the fair value option for its mortgage-backed securities and U.S. Treasury securities and, as a result, the unrealized gains and losses on these investments are recorded in accumulated other comprehensive loss. For more information, see Notes 8 and 18. Joint ventures The Company accounts for unconsolidated joint ventures using either the equity method or proportionate consolidation. The Company currently holds interests between 33 percent and 50 percent in joint ventures formed primarily for the purpose of pooling resources on construction contracts. Proportionate consolidation is used for joint ventures that include unincorporated legal entities and activities of the joint venture which are construction-related. For those joint ventures accounted for under proportionate consolidation, only the Company’s pro rata share of assets, liabilities, revenues and expenses are included in the Company’s balance sheet and results of operations. For those joint ventures accounted for using proportionate consolidation, the Company recorded in its Consolidated Statements of Income $14.7 million and $69.7 million of revenue for the years ended December 31, 2021 and 2020, respectively, and $4.7 million and $20.6 million of operating income for the years ended December 31, 2021 and 2020, respectively. At December 31, 2021 and 2020, the Company had receivables from these joint ventures of $1.2 million and $1.8 million, respectively. For those joint ventures accounted for under the equity method, the Company's investment balances for the joint venture is included in Investments in the Consolidated Balance Sheets and the Company’s pro rata share of net income is included in Other income in the Consolidated Statements of Income. The Company’s investments in equity method joint ventures at December 31, 2021 and 2020, were a net asset of $1.3 million and $425,000, respectively. In 2021 and 2020, the Company recognized income (loss) from equity method joint ventures of $892,000 and $(32,000), respectively. Derivative instruments The Company enters into commodity price derivative contracts in order to minimize the price volatility associated with customer natural gas costs at its natural gas distribution segment. These derivatives are not designated as hedging instruments and are recorded in the Consolidated Balance Sheets at fair value. Changes in the fair value of these derivatives along with any contract settlements are recorded each period in regulatory assets or liabilities in accordance with regulatory accounting. The Company does not enter into any derivatives for trading or other speculative purposes. During 2021 and 2020, the Company entered into commodity price derivative contracts securing the purchase of 450,000 MMBtu and 1.4 million MMBtu of natural gas, respectively. Leases Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company recognizes leases with an original lease term of 12 months or less in income on a straight-line basis over the term of the lease and does not recognize a corresponding right-of-use asset or lease liability. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue. The discount rate used to calculate the present value of the lease liabilities is based upon the implied rate within each contract. If the rate is unknown or cannot be determined, the Company uses an incremental borrowing rate, which is determined by the length of the contract, asset class and the Company's borrowing rates, as of the commencement date of the contract. Asset retirement obligations The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes a cost by increasing the carrying amount of the related long-lived asset. Over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. Upon settlement of the liability, the Company either settles the obligation for the recorded amount or incurs a gain or loss at its non-regulated operations or incurs a regulatory asset or liability at its regulated operations. Stock-based compensation The Company determines compensation expense for stock-based awards based on the estimated fair values at the grant date and recognizes the related compensation expense over the vesting period. The Company uses the straight-line amortization method to recognize compensation expense related to restricted stock, which only has a service condition. This method recognizes stock compensation expense on a straight-line basis over the requisite service period for the entire award. The Company recognizes compensation expense related to performance awards that vest based on performance metrics and service conditions on a straight-line basis over the service period. Inception-to-date expense is adjusted based upon the determination of the potential achievement of the performance target at each reporting date. The Company recognizes compensation expense related

Revenue from Contract with Cust

Revenue from Contract with Customer	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue from contracts from 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. As part of the adoption of ASC 606 - Revenue from Contracts with Customers , the Company elected the practical expedient to recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that the Company otherwise would have recognized is 12 months or less. Disaggregation In the following table, 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 17. Year ended December 31, 2021 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 126,841 $ 544,721 $ — $ — $ — $ — $ 671,562 Commercial utility sales 137,556 328,285 — — — — 465,841 Industrial utility sales 41,757 30,964 — — — — 72,721 Other utility sales 7,051 — — — — — 7,051 Natural gas transportation — 48,408 114,001 — — — 162,409 Natural gas storage — — 14,680 — — — 14,680 Contracting services — — — 1,017,471 — — 1,017,471 Construction materials — — — 1,712,503 — — 1,712,503 Intrasegment eliminations — — — (501,044) — — (501,044) Electrical & mechanical specialty contracting — — — — 1,324,419 — 1,324,419 Transmission & distribution specialty contracting — — — — 677,074 — 677,074 Other 42,902 10,567 13,667 — 557 13,714 81,407 Intersegment eliminations (543) (576) (59,678) (624) (2,555) (13,630) (77,606) Revenues from contracts with customers 355,564 962,369 82,670 2,228,306 1,999,495 84 5,628,488 Revenues out of scope (6,525) 8,995 188 — 49,587 — 52,245 Total external operating revenues $ 349,039 $ 971,364 $ 82,858 $ 2,228,306 $ 2,049,082 $ 84 $ 5,680,733 Year ended December 31, 2020 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 122,663 $ 476,388 $ — $ — $ — $ — $ 599,051 Commercial utility sales 131,477 277,873 — — — — 409,350 Industrial utility sales 36,744 26,243 — — — — 62,987 Other utility sales 6,634 — — — — — 6,634 Natural gas transportation — 45,546 111,686 — — — 157,232 Natural gas gathering — — 4,865 — — — 4,865 Natural gas storage — — 14,918 — — — 14,918 Contracting services — — — 1,069,665 — — 1,069,665 Construction materials — — — 1,659,152 — — 1,659,152 Intrasegment eliminations — — — (550,815) — — (550,815) Electrical & mechanical specialty contracting — — — — 1,397,124 — 1,397,124 Transmission & distribution specialty contracting — — — — 649,486 — 649,486 Other 32,452 10,753 12,216 — 1,541 11,903 68,865 Intersegment eliminations (491) (534) (58,531) (417) (5,038) (11,958) (76,969) Revenues from contracts with customers 329,479 836,269 85,154 2,177,585 2,043,113 (55) 5,471,545 Revenues out of scope 2,059 11,382 192 — 47,572 — 61,205 Total external operating revenues $ 331,538 $ 847,651 $ 85,346 $ 2,177,585 $ 2,090,685 $ (55) $ 5,532,750 Year ended December 31, 2019 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 125,369 $ 483,452 $ — $ — $ — $ — $ 608,821 Commercial utility sales 141,596 296,835 — — — — 438,431 Industrial utility sales 37,765 26,895 — — — — 64,660 Other utility sales 7,408 — — — — — 7,408 Natural gas transportation — 45,449 101,665 — — — 147,114 Natural gas gathering — — 9,164 — — — 9,164 Natural gas storage — — 11,708 — — — 11,708 Contracting services — — — 1,088,633 — — 1,088,633 Construction materials — — — 1,627,833 — — 1,627,833 Intrasegment eliminations — — — (525,749) — — (525,749) Electrical & mechanical specialty contracting — — — — 1,266,196 — 1,266,196 Transmission & distribution specialty contracting — — — — 531,882 — 531,882 Other 35,574 12,726 17,687 — 131 16,551 82,669 Intersegment eliminations — — (56,252) (1,066) (3,370) (16,461) (77,149) Revenues from contracts with customers 347,712 865,357 83,972 2,189,651 1,794,839 90 5,281,621 Revenues out of scope 4,013 (135) 220 — 51,057 — 55,155 Total external operating revenues $ 351,725 $ 865,222 $ 84,192 $ 2,189,651 $ 1,845,896 $ 90 $ 5,336,776 Presented in the previous tables are intrasegment revenues within the construction materials and contracting segment to highlight the focus on vertical integration as this segment sells materials to both third parties and internal customers. Due to consolidation requirements, these revenues must be eliminated against construction materials to arrive at the external operating revenue total for the segment. 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 contracting services 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: December 31, 2021 December 31, 2020 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 125,742 $ 104,345 $ 21,397 Receivables, net Contract liabilities - current (179,140) (158,603) (20,537) Accounts payable Contract liabilities - noncurrent (118) (52) (66) Noncurrent liabilities - other Net contract liabilities $ (53,516) $ (54,310) $ 794 December 31, 2020 December 31, 2019 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 104,345 $ 109,078 $ (4,733) Receivables, net Contract liabilities - current (158,603) (142,768) (15,835) Accounts payable Contract liabilities - noncurrent (52) (19) (33) Noncurrent liabilities - other Net contract liabilities $ (54,310) $ (33,709) $ (20,601) The Company recognized $155.0 million and $138.2 million in revenue for the years ended December 31, 2021 and 2020, respectively, which was previously included in contract liabilities at December 31, 2020 and 2019, respectively. The Company recognized a net increase in revenues of $66.3 million and $58.8 million for the years ended December 31, 2021 and 2020, respectively, from performance obligations satisfied in prior periods. Remaining performance obligations The remaining performance obligations, also referred to as backlog, at the construction materials and contracting and construction services segments include 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 construction 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 that 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 less than five and one years, respectively.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
Business combination disclosure	Business Combinations The following acquisitions were accounted for as business combinations in accordance with ASC 805 - Business Combinations. The results of the business combinations have been included in the Company's Consolidated Financial Statements beginning on the acquisition date. Pro forma financial amounts reflecting the effects of the business combinations are not presented, as none of these business combinations, individually or in the aggregate, were material to the Company's financial position or results of operations. The acquisitions are also subject to customary adjustments based on, among other things, the amount of cash, debt and working capital in the business as of the closing date. The amounts included in the Consolidated Balance Sheets for these adjustments are considered provisional until final settlement has occurred. In 2021 and 2020, the construction materials and contracting segment's acquisitions included: • Baker Rock Resources and Oregon Mainline Paving, two premier construction materials companies located around the Portland, Oregon metro area, acquired in November 2021. At December 31, 2021, the purchase price allocation was preliminary and will be finalized within 12 months of the acquisition date. • Mt. Hood Rock, a construction aggregates business in Oregon, acquired in April 2021. At December 31, 2021, the purchase price allocation was preliminary and will be finalized within 12 months of the acquisition date. • The assets of McMurry Ready-Mix Co., an aggregates and concrete supplier in Wyoming, acquired in December 2020. In the third quarter of 2021, the Company finalized the provisional accounting and recorded an immaterial measurement period adjustment. • The assets of Oldcastle Infrastructure Spokane, a prestressed-concrete business in Washington, acquired in February 2020. As of December 31, 2020, the purchase price adjustments had been settled with no material adjustments to the provisional accounting. In February 2020, the construction services segment acquired PerLectric, Inc., an electrical construction company in Virginia. As of March 31, 2021, the purchase price adjustments had been settled with no material adjustments to the provisional accounting. The total purchase price for acquisitions that occurred in 2021 was $236.1 million, subject to certain adjustments, with cash acquired totaling $900,000. The purchase price includes consideration paid of $235.2 million. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2021 were as follows: $17.0 million to current assets; $179.8 million to property, plant and equipment; $50.6 million to goodwill; $2.2 million to other intangible assets; $8.7 million to current liabilities; $2.5 million to noncurrent liabilities - other and $3.2 million to deferred tax liabilities. The Company issued debt to finance these acquisitions. The total purchase price for acquisitions that occurred in 2020 was $110.2 million, subject to certain adjustments, with cash acquired totaling $1.7 million. The purchase price includes consideration paid of $106.0 million and $2.5 million of indemnity holdback liabilities. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2020 were as follows: $54.8 million to current assets; $27.1 million to property, plant and equipment; $33.6 million to goodwill; $19.0 million to other intangible assets; $22.6 million to current liabilities; $300,000 to noncurrent liabilities - other and $1.4 million to asset retirement obligations. The $2.5 million indemnity holdback liability related to 2020 acquisitions was paid in 2021. The Company issued debt to finance these acquisitions. Costs incurred for acquisitions are included in operation and maintenance expense on the Consolidated Statements of Income and were not material for the years ended December 31, 2021, 2020 and 2019.

Property, Plant, and Equipment

Property, Plant, and Equipment	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment Disclosure	Property, Plant and Equipment Property, plant and equipment at December 31 was as follows: 2021 2020 Weighted (Dollars in thousands, where applicable) Regulated: Electric: Generation $ 1,056,632 $ 1,133,390 48 Distribution 474,037 464,442 47 Transmission 562,080 524,155 65 Construction in progress 62,781 61,766 — Other 140,117 139,650 14 Natural gas distribution: Distribution 2,427,779 2,302,121 50 Transmission 107,721 104,695 60 Storage 34,997 33,014 39 General 197,653 198,211 14 Construction in progress 21,741 16,836 — Other 225,272 213,976 14 Pipeline: Transmission 673,344 665,567 46 Storage 57,670 52,632 53 Construction in progress 263,640 46,690 — Other 50,477 49,640 17 Non-regulated: Pipeline: Construction in progress 18 4 — Other 6,719 7,164 10 Construction materials and contracting: Land 149,066 132,948 — Buildings and improvements 149,262 130,417 21 Machinery, vehicles and equipment 1,414,260 1,284,604 12 Construction in progress 50,425 23,803 — Aggregate reserves 584,683 456,704 * Construction services: Land 6,513 7,218 — Buildings and improvements 39,039 41,674 24 Machinery, vehicles and equipment 166,739 163,080 7 Other 13,467 8,824 2 Other: Land 2,648 2,648 — Other 34,069 34,897 7 Less accumulated depreciation, depletion and amortization 3,216,461 3,133,831 Net property, plant and equipment $ 5,756,388 $ 5,166,939 * Depleted on the units-of-production method based on recoverable aggregate reserves.

Regulatory assets and liabiliti

Regulatory assets and liabilities	12 Months Ended
	Dec. 31, 2021
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 as of December 31: Estimated Recovery or Refund Period * 2021 2020 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 86,371 $ 42,481 Decoupling Up to 1 year 9,131 703 Conservation programs Up to 1 year 8,225 7,117 Cost recovery mechanisms Up to 1 year 4,536 10,645 Other Up to 1 year 10,428 7,581 118,691 68,527 Noncurrent: Pension and postretirement benefits ** 142,681 155,942 Plant costs/asset retirement obligations Over plant lives 63,116 71,740 Plant to be retired - 50,070 65,919 Cost recovery mechanisms Up to 10 years 44,870 16,245 Manufactured gas plant sites remediation - 26,053 26,429 Taxes recoverable from customers Over plant lives 12,339 10,785 Natural gas costs recoverable through rate adjustments Up to 2 years 5,186 21,539 Long-term debt refinancing costs Up to 39 years 3,794 4,426 Other Up to 17 years 9,742 6,356 357,851 379,381 Total regulatory assets $ 476,542 $ 447,908 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year $ 6,700 $ 18,565 Taxes refundable to customers Up to 1 year 3,841 3,557 Electric fuel and purchased power deferral Up to 1 year — 3,667 Other Up to 1 year 5,762 5,661 16,303 31,450 Noncurrent: Taxes refundable to customers Over plant lives 215,421 227,850 Plant removal and decommissioning costs Over plant lives 168,152 167,171 Pension and postretirement benefits ** 20,434 16,989 Other Up to 20 years 24,783 16,065 428,790 428,075 Total regulatory liabilities $ 445,093 $ 459,525 Net regulatory position $ 31,449 $ (11,617) * 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. As of December 31, 2021 and 2020, approximately $296.6 million and $332.5 million, respectively, of regulatory assets were not earning a rate of return but are expected to be recovered from customers in future rates. These assets are largely comprised of the unfunded portion of pension and postretirement benefits, asset retirement obligations, accelerated depreciation on plant retirement and the estimated future cost of manufactured gas plant site remediation. In February 2021, a prolonged period of unseasonably cold temperatures in the central United States significantly increased the demand for electric and natural gas services and contributed to increased market prices. Overall, Montana-Dakota and Great Plains incurred approximately $44.0 million in increased natural gas costs in order to maintain services for its customers. These extraordinary natural gas costs were recorded as regulatory assets as they are expected to be recovered from customers. Montana-Dakota and Great Plains have received approval for the recovery of purchased gas adjustments related to the cold-weather event in all jurisdictions impacted, including out-of-cycle purchased gas adjustment requests in most jurisdictions. For a discussion of the Company's most recent cases by jurisdiction, see Note 20. In 2019, the Company experienced increased natural gas costs in Washington from the rupture of the Enbridge pipeline in Canada in late 2018. As a result, the Company requested, and the WUTC approved, recovery of the balance of natural gas costs recoverable related to this period of time over three years rather than its normal one-year recovery period. 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. The first unit ceased operations on March 31, 2021, and the Company subsequently began amortizing plant retirement and closure costs related to this facility. During 2021, the Company received approval from the NDPSC and the SDPUC to offset the savings associated with the cessation of operations of this unit with the amortization of the deferred regulatory assets and moved the costs being recovered for this facility from plant retirement to cost recovery mechanisms in the previous table. The two remaining units are being retired during the first quarter of 2022. 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 removed from the balance sheet and included in the statement of income or accumulated other comprehensive loss in the period in which the discontinuance of regulatory accounting occurs.

Goodwill and other intangible a

Goodwill and other intangible assets	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other intangible assets	Goodwill and Other Intangible Assets The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2021 Goodwill Measurement Period Balance at December 31, 2021 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 226,003 50,640 (217) 276,426 Construction services 143,224 — — 143,224 Total $ 714,963 $ 50,640 $ (217) $ 765,386 Balance at January 1, 2020 Goodwill Acquired Measurement Period Balance at December 31, 2020 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 217,234 8,778 (9) 226,003 Construction services 118,388 24,436 400 143,224 Total $ 681,358 $ 33,214 $ 391 $ 714,963 Other amortizable intangible assets at December 31 were as follows: 2021 2020 (In thousands) Customer relationships $ 29,740 $ 28,836 Less accumulated amortization 10,650 6,887 19,090 21,949 Noncompete agreements 4,591 3,941 Less accumulated amortization 2,856 2,309 1,735 1,632 Other 12,601 12,927 Less accumulated amortization 10,848 11,012 1,753 1,915 Total $ 22,578 $ 25,496 The previous tables include goodwill and intangible assets associated with the business combinations completed during 2021 and 2020. For more information related to these business combinations, see Note 4. Amortization expense for amortizable intangible assets for the years ended December 31, 2021, 2020 and 2019, was $5.1 million, $9.0 million and $2.4 million, respectively. The amounts of estimated amortization expense for identifiable intangible assets as of December 31, 2021, were: 2022 2023 2024 2025 2026 Thereafter (In thousands) Amortization expense $ 4,928 $ 4,578 $ 4,308 $ 2,314 $ 1,693 $ 4,757

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2021
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 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 $109.6 million and $100.1 million at December 31, 2021 and 2020, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gains on these investments for the years ended December 31, 2021, 2020 and 2019, were $7.2 million, $13.1 million and $13.2 million, 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: December 31, 2021 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,702 $ 51 $ 47 $ 8,706 U.S. Treasury securities 2,407 — 11 2,396 Total $ 11,109 $ 51 $ 58 $ 11,102 December 31, 2020 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 9,799 $ 156 $ 9 $ 9,946 U.S. Treasury securities 1,386 — 5 1,381 Total $ 11,185 $ 156 $ 14 $ 11,327 The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Money market funds $ — $ 10,190 $ — $ 10,190 Insurance contract* — 109,603 — 109,603 Available-for-sale securities: Mortgage-backed securities — 8,706 — 8,706 U.S. Treasury securities — 2,396 — 2,396 Total assets measured at fair value $ — $ 130,895 $ — $ 130,895 * The insurance contract invests approximately 61 percent in fixed-income investments, 17 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 7 percent in common stock of small-cap companies, 5 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Money market funds $ — $ 8,917 $ — $ 8,917 Insurance contract* — 100,104 — 100,104 Available-for-sale securities: Mortgage-backed securities — 9,946 — 9,946 U.S. Treasury securities — 1,381 — 1,381 Total assets measured at fair value $ — $ 120,348 $ — $ 120,348 * The insurance contract invests approximately 57 percent in fixed-income investments, 18 percent in common stock of large-cap companies, 9 percent in common stock of mid-cap companies, 9 percent in common stock of small-cap companies, 5 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 contract is 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 performed a fair value assessment of the assets acquired and liabilities assumed in the business combinations that occurred during 2021 and 2020. For more information on these Level 2 and Level 3 fair value measurements, see Notes 2 and 4. 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 at December 31 was as follows: 2021 2020 (In thousands) Carrying Amount $ 2,741,900 $ 2,213,130 Fair Value $ 2,984,866 $ 2,537,289 The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values.

Debt

Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Debt	Debt Certain debt instruments of the Company's subsidiaries, including those discussed later, contain restrictive and financial covenants and cross-default provisions. In order to borrow under the debt agreements, the subsidiary companies must be in compliance with the applicable covenants and certain other conditions, all of which the subsidiaries, as applicable, were in compliance with at December 31, 2021. In the event the subsidiaries do not comply with the applicable covenants and other conditions, alternative sources of funding may need to be pursued. The following table summarizes the outstanding revolving credit facilities of the Company's subsidiaries: Company Facility Facility Amount Outstanding at December 31, 2021 Amount Outstanding at December 31, 2020 Letters of Credit at December 31, 2021 Expiration (In millions) Montana-Dakota Utilities Co. Commercial paper/Revolving credit agreement (a) $ 175.0 $ 64.9 $ 87.7 $ — 12/19/24 Cascade Natural Gas Corporation Revolving credit agreement $ 100.0 (b) $ 71.0 $ 54.0 $ 2.2 (c) 6/7/24 Intermountain Gas Company Revolving credit agreement $ 85.0 (d) $ 56.5 $ 41.9 $ — 6/7/24 Centennial Energy Holdings, Inc. Commercial paper/Revolving credit agreement (e) $ 600.0 $ 385.4 $ 37.9 $ — 12/19/24 (a) The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Montana-Dakota on stated conditions, up to a maximum of $225.0 million). There were no amounts outstanding under the revolving credit agreement. (b) Certain provisions allow for increased borrowings, up to a maximum of $125.0 million. (c) (Outstanding letter(s) of credit reduce the amount available under the credit agreement. (d) (Certain provisions allow for increased borrowings, up to a maximum of $110.0 million. (e) The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Centennial on stated conditions, up to a maximum of $700.0 million). There were no amounts outstanding under the revolving credit agreement. The respective commercial paper programs are supported by revolving credit agreements. While the amount of commercial paper outstanding does not reduce available capacity under the respective revolving credit agreements, Montana-Dakota and Centennial do not issue commercial paper in an aggregate amount exceeding the available capacity under their credit agreements. The commercial paper 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's subsidiaries. Short-term debt Montana-Dakota On March 8, 2021, Montana-Dakota entered into a $50.0 million term loan agreement with a LIBOR-based variable interest rate and a maturity date of March 7, 2022. At December 31, 2021, Montana-Dakota had no amount outstanding under the agreement. The agreement contains customary covenants and provisions, including a covenant of Montana-Dakota 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 Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at December 31, 2021 2021 2020 (In thousands) Senior Notes due on dates ranging from October 22, 2022 to September 15, 2061 4.32 % $ 2,125,000 $ 1,950,000 Commercial paper supported by revolving credit agreements .40 % 450,300 125,600 Credit agreements due on June 7, 2024 1.94 % 127,500 95,900 Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029 7.32 % 35,000 35,000 Term Loan Agreement due on September 3, 2032 2.00 % 7,700 8,400 Other notes due on dates ranging from January 2, 2022 to January 1, 2061 1.03 % 2,564 4,034 Less unamortized debt issuance costs 6,090 5,803 Less discount 74 1 Total long-term debt 2,741,900 2,213,130 Less current maturities 148,053 1,555 Net long-term debt $ 2,593,847 $ 2,211,575 Montana-Dakota Montana-Dakota's revolving credit agreement supports its commercial paper program. Commercial paper borrowings under this agreement are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued commercial paper borrowings. The credit agreement contains customary covenants and provisions, including covenants of Montana-Dakota not to permit, as of the end of any fiscal quarter, the ratio of funded debt to total capitalization (determined on a consolidated basis) to be greater than 65 percent. Other covenants include limitations on the sale of certain assets and on the making of certain loans and investments. On September 15, 2021, Montana-Dakota entered into a $125.0 million note purchase agreement with maturity dates ranging from September 15, 2051 to September 15, 2061, at a weighted average interest rate of 3.23 percent. On September 15, 2021 and December 15, 2021, Montana-Dakota issued $75.0 million and $50.0 million, respectively, in senior notes under the note purchase agreement. The agreement contains customary covenants and provisions, including a covenant of Montana-Dakota not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. Montana-Dakota's ratio of total debt to total capitalization at December 31, 2021, was 51 percent. Cascade 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 Cascade not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. Other covenants include restrictions on the sale of certain assets, limitations on indebtedness and the making of certain investments. Cascade's ratio of total debt to total capitalization at December 31, 2021, was 51 percent. Intermountain 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 Intermountain not to permit, at any time, the ratio of total debt to total capitalization to be greater than 65 percent. Other covenants include restrictions on the sale of certain assets, limitations on indebtedness and the making of certain investments. Intermountain's ratio of total debt to total capitalization at December 31, 2021, was 50 percent. Centennial Centennial's revolving credit agreement supports its commercial paper program. Commercial paper borrowings under this agreement are classified as long-term debt as they are intended to be refinanced on a long-term basis through continued commercial paper borrowings. Centennial's revolving credit agreement contains customary covenants and provisions, including a covenant of Centennial not to permit, as of the end of any fiscal quarter, the ratio of total consolidated debt to total consolidated capitalization to be greater than 65 percent. Other covenants include restricted payments, restrictions on the sale of certain assets, limitations on subsidiary indebtedness, minimum consolidated net worth, limitations on priority debt and the making of certain loans and investments. Centennial's ratio of total debt to total capitalization, as defined by its debt covenants, at December 31, 2021, was 43 percent. Certain of Centennial's financing agreements contain cross-default provisions. These provisions state that if Centennial or any subsidiary of Centennial fails to make any payment with respect to any indebtedness or contingent obligation, in excess of a specified amount, under any agreement that causes such indebtedness to be due prior to its stated maturity or the contingent obligation to become payable, the applicable agreements will be in default. WBI Energy Transmission WBI Energy Transmission has a $300.0 million uncommitted note purchase and private shelf agreement with an expiration date of May 16, 2022. WBI Energy Transmission had $195.0 million of notes outstanding at December 31, 2021, which reduced the remaining capacity under this uncommitted private shelf agreement to $105.0 million. This agreement contains customary covenants and provisions, including a covenant of WBI Energy Transmission not to permit, as of the end of any fiscal quarter, the ratio of total debt to total capitalization to be greater than 55 percent. Other covenants include a limitation on priority debt and restrictions on the sale of certain assets and the making of certain investments. On December 23, 2021, WBI Energy Transmission entered into a $50.0 million note purchase agreement with a maturity date of December 23, 2041, at an interest rate of 3.67 percent. The agreement contains customary covenants and provisions, including a covenant of WBI Energy Transmission not to permit, at any time, the ratio of total debt to total capitalization to be greater than 55 percent. WBI Energy Transmission's ratio of total debt to total capitalization at December 31, 2021, was 38 percent. Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, for the five years and thereafter following December 31, 2021, were as follows: 2022 2023 2024 2025 2026 Thereafter (In thousands) Long-term debt maturities $ 148,053 $ 77,925 $ 638,604 $ 177,802 $ 140,802 $ 1,564,878

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases of Lessee Disclosure	Leases Most of the leases the Company enters into are for equipment, buildings, easements and vehicles as part of their ongoing operations. The Company also leases certain equipment to third parties through its utility and construction services segments. The Company determines if an arrangement contains a lease at inception of a contract and accounts for all leases in accordance with ASC 842 - Leases. The recognition of leases requires the Company to make estimates and assumptions that affect the lease classification and the assets and liabilities recorded. The accuracy of lease assets and liabilities reported on the Consolidated Financial Statements depends on, among other things, management's estimates of interest rates used to discount the lease assets and liabilities to their present value, as well as the lease terms based on the unique facts and circumstances of each lease. Lessee accounting The leases the Company has entered into as part of its ongoing operations are considered operating leases and are recognized on the Consolidated Balance Sheets as operating lease right-of-use assets, operating lease liabilities due within one year and, if applicable, noncurrent liabilities - operating lease liabilities. The corresponding lease costs are included in operation and maintenance expense on the Consolidated Statements of Income. Generally, the leases for vehicles and equipment have a term of five years or less and buildings and easements have a longer term of up to 35 years or more. To date, the Company does not have any residual value guarantee amounts probable of being owed to a lessor, financing leases or material agreements with related parties. The following tables provide information on the Company's operating leases at and for the years ended December 31: 2021 2020 (In thousands) Lease costs: Short-term lease cost $ 132,449 $ 135,376 Operating lease cost 46,622 45,319 Variable lease cost 1,516 1,319 $ 180,587 $ 182,014 2021 2020 (Dollars in thousands) Weighted average remaining lease term 2.67 years 2.73 years Weighted average discount rate 3.54 % 4.03 % Cash paid for amounts included in the measurement of lease liabilities $ 43,489 $ 45,043 The reconciliation of future undiscounted cash flows to operating lease liabilities presented on the Consolidated Balance Sheet at December 31, 2021, was as follows: (In thousands) 2022 $ 38,605 2023 27,460 2024 19,732 2025 12,278 2026 6,681 Thereafter 44,039 Total 148,795 Less discount 24,174 Total operating lease liabilities $ 124,621
Leases of Lessor Disclosure	Lessor accounting 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 $50.1 million and $48.0 million for the years ended December 31, 2021 and 2020, respectively. At December 31, 2021, the Company had $9.2 million of lease receivables with a majority due within 12 months or less.

Asset retirement obligations

Asset retirement obligations	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation [Abstract]
Asset retirement obligations	Asset Retirement Obligations The Company records obligations related to retirement costs of natural gas distribution mains and lines, natural gas transmission lines, natural gas storage wells, decommissioning of certain electric generating facilities, reclamation of certain aggregate properties, special handling and disposal of hazardous materials at certain electric generating facilities, natural gas distribution facilities and buildings, and certain other obligations as asset retirement obligations. A reconciliation of the Company's liability, which the current portion is included in other accrued liabilities on the Consolidated Balance Sheets, for the years ended December 31 was as follows: 2021 2020 (In thousands) Balance at beginning of year $ 446,919 $ 417,575 Liabilities incurred 12,454 11,560 Liabilities acquired 1,805 1,378 Liabilities settled (15,155) (5,369) Accretion expense* 21,214 21,668 Revisions in estimates 1,449 107 Balance at end of year $ 468,686 $ 446,919 * Includes $19.6 million and $20.1 million in 2021 and 2020, respectively, recorded to regulatory assets. The Company believes that largely all expenses related to asset retirement obligations at the Company's regulated operations will be recovered in rates over time and, accordingly, defers such expenses as regulatory assets. For more information on the Company's regulatory assets and liabilities, see Note 6.

Equity

Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders' Equity Note Disclosure	Equity The Company depends on earnings and dividends from its subsidiaries to pay dividends on common stock. The Company has paid quarterly dividends for 84 consecutive years with an increase in the dividend amount for the last 31 consecutive years. For the years ended December 31, 2021, 2020 and 2019, dividends declared on common stock were $.8550, $.8350 and $.8150 per common share, respectively. Dividends on common stock are paid quarterly to the stockholders of record less than 30 days prior to the distribution date. For the years ended December 31, 2021, 2020 and 2019, the dividends declared to common stockholders were $173.0 million, $167.4 million and $162.1 million, respectively. The declaration and payment of dividends of the Company is at the sole discretion of the board of directors. In addition, the Company's subsidiaries are generally restricted to paying dividends out of capital accounts or net assets. The following discusses the most restrictive limitations. Pursuant to a covenant under its revolving credit agreement, Centennial may only declare or pay distributions if, as of the last day of any fiscal quarter, the ratio of Centennial's average consolidated indebtedness as of the last day of such fiscal quarter and each of the preceding three fiscal quarters to Centennial's Consolidated trailing 12 month EBITDA does not exceed 3.5 to 1. In addition, certain credit agreements and regulatory limitations of the Company's subsidiaries also contain restrictions on dividend payments. The most restrictive limitation requires the Company's subsidiaries not to permit the ratio of funded debt to capitalization to be greater than 65 percent. Based on this limitation, approximately $1.7 billion of the net assets of the Company's subsidiaries, which represents common stockholders' equity including retained earnings, would be restricted from use for dividend payments at December 31, 2021. The Company currently has a shelf registration statement on file with the SEC, under which the Company may issue and sell any combination of common stock and debt securities. The Company may sell such securities if warranted by market conditions and the Company's capital requirements. Any public offer and sale of such securities will be made only by means of a prospectus meeting the requirements of the Securities Act and the rules and regulations thereunder. In August 2020, the Company amended the Distribution Agreement dated February 22, 2019, with J.P. Morgan Securities LLC and MUFG Securities Americas Inc., as sales agents. This agreement, as amended, allows the offering, issuance and sale of up to 6.4 million shares of the Company's common stock in connection with an “at-the-market” offering. The common stock may be offered for sale, from time to time, in accordance with the terms and conditions of the agreement. As of December 31, 2021, the Company had capacity to issue up to 3.6 million additional shares of common stock under the "at-the-market" offering program. Details of the Company's "at-the-market" offering activity for the years ended December 31 was as follows: 2021 2020 (In millions) Shares issued 2.8 — Net proceeds * $ 88.8 $ — Issuance costs $ 1.2 $ — * Net proceeds were used for capital expenditures. The K-Plan provides participants the option to invest in the Company's common stock. For the years ended December 31, 2021, 2020 and 2019, the K-Plan purchased shares of common stock on the open market or issued original issue common stock of the Company. At December 31, 2021, there were 7.2 million shares of common stock reserved for original issuance under the K-Plan.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-based compensation	Stock-Based Compensation The Company has stock-based compensation plans under which it is currently authorized to grant restricted stock and other stock awards. As of December 31, 2021, there were 3.7 million remaining shares available to grant under these plans. The Company either purchases shares on the open market or issues new shares of common stock to satisfy the vesting of stock-based awards. Total stock-based compensation expense (after tax) was $12.0 million, $10.8 million and $6.5 million in 2021, 2020 and 2019, respectively. As of December 31, 2021, total remaining unrecognized compensation expense related to stock-based compensation was approximately $10.9 million (before income taxes) which will be amortized over a weighted average period of 1.6 years. Stock awards Non-employee directors receive shares of common stock in addition to and in lieu of cash payment for directors' fees. There were 41,925 shares with a fair value of $1.2 million, 45,273 shares with a fair value of $1.1 million and 41,644 shares with a fair value of $1.2 million issued to non-employee directors during the years ended December 31, 2021, 2020 and 2019, respectively. Restricted stock awards In February 2021, key employees were granted restricted stock awards under the long-term performance-based incentive plan. The shares vest over three years, contingent on continued employment. Compensation expense is recognized over the vesting period. At December 31, 2021, the number of outstanding shares granted was 93,700 with a weighted average grant-date fair value of $27.35 per share. Performance share awards Since 2003, key employees of the Company have been granted performance share awards each year under the long-term performance-based incentive plan. Entitlement to performance shares is established by either the market condition or the performance metrics and service condition relative to the designated award. Target grants of performance shares outstanding at December 31, 2021, were as follows: Grant Date Performance Target Grant February 2020 2020-2022 273,918 February 2021 2021-2023 281,129 Under the market condition for these performance share awards, participants may earn from zero to 200 percent of the apportioned target grant of shares based on the Company's total shareholder return relative to that of the selected peer group. Compensation expense is based on the grant-date fair value as determined by Monte Carlo simulation. The blended volatility term structure ranges are comprised of 50 percent historical volatility and 50 percent implied volatility. Risk-free interest rates were based on U.S. Treasury security rates in effect as of the grant date. Assumptions used for grants applicable to the market condition for certain performance shares issued in 2021, 2020 and 2019 were: 2021 2020 2019 Weighted average grant-date fair value $37.96 $40.75 $35.07 Blended volatility range 35.37% - 46.35% 15.30% - 15.97% 19.50% - 19.69% Risk-free interest rate range .02% - .20% 1.45% - 1.62% 2.46% - 2.55% Weighted average discounted dividends per share $3.16 $2.91 $2.85 Under the performance conditions for these performance share awards, participants may earn from zero to 200 percent of the apportioned target grant of shares. The performance conditions are based on the Company's compound annual growth rate in earnings from continuing operations before interest, taxes, depreciation, depletion and amortization and the Company's compound annual growth rate in earnings from continuing operations. The weighted average grant-date fair value per share for the performance shares applicable to these performance conditions issued in 2021, 2020 and 2019 was $27.35, $31.63 and $26.25, respectively. The fair value of the performance shares that vested during the years ended December 31, 2021, 2020 and 2019, was $13.7 million, $9.7 million and $9.7 million, respectively. A summary of the status of the performance share awards for the year ended December 31, 2021, was as follows: Number of Weighted Nonvested at beginning of period 613,174 $ 33.24 Granted 284,104 32.66 Additional performance shares earned 116,467 22.68 Less: Vested 443,661 28.57 Forfeited 15,037 35.49 Nonvested at end of period 555,047 $ 34.40

Accumulated other comprehensive

Accumulated other comprehensive loss	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Accumulated other comprehensive loss	Accumulated Other Comprehensive Loss The Company's accumulated other comprehensive loss is comprised of losses on derivative instruments qualifying as hedges, postretirement liability adjustments and gain (loss) on available-for-sale investments. The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Post- Net Total (In thousands) At December 31, 2019 $ (1,430) $ (40,734) $ 62 $ (42,102) Other comprehensive loss before reclassifications — (8,395) (1) (8,396) Amounts reclassified from accumulated other comprehensive loss 446 1,922 52 2,420 Net current-period other comprehensive income (loss) 446 (6,473) 51 (5,976) At December 31, 2020 (984) (47,207) 113 (48,078) Other comprehensive income (loss) before reclassifications — 4,876 (252) 4,624 Amounts reclassified from accumulated other comprehensive loss 446 1,870 134 2,450 Net current-period other comprehensive income (loss) 446 6,746 (118) 7,074 At December 31, 2021 $ (538) $ (40,461) $ (5) $ (41,004) 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 for the years ended December 31 were as follows: 2021 2020 Location on Consolidated (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (591) $ (591) Interest expense 145 145 Income taxes (446) (446) Amortization of postretirement liability losses included in net periodic benefit cost (2,485) (2,552) Other income 615 630 Income taxes (1,870) (1,922) Reclassification adjustment for loss on available-for-sale investments included in net income (170) (66) Other income 36 14 Income taxes (134) (52) Total reclassifications $ (2,450) $ (2,420)

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income taxes	Income Taxes The components of income before income taxes from continuing operations for each of the years ended December 31 were as follows: 2021 2020 2019 (In thousands) United States $ 466,651 $ 474,856 $ 398,532 Foreign — 261 (87) Income before income taxes from continuing operations $ 466,651 $ 475,117 $ 398,445 Income tax expense (benefit) from continuing operations for the years ended December 31 was as follows: 2021 2020 2019 (In thousands) Current: Federal $ 17,121 $ 65,006 $ (3,502) State 11,549 21,234 3,366 Foreign — 151 — 28,670 86,391 (136) Deferred: Income taxes: Federal 45,885 (3,735) 50,218 State 12,610 (625) 12,098 Investment tax credit - net 1,755 2,559 1,099 60,250 (1,801) 63,415 Total income tax expense $ 88,920 $ 84,590 $ 63,279 Components of deferred tax assets and deferred tax liabilities at December 31 were as follows: 2021 2020 (In thousands) Deferred tax assets: Postretirement $ 45,752 $ 51,495 Compensation-related 37,917 40,477 Operating lease liabilities 26,710 25,963 Asset retirement obligations 8,696 8,060 Legal and environmental contingencies 8,603 9,467 Customer advances 7,683 7,463 Payroll tax deferral 6,940 14,010 Other 39,960 37,944 Total deferred tax assets 182,261 194,879 Deferred tax liabilities: Basis differences on property, plant and equipment 585,095 536,966 Postretirement 48,302 49,233 Operating lease right-of-use-assets 26,570 25,858 Intangible assets 21,074 19,514 Other 81,070 67,922 Total deferred tax liabilities 762,111 699,493 Valuation allowance 12,112 11,484 Net deferred income tax liability $ 591,962 $ 516,098 As of December 31, 2021 and 2020, the Company had various state income tax net operating loss carryforwards of $164.8 million and $151.5 million, respectively, and federal and state income tax credit carryforwards, excluding alternative minimum tax credit carryforwards, of $35.6 million and $37.1 million, respectively. The state credits include various regulatory investment tax credits of approximately $35.0 million and $36.3 million at December 31, 2021 and 2020, respectively. The state income tax credit carryforwards are due to expire between 2024 and 2035. Changes in tax regulations or assumptions regarding current and future taxable income could require additional valuation allowances in the future. The following table reconciles the change in the net deferred income tax liability from December 31, 2020, to December 31, 2021, to deferred income tax expense: 2021 (In thousands) Change in net deferred income tax liability from the preceding table $ 75,864 Deferred taxes associated with other comprehensive loss (2,355) Excess deferred income tax amortization (10,295) Other (2,964) Deferred income tax expense for the period $ 60,250 Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows: Years ended December 31, 2021 2020 2019 Amount % Amount % Amount % (Dollars in thousands) Computed tax at federal statutory rate $ 97,997 21.0 $ 99,775 21.0 $ 83,674 21.0 Increases (reductions) resulting from: State income taxes, net of federal income tax 19,496 4.2 17,845 3.8 14,029 3.5 Federal renewable energy credit (13,914) (3.0) (16,009) (3.4) (15,843) (4.0) Tax compliance and uncertain tax positions (477) (.1) (3,543) (.7) (2,739) (.7) Excess deferred income tax amortization (10,295) (2.2) (12,517) (2.6) (11,904) (3.0) Other (3,887) (.8) (961) (.3) (3,938) (.9) Total income tax expense $ 88,920 19.1 $ 84,590 17.8 $ 63,279 15.9 The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, and various state, local and foreign jurisdictions. The Company is no longer subject to U.S. federal or non-U.S. income tax examinations by tax authorities for years ending prior to 2018. With few exceptions, as of December 31, 2021, the Company is no longer subject to state and local income tax examinations by tax authorities for years ending prior to 2018. For the years ended December 31, 2021, 2020 and 2019, total reserves for uncertain tax positions were not material. The Company recognizes interest and penalties accrued relative to unrecognized tax benefits in income tax expense.

Cash flow information

Cash flow information	12 Months Ended
	Dec. 31, 2021
Supplemental Cash Flow Information [Abstract]
Cash flow information	Cash Flow Information Cash expenditures for interest and income taxes for the years ended December 31 were as follows: 2021 2020 2019 (In thousands) Interest, net* $ 91,165 $ 88,681 $ 93,414 Income taxes paid (refunded), net** $ 71,079 $ 65,536 $ (8,475) * AFUDC - borrowed was $2.8 million, $2.6 million and $2.8 million for the years ended December 31, 2021, 2020 and 2019, respectively. ** Income taxes paid (refunded), including discontinued operations, were $70.9 million, $59.4 million and $(9.4) million for the years ended December 31, 2021, 2020 and 2019, respectively. Noncash investing and financing transactions at December 31 were as follows: 2021 2020 2019 (In thousands) Property, plant and equipment additions in accounts payable $ 57,605 $ 26,082 $ 46,119 Right-of-use assets obtained in exchange for new operating lease liabilities $ 55,987 $ 54,356 $ 54,880 Debt assumed in connection with a business combination $ 10 $ — $ 1,163 Accrual for holdback payment related to a business combination $ — $ 2,500 $ —

Business segment data

Business segment data	12 Months Ended
	Dec. 31, 2021
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 and other energy-related services. The construction materials and contracting segment mines, processes and sells construction aggregates (crushed stone, sand and gravel); produces and sells asphalt mix; and supplies ready-mix concrete. This segment focuses on vertical integration of its contracting services with its construction materials to support the aggregate-based product lines including aggregate placement, asphalt and concrete paving, and site development and grading. Although not common to all locations, other products include the sale of cement, asphalt oil for various commercial and roadway applications, various finished concrete products and other building materials and related contracting services. This segment operates in the central, southern and western United States, including Alaska and Hawaii. 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 country. These specialty contracting services are provided to utilities and 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 distribution of transmission 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 and certain general and administrative costs (reflected in operation and maintenance expense) and interest expense, which were previously allocated to the refining business and Fidelity and do not meet the criteria for income (loss) from discontinued operations. Discontinued operations include 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. Information on the Company's segments as of December 31 and for the years then ended was as follows: 2021 2020 2019 (In thousands) External operating revenues: Regulated operations: Electric $ 349,039 $ 331,538 $ 351,725 Natural gas distribution 971,364 847,651 865,222 Pipeline 69,940 69,957 62,357 1,390,343 1,249,146 1,279,304 Non-regulated operations: Pipeline 12,918 15,389 21,835 Construction materials and contracting 2,228,306 2,177,585 2,189,651 Construction services 2,049,082 2,090,685 1,845,896 Other 84 (55) 90 4,290,390 4,283,604 4,057,472 Total external operating revenues $ 5,680,733 $ 5,532,750 $ 5,336,776 Intersegment operating revenues: Regulated operations: Electric $ 543 $ 491 $ — Natural gas distribution 576 534 — Pipeline 58,989 57,977 56,037 60,108 59,002 56,037 Non-regulated operations: Pipeline 689 554 215 Construction materials and contracting 624 417 1,066 Construction services 2,555 5,038 3,370 Other 13,630 11,958 16,461 17,498 17,967 21,112 Intersegment eliminations (77,606) (76,969) (77,149) Total intersegment operating revenues $ — $ — $ — Depreciation, depletion and amortization: Electric $ 66,750 $ 62,998 $ 58,721 Natural gas distribution 86,065 84,580 79,564 Pipeline 20,569 21,669 21,220 Construction materials and contracting 100,974 89,626 77,450 Construction services 20,270 23,523 17,038 Other 4,586 2,704 2,024 Total depreciation, depletion and amortization $ 299,214 $ 285,100 $ 256,017 Operating income (loss): Electric $ 66,335 $ 63,434 $ 64,039 Natural gas distribution 89,173 73,082 69,188 Pipeline 48,078 49,436 42,796 Construction materials and contracting 191,077 214,498 179,955 Construction services 145,754 147,644 126,426 Other (6,198) (3,169) (1,184) Total operating income $ 534,219 $ 544,925 $ 481,220 2021 2020 2019 (In thousands) Interest expense: Electric $ 26,712 $ 26,699 $ 25,334 Natural gas distribution 37,265 36,798 35,488 Pipeline 7,010 7,622 7,198 Construction materials and contracting 19,218 20,577 23,792 Construction services 3,540 4,095 5,331 Other 342 883 1,859 Intersegment eliminations (103) (155) (415) Total interest expense $ 93,984 $ 96,519 $ 98,587 Income tax expense (benefit): Electric $ (7,626) $ (11,636) $ (12,650) Natural gas distribution 8,366 5,746 1,405 Pipeline 9,594 7,650 7,219 Construction materials and contracting 43,459 47,431 37,389 Construction services 35,426 35,797 29,973 Other (299) (398) (57) Total income tax expense $ 88,920 $ 84,590 $ 63,279 Net income (loss): Regulated operations: Electric $ 51,906 $ 55,601 $ 54,763 Natural gas distribution 51,596 44,049 39,517 Pipeline 39,583 35,453 28,255 143,085 135,103 122,535 Non-regulated operations: Pipeline 1,313 1,559 1,348 Construction materials and contracting 129,755 147,325 120,371 Construction services 109,402 109,721 92,998 Other (5,824) (3,181) (2,086) 234,646 255,424 212,631 Income from continuing operations 377,731 390,527 335,166 Income (loss) from discontinued operations, net of tax 400 (322) 287 Net income $ 378,131 $ 390,205 $ 335,453 Capital expenditures: Electric $ 82,427 $ 114,676 $ 99,449 Natural gas distribution 170,411 193,048 206,799 Pipeline 234,803 62,224 71,477 Construction materials and contracting 417,524 191,635 190,092 Construction services 29,140 83,651 60,500 Other 1,501 3,045 8,181 Total capital expenditures (a) $ 935,806 $ 648,279 $ 636,498 2021 2020 2019 (In thousands) Assets: Electric (b) $ 1,810,695 $ 2,123,693 $ 1,680,194 Natural gas distribution (b) 2,929,519 2,302,770 2,574,965 Pipeline 913,945 703,377 677,482 Construction materials and contracting 2,161,653 1,798,493 1,684,161 Construction services 845,262 818,662 761,127 Other (c) 248,489 305,157 303,279 Assets held for sale 872 1,220 1,851 Total assets $ 8,910,435 $ 8,053,372 $ 7,683,059 Property, plant and equipment: Electric (b) $ 2,295,646 $ 2,323,403 $ 2,227,145 Natural gas distribution (b) 3,015,164 2,868,853 2,688,123 Pipeline 1,051,868 821,697 834,215 Construction materials and contracting 2,347,696 2,028,476 1,910,562 Construction services 225,758 220,796 213,370 Other 36,717 37,545 35,213 Less accumulated depreciation, depletion and amortization 3,216,461 3,133,831 2,991,486 Net property, plant and equipment $ 5,756,388 $ 5,166,939 $ 4,917,142 (a) Capital expenditures for 2021, 2020 and 2019 include noncash transactions such as capital expenditure-related accounts payable, AFUDC and accrual of holdback payments in connection with acquisitions totaling $38.7 million, $(15.7) million and $4.8 million, respectively. (b) Includes allocations of common utility property. (c) Includes assets not directly assignable to a business (i.e. cash and cash equivalents, certain accounts receivable, certain investments and other miscellaneous current and deferred assets).

Employee benefit plans

Employee benefit plans	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Pension and other postretirement benefit plans The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. The Company uses a measurement date of December 31 for all of its pension and postretirement benefit plans. Prior to 2013, defined benefit pension plan benefits and accruals for all nonunion and certain union plans were frozen and on June 30, 2015, the remaining union plan was frozen. These employees were eligible to receive additional defined contribution plan benefits. Effective January 1, 2010, eligibility to receive retiree medical benefits was modified at certain of the Company's businesses. Employees who had attained age 55 with 10 years of continuous service by December 31, 2010, were provided the option to choose between a pre-65 comprehensive medical plan coupled with a Medicare supplement or a specified company funded Retiree Reimbursement Account, regardless of when they retire. All other eligible employees must meet the new eligibility criteria of age 60 and 10 years of continuous service at the time they retire to be eligible for a specified company funded Retiree Reimbursement Account. Employees hired after December 31, 2009, will not be eligible for retiree medical benefits at certain of the Company's businesses. In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage was replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through an exchange. Changes in benefit obligation and plan assets and amounts recognized in the Consolidated Balance Sheets at December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Change in benefit obligation: (In thousands) Benefit obligation at beginning of year $ 437,360 $ 421,166 $ 86,155 $ 83,614 Service cost — — 1,600 1,532 Interest cost 9,819 12,093 1,862 2,437 Plan participants' contributions — — 641 752 Actuarial (gain) loss (12,140) 27,737 (12,802) 2,203 Benefits paid (23,542) (23,636) (3,996) (4,383) Benefit obligation at end of year 411,497 437,360 73,460 86,155 Change in net plan assets: Fair value of plan assets at beginning of year 383,834 365,264 101,639 94,587 Actual return on plan assets 12,817 42,206 1,398 10,249 Employer contribution — — 476 434 Plan participants' contributions — — 641 752 Benefits paid (23,542) (23,636) (3,996) (4,383) Fair value of net plan assets at end of year 373,109 383,834 100,158 101,639 Funded status - over (under) $ (38,388) $ (53,526) $ 26,698 $ 15,484 Amounts recognized in the Consolidated Balance Sheets at December 31: Noncurrent assets - other $ — $ — $ 45,863 $ 36,769 Other accrued liabilities — — 544 622 Noncurrent liabilities - other 38,388 53,526 18,621 20,663 Benefit obligation assets (liabilities) - net amount recognized $ (38,388) $ (53,526) $ 26,698 $ 15,484 Amounts recognized in accumulated other comprehensive loss: Actuarial loss $ 25,976 $ 27,527 $ 2,367 $ 5,557 Prior service credit — — (290) (634) Total $ 25,976 $ 27,527 $ 2,077 $ 4,923 Amounts recognized in regulatory assets or liabilities: Actuarial (gain) loss $ 142,166 $ 154,013 $ (14,727) $ (8,228) Prior service credit — — (5,193) (6,808) Total $ 142,166 $ 154,013 $ (19,920) $ (15,036) Employer contributions and benefits paid in the preceding table include only those amounts contributed directly to, or paid directly from, plan assets. Amounts related to regulated operations are recorded as regulatory assets or liabilities and are expected to be reflected in rates charged to customers over time. For more information on regulatory assets and liabilities, see Note 6. In 2021, the actuarial gain recognized in the benefit obligation was primarily the result of an increase in the discount rate. In 2020, the actuarial loss recognized in the benefit obligation was primarily the result of a decrease in the discount rate. For more information on the discount rates, see the table below. Unrecognized pension actuarial losses in excess of 10 percent of the greater of the projected benefit obligation or the market-related value of assets are amortized over the average life expectancy of plan participants for frozen plans. The market-related value of assets is determined using a five-year average of assets. The pension plans all have accumulated benefit obligations in excess of plan assets. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans at December 31 were as follows: 2021 2020 (In thousands) Projected benefit obligation $ 411,497 $ 437,360 Accumulated benefit obligation $ 411,497 $ 437,360 Fair value of plan assets $ 373,109 $ 383,834 The components of net periodic benefit cost (credit), other than the service cost component, are included in other income on the Consolidated Statements of Income. Prior service credit is amortized on a straight-line basis over the average remaining service period of active participants. These components related to the Company's pension and other postretirement benefit plans for the years ended December 31 were as follows: Pension Benefits Other 2021 2020 2019 2021 2020 2019 Components of net periodic benefit cost (credit): (In thousands) Service cost $ — $ — $ — $ 1,600 $ 1,532 $ 1,142 Interest cost 9,819 12,093 15,225 1,862 2,437 2,986 Expected return on assets (19,576) (19,949) (18,236) (5,098) (5,019) (4,804) Amortization of prior service credit — — — (1,398) (1,398) (1,398) Recognized net actuarial loss 8,017 7,172 5,548 24 287 353 Net periodic benefit cost (credit), including amount capitalized (1,740) (684) 2,537 (3,010) (2,161) (1,721) Less amount capitalized — — — 150 156 113 Net periodic benefit cost (credit) (1,740) (684) 2,537 (3,160) (2,317) (1,834) Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss: Net (gain) loss (265) 934 (144) (2,811) (259) (127) Amortization of actuarial loss (1,286) (1,155) (904) (135) (306) (110) Amortization of prior service credit — — — 100 101 100 Total recognized in accumulated other comprehensive loss (1,551) (221) (1,048) (2,846) (464) (137) Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities: Net (gain) loss (5,116) 4,546 189 (6,292) (3,793) (8,168) Amortization of actuarial gain (loss) (6,731) (6,017) (4,644) 110 19 (242) Amortization of prior service credit — — — 1,298 1,297 1,297 Total recognized in regulatory assets or liabilities (11,847) (1,471) (4,455) (4,884) (2,477) (7,113) Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities $ (15,138) $ (2,376) $ (2,966) $ (10,890) $ (5,258) $ (9,084) Weighted average assumptions used to determine benefit obligations at December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Discount rate 2.64 % 2.30 % 2.66 % 2.30 % Expected return on plan assets 6.00 % 6.00 % 5.50 % 5.50 % Rate of compensation increase N/A N/A 3.00 % 3.00 % Weighted average assumptions used to determine net periodic benefit cost (credit) for the years ended December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Discount rate 2.30 % 2.96 % 2.30 % 3.00 % Expected return on plan assets 6.00 % 6.25 % 5.50 % 5.75 % Rate of compensation increase N/A N/A 3.00 % 3.00 % The expected rate of return on pension plan assets is based on a targeted asset allocation range determined by the funded ratio of the plan. As of December 31, 2021, the expected rate of return on pension plan assets is based on the targeted asset allocation range of 35 percent to 45 percent equity securities and 55 percent to 65 percent fixed-income securities and the expected rate of return from these asset categories. The expected rate of return on other postretirement plan assets is based on the targeted asset allocation range of 10 percent equity securities and 90 percent fixed-income securities and the expected rate of return from these asset categories. The expected return on plan assets for other postretirement benefits reflects insurance-related investment costs. Health care rate assumptions for the Company's other postretirement benefit plans as of December 31 were as follows: 2021 2020 Health care trend rate assumed for next year 7.0 % 7.0 % Health care cost trend rate - ultimate 4.5 % 4.5 % Year in which ultimate trend rate achieved 2031 2031 The Company's other postretirement benefit plans include health care and life insurance benefits for certain retirees. The plans underlying these benefits may require contributions by the retiree depending on such retiree's age and years of service at retirement or the date of retirement. The Company contributes a flat dollar amount to the monthly premiums which is updated annually on January 1. The Company does not expect to contribute to its defined benefit pension plans in 2022 due to an additional $20.0 million contributed to the plans in 2019 creating prefunding credits to be used in future years. The Company expects to contribute approximately $601,000 to its postretirement benefit plans in 2022. The following benefit payments, which reflect future service, as appropriate, and expected Medicare Part D subsidies at December 31, 2021, are as follows: Years Pension Other Expected (In thousands) 2022 $ 24,644 $ 4,393 $ 70 2023 24,766 4,522 65 2024 24,897 4,572 58 2025 24,739 4,612 52 2026 24,571 4,642 46 2027-2031 117,413 17,867 157 Outside investment managers manage the Company's pension and postretirement assets. The Company's investment policy with respect to pension and other postretirement assets is to make investments solely in the interest of the participants and beneficiaries of the plans and for the exclusive purpose of providing benefits accrued and defraying the reasonable expenses of administration. The Company strives to maintain investment diversification to assist in minimizing the risk of large losses. The Company's policy guidelines allow for investment of funds in cash equivalents, fixed-income securities and equity securities. The guidelines prohibit investment in commodities and futures contracts, equity private placement, employer securities, leveraged or derivative securities, options, direct real estate investments, precious metals, venture capital and limited partnerships. The guidelines also prohibit short selling and margin transactions. The Company's practice is to periodically review and rebalance asset categories based on its targeted asset allocation percentage policy. 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 pension plans' assets are determined using the market approach. The carrying value of the pension plans' Level 2 cash equivalents approximates fair value and is determined using observable inputs in active markets or the net asset value of shares held at year end, which is determined using other observable inputs including pricing from outside sources. The estimated fair value of the pension plans' Level 1 and Level 2 equity securities are based on the closing price reported on the active market on which the individual securities are traded or other known sources including pricing from outside sources. The estimated fair value of the pension plans' Level 1 and Level 2 collective and mutual funds are based on the net asset value of shares held at year end, based on either published market quotations on active markets or other known sources including pricing from outside sources. The estimated fair value of the pension plans' Level 2 corporate and municipal bonds is determined using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, future cash flows and other reference data. The estimated fair value of the pension plans' Level 1 U.S. Government securities are valued based on quoted prices on an active market. The estimated fair value of the pension plans' Level 2 U.S. Government securities are valued mainly using other observable inputs, including benchmark yields, reported trades, broker/dealer quotes, bids, offers, to be announced prices, future cash flows and other reference data. The estimated fair value of the pension plans' Level 2 pooled separate accounts are determined using observable inputs in active markets or the net asset value of shares held at year end, or other observable inputs. Some of these securities are valued using pricing from outside sources. All investments measured at net asset value in the tables that follow are invested in commingled funds, separate accounts or common collective trusts which do not have publicly quoted prices. The fair value of the commingled funds, separate accounts and common collective trusts are determined based on the net asset value of the underlying investments. The fair value of the underlying investments held by the commingled funds, separate accounts and common collective trusts is generally based on quoted prices in active markets. 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 fair value of the Company's pension plans' assets (excluding cash) by class were as follows: Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Cash equivalents $ — $ 4,637 $ — $ 4,637 Equity securities: U.S. companies 7,483 — — 7,483 International companies — 1,279 — 1,279 Collective and mutual funds (a) 167,093 41,383 — 208,476 Corporate bonds — 125,167 — 125,167 Municipal bonds — 7,507 — 7,507 U.S. Government securities 7,113 1,902 — 9,015 Pooled separate accounts (b) — 3,088 — 3,088 Investments measured at net asset value (c) — — — 6,457 Total assets measured at fair value $ 181,689 $ 184,963 $ — $ 373,109 (a) Collective and mutual funds invest approximately 37 percent in corporate bonds, 19 percent in common stock of international companies, 16 percent in common stock of large-cap U.S. companies, 9 percent in U.S. Government securities and 19 percent in other investments. (b) Pooled separate accounts are invested 100 percent in cash and cash equivalents. (c) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Cash equivalents $ — $ 7,841 $ — $ 7,841 Equity securities: U.S. companies 12,844 — — 12,844 International companies — 1,727 — 1,727 Collective and mutual funds (a) 177,397 55,788 — 233,185 Corporate bonds — 92,809 — 92,809 Municipal bonds — 10,126 — 10,126 U.S. Government securities 11,177 2,695 — 13,872 Investments measured at net asset value (b) — — — 11,430 Total assets measured at fair value $ 201,418 $ 170,986 $ — $ 383,834 (a) Collective and mutual funds invest approximately 36 percent in corporate bonds, 24 percent in common stock of international companies, 18 percent in common stock of large-cap U.S. companies, 8 percent in cash equivalents, 5 percent in U.S. Government securities and 9 percent in other investments. (b) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. The estimated fair values of the Company's other postretirement benefit plans' assets are determined using the market approach. The estimated fair value of the other postretirement benefit plans' Level 2 cash equivalents is valued at the net asset value of shares held at year end, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the other postretirement benefit plans' Level 1 and Level 2 equity securities is based on the closing price reported on the active market on which the individual securities are traded or other known sources including pricing from outside sources . The estimated fair value of the other postretirement benefit plans' Level 2 insurance contract is 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 fair value of the Company's other postretirement benefit plans' assets (excluding cash) by asset class were as follows: Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Cash equivalents $ — $ 4,281 $ — $ 4,281 Equity securities: U.S. companies 2,332 — — 2,332 International companies — 1 — 1 Collective and mutual funds (a) 4 90 — 94 Insurance contract (b) — 93,447 — 93,447 Investments measured at net asset value (c) — — — 3 Total assets measured at fair value $ 2,336 $ 97,819 $ — $ 100,158 (a) Collective and mutual funds invest approximately 37 percent in corporate bonds, 19 percent in common stock of international companies, 16 percent in common stock of large-cap U.S. companies, 9 percent in U.S. Government securities and 19 percent in other investments. (b) The insurance contract invests approximately 58 percent in corporate bonds, 13 percent in U.S. Government securities, 13 percent in common stock of large-cap U.S. companies, 5 percent in common stock of small-cap U.S. companies and 11 percent in other investments. (c) In accordance with ASC 820 - Fair Value , certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Cash equivalents $ — $ 3,517 $ — $ 3,517 Equity securities: U.S. companies 1,850 — — 1,850 International companies — 2 — 2 Collective and mutual funds (a) 10 147 — 157 Insurance contract (b) — 96,103 — 96,103 Investments measured at net asset value (c) — — — 10 Total assets measured at fair value $ 1,860 $ 99,769 $ — $ 101,639 (a) Collective and mutual funds invest approximately 36 percent in corporate bonds, 24 percent in common stock of international companies, 18 percent in common stock of large-cap U.S. companies, 8 percent in cash equivalents, 5 percent in U.S. Government securities and 9 percent in other investments. (b) The insurance contract invests approximately 67 percent in corporate bonds, 10 percent in common stock of large-cap U.S. companies, 12 percent in U.S. Government securities, 4 percent in common stock of small-cap U.S. companies, 1 percent in cash equivalents and 6 percent in other investments. (c) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. Nonqualified 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 that generally provide for defined benefit payments at age 65 following the employee's retirement or, upon death, to their beneficiaries for a 15-year period. In February 2016, the Company froze the unfunded, nonqualified defined benefit plans to new participants and eliminated benefit increases. Vesting for participants not fully vested was retained. The projected benefit obligation and accumulated benefit obligation for these plans at December 31 were as follows: 2021 2020 (In thousands) Projected benefit obligation $ 92,918 $ 101,242 Accumulated benefit obligation $ 92,918 $ 101,242 The components of net periodic benefit cost are included in other income on the Consolidated Statements of Income. These components related to the Company's nonqualified defined benefit plans for the years ended December 31 were as follows: 2021 2020 2019 (In thousands) Components of net periodic benefit cost: Service cost $ — $ 58 $ 109 Interest cost 1,912 2,606 3,473 Recognized net actuarial loss 1,164 1,192 764 Net periodic benefit cost $ 3,076 $ 3,856 $ 4,346 Weighted average assumptions used at December 31 were as follows: 2021 2020 Benefit obligation discount rate 2.39 % 1.97 % Benefit obligation rate of compensation increase N/A N/A Net periodic benefit cost discount rate 1.97 % 2.73 % Net periodic benefit cost rate of compensation increase N/A N/A The amount of future benefit payments for the unfunded, nonqualified defined benefit plans at December 31, 2021, are expected to aggregate as follows: 2022 2023 2024 2025 2026 2027-2031 (In thousands) Nonqualified benefits $ 6,877 $ 6,890 $ 7,354 $ 7,537 $ 7,609 $ 31,983 In 2012, the Company established a nonqualified defined contribution plan for certain key management employees. In 2020, the plan was frozen to new participants and no new Company contributions will be made to the plan after December 31, 2020. Vesting for participants not fully vested was retained. A new nonqualified defined contribution plan was adopted in 2020, effective January 1, 2021, to replace the plan originally established in 2012 with similar provisions. Expenses incurred under these plans for 2021, 2020 and 2019 were $2.4 million, $1.8 million and $1.6 million, respectively. The amount of investments that the Company anticipates using to satisfy obligations under these plans at December 31 was as follows: 2021 2020 (In thousands) Investments Insurance contract* $ 109,603 $ 100,104 Life insurance** 38,356 39,779 Other 10,190 8,917 Total investments $ 158,149 $ 148,800 * For more information on the insurance contract, see Note 8. ** Investments of life insurance are carried on plan participants (payable upon the employee's death). Defined contribution plans The Company sponsors various defined contribution plans for eligible employees and the costs incurred under these plans were $45.4 million in 2021, $50.1 million in 2020 and $51.8 million in 2019. Multiemployer plans The Company contributes to a number of MEPPs under the terms of collective-bargaining agreements that cover its union-represented employees. The risks of participating in these multiemployer plans are different from single-employer plans in the following aspects: • Assets contributed to the MEPP by one employer may be used to provide benefits to employees of other participating employers • If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers • If the Company chooses to stop participating in some of its MEPPs, the Company may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability The Company's participation in these plans is outlined in the following table. Unless otherwise noted, the most recent Pension Protection Act zone status available in 2021 and 2020 is for the plan's year-end at December 31, 2020, and December 31, 2019, respectively. The zone status is based on information that the Company received from the plan and is certified by the plan's actuary. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the yellow zone are between 65 percent and 80 percent funded, and plans in the green zone are at least 80 percent funded. EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending/Implemented Contributions Surcharge Imposed Expiration Date Pension Fund 2021 2020 2021 2020 2019 (In thousands) Edison Pension Plan 936061681-001 Green Green No $ 18,331 $ 16,121 $ 12,252 No 12/31/2023 IBEW Local 212 Pension Trust 316127280-001 Green as of 4/30/2021 Green as of 4/30/2020 No 1,733 1,521 1,110 No 6/1/2025 IBEW Local 357 Pension Plan A 886023284-001 Green Green No 6,485 9,913 10,162 No 5/31/2024 IBEW Local 82 Pension Plan 316127268-001 Green as of 6/30/2021 Green as of 6/30/2020 No 1,353 1,373 1,662 No 12/3/2023 Idaho Plumbers and Pipefitters Pension Plan 826010346-001 Green as of 5/31/2021 Green as of 5/31/2020 No 1,528 1,370 1,307 No 3/31/2023 National Electrical Benefit Fund 530181657-001 Green Green No 14,361 14,484 12,679 No 5/31/2021- 5/31/2026 * Pension and Retirement Plan of Plumbers and Pipefitters Local 525 886003864-001 Green Green No 4,345 6,266 4,747 No 9/30/2024 Pension Trust Fund for Operating Engineers 946090764-001 Yellow Yellow Implemented 2,495 2,680 2,598 No 6/15/2022- 6/30/2023 Sheet Metal Workers Pension Plan of Southern CA, AZ, and NV 956052257-001 Yellow Yellow Implemented 2,615 3,255 2,119 No 6/30/2024 Southern California IBEW-NECA Pension Trust Fund 956392774-001 Yellow as of 6/30/2021 Yellow as of 6/30/2020 Implemented 2,746 1,714 1,477 No 6/30/2022- 5/31/2026 Western Conference of Teamsters Pension Plan 916145047-001 Green Green No 3,006 3,025 2,814 No 12/31/2023- 12/31/2025 Other funds 23,390 23,722 19,598 Total contributions $ 82,388 $ 85,444 $ 72,525 * Plan includes contributions required by collective bargaining agreements which have expired but contain provisions automatically renewing their terms in the absence of a subsequent negotiated agreement. The Company was listed in the plans' Forms 5500 as providing more than 5 percent of the total contributions for the following plans and plan years: Pension Fund Year Contributions to Plan Exceeded More Than 5 Percent Edison Pension Plan 2020 and 2019 IBEW Local 82 Pension Plan 2020 and 2019 IBEW Local 124 Pension Trust Fund 2020 and 2019 IBEW Local 212 Pension Trust Fund 2020 and 2019 IBEW Local 357 Pension Plan A 2020 and 2019 IBEW Local 648 Pension Plan 2020 and 2019 IBEW Local 683 Pension Fund Pension Plan 2020 and 2019 IBEW Local Union No 226 Open End Pension Fund 2020 and 2019 Idaho Plumbers and Pipefitters Pension Plan 2020 and 2019 International Union of Operating Engineers Local 701 Pension Trust Fund 2020 and 2019 Minnesota Teamsters Construction Division Pension Fund 2020 and 2019 Pension and Retirement Plan of Plumbers and Pipefitters Local 525 2020 and 2019 Southwest Marine Pension Trust 2020 and 2019 The Company also contributes to a number of multiemployer other postretirement plans under the terms of collective-bargaining agreements that cover its union-represented employees. These plans provide benefits such as health insurance, disability insurance and life insurance to retired union employees. Many of the multiemployer other postretirement plans are combined with active multiemployer health and welfare plans. The Company's total contributions to its multiemployer other postretirement plans, which also includes contributions to active multiemployer health and welfare plans, were $66.1 million, $63.8 million and $59.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. Amounts contributed in 2021, 2020 and 2019 to defined contribution multiemployer plans were $54.8 million, $54.2 million and $49.2 million, respectively.

Jointly owned facilities

Jointly owned facilities	12 Months Ended
	Dec. 31, 2021
Regulated Operations [Abstract]
Jointly owned facilities	Jointly Owned Facilities The consolidated financial statements include the Company's ownership interests in three coal-fired electric generating facilities (Big Stone Station, Coyote Station and Wygen III) and one major transmission line (BSSE). Each owner of the jointly owned facilities is responsible for financing its investment. The Company's share of the jointly owned facilities operating expenses was reflected in the appropriate categories of operating expenses (electric fuel and purchased power; operation and maintenance; and taxes, other than income) in the Consolidated Statements of Income. At December 31, the Company's share of the cost of utility plant in service, construction work in progress and related accumulated depreciation for the jointly owned facilities was as follows: Ownership Percentage 2021 2020 (In thousands) Big Stone Station: 22.7 % Utility plant in service $ 157,259 $ 155,967 Construction work in progress 571 104 Less accumulated depreciation 47,293 45,435 $ 110,537 $ 110,636 BSSE: 50.0 % Utility plant in service $ 107,424 $ 107,442 Construction work in progress — — Less accumulated depreciation 4,506 2,682 $ 102,918 $ 104,760 Coyote Station: 25.0 % Utility plant in service $ 157,764 $ 159,784 Construction work in progress 784 323 Less accumulated depreciation 109,202 108,852 $ 49,346 $ 51,255 Wygen III: 25.0 % Utility plant in service $ 66,357 $ 66,101 Construction work in progress 108 232 Less accumulated depreciation 11,383 10,038 $ 55,082 $ 56,295

Regulatory matters

Regulatory matters	12 Months Ended
	Dec. 31, 2021
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. 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. MNPUC Great Plains defers the difference between the actual cost of gas spent to serve customers and that recovered from customers on a monthly basis. Annually, Great Plains prepares a true-up pursuant to the purchased gas adjustment tariff. On August 30, 2021, the MNPUC issued an order to allow Great Plains recovery of an out-of-cycle cost of gas adjustment of $8.8 million over a period of 27 months. The order was effective September 1, 2021, and is subject to a prudence review by the MNPUC. The requested increase was for the February 2021 extreme cold weather, primarily in the central United States, and market conditions surrounding the natural gas commodity market. The MNPUC prudence review is pending with an order to be issued on or before August 29, 2022. 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 November 1, 2021, Montana-Dakota filed an annual update to its renewable resource cost adjustment requesting to recover a revised revenue requirement of approximately $12.4 million annually, not including the prior period true-up adjustment. The update reflects a decrease of approximately $2.0 million from the revenues currently included in rates. On January 26, 2022, the NDPSC approved the decrease with rates effective February 1, 2022. SDPUC On March 11, 2021, Montana-Dakota filed an informational update to the infrastructure rider rate tariff with the SDPUC related to the retirement of Unit 1 at Lewis & Clark Station. The filing includes the annual revenue requirement offset by the related amortization of the accelerated depreciation on the plant, net of excess deferred income taxes, and the decommissioning costs projected to be incurred in 2021 resulting in no impact to customers. On November 15, 2021, the SDPUC approved the request. WUTC On September 30, 2021, Cascade filed an application with the WUTC for a natural gas rate increase of approximately $13.7 million annually or approximately 5.1 percent above current rates. The requested increase was primarily to recover investments made in infrastructure upgrades, as well as to recover 2021 wage increases. The WUTC has 11 months to render a final decision on the rate case. This matter is pending before the WUTC. FERC On September 1, 2021, Montana-Dakota filed an update to its transmission formula rate under the MISO tariff for its multi-value project for $13.4 million, which was effective January 1, 2022.

Commitments and contingencies

Commitments and contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and 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 December 31, 2021 and 2020, the Company accrued liabilities which have not been discounted, including liabilities held for sale, of $37.0 million and $41.5 million, respectively. At December 31, 2021 and 2020, the Company also recorded corresponding insurance receivables of $14.1 million and $17.5 million, respectively, and regulatory assets of $21.2 million and $21.3 million, respectively, related to the accrued liabilities. The accruals are for contingencies resulting from litigation, production taxes, royalty claims 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 Portland Harbor Site In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of the riverbed site adjacent to a commercial property site acquired by Knife River - Northwest from Georgia-Pacific West, Inc. along the Willamette River. The riverbed site is part of the Portland, Oregon, Harbor Superfund Site where the EPA wants responsible parties to share in the costs of cleanup. The EPA entered into a consent order with certain other PRPs referred to as the Lower Willamette Group for a remedial investigation and feasibility study. The Lower Willamette Group has indicated that it has incurred over $115.0 million in investigation related costs. Knife River - Northwest has joined with approximately 100 other PRPs, including the Lower Willamette Group members, in a voluntary process to establish an allocation of costs for the site. Costs to be allocated would include costs incurred by the Lower Willamette Group as well as costs to implement and fund remediation of the site. In January 2017, the EPA issued a Record of Decision adopting a selected remedy which is expected to take 13 years to complete with a then estimated present value of approximately $1 billion. Corrective action will not be taken until remedial design/remedial action plans are approved by the EPA. In 2020, the EPA encouraged certain PRPs to enter into consent agreements to perform remedial design covering the entire site and proposed dividing the site into multiple subareas for remedial design. Certain PRPs executed consent agreements for remedial design work and certain others were issued unilateral administrative orders to perform design work. Knife River - Northwest is not subject to either a voluntary agreement or unilateral order to perform remedial design work. In February 2021, the EPA announced that 100 percent of the site's area requiring active cleanup is in the remedial design process. Site-wide remediation activities are not expected to commence for a number of years. Knife River - Northwest was also notified that the Portland Harbor Natural Resource Trustee Council intends to perform an injury assessment to natural resources resulting from the release of hazardous substances at the site. It is not possible to estimate the costs of natural resource damages until an assessment is completed and allocations are undertaken. At this time, Knife River - Northwest does not believe it is a responsible party and has notified Georgia-Pacific West, Inc., that it intends to seek indemnity for liabilities incurred in relation to the above matters pursuant to the terms of their sale agreement. The Company believes it is not probable that it will incur any material environmental remediation costs or damages in relation to the above referenced matter. Manufactured Gas Plant Sites Claims have been made against Cascade for cleanup of environmental contamination at manufactured gas plant sites operated by Cascade's predecessors and a similar claim has been made against Montana-Dakota for a site operated by Montana-Dakota and its predecessors. Any accruals related to these claims are reflected in regulatory assets. For more information, see Note 6. Demand has been made of Montana-Dakota to participate in investigation and remediation of environmental contamination at a site in Missoula, Montana. The site operated as a former manufactured gas plant from approximately 1907 to 1938 when it was converted to a butane-air plant that operated until 1956. Montana-Dakota or its predecessors owned or controlled the site for a period of the time it operated as a manufactured gas plant and Montana-Dakota operated the butane-air plant from 1940 to 1951, at which time it sold the plant. There are no documented wastes or by-products resulting from the mixing or distribution of butane-air gas. Preliminary assessment of a portion of the site provided a recommended remedial alternative for that portion of approximately $560,000. However, the recommended remediation would not address any potential contamination to adjacent parcels that may be impacted from historic operations of the manufactured gas plant. An environmental assessment was started in 2020, which is estimated to cost approximately $823,000. The environmental assessment report is expected to be submitted to the MTDEQ in 2022. Montana-Dakota and another party agreed to voluntarily investigate and remediate the site and that Montana-Dakota will pay two-thirds of the costs for further investigation and remediation of the site. Montana-Dakota has accrued costs of $419,000 for the remediation and investigation costs, and has incurred costs of $505,000 as of December 31, 2021. Montana-Dakota received notice from a prior insurance carrier that it will participate in payment of defense costs incurred in relation to the claim. On December 9, 2021, Montana Dakota filed an application with the MTPSC for deferred accounting treatment for costs associated with the investigation and remediation of the site. This matter is pending before the MTPSC. A claim was made against Cascade for contamination at the Bremerton Gasworks Superfund Site in Bremerton, Washington, which was received in 1997. A preliminary investigation has found soil and groundwater at the site contain impacts requiring further investigation and cleanup. The EPA conducted a Targeted Brownfields Assessment of the site and released a report summarizing the results of that assessment in August 2009. The assessment confirmed that impacts have affected soil and groundwater at the site, as well as sediments in the adjacent Port Washington Narrows. In April 2010, the Washington DOE issued notice it considered Cascade a PRP for hazardous substances at the site. In May 2012, the EPA added the site to the National Priorities List of Superfund sites. Cascade entered into an administrative settlement agreement and consent order with the EPA regarding the scope and schedule for a remedial investigation and feasibility study for the site. Current estimates for the cost to complete the remedial investigation and feasibility study are approximately $7.6 million of which $5.3 million has been incurred as of December 31, 2021. Based on the site investigation, preliminary remediation alternative costs were provided by consultants in August 2020. The preliminary information received through the completion of the data report allowed for the projection of possible costs for a variety of site configurations, remedial measures and potential natural resource damage claims of between $13.6 million and $71.0 million. At December 31, 2021, Cascade has accrued $2.3 million for the remedial investigation and feasibility study, as well as $17.5 million for remediation of this site. The accrual for remediation costs will be reviewed and adjusted, if necessary, after the completion of the feasibility study. In April 2010, Cascade filed a petition with the WUTC for authority to defer the costs incurred in relation to the environmental remediation of this site. The WUTC approved the petition in September 2010, subject to conditions set forth in the order. A claim was made against Cascade for impacts at a site in Bellingham, Washington. Cascade received notice from a party in May 2008 that Cascade may be a PRP, along with other parties, for impacts from a manufactured gas plant owned by Cascade and its predecessor from about 1946 to 1962. Other PRPs reached an agreed order and work plan with the Washington DOE for completion of a remedial investigation and feasibility study for the site. A feasibility study prepared for one of the PRPs in March 2018 identifies five cleanup action alternatives for the site with estimated costs ranging from $8.0 million to $20.4 million with a selected preferred alternative having an estimated total cost of $9.3 million. The other PRPs developed a cleanup action plan and completed public review in 2020. Development of design documents is anticipated to be completed by the end of 2022 with the remedy construction expected to occur in 2023. Cascade believes its proportional share of any liability will be relatively small in comparison to other PRPs. The plant manufactured gas from coal between approximately 1890 and 1946. In 1946, shortly after Cascade's predecessor acquired the plant, the plant converted to a propane-air gas facility. There are no documented wastes or by-products resulting from the mixing or distribution of propane-air gas. Cascade has recorded an accrual for this site for an amount that is not material. The Company has received notices from and entered into agreements with certain of its insurance carriers that they will participate in the defense for certain contamination claims subject to full and complete reservations of rights and defenses to insurance coverage. To the extent these claims are not covered by insurance, the Company intends to seek recovery of remediation costs through its natural gas rates charged to customers. Purchase commitments The Company has entered into various commitments largely consisting of contracts for natural gas and coal supply; purchased power; natural gas transportation and storage; royalties; information technology; and construction materials. Certain of these contracts are subject to variability in volume and price. The commitment terms vary in length, up to 38 years. The commitments under these contracts as of December 31, 2021, were: 2022 2023 2024 2025 2026 Thereafter (In thousands) Purchase commitments $ 589,898 $ 200,667 $ 141,383 $ 99,545 $ 86,628 $ 731,679 These commitments were not reflected in the Company's consolidated financial statements. Amounts purchased under various commitments for the years ended December 31, 2021, 2020 and 2019, were $849.3 million, $666.0 million and $686.5 million, respectively. 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 December 31, 2021, the fixed maximum amounts guaranteed under these agreements aggregated $134.8 million. Certain of the guarantees also have no fixed maximum amounts specified. The amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $28.6 million in 2022; $45.2 million in 2023; $50.2 million in 2024; $800,000 in 2025; $800,000 in 2026; $200,000 thereafter; and $9.0 million, which has no scheduled maturity date. There were no amounts outstanding under the previously mentioned guarantees at December 31, 2021. 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 December 31, 2021, the fixed maximum amounts guaranteed under these letters of credit aggregated $25.7 million. The amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $25.2 million in 2022 and $500,000 in 2023. There were no amounts outstanding under the previously mentioned letters of credit at December 31, 2021. 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, Knife River 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, Knife River 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 December 31, 2021. 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 December 31, 2021, approximately $934.4 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 December 31, 2021, 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 $31.5 million.

Schedule I-Condensed Financial

Schedule I-Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2021
Condensed Financial Information Disclosure [Abstract]
Schedule I-Condensed Financial Information of Registrant	Condensed Financial Information of Registrant (Unconsolidated) Condensed Statements of Income and Comprehensive Income Years ended December 31, 2021 2020 2019 (In thousands) Equity in earnings of subsidiaries from continuing operations $ 377,731 $ 390,527 $ 335,166 Income from continuing operations 377,731 390,527 335,166 Equity in earnings (loss) of subsidiaries from discontinued operations 400 (322) 287 Net income $ 378,131 $ 390,205 $ 335,453 Comprehensive income $ 385,205 $ 384,229 $ 331,693 The accompanying notes are an integral part of these condensed financial statements. Condensed Balance Sheets December 31, 2021 2020 (In thousands, except shares and per share amounts) Assets Current assets: Cash and cash equivalents $ 6,159 $ 8,781 Receivables, net 6,120 4,865 Accounts receivable from subsidiaries 49,696 50,539 Prepayments and other current assets 2,528 1,612 Total current assets 64,503 65,797 Noncurrent assets Investments 55,686 52,000 Investment in subsidiaries 3,368,537 3,069,956 Deferred income taxes 7,364 9,691 Operating lease right-of-use assets 114 56 Other 26,558 28,866 Total noncurrent assets 3,458,259 3,160,569 Total assets $ 3,522,762 $ 3,226,366 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 2,546 $ 2,135 Accounts payable to subsidiaries 6,133 5,412 Taxes payable 1,672 4,056 Dividends payable 44,229 42,611 Accrued compensation 4,098 7,825 Operating lease liabilities due within one year 52 40 Other accrued liabilities 7,309 6,881 Total current liabilities 66,039 68,960 Noncurrent liabilities: Operating lease liabilities 62 16 Other 73,787 78,285 Total noncurrent liabilities 73,849 78,301 Commitments and contingencies Stockholders' equity: Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 203,889,661 at December 31, 2021 and 201,061,198 at December 31, 2020 203,889 201,061 Other paid-in capital 1,461,205 1,371,385 Retained earnings 1,762,410 1,558,363 Accumulated other comprehensive loss (41,004) (48,078) Treasury stock at cost - 538,921 shares (3,626) (3,626) Total stockholders' equity 3,382,874 3,079,105 Total liabilities and stockholders' equity $ 3,522,762 $ 3,226,366 The accompanying notes are an integral part of these condensed financial statements. Condensed Statements of Cash Flows Years ended December 31, 2021 2020 2019 (In thousands) Net cash provided by operating activities $ 187,297 $ 226,642 $ 168,520 Investing activities: Investments in and advances to subsidiaries (102,000) (67,000) (120,000) Advances from subsidiaries — — 17,000 Investments (391) (4) (236) Net cash used in investing activities (102,391) (67,004) (103,236) Financing activities: Proceeds from issuance of common stock 88,767 3,385 106,848 Dividends paid (171,354) (166,405) (160,256) Repurchase of common stock (2,992) — — Tax withholding on stock-based compensation (1,949) (163) (1,821) Net cash used in financing activities (87,528) (163,183) (55,229) Increase (decrease) in cash and cash equivalents (2,622) (3,545) 10,055 Cash and cash equivalents - beginning of year 8,781 12,326 2,271 Cash and cash equivalents - end of year $ 6,159 $ 8,781 $ 12,326 The accompanying notes are an integral part of these condensed financial statements. Note 1 - Summary of Significant Accounting Policies Basis of presentation The condensed financial information reported in Schedule I is being presented to comply with Rule 12-04 of Regulation S-X. The information is unconsolidated and is presented for the parent company only, MDU Resources Group, Inc. (the Company) as of and for the years ended December 31, 2021, 2020 and 2019. In Schedule I, investments in subsidiaries are presented under the equity method of accounting where the assets and liabilities of the subsidiaries are not consolidated. The investments in net assets of the subsidiaries are recorded on the Condensed Balance Sheets. The income from subsidiaries is reported as equity in earnings of subsidiaries on the Condensed Statements of Income. The material cash inflows on the Condensed Statements of Cash Flows are primarily from the dividends and other payments received from its subsidiaries and the proceeds raised from the issuance of equity securities. The consolidated financial statements of the Company reflect certain businesses as discontinued operations. These statements should be read in conjunction with the consolidated financial statements and notes thereto of the Company. Earnings per common share Please refer to the Consolidated Statements of Income of the registrant for earnings per common share. In addition, see Item 8 - Note 2 for information on the computation of earnings per common share. Note 2 - Debt At December 31, 2021, the Company had no long-term debt maturities. For more information on debt, see Item 8 - Note 9. Note 3 - Dividends The Company depends on earnings and dividends from its subsidiaries to pay dividends on common stock. Cash dividends paid to the Company by subsidiaries were $188.1 million, $228.4 million and $177.1 million for the years ended December 31, 2021, 2020 and 2019, respectively.

Basis of Presentation (Policies

Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of presentation	The abbreviations and acronyms used throughout are defined following the Notes to Consolidated Financial Statements. The consolidated financial statements of the Company include the accounts of the following businesses: electric, natural gas distribution, pipeline, construction materials and contracting, construction services and other. The electric and natural gas distribution businesses, as well as a portion of the pipeline business, are regulated. Construction materials and contracting, construction services and the other businesses, as well as a portion of the pipeline business, are non-regulated. For further descriptions of the Company's businesses, see Note 17. Beginning in March 2020, governmental restrictions and guidelines implemented to control the spread of COVID-19 reduced commercial and interpersonal activity throughout the Company's areas of operation. Most of the Company's products and services are considered essential to America and its communities and, as a result, operations have generally continued through the COVID-19 pandemic and reopening of the country's economy. The Company has assessed the impacts of the COVID-19 pandemic on its results of operations for the years ended December 31, 2021 and 2020, and determined there were no material adverse impacts. The assets and liabilities of the Company's discontinued operations have been classified as held for sale and are included in prepayments and other current assets, noncurrent assets - other and other accrued liabilities on the Consolidated Balance Sheets and are not material to the financial statements for any period presented. The results and supporting activities are shown in income (loss) from discontinued operations on the Consolidated Statements of Income. Unless otherwise indicated, the amounts presented in the accompanying notes to the consolidated financial statements relate to the Company's continuing operations. In 2021, the Company made changes to the presentation of the Consolidated Statements of Cash Flows to provide further clarity on the sources and uses of net cash provided by operating activities and net cash provided by (used in) financing activities. Certain prior year amounts have been reclassified to conform to the current year presentation. These reclassifications did not impact total net cash provided by operating activities or net cash provided by (used in) financing activities for the years ended December 31, 2020 and 2019. Management has also evaluated the impact of events occurring after December 31, 2021, up to the date of issuance of these consolidated financial statements on February 23, 2022, that would require recognition or disclosure in the financial statements.
Consolidation, Policy	Principles of consolidation The consolidated financial statements were prepared in accordance with GAAP and include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation, except for certain transactions related to the Company's regulated operations in accordance with GAAP. For more information on intercompany revenues, see Note 17. The statements also include the Company's ownership interests in the assets, liabilities and expenses of jointly owned electric transmission and generating facilities. See Note 19 for additional information.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Estimates are used for items such as long-lived assets and goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; aggregate reserves; property depreciable lives; tax provisions; revenue recognized using the cost-to-cost measure of progress for contracts; expected credit losses; environmental and other loss contingencies; regulatory assets expected to be recovered in rates charged to customers; costs on construction contracts; unbilled revenues; actuarially determined benefit costs; asset retirement obligations; lease classification; present value of right-of-use assets and lease liabilities; and the valuation of stock-based compensation. As additional information becomes available, or actual amounts are determinable, the recorded estimates are revised. Consequently, operating results can be affected by revisions to prior accounting estimates.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [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 financial statements and or disclosures: Standard Description Effective date Impact on financial statements/disclosures Recently adopted accounting standards ASU 2018-14 - Changes to the Disclosure Requirements for Defined Benefit Plans In August 2018, the FASB issued guidance on modifying the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans as part of the disclosure framework project. The guidance removed disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and added disclosure requirements identified as relevant. The guidance added, among other things, the requirement to include an explanation for significant gains and losses related to changes in benefit obligations for the period. The guidance removed, among other things, the disclosure requirement to disclose the amount of net periodic benefit costs to be amortized over the next fiscal year from accumulated other comprehensive income (loss) and the effects a one percentage point change in assumed health care cost trend rates will have on certain benefit components. January 1, 2021 The Company determined the guidance did not materially impact its consolidated financial statement disclosures. ASU 2019-12 - Simplifying the Accounting for Income Taxes In December 2019, the FASB issued guidance on simplifying the accounting for income taxes by removing certain exceptions in ASC 740 and providing simplification amendments. The guidance removed exceptions on intraperiod tax allocations and reporting and provided simplification on accounting for franchise taxes, tax basis goodwill and tax law changes. January 1, 2021 The Company determined the guidance did not materially impact its results of operations, financial position, cash flows or disclosures. Recently issued accounting standards not yet adopted 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 identify a replacement rate by June 30, 2023. Effective as of March 12, 2020 and will continue through December 31, 2022 The Company has updated its credit agreements to include language regarding the successor or alternate rate to LIBOR, and a review of other contracts and agreements is on-going. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures. ASU 2021-10 - Government Assistance In November 2021, the FASB issued guidance on modifying the disclosure requirements to increase the transparency of government assistance including disclosure of the types of assistance, an entity's accounting for the assistance and the effect of the assistance on an entity's financial statements. January 1, 2022 The Company is currently evaluating the impact the guidance will have on its disclosures for the year ended December 31, 2022.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.
Revenue recognition	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 electric and natural gas distribution segments generate revenue from the sales of electric and natural gas products and services, which includes retail and transportation services. These segments establish a customer's retail or transportation service account based on the customer's application/ contract for service, which indicates approval of a contract for service. The contract identifies an obligation to provide service in exchange for delivering or standing ready to deliver the identified commodity; and the customer is obligated to pay for the service as provided in the applicable tariff. The product sales are based on a fixed rate that includes a base and per-unit rate, which are included in approved tariffs as determined by state or federal regulatory agencies. The quantity of the commodity consumed or transported determines the total per-unit revenue. The service provided, along with the product consumed or transported, are a single performance obligation because both are required in combination to successfully transfer the contracted product or service to the customer. Revenues are recognized over time as customers receive and consume the products and services. The method of measuring progress toward the completion of the single performance obligation is on a per-unit output method basis, with revenue recognized based on the direct measurement of the value to the customer of the goods or services transferred to date. For contracts governed by the Company’s utility tariffs, amounts are billed monthly with the amount due between 15 and 22 days of receipt of the invoice depending on the applicable state’s tariff. For other contracts not governed by tariff, payment terms are net 30 days. At this time, the segment has no material obligations for returns, refunds or other similar obligations. The pipeline segment generates revenue from providing natural gas transportation and underground storage services, as well as other energy-related services to both third parties and internal customers, largely the natural gas distribution segment. The pipeline segment establishes a contract with a customer based upon the customer’s request for firm or interruptible natural gas transportation or storage service(s). The contract identifies an obligation for the segment to provide the requested service(s) in exchange for consideration from the customer over a specified term. Depending on the type of service(s) requested and contracted, the service provided may include transporting or storing an identified quantity of natural gas and/or standing ready to deliver or store an identified quantity of natural gas. Natural gas transportation and storage revenues are based on fixed rates, which may include reservation fees and/or per-unit commodity rates. The services provided by the segment are generally treated as single performance obligations satisfied over time simultaneous to when the service is provided and revenue is recognized. Rates for the segment’s regulated services are based on its FERC approved tariff or customer negotiated rates, and rates for its non-regulated services are negotiated with its customers and set forth in the contract. For contracts governed by the company’s tariff, amounts are billed on or before the ninth business day of the following month and the amount is due within 12 days of receipt of the invoice. For other contracts not governed by the tariff, payment terms are net 30 days. At this time, the segment has no material obligations for returns, refunds or other similar obligations. The construction materials and contracting segment generates revenue from contracting services and construction materials sales. This segment focuses on the vertical integration of its contracting services with its construction materials to support the aggregate-based product lines. This segment provides contracting services to a customer when a contract has been signed by both the customer and a representative of the segment obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services this segment provides generally includes integrating a set of services and related construction materials into a single project to create a distinct bundle of goods and services, which the Company evaluates to determine whether a separate performance obligation exists. The transaction price is the original contract price plus any subsequent change orders and variable consideration. Examples of variable consideration that exist in this segment's contracts include liquidated damages; performance bonuses or incentives and penalties; claims; unapproved/unpriced change orders; and index pricing. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using estimation methods that best predict the most likely amount of consideration the Company expects to be entitled to or expects to incur. The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management's estimates made in determining the value of variable consideration recorded. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Revenue is recognized over time using an input method based on the cost-to-cost measure of progress on a project. This is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. This segment also sells construction materials to third parties and internal customers. The contract for material sales is the use of a sales order or an invoice, which includes the pricing and payment terms. All material contracts contain a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations. The construction services segment generates revenue from specialty contracting services which also includes the sale of construction equipment and other supplies. This segment provides specialty contracting services to a customer when a contract has been signed by both the customer and a representative of the segment obligating a service to be provided in exchange for the consideration identified in the contract. The nature of the services this segment provides generally includes multiple promised goods and services in a single project to create a distinct bundle of goods and services, which the Company evaluates to determine whether a separate performance obligation exists. The transaction price is the original contract price plus any subsequent change orders and variable consideration. Examples of variable consideration that exist in this segment's contracts include claims, unapproved/unpriced change orders, bonuses, incentives, penalties and liquidated damages. The variable amounts usually arise upon achievement of certain performance metrics or change in project scope. The Company estimates the amount of revenue to be recognized on variable consideration using estimation methods that best predict the most likely amount of consideration the Company expects to be entitled to or expects to incur. The Company includes variable consideration in the estimated transaction price to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur or when the uncertainty associated with the variable consideration is resolved. Changes in circumstances could impact management's estimates made in determining the value of variable consideration recorded. The Company updates its estimate of the transaction price each reporting period and the effect of variable consideration on the transaction price is recognized as an adjustment to revenue on a cumulative catch-up basis. Revenue is recognized over time using the input method based on the measurement of progress on a project. The input method is the preferred method of measuring revenue because the costs incurred have been determined to represent the best indication of the overall progress toward the transfer of such goods or services promised to a customer. This segment also sells construction equipment and other supplies to third parties and internal customers. The contract for these sales is the use of a sales order or invoice, which includes the pricing and payment terms. All such contracts include a single performance obligation for the delivery of a single distinct product or a distinct separately identifiable bundle of products and services. Revenue is recognized at a point in time when the performance obligation has been satisfied with the delivery of the products or services. The warranties associated with the sales are those consistent with a standard warranty that the product meets certain specifications for quality or those required by law. For most contracts, amounts billed to customers are due within 30 days of receipt. There are no material obligations for returns, refunds or other similar obligations. The Company recognizes all other revenues when services are rendered or goods are delivered.
Legal costs	The Company expenses external legal fees as they are incurred.
Business combinations policy	For all business combinations, the Company preliminarily allocates the purchase price of the acquisitions to the assets acquired and liabilities assumed based on their estimated fair values as of the acquisition dates and are considered provisional until final fair values are determined or the measurement period has passed. The Company expects to record adjustments as it accumulates the information needed to estimate the fair value of assets acquired and liabilities assumed, including working capital balances, estimated fair value of identifiable intangible assets, property, plant and equipment, total consideration and goodwill. The excess of the purchase price over the aggregate fair values is recorded as goodwill. The Company calculated the fair value of the assets acquired in 2021 and 2020 using a market or cost approach (or a combination of both). Fair values for some of the assets were determined based on Level 3 inputs including estimated future cash flows, discount rates, growth rates, sales projections, retention rates and terminal values, all of which require significant management judgment and are susceptible to change. The final fair value of the net assets acquired may result in adjustments to the assets and liabilities, including goodwill, and will be made as soon as practical, but no later than 12 months from the respective acquisition dates. Any subsequent measurement period adjustments are not expected to have a material impact on the Company's results of operations.
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 3. The Company's trade receivables are all due in 12 months or less.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 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.
Property, Plant and Equipment, Policy	Additions to property, plant and equipment are recorded at cost. When regulated assets are retired, or otherwise disposed of in the ordinary course of business, the original cost of the asset is charged to accumulated depreciation. With respect to the retirement or disposal of all other assets, the resulting gains or losses are recognized as a component of income. The Company is permitted to capitalize AFUDC on regulated construction projects and to include such amounts in rate base when the related facilities are placed in service. In addition, the Company capitalizes interest, when applicable, on certain construction projects associated with its other operations.
Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy	The Company reviews the carrying values of its long-lived assets, excluding goodwill, whenever events or changes in circumstances indicate that such carrying values may not be recoverable. The determination of whether an impairment has occurred is based on an estimate of undiscounted future cash flows attributable to the assets, compared to the carrying value of the assets. If impairment has occurred, the amount of the impairment recognized is determined by estimating the fair value of the assets and recording a loss if the carrying value is greater than the fair value.
Regulatory assets and liabilities	The Company's regulated businesses are subject to various state and federal agency regulations. The accounting policies followed by these businesses are generally subject to the Uniform System of Accounts of the FERC as well as the provisions of ASC 980 - Regulated Operations . These accounting policies differ in some respects from those used by the Company's non-regulated businesses. The Company's regulated businesses account for certain income and expense items under the provisions of regulatory accounting, which requires these businesses to defer as regulatory assets or liabilities certain items that would have otherwise been reflected as expense or income, respectively. The Company records regulatory assets or liabilities at the time the Company determines the amounts to be recoverable in current or future rates. Regulatory assets and liabilities are being amortized consistently with the regulatory treatment established by the FERC and the applicable state public service commission. See Note 6 for more information regarding the nature and amounts of these regulatory deferrals.
Natural gas costs recoverable or refundable through rate adjustments	Under the terms of certain orders of the applicable state public service commissions, the Company is deferring natural gas commodity, transportation and storage costs that are greater or less than amounts presently being recovered through its existing rate schedules. Such orders generally provide that these amounts are recoverable or refundable through rate adjustments
Goodwill	Goodwill represents the excess of the purchase price over the fair value of identifiable net tangible and intangible assets acquired in a business combination. Goodwill is required to be tested for impairment annually, which the Company completes in the fourth quarter, or more frequently if events or changes in circumstances indicate that goodwill may be impaired.
Investment, Policy	The Company's investments include the cash surrender value of life insurance policies, an insurance contract, mortgage-backed securities and U.S. Treasury securities. The Company measures its investment in the insurance contract at fair value with any unrealized gains and losses recorded on the Consolidated Statements of Income. The Company has not elected the fair value option for its mortgage-backed securities and U.S. Treasury securities and, as a result, the unrealized gains and losses on these investments are recorded in accumulated other comprehensive loss. For more information, see Notes 8 and 18
Joint ventures	The Company accounts for unconsolidated joint ventures using either the equity method or proportionate consolidation. The Company currently holds interests between 33 percent and 50 percent in joint ventures formed primarily for the purpose of pooling resources on construction contracts. Proportionate consolidation is used for joint ventures that include unincorporated legal entities and activities of the joint venture which are construction-related. For those joint ventures accounted for under proportionate consolidation, only the Company’s pro rata share of assets, liabilities, revenues and expenses are included in the Company’s balance sheet and results of operations.
Derivative Instruments	The Company enters into commodity price derivative contracts in order to minimize the price volatility associated with customer natural gas costs at its natural gas distribution segment. These derivatives are not designated as hedging instruments and are recorded in the Consolidated Balance Sheets at fair value. Changes in the fair value of these derivatives along with any contract settlements are recorded each period in regulatory assets or liabilities in accordance with regulatory accounting. The Company does not enter into any derivatives for trading or other speculative purposes.
Leases	Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company recognizes leases with an original lease term of 12 months or less in income on a straight-line basis over the term of the lease and does not recognize a corresponding right-of-use asset or lease liability. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue. The discount rate used to calculate the present value of the lease liabilities is based upon the implied rate within each contract. If the rate is unknown or cannot be determined, the Company uses an incremental borrowing rate, which is determined by the length of the contract, asset class and the Company's borrowing rates, as of the commencement date of the contract.
Asset retirement obligation	The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes a cost by increasing the carrying amount of the related long-lived asset. Over time, the liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. Upon settlement of the liability, the Company either settles the obligation for the recorded amount or incurs a gain or loss at its non-regulated operations or incurs a regulatory asset or liability at its regulated operations.
Stock-based compensation	The Company determines compensation expense for stock-based awards based on the estimated fair values at the grant date and recognizes the related compensation expense over the vesting period. The Company uses the straight-line amortization method to recognize compensation expense related to restricted stock, which only has a service condition. This method recognizes stock compensation expense on a straight-line basis over the requisite service period for the entire award. The Company recognizes compensation expense related to performance awards that vest based on performance metrics and service conditions on a straight-line basis over the service period. Inception-to-date expense is adjusted based upon the determination of the potential achievement of the performance target at each reporting date. The Company recognizes compensation expense related to performance awards with market-based performance metrics on a straight-line basis over the requisite service period.The Company records the compensation expense for performance share awards using an estimated forfeiture rate. The estimated forfeiture rate is calculated based on an average of actual historical forfeitures. The Company also performs an analysis of any known factors at the time of the calculation to identify any necessary adjustments to the average historical forfeiture rate. At the time actual forfeitures become more than estimated forfeitures, the Company records compensation expense using actual forfeitures
Earnings (loss) per common share	Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the year. 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 year, plus the effect of nonvested performance share awards and restricted stock units.
Income Tax, Policy	The Company provides deferred federal and state income taxes on all temporary differences between the book and tax basis of the Company's assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. Excess deferred income tax balances associated with the Company's rate-regulated activities have been recorded as a regulatory liability and are included in other liabilities. These regulatory liabilities are expected to be reflected as a reduction in future rates charged to customers in accordance with applicable regulatory procedures. The Company uses the deferral method of accounting for investment tax credits and amortizes the credits on regulated electric and natural gas distribution plant over various periods that conform to the ratemaking treatment prescribed by the applicable state public service commissions.
Income tax uncertainties	The Company records uncertain tax positions in accordance with accounting guidance on accounting for income taxes on the basis of a two-step process in which (1) the Company determines whether it is more-likely-than-not that the tax position will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, the Company recognizes the largest amount of the tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. Tax positions that do not meet the more-likely-than-not criteria are reflected as a tax liability. The Company recognizes interest and penalties accrued related to unrecognized tax benefits in income taxes.
Variable interest entities	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. GAAP provides a framework for identifying VIEs and determining when a company should include the assets, liabilities, noncontrolling interest and results of activities of a VIE in its consolidated financial statements. A VIE should be consolidated if a party with an ownership, contractual or other financial interest in the VIE (a variable interest holder) has the power to direct the VIE's most significant activities and the obligation to absorb losses or right to receive benefits of the VIE that could be significant to the VIE. A variable interest holder that consolidates the VIE is called the primary beneficiary. Upon consolidation, the primary beneficiary generally must initially record all of the VIE's assets, liabilities and noncontrolling interests at fair value and subsequently account for the VIE as if it were consolidated. The Company's evaluation of whether it qualifies as the primary beneficiary of a VIE involves significant judgments, estimates and assumptions and includes a qualitative analysis of the activities that most significantly impact the VIE's economic performance and whether the Company has the power to direct those activities, the design of the entity, the rights of the parties and the purpose of the arrangement.

Revenue from Contract with Cu_2

Revenue from Contract with Customer (Policies)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	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. As part of the adoption of ASC 606 - Revenue from Contracts with Customers , the Company elected the practical expedient to recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that the Company otherwise would have recognized is 12 months or less.

Accumulated other comprehensi_2

Accumulated other comprehensive loss (Policies)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Accumulated other comprehensive loss (Policy)	The Company's accumulated other comprehensive loss is comprised of losses on derivative instruments qualifying as hedges, postretirement liability adjustments and gain (loss) on available-for-sale investments.

Business segment data (Policies

Business segment data (Policies)	12 Months Ended
	Dec. 31, 2021
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.

Commitment and Contingencies (P

Commitment and Contingencies (Policies)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies, Policy	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.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Financing Receivable, Allowance for Credit Loss	Details of the Company's expected credit losses were as follows: Electric Natural gas Pipeline Construction Construction Total (In thousands) At January 1, 2020 $ 328 $ 1,056 $ — $ 5,357 $ 1,756 $ 8,497 Current expected credit loss provision* 1,517 3,187 2 1,447 4,832 10,985 Less write-offs charged against the allowance 1,289 2,511 — 640 866 5,306 Credit loss recoveries collected 343 839 — — — 1,182 At December 31, 2020 899 2,571 2 6,164 5,722 15,358 Current expected credit loss provision* 1,099 2,188 — 68 (2,250) 1,105 Less write-offs charged against the allowance 2,139 4,072 — 826 1,032 8,069 Credit loss recoveries collected 410 819 — — 93 1,322 At December 31, 2021 $ 269 $ 1,506 $ 2 $ 5,406 $ 2,533 $ 9,716
Contract receivable retainage	Amounts representing balances billed but not paid by customers under retainage provisions in contracts at December 31 were as follows: 2021 2020 (In thousands) Short-term retainage* $ 70,600 $ 100,054 Long-term retainage** 10,742 2,761 Total retainage $ 81,342 $ 102,815 * Expected to be paid within 12 months or less and included in receivables, net. ** Included in noncurrent assets - other.
Inventories	Inventories at December 31 consisted of: 2021 2020 (In thousands) Aggregates held for resale $ 184,363 $ 175,782 Asphalt oil 57,002 28,238 Materials and supplies 30,629 25,142 Merchandise for resale 28,501 21,087 Natural gas in storage (current) 18,867 21,919 Other 16,247 18,999 Total $ 335,609 $ 291,167
AFUDC and interest capitailized	The amount of AFUDC for the years ended December 31 was as follows: 2021 2020 2019 (In thousands) AFUDC - borrowed $ 2,833 $ 2,640 $ 2,807 AFUDC - equity $ 6,961 $ 1,270 $ 698
Schedule of earnings per share reconciliation	A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows: 2021 2020 2019 (In thousands) Weighted average common shares outstanding - basic 202,076 200,502 198,612 Effect of dilutive performance share awards 307 69 14 Weighted average common shares outstanding - diluted 202,383 200,571 198,626 Shares excluded from the calculation of diluted earnings per share — 164 164

Revenue from contracts with cus

Revenue from contracts with customers (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	Disaggregation In the following table, 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 17. Year ended December 31, 2021 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 126,841 $ 544,721 $ — $ — $ — $ — $ 671,562 Commercial utility sales 137,556 328,285 — — — — 465,841 Industrial utility sales 41,757 30,964 — — — — 72,721 Other utility sales 7,051 — — — — — 7,051 Natural gas transportation — 48,408 114,001 — — — 162,409 Natural gas storage — — 14,680 — — — 14,680 Contracting services — — — 1,017,471 — — 1,017,471 Construction materials — — — 1,712,503 — — 1,712,503 Intrasegment eliminations — — — (501,044) — — (501,044) Electrical & mechanical specialty contracting — — — — 1,324,419 — 1,324,419 Transmission & distribution specialty contracting — — — — 677,074 — 677,074 Other 42,902 10,567 13,667 — 557 13,714 81,407 Intersegment eliminations (543) (576) (59,678) (624) (2,555) (13,630) (77,606) Revenues from contracts with customers 355,564 962,369 82,670 2,228,306 1,999,495 84 5,628,488 Revenues out of scope (6,525) 8,995 188 — 49,587 — 52,245 Total external operating revenues $ 349,039 $ 971,364 $ 82,858 $ 2,228,306 $ 2,049,082 $ 84 $ 5,680,733 Year ended December 31, 2020 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 122,663 $ 476,388 $ — $ — $ — $ — $ 599,051 Commercial utility sales 131,477 277,873 — — — — 409,350 Industrial utility sales 36,744 26,243 — — — — 62,987 Other utility sales 6,634 — — — — — 6,634 Natural gas transportation — 45,546 111,686 — — — 157,232 Natural gas gathering — — 4,865 — — — 4,865 Natural gas storage — — 14,918 — — — 14,918 Contracting services — — — 1,069,665 — — 1,069,665 Construction materials — — — 1,659,152 — — 1,659,152 Intrasegment eliminations — — — (550,815) — — (550,815) Electrical & mechanical specialty contracting — — — — 1,397,124 — 1,397,124 Transmission & distribution specialty contracting — — — — 649,486 — 649,486 Other 32,452 10,753 12,216 — 1,541 11,903 68,865 Intersegment eliminations (491) (534) (58,531) (417) (5,038) (11,958) (76,969) Revenues from contracts with customers 329,479 836,269 85,154 2,177,585 2,043,113 (55) 5,471,545 Revenues out of scope 2,059 11,382 192 — 47,572 — 61,205 Total external operating revenues $ 331,538 $ 847,651 $ 85,346 $ 2,177,585 $ 2,090,685 $ (55) $ 5,532,750 Year ended December 31, 2019 Electric Natural gas distribution Pipeline Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 125,369 $ 483,452 $ — $ — $ — $ — $ 608,821 Commercial utility sales 141,596 296,835 — — — — 438,431 Industrial utility sales 37,765 26,895 — — — — 64,660 Other utility sales 7,408 — — — — — 7,408 Natural gas transportation — 45,449 101,665 — — — 147,114 Natural gas gathering — — 9,164 — — — 9,164 Natural gas storage — — 11,708 — — — 11,708 Contracting services — — — 1,088,633 — — 1,088,633 Construction materials — — — 1,627,833 — — 1,627,833 Intrasegment eliminations — — — (525,749) — — (525,749) Electrical & mechanical specialty contracting — — — — 1,266,196 — 1,266,196 Transmission & distribution specialty contracting — — — — 531,882 — 531,882 Other 35,574 12,726 17,687 — 131 16,551 82,669 Intersegment eliminations — — (56,252) (1,066) (3,370) (16,461) (77,149) Revenues from contracts with customers 347,712 865,357 83,972 2,189,651 1,794,839 90 5,281,621 Revenues out of scope 4,013 (135) 220 — 51,057 — 55,155 Total external operating revenues $ 351,725 $ 865,222 $ 84,192 $ 2,189,651 $ 1,845,896 $ 90 $ 5,336,776
Contract balances	The changes in contract assets and liabilities were as follows: December 31, 2021 December 31, 2020 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 125,742 $ 104,345 $ 21,397 Receivables, net Contract liabilities - current (179,140) (158,603) (20,537) Accounts payable Contract liabilities - noncurrent (118) (52) (66) Noncurrent liabilities - other Net contract liabilities $ (53,516) $ (54,310) $ 794 December 31, 2020 December 31, 2019 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 104,345 $ 109,078 $ (4,733) Receivables, net Contract liabilities - current (158,603) (142,768) (15,835) Accounts payable Contract liabilities - noncurrent (52) (19) (33) Noncurrent liabilities - other Net contract liabilities $ (54,310) $ (33,709) $ (20,601)

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment at December 31 was as follows: 2021 2020 Weighted (Dollars in thousands, where applicable) Regulated: Electric: Generation $ 1,056,632 $ 1,133,390 48 Distribution 474,037 464,442 47 Transmission 562,080 524,155 65 Construction in progress 62,781 61,766 — Other 140,117 139,650 14 Natural gas distribution: Distribution 2,427,779 2,302,121 50 Transmission 107,721 104,695 60 Storage 34,997 33,014 39 General 197,653 198,211 14 Construction in progress 21,741 16,836 — Other 225,272 213,976 14 Pipeline: Transmission 673,344 665,567 46 Storage 57,670 52,632 53 Construction in progress 263,640 46,690 — Other 50,477 49,640 17 Non-regulated: Pipeline: Construction in progress 18 4 — Other 6,719 7,164 10 Construction materials and contracting: Land 149,066 132,948 — Buildings and improvements 149,262 130,417 21 Machinery, vehicles and equipment 1,414,260 1,284,604 12 Construction in progress 50,425 23,803 — Aggregate reserves 584,683 456,704 * Construction services: Land 6,513 7,218 — Buildings and improvements 39,039 41,674 24 Machinery, vehicles and equipment 166,739 163,080 7 Other 13,467 8,824 2 Other: Land 2,648 2,648 — Other 34,069 34,897 7 Less accumulated depreciation, depletion and amortization 3,216,461 3,133,831 Net property, plant and equipment $ 5,756,388 $ 5,166,939 * Depleted on the units-of-production method based on recoverable aggregate reserves.

Regulatory assets and liabili_2

Regulatory assets and liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory assets	The following table summarizes the individual components of unamortized regulatory assets and liabilities as of December 31: Estimated Recovery or Refund Period * 2021 2020 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 86,371 $ 42,481 Decoupling Up to 1 year 9,131 703 Conservation programs Up to 1 year 8,225 7,117 Cost recovery mechanisms Up to 1 year 4,536 10,645 Other Up to 1 year 10,428 7,581 118,691 68,527 Noncurrent: Pension and postretirement benefits ** 142,681 155,942 Plant costs/asset retirement obligations Over plant lives 63,116 71,740 Plant to be retired - 50,070 65,919 Cost recovery mechanisms Up to 10 years 44,870 16,245 Manufactured gas plant sites remediation - 26,053 26,429 Taxes recoverable from customers Over plant lives 12,339 10,785 Natural gas costs recoverable through rate adjustments Up to 2 years 5,186 21,539 Long-term debt refinancing costs Up to 39 years 3,794 4,426 Other Up to 17 years 9,742 6,356 357,851 379,381 Total regulatory assets $ 476,542 $ 447,908 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year $ 6,700 $ 18,565 Taxes refundable to customers Up to 1 year 3,841 3,557 Electric fuel and purchased power deferral Up to 1 year — 3,667 Other Up to 1 year 5,762 5,661 16,303 31,450 Noncurrent: Taxes refundable to customers Over plant lives 215,421 227,850 Plant removal and decommissioning costs Over plant lives 168,152 167,171 Pension and postretirement benefits ** 20,434 16,989 Other Up to 20 years 24,783 16,065 428,790 428,075 Total regulatory liabilities $ 445,093 $ 459,525 Net regulatory position $ 31,449 $ (11,617) * 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 as of December 31: Estimated Recovery or Refund Period * 2021 2020 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 86,371 $ 42,481 Decoupling Up to 1 year 9,131 703 Conservation programs Up to 1 year 8,225 7,117 Cost recovery mechanisms Up to 1 year 4,536 10,645 Other Up to 1 year 10,428 7,581 118,691 68,527 Noncurrent: Pension and postretirement benefits ** 142,681 155,942 Plant costs/asset retirement obligations Over plant lives 63,116 71,740 Plant to be retired - 50,070 65,919 Cost recovery mechanisms Up to 10 years 44,870 16,245 Manufactured gas plant sites remediation - 26,053 26,429 Taxes recoverable from customers Over plant lives 12,339 10,785 Natural gas costs recoverable through rate adjustments Up to 2 years 5,186 21,539 Long-term debt refinancing costs Up to 39 years 3,794 4,426 Other Up to 17 years 9,742 6,356 357,851 379,381 Total regulatory assets $ 476,542 $ 447,908 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments Up to 1 year $ 6,700 $ 18,565 Taxes refundable to customers Up to 1 year 3,841 3,557 Electric fuel and purchased power deferral Up to 1 year — 3,667 Other Up to 1 year 5,762 5,661 16,303 31,450 Noncurrent: Taxes refundable to customers Over plant lives 215,421 227,850 Plant removal and decommissioning costs Over plant lives 168,152 167,171 Pension and postretirement benefits ** 20,434 16,989 Other Up to 20 years 24,783 16,065 428,790 428,075 Total regulatory liabilities $ 445,093 $ 459,525 Net regulatory position $ 31,449 $ (11,617) * 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.

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	12 Months Ended
	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	The changes in the carrying amount of goodwill were as follows: Balance at January 1, 2021 Goodwill Measurement Period Balance at December 31, 2021 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 226,003 50,640 (217) 276,426 Construction services 143,224 — — 143,224 Total $ 714,963 $ 50,640 $ (217) $ 765,386 Balance at January 1, 2020 Goodwill Acquired Measurement Period Balance at December 31, 2020 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 217,234 8,778 (9) 226,003 Construction services 118,388 24,436 400 143,224 Total $ 681,358 $ 33,214 $ 391 $ 714,963
Other amortizable intangible assets	Other amortizable intangible assets at December 31 were as follows: 2021 2020 (In thousands) Customer relationships $ 29,740 $ 28,836 Less accumulated amortization 10,650 6,887 19,090 21,949 Noncompete agreements 4,591 3,941 Less accumulated amortization 2,856 2,309 1,735 1,632 Other 12,601 12,927 Less accumulated amortization 10,848 11,012 1,753 1,915 Total $ 22,578 $ 25,496
Estimated amortization expense	The amounts of estimated amortization expense for identifiable intangible assets as of December 31, 2021, were: 2022 2023 2024 2025 2026 Thereafter (In thousands) Amortization expense $ 4,928 $ 4,578 $ 4,308 $ 2,314 $ 1,693 $ 4,757

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Debt Securities, Available-for-sale	Details of available-for-sale securities were as follows: December 31, 2021 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 8,702 $ 51 $ 47 $ 8,706 U.S. Treasury securities 2,407 — 11 2,396 Total $ 11,109 $ 51 $ 58 $ 11,102 December 31, 2020 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 9,799 $ 156 $ 9 $ 9,946 U.S. Treasury securities 1,386 — 5 1,381 Total $ 11,185 $ 156 $ 14 $ 11,327
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 Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Money market funds $ — $ 10,190 $ — $ 10,190 Insurance contract* — 109,603 — 109,603 Available-for-sale securities: Mortgage-backed securities — 8,706 — 8,706 U.S. Treasury securities — 2,396 — 2,396 Total assets measured at fair value $ — $ 130,895 $ — $ 130,895 * The insurance contract invests approximately 61 percent in fixed-income investments, 17 percent in common stock of large-cap companies, 8 percent in common stock of mid-cap companies, 7 percent in common stock of small-cap companies, 5 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Money market funds $ — $ 8,917 $ — $ 8,917 Insurance contract* — 100,104 — 100,104 Available-for-sale securities: Mortgage-backed securities — 9,946 — 9,946 U.S. Treasury securities — 1,381 — 1,381 Total assets measured at fair value $ — $ 120,348 $ — $ 120,348 * The insurance contract invests approximately 57 percent in fixed-income investments, 18 percent in common stock of large-cap companies, 9 percent in common stock of mid-cap companies, 9 percent in common stock of small-cap companies, 5 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 at December 31 was as follows: 2021 2020 (In thousands) Carrying Amount $ 2,741,900 $ 2,213,130 Fair Value $ 2,984,866 $ 2,537,289

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Outstanding credit facilities	The following table summarizes the outstanding revolving credit facilities of the Company's subsidiaries: Company Facility Facility Amount Outstanding at December 31, 2021 Amount Outstanding at December 31, 2020 Letters of Credit at December 31, 2021 Expiration (In millions) Montana-Dakota Utilities Co. Commercial paper/Revolving credit agreement (a) $ 175.0 $ 64.9 $ 87.7 $ — 12/19/24 Cascade Natural Gas Corporation Revolving credit agreement $ 100.0 (b) $ 71.0 $ 54.0 $ 2.2 (c) 6/7/24 Intermountain Gas Company Revolving credit agreement $ 85.0 (d) $ 56.5 $ 41.9 $ — 6/7/24 Centennial Energy Holdings, Inc. Commercial paper/Revolving credit agreement (e) $ 600.0 $ 385.4 $ 37.9 $ — 12/19/24 (a) The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Montana-Dakota on stated conditions, up to a maximum of $225.0 million). There were no amounts outstanding under the revolving credit agreement. (b) Certain provisions allow for increased borrowings, up to a maximum of $125.0 million. (c) (Outstanding letter(s) of credit reduce the amount available under the credit agreement. (d) (Certain provisions allow for increased borrowings, up to a maximum of $110.0 million. (e) The commercial paper program is supported by a revolving credit agreement with various banks (provisions allow for increased borrowings, at the option of Centennial on stated conditions, up to a maximum of $700.0 million). There were no amounts outstanding under the revolving credit agreement.
Long term debt outstanding	Long-term debt outstanding was as follows: Weighted Average Interest Rate at December 31, 2021 2021 2020 (In thousands) Senior Notes due on dates ranging from October 22, 2022 to September 15, 2061 4.32 % $ 2,125,000 $ 1,950,000 Commercial paper supported by revolving credit agreements .40 % 450,300 125,600 Credit agreements due on June 7, 2024 1.94 % 127,500 95,900 Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029 7.32 % 35,000 35,000 Term Loan Agreement due on September 3, 2032 2.00 % 7,700 8,400 Other notes due on dates ranging from January 2, 2022 to January 1, 2061 1.03 % 2,564 4,034 Less unamortized debt issuance costs 6,090 5,803 Less discount 74 1 Total long-term debt 2,741,900 2,213,130 Less current maturities 148,053 1,555 Net long-term debt $ 2,593,847 $ 2,211,575
Schedule of debt maturities	Long-term debt maturities, which excludes unamortized debt issuance costs and discount, for the five years and thereafter following December 31, 2021, were as follows: 2022 2023 2024 2025 2026 Thereafter (In thousands) Long-term debt maturities $ 148,053 $ 77,925 $ 638,604 $ 177,802 $ 140,802 $ 1,564,878

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Lease, Cost	The following tables provide information on the Company's operating leases at and for the years ended December 31: 2021 2020 (In thousands) Lease costs: Short-term lease cost $ 132,449 $ 135,376 Operating lease cost 46,622 45,319 Variable lease cost 1,516 1,319 $ 180,587 $ 182,014 2021 2020 (Dollars in thousands) Weighted average remaining lease term 2.67 years 2.73 years Weighted average discount rate 3.54 % 4.03 % Cash paid for amounts included in the measurement of lease liabilities $ 43,489 $ 45,043
Lessee, Operating Lease, Liability, Maturity	The reconciliation of future undiscounted cash flows to operating lease liabilities presented on the Consolidated Balance Sheet at December 31, 2021, was as follows: (In thousands) 2022 $ 38,605 2023 27,460 2024 19,732 2025 12,278 2026 6,681 Thereafter 44,039 Total 148,795 Less discount 24,174 Total operating lease liabilities $ 124,621

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation [Abstract]
Reconciliation of the company's asset retirement obligation	A reconciliation of the Company's liability, which the current portion is included in other accrued liabilities on the Consolidated Balance Sheets, for the years ended December 31 was as follows: 2021 2020 (In thousands) Balance at beginning of year $ 446,919 $ 417,575 Liabilities incurred 12,454 11,560 Liabilities acquired 1,805 1,378 Liabilities settled (15,155) (5,369) Accretion expense* 21,214 21,668 Revisions in estimates 1,449 107 Balance at end of year $ 468,686 $ 446,919 * Includes $19.6 million and $20.1 million in 2021 and 2020, respectively, recorded to regulatory assets.

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Schedule of Stock by Class	2021 2020 (In millions) Shares issued 2.8 — Net proceeds * $ 88.8 $ — Issuance costs $ 1.2 $ — * Net proceeds were used for capital expenditures.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Target grants performance share	Target grants of performance shares outstanding at December 31, 2021, were as follows: Grant Date Performance Target Grant February 2020 2020-2022 273,918 February 2021 2021-2023 281,129
Schedule of share-based payment award, performance shares, valuation assumptions	Assumptions used for grants applicable to the market condition for certain performance shares issued in 2021, 2020 and 2019 were: 2021 2020 2019 Weighted average grant-date fair value $37.96 $40.75 $35.07 Blended volatility range 35.37% - 46.35% 15.30% - 15.97% 19.50% - 19.69% Risk-free interest rate range .02% - .20% 1.45% - 1.62% 2.46% - 2.55% Weighted average discounted dividends per share $3.16 $2.91 $2.85
Summary of the status of the performance share awards	A summary of the status of the performance share awards for the year ended December 31, 2021, was as follows: Number of Weighted Nonvested at beginning of period 613,174 $ 33.24 Granted 284,104 32.66 Additional performance shares earned 116,467 22.68 Less: Vested 443,661 28.57 Forfeited 15,037 35.49 Nonvested at end of period 555,047 $ 34.40

Accumulated other comprehensi_3

Accumulated other comprehensive loss (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Accumulated comprehensive loss	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Post- Net Total (In thousands) At December 31, 2019 $ (1,430) $ (40,734) $ 62 $ (42,102) Other comprehensive loss before reclassifications — (8,395) (1) (8,396) Amounts reclassified from accumulated other comprehensive loss 446 1,922 52 2,420 Net current-period other comprehensive income (loss) 446 (6,473) 51 (5,976) At December 31, 2020 (984) (47,207) 113 (48,078) Other comprehensive income (loss) before reclassifications — 4,876 (252) 4,624 Amounts reclassified from accumulated other comprehensive loss 446 1,870 134 2,450 Net current-period other comprehensive income (loss) 446 6,746 (118) 7,074 At December 31, 2021 $ (538) $ (40,461) $ (5) $ (41,004)
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 for the years ended December 31 were as follows: 2021 2020 Location on Consolidated (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (591) $ (591) Interest expense 145 145 Income taxes (446) (446) Amortization of postretirement liability losses included in net periodic benefit cost (2,485) (2,552) Other income 615 630 Income taxes (1,870) (1,922) Reclassification adjustment for loss on available-for-sale investments included in net income (170) (66) Other income 36 14 Income taxes (134) (52) Total reclassifications $ (2,450) $ (2,420)

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Components of income before income taxes	The components of income before income taxes from continuing operations for each of the years ended December 31 were as follows: 2021 2020 2019 (In thousands) United States $ 466,651 $ 474,856 $ 398,532 Foreign — 261 (87) Income before income taxes from continuing operations $ 466,651 $ 475,117 $ 398,445
Income tax expense	Income tax expense (benefit) from continuing operations for the years ended December 31 was as follows: 2021 2020 2019 (In thousands) Current: Federal $ 17,121 $ 65,006 $ (3,502) State 11,549 21,234 3,366 Foreign — 151 — 28,670 86,391 (136) Deferred: Income taxes: Federal 45,885 (3,735) 50,218 State 12,610 (625) 12,098 Investment tax credit - net 1,755 2,559 1,099 60,250 (1,801) 63,415 Total income tax expense $ 88,920 $ 84,590 $ 63,279
Deferred tax assets and deferred tax liabilities	Components of deferred tax assets and deferred tax liabilities at December 31 were as follows: 2021 2020 (In thousands) Deferred tax assets: Postretirement $ 45,752 $ 51,495 Compensation-related 37,917 40,477 Operating lease liabilities 26,710 25,963 Asset retirement obligations 8,696 8,060 Legal and environmental contingencies 8,603 9,467 Customer advances 7,683 7,463 Payroll tax deferral 6,940 14,010 Other 39,960 37,944 Total deferred tax assets 182,261 194,879 Deferred tax liabilities: Basis differences on property, plant and equipment 585,095 536,966 Postretirement 48,302 49,233 Operating lease right-of-use-assets 26,570 25,858 Intangible assets 21,074 19,514 Other 81,070 67,922 Total deferred tax liabilities 762,111 699,493 Valuation allowance 12,112 11,484 Net deferred income tax liability $ 591,962 $ 516,098
Schedule of change in net deferred income tax liability reconciliation	The following table reconciles the change in the net deferred income tax liability from December 31, 2020, to December 31, 2021, to deferred income tax expense: 2021 (In thousands) Change in net deferred income tax liability from the preceding table $ 75,864 Deferred taxes associated with other comprehensive loss (2,355) Excess deferred income tax amortization (10,295) Other (2,964) Deferred income tax expense for the period $ 60,250
Reconciliation of income tax expense (benefit) at statutory federal rate versus actual rate	Total income tax expense differs from the amount computed by applying the statutory federal income tax rate to income before taxes. The reasons for this difference were as follows: Years ended December 31, 2021 2020 2019 Amount % Amount % Amount % (Dollars in thousands) Computed tax at federal statutory rate $ 97,997 21.0 $ 99,775 21.0 $ 83,674 21.0 Increases (reductions) resulting from: State income taxes, net of federal income tax 19,496 4.2 17,845 3.8 14,029 3.5 Federal renewable energy credit (13,914) (3.0) (16,009) (3.4) (15,843) (4.0) Tax compliance and uncertain tax positions (477) (.1) (3,543) (.7) (2,739) (.7) Excess deferred income tax amortization (10,295) (2.2) (12,517) (2.6) (11,904) (3.0) Other (3,887) (.8) (961) (.3) (3,938) (.9) Total income tax expense $ 88,920 19.1 $ 84,590 17.8 $ 63,279 15.9

Cash flow information (Tables)

Cash flow information (Tables)	12 Months Ended
	Dec. 31, 2021
Supplemental Cash Flow Information [Abstract]
Cash expenditures for interest and income taxes and noncash investing transactions	Cash expenditures for interest and income taxes for the years ended December 31 were as follows: 2021 2020 2019 (In thousands) Interest, net* $ 91,165 $ 88,681 $ 93,414 Income taxes paid (refunded), net** $ 71,079 $ 65,536 $ (8,475) * AFUDC - borrowed was $2.8 million, $2.6 million and $2.8 million for the years ended December 31, 2021, 2020 and 2019, respectively. ** Income taxes paid (refunded), including discontinued operations, were $70.9 million, $59.4 million and $(9.4) million for the years ended December 31, 2021, 2020 and 2019, respectively. Noncash investing and financing transactions at December 31 were as follows: 2021 2020 2019 (In thousands) Property, plant and equipment additions in accounts payable $ 57,605 $ 26,082 $ 46,119 Right-of-use assets obtained in exchange for new operating lease liabilities $ 55,987 $ 54,356 $ 54,880 Debt assumed in connection with a business combination $ 10 $ — $ 1,163 Accrual for holdback payment related to a business combination $ — $ 2,500 $ —

Business segment data (Tables)

Business segment data (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Information on the Company's businesses	Information on the Company's segments as of December 31 and for the years then ended was as follows: 2021 2020 2019 (In thousands) External operating revenues: Regulated operations: Electric $ 349,039 $ 331,538 $ 351,725 Natural gas distribution 971,364 847,651 865,222 Pipeline 69,940 69,957 62,357 1,390,343 1,249,146 1,279,304 Non-regulated operations: Pipeline 12,918 15,389 21,835 Construction materials and contracting 2,228,306 2,177,585 2,189,651 Construction services 2,049,082 2,090,685 1,845,896 Other 84 (55) 90 4,290,390 4,283,604 4,057,472 Total external operating revenues $ 5,680,733 $ 5,532,750 $ 5,336,776 Intersegment operating revenues: Regulated operations: Electric $ 543 $ 491 $ — Natural gas distribution 576 534 — Pipeline 58,989 57,977 56,037 60,108 59,002 56,037 Non-regulated operations: Pipeline 689 554 215 Construction materials and contracting 624 417 1,066 Construction services 2,555 5,038 3,370 Other 13,630 11,958 16,461 17,498 17,967 21,112 Intersegment eliminations (77,606) (76,969) (77,149) Total intersegment operating revenues $ — $ — $ — Depreciation, depletion and amortization: Electric $ 66,750 $ 62,998 $ 58,721 Natural gas distribution 86,065 84,580 79,564 Pipeline 20,569 21,669 21,220 Construction materials and contracting 100,974 89,626 77,450 Construction services 20,270 23,523 17,038 Other 4,586 2,704 2,024 Total depreciation, depletion and amortization $ 299,214 $ 285,100 $ 256,017 Operating income (loss): Electric $ 66,335 $ 63,434 $ 64,039 Natural gas distribution 89,173 73,082 69,188 Pipeline 48,078 49,436 42,796 Construction materials and contracting 191,077 214,498 179,955 Construction services 145,754 147,644 126,426 Other (6,198) (3,169) (1,184) Total operating income $ 534,219 $ 544,925 $ 481,220 2021 2020 2019 (In thousands) Interest expense: Electric $ 26,712 $ 26,699 $ 25,334 Natural gas distribution 37,265 36,798 35,488 Pipeline 7,010 7,622 7,198 Construction materials and contracting 19,218 20,577 23,792 Construction services 3,540 4,095 5,331 Other 342 883 1,859 Intersegment eliminations (103) (155) (415) Total interest expense $ 93,984 $ 96,519 $ 98,587 Income tax expense (benefit): Electric $ (7,626) $ (11,636) $ (12,650) Natural gas distribution 8,366 5,746 1,405 Pipeline 9,594 7,650 7,219 Construction materials and contracting 43,459 47,431 37,389 Construction services 35,426 35,797 29,973 Other (299) (398) (57) Total income tax expense $ 88,920 $ 84,590 $ 63,279 Net income (loss): Regulated operations: Electric $ 51,906 $ 55,601 $ 54,763 Natural gas distribution 51,596 44,049 39,517 Pipeline 39,583 35,453 28,255 143,085 135,103 122,535 Non-regulated operations: Pipeline 1,313 1,559 1,348 Construction materials and contracting 129,755 147,325 120,371 Construction services 109,402 109,721 92,998 Other (5,824) (3,181) (2,086) 234,646 255,424 212,631 Income from continuing operations 377,731 390,527 335,166 Income (loss) from discontinued operations, net of tax 400 (322) 287 Net income $ 378,131 $ 390,205 $ 335,453 Capital expenditures: Electric $ 82,427 $ 114,676 $ 99,449 Natural gas distribution 170,411 193,048 206,799 Pipeline 234,803 62,224 71,477 Construction materials and contracting 417,524 191,635 190,092 Construction services 29,140 83,651 60,500 Other 1,501 3,045 8,181 Total capital expenditures (a) $ 935,806 $ 648,279 $ 636,498 2021 2020 2019 (In thousands) Assets: Electric (b) $ 1,810,695 $ 2,123,693 $ 1,680,194 Natural gas distribution (b) 2,929,519 2,302,770 2,574,965 Pipeline 913,945 703,377 677,482 Construction materials and contracting 2,161,653 1,798,493 1,684,161 Construction services 845,262 818,662 761,127 Other (c) 248,489 305,157 303,279 Assets held for sale 872 1,220 1,851 Total assets $ 8,910,435 $ 8,053,372 $ 7,683,059 Property, plant and equipment: Electric (b) $ 2,295,646 $ 2,323,403 $ 2,227,145 Natural gas distribution (b) 3,015,164 2,868,853 2,688,123 Pipeline 1,051,868 821,697 834,215 Construction materials and contracting 2,347,696 2,028,476 1,910,562 Construction services 225,758 220,796 213,370 Other 36,717 37,545 35,213 Less accumulated depreciation, depletion and amortization 3,216,461 3,133,831 2,991,486 Net property, plant and equipment $ 5,756,388 $ 5,166,939 $ 4,917,142 (a) Capital expenditures for 2021, 2020 and 2019 include noncash transactions such as capital expenditure-related accounts payable, AFUDC and accrual of holdback payments in connection with acquisitions totaling $38.7 million, $(15.7) million and $4.8 million, respectively. (b) Includes allocations of common utility property. (c) Includes assets not directly assignable to a business (i.e. cash and cash equivalents, certain accounts receivable, certain investments and other miscellaneous current and deferred assets).

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Schedule of amounts recognized in balance sheet	Changes in benefit obligation and plan assets and amounts recognized in the Consolidated Balance Sheets at December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Change in benefit obligation: (In thousands) Benefit obligation at beginning of year $ 437,360 $ 421,166 $ 86,155 $ 83,614 Service cost — — 1,600 1,532 Interest cost 9,819 12,093 1,862 2,437 Plan participants' contributions — — 641 752 Actuarial (gain) loss (12,140) 27,737 (12,802) 2,203 Benefits paid (23,542) (23,636) (3,996) (4,383) Benefit obligation at end of year 411,497 437,360 73,460 86,155 Change in net plan assets: Fair value of plan assets at beginning of year 383,834 365,264 101,639 94,587 Actual return on plan assets 12,817 42,206 1,398 10,249 Employer contribution — — 476 434 Plan participants' contributions — — 641 752 Benefits paid (23,542) (23,636) (3,996) (4,383) Fair value of net plan assets at end of year 373,109 383,834 100,158 101,639 Funded status - over (under) $ (38,388) $ (53,526) $ 26,698 $ 15,484 Amounts recognized in the Consolidated Balance Sheets at December 31: Noncurrent assets - other $ — $ — $ 45,863 $ 36,769 Other accrued liabilities — — 544 622 Noncurrent liabilities - other 38,388 53,526 18,621 20,663 Benefit obligation assets (liabilities) - net amount recognized $ (38,388) $ (53,526) $ 26,698 $ 15,484 Amounts recognized in accumulated other comprehensive loss: Actuarial loss $ 25,976 $ 27,527 $ 2,367 $ 5,557 Prior service credit — — (290) (634) Total $ 25,976 $ 27,527 $ 2,077 $ 4,923 Amounts recognized in regulatory assets or liabilities: Actuarial (gain) loss $ 142,166 $ 154,013 $ (14,727) $ (8,228) Prior service credit — — (5,193) (6,808) Total $ 142,166 $ 154,013 $ (19,920) $ (15,036)
The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for the pension plans with accumulated benefit obligations in excess of plan assets	The pension plans all have accumulated benefit obligations in excess of plan assets. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans at December 31 were as follows: 2021 2020 (In thousands) Projected benefit obligation $ 411,497 $ 437,360 Accumulated benefit obligation $ 411,497 $ 437,360 Fair value of plan assets $ 373,109 $ 383,834 The projected benefit obligation and accumulated benefit obligation for these plans at December 31 were as follows: 2021 2020 (In thousands) Projected benefit obligation $ 92,918 $ 101,242 Accumulated benefit obligation $ 92,918 $ 101,242
Components of net periodic benefit cost	The components of net periodic benefit cost (credit), other than the service cost component, are included in other income on the Consolidated Statements of Income. Prior service credit is amortized on a straight-line basis over the average remaining service period of active participants. These components related to the Company's pension and other postretirement benefit plans for the years ended December 31 were as follows: Pension Benefits Other 2021 2020 2019 2021 2020 2019 Components of net periodic benefit cost (credit): (In thousands) Service cost $ — $ — $ — $ 1,600 $ 1,532 $ 1,142 Interest cost 9,819 12,093 15,225 1,862 2,437 2,986 Expected return on assets (19,576) (19,949) (18,236) (5,098) (5,019) (4,804) Amortization of prior service credit — — — (1,398) (1,398) (1,398) Recognized net actuarial loss 8,017 7,172 5,548 24 287 353 Net periodic benefit cost (credit), including amount capitalized (1,740) (684) 2,537 (3,010) (2,161) (1,721) Less amount capitalized — — — 150 156 113 Net periodic benefit cost (credit) (1,740) (684) 2,537 (3,160) (2,317) (1,834) Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss: Net (gain) loss (265) 934 (144) (2,811) (259) (127) Amortization of actuarial loss (1,286) (1,155) (904) (135) (306) (110) Amortization of prior service credit — — — 100 101 100 Total recognized in accumulated other comprehensive loss (1,551) (221) (1,048) (2,846) (464) (137) Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities: Net (gain) loss (5,116) 4,546 189 (6,292) (3,793) (8,168) Amortization of actuarial gain (loss) (6,731) (6,017) (4,644) 110 19 (242) Amortization of prior service credit — — — 1,298 1,297 1,297 Total recognized in regulatory assets or liabilities (11,847) (1,471) (4,455) (4,884) (2,477) (7,113) Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities $ (15,138) $ (2,376) $ (2,966) $ (10,890) $ (5,258) $ (9,084) The components of net periodic benefit cost are included in other income on the Consolidated Statements of Income. These components related to the Company's nonqualified defined benefit plans for the years ended December 31 were as follows: 2021 2020 2019 (In thousands) Components of net periodic benefit cost: Service cost $ — $ 58 $ 109 Interest cost 1,912 2,606 3,473 Recognized net actuarial loss 1,164 1,192 764 Net periodic benefit cost $ 3,076 $ 3,856 $ 4,346
Weighted average assumptions used to determine benefit obligations and net periodic benefit costs	Weighted average assumptions used to determine benefit obligations at December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Discount rate 2.64 % 2.30 % 2.66 % 2.30 % Expected return on plan assets 6.00 % 6.00 % 5.50 % 5.50 % Rate of compensation increase N/A N/A 3.00 % 3.00 % Weighted average assumptions used to determine net periodic benefit cost (credit) for the years ended December 31 were as follows: Pension Benefits Other 2021 2020 2021 2020 Discount rate 2.30 % 2.96 % 2.30 % 3.00 % Expected return on plan assets 6.00 % 6.25 % 5.50 % 5.75 % Rate of compensation increase N/A N/A 3.00 % 3.00 % Weighted average assumptions used at December 31 were as follows: 2021 2020 Benefit obligation discount rate 2.39 % 1.97 % Benefit obligation rate of compensation increase N/A N/A Net periodic benefit cost discount rate 1.97 % 2.73 % Net periodic benefit cost rate of compensation increase N/A N/A
Health care rate assumptions for the Company's other postretirement benefit plans	Health care rate assumptions for the Company's other postretirement benefit plans as of December 31 were as follows: 2021 2020 Health care trend rate assumed for next year 7.0 % 7.0 % Health care cost trend rate - ultimate 4.5 % 4.5 % Year in which ultimate trend rate achieved 2031 2031
Benefit payments expected to be paid	The following benefit payments, which reflect future service, as appropriate, and expected Medicare Part D subsidies at December 31, 2021, are as follows: Years Pension Other Expected (In thousands) 2022 $ 24,644 $ 4,393 $ 70 2023 24,766 4,522 65 2024 24,897 4,572 58 2025 24,739 4,612 52 2026 24,571 4,642 46 2027-2031 117,413 17,867 157 The amount of future benefit payments for the unfunded, nonqualified defined benefit plans at December 31, 2021, are expected to aggregate as follows: 2022 2023 2024 2025 2026 2027-2031 (In thousands) Nonqualified benefits $ 6,877 $ 6,890 $ 7,354 $ 7,537 $ 7,609 $ 31,983
The fair value of the pension and postretirement net plan assets by class	The fair value of the Company's pension plans' assets (excluding cash) by class were as follows: Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Cash equivalents $ — $ 4,637 $ — $ 4,637 Equity securities: U.S. companies 7,483 — — 7,483 International companies — 1,279 — 1,279 Collective and mutual funds (a) 167,093 41,383 — 208,476 Corporate bonds — 125,167 — 125,167 Municipal bonds — 7,507 — 7,507 U.S. Government securities 7,113 1,902 — 9,015 Pooled separate accounts (b) — 3,088 — 3,088 Investments measured at net asset value (c) — — — 6,457 Total assets measured at fair value $ 181,689 $ 184,963 $ — $ 373,109 (a) Collective and mutual funds invest approximately 37 percent in corporate bonds, 19 percent in common stock of international companies, 16 percent in common stock of large-cap U.S. companies, 9 percent in U.S. Government securities and 19 percent in other investments. (b) Pooled separate accounts are invested 100 percent in cash and cash equivalents. (c) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Cash equivalents $ — $ 7,841 $ — $ 7,841 Equity securities: U.S. companies 12,844 — — 12,844 International companies — 1,727 — 1,727 Collective and mutual funds (a) 177,397 55,788 — 233,185 Corporate bonds — 92,809 — 92,809 Municipal bonds — 10,126 — 10,126 U.S. Government securities 11,177 2,695 — 13,872 Investments measured at net asset value (b) — — — 11,430 Total assets measured at fair value $ 201,418 $ 170,986 $ — $ 383,834 (a) Collective and mutual funds invest approximately 36 percent in corporate bonds, 24 percent in common stock of international companies, 18 percent in common stock of large-cap U.S. companies, 8 percent in cash equivalents, 5 percent in U.S. Government securities and 9 percent in other investments. (b) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. The fair value of the Company's other postretirement benefit plans' assets (excluding cash) by asset class were as follows: Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2021 (In thousands) Assets: Cash equivalents $ — $ 4,281 $ — $ 4,281 Equity securities: U.S. companies 2,332 — — 2,332 International companies — 1 — 1 Collective and mutual funds (a) 4 90 — 94 Insurance contract (b) — 93,447 — 93,447 Investments measured at net asset value (c) — — — 3 Total assets measured at fair value $ 2,336 $ 97,819 $ — $ 100,158 (a) Collective and mutual funds invest approximately 37 percent in corporate bonds, 19 percent in common stock of international companies, 16 percent in common stock of large-cap U.S. companies, 9 percent in U.S. Government securities and 19 percent in other investments. (b) The insurance contract invests approximately 58 percent in corporate bonds, 13 percent in U.S. Government securities, 13 percent in common stock of large-cap U.S. companies, 5 percent in common stock of small-cap U.S. companies and 11 percent in other investments. (c) In accordance with ASC 820 - Fair Value , certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. Fair Value Measurements Quoted Prices Significant Significant Balance at December 31, 2020 (In thousands) Assets: Cash equivalents $ — $ 3,517 $ — $ 3,517 Equity securities: U.S. companies 1,850 — — 1,850 International companies — 2 — 2 Collective and mutual funds (a) 10 147 — 157 Insurance contract (b) — 96,103 — 96,103 Investments measured at net asset value (c) — — — 10 Total assets measured at fair value $ 1,860 $ 99,769 $ — $ 101,639 (a) Collective and mutual funds invest approximately 36 percent in corporate bonds, 24 percent in common stock of international companies, 18 percent in common stock of large-cap U.S. companies, 8 percent in cash equivalents, 5 percent in U.S. Government securities and 9 percent in other investments. (b) The insurance contract invests approximately 67 percent in corporate bonds, 10 percent in common stock of large-cap U.S. companies, 12 percent in U.S. Government securities, 4 percent in common stock of small-cap U.S. companies, 1 percent in cash equivalents and 6 percent in other investments. (c) In accordance with ASC 820 - Fair Value, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statement of financial condition. The amount of investments that the Company anticipates using to satisfy obligations under these plans at December 31 was as follows: 2021 2020 (In thousands) Investments Insurance contract* $ 109,603 $ 100,104 Life insurance** 38,356 39,779 Other 10,190 8,917 Total investments $ 158,149 $ 148,800 * For more information on the insurance contract, see Note 8. ** Investments of life insurance are carried on plan participants (payable upon the employee's death).
Schedule of Multiemployer Plans [Table Text Block]	EIN/Pension Plan Number Pension Protection Act Zone Status FIP/RP Status Pending/Implemented Contributions Surcharge Imposed Expiration Date Pension Fund 2021 2020 2021 2020 2019 (In thousands) Edison Pension Plan 936061681-001 Green Green No $ 18,331 $ 16,121 $ 12,252 No 12/31/2023 IBEW Local 212 Pension Trust 316127280-001 Green as of 4/30/2021 Green as of 4/30/2020 No 1,733 1,521 1,110 No 6/1/2025 IBEW Local 357 Pension Plan A 886023284-001 Green Green No 6,485 9,913 10,162 No 5/31/2024 IBEW Local 82 Pension Plan 316127268-001 Green as of 6/30/2021 Green as of 6/30/2020 No 1,353 1,373 1,662 No 12/3/2023 Idaho Plumbers and Pipefitters Pension Plan 826010346-001 Green as of 5/31/2021 Green as of 5/31/2020 No 1,528 1,370 1,307 No 3/31/2023 National Electrical Benefit Fund 530181657-001 Green Green No 14,361 14,484 12,679 No 5/31/2021- 5/31/2026 * Pension and Retirement Plan of Plumbers and Pipefitters Local 525 886003864-001 Green Green No 4,345 6,266 4,747 No 9/30/2024 Pension Trust Fund for Operating Engineers 946090764-001 Yellow Yellow Implemented 2,495 2,680 2,598 No 6/15/2022- 6/30/2023 Sheet Metal Workers Pension Plan of Southern CA, AZ, and NV 956052257-001 Yellow Yellow Implemented 2,615 3,255 2,119 No 6/30/2024 Southern California IBEW-NECA Pension Trust Fund 956392774-001 Yellow as of 6/30/2021 Yellow as of 6/30/2020 Implemented 2,746 1,714 1,477 No 6/30/2022- 5/31/2026 Western Conference of Teamsters Pension Plan 916145047-001 Green Green No 3,006 3,025 2,814 No 12/31/2023- 12/31/2025 Other funds 23,390 23,722 19,598 Total contributions $ 82,388 $ 85,444 $ 72,525 * Plan includes contributions required by collective bargaining agreements which have expired but contain provisions automatically renewing their terms in the absence of a subsequent negotiated agreement. The Company was listed in the plans' Forms 5500 as providing more than 5 percent of the total contributions for the following plans and plan years: Pension Fund Year Contributions to Plan Exceeded More Than 5 Percent Edison Pension Plan 2020 and 2019 IBEW Local 82 Pension Plan 2020 and 2019 IBEW Local 124 Pension Trust Fund 2020 and 2019 IBEW Local 212 Pension Trust Fund 2020 and 2019 IBEW Local 357 Pension Plan A 2020 and 2019 IBEW Local 648 Pension Plan 2020 and 2019 IBEW Local 683 Pension Fund Pension Plan 2020 and 2019 IBEW Local Union No 226 Open End Pension Fund 2020 and 2019 Idaho Plumbers and Pipefitters Pension Plan 2020 and 2019 International Union of Operating Engineers Local 701 Pension Trust Fund 2020 and 2019 Minnesota Teamsters Construction Division Pension Fund 2020 and 2019 Pension and Retirement Plan of Plumbers and Pipefitters Local 525 2020 and 2019 Southwest Marine Pension Trust 2020 and 2019

Jointly owned facilities (Table

Jointly owned facilities (Tables)	12 Months Ended
	Dec. 31, 2021
Regulated Operations [Abstract]
Company's share of the cost of utility plant in service and related accumulated depreciation for the stations	At December 31, the Company's share of the cost of utility plant in service, construction work in progress and related accumulated depreciation for the jointly owned facilities was as follows: Ownership Percentage 2021 2020 (In thousands) Big Stone Station: 22.7 % Utility plant in service $ 157,259 $ 155,967 Construction work in progress 571 104 Less accumulated depreciation 47,293 45,435 $ 110,537 $ 110,636 BSSE: 50.0 % Utility plant in service $ 107,424 $ 107,442 Construction work in progress — — Less accumulated depreciation 4,506 2,682 $ 102,918 $ 104,760 Coyote Station: 25.0 % Utility plant in service $ 157,764 $ 159,784 Construction work in progress 784 323 Less accumulated depreciation 109,202 108,852 $ 49,346 $ 51,255 Wygen III: 25.0 % Utility plant in service $ 66,357 $ 66,101 Construction work in progress 108 232 Less accumulated depreciation 11,383 10,038 $ 55,082 $ 56,295

Commitment and Contingencies Di

Commitment and Contingencies Disclosure (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Purchase commitments	The commitment terms vary in length, up to 38 years. The commitments under these contracts as of December 31, 2021, were: 2022 2023 2024 2025 2026 Thereafter (In thousands) Purchase commitments $ 589,898 $ 200,667 $ 141,383 $ 99,545 $ 86,628 $ 731,679

Accounting Policies - Receivabl

Accounting Policies - Receivables Past Due 90 Days (Details 1) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Accounts Receivable, Noncurrent, 90 Days or More Past Due, Still Accruing	$ 44.8	$ 43.9

Accounting Policies - CECL Tabl

Accounting Policies - CECL Table (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Accounts Receivable, Credit Loss Expense (Reversal)	$ 1,085	$ 10,576	$ 7,864
Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	9,716	15,358	8,497
Accounts Receivable, Credit Loss Expense (Reversal)	1,105	10,985
Accounts Receivable, Allowance for Credit Loss, Writeoff	8,069	5,306
Accounts Receivable, Allowance for Credit Loss, Recovery	1,322	1,182
Electric | Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	269	899	328
Accounts Receivable, Credit Loss Expense (Reversal)	1,099	1,517
Accounts Receivable, Allowance for Credit Loss, Writeoff	2,139	1,289
Accounts Receivable, Allowance for Credit Loss, Recovery	410	343
Natural gas distribution | Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	1,506	2,571	1,056
Accounts Receivable, Credit Loss Expense (Reversal)	2,188	3,187
Accounts Receivable, Allowance for Credit Loss, Writeoff	4,072	2,511
Accounts Receivable, Allowance for Credit Loss, Recovery	819	839
Pipeline | Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	2	2	0
Accounts Receivable, Credit Loss Expense (Reversal)	0	2
Accounts Receivable, Allowance for Credit Loss, Writeoff	0	0
Accounts Receivable, Allowance for Credit Loss, Recovery	0	0
Construction materials and contracting | Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	5,406	6,164	5,357
Accounts Receivable, Credit Loss Expense (Reversal)	68	1,447
Accounts Receivable, Allowance for Credit Loss, Writeoff	826	640
Accounts Receivable, Allowance for Credit Loss, Recovery	0	0
Construction services | Trade Accounts Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for doubtful accounts	2,533	5,722	$ 1,756
Accounts Receivable, Credit Loss Expense (Reversal)	(2,250)	4,832
Accounts Receivable, Allowance for Credit Loss, Writeoff	1,032	866
Accounts Receivable, Allowance for Credit Loss, Recovery	$ 93	$ 0

Accounting Policies - Accrued U

Accounting Policies - Accrued Unbilled Revenue (Details 3) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Accrued unbilled revenue at MDU Energy Capital	$ 144.9	$ 94

Accounting Policies - Retainage

Accounting Policies - Retainage (Details 4) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Contract Receivable Retainage, Next Twelve Months	$ 70,600	$ 100,054
Contract Receivable Retainage, after Next Twelve Months	10,742	2,761
Contract Receivable Retainage	$ 81,342	$ 102,815

Accounting Policies - Inventory

Accounting Policies - Inventory (Details 5) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory and natural gas in storage [Line Items]
Aggregates held for resale	$ 184,363	$ 175,782
Asphalt oil	57,002	28,238
Materials and supplies	30,629	25,142
Merchandise for resale	28,501	21,087
Natural gas in storage (current)	18,867	21,919
Other	16,247	18,999
Total	335,609	291,167
Natural gas in storage (noncurrent)	$ 47,500	$ 47,500

Accounting Policies - PPE (Deta

Accounting Policies - PPE (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, plant and equipment [Line Items]
Allowance for Funds Used During Construction, Capitalized Interest	$ 2,833	$ 2,640	$ 2,807
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	$ 6,961	$ 1,270	$ 698

Accounting Policies - Impairmen

Accounting Policies - Impairment of Long-Lived Assets (Details 7) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Impairment of Long-Lived Assets to be Disposed of	$ 0	$ 0	$ 0

Natural Gas Costs Recoverable o

Natural Gas Costs Recoverable or Refundable through Rate Adjustments (Details 8) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Natural gas costs refundable	$ 6.7	$ 18.6
Natural gas costs recoverable	$ 91.6	$ 64

Accounting Policies - Goodwill

Accounting Policies - Goodwill (Details 9) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Goodwill, Impairment Loss	$ 0	$ 0	$ 0

Accounting Policies - Joint Ven

Accounting Policies - Joint Ventures (Details 10) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Revenues	$ 5,680,733	$ 5,532,750	$ 5,336,776
Operating income	534,219	544,925	$ 481,220
Receivables	946,741	873,986
Equity Method Investment, Nonconsolidated Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	1,300	425
Income (Loss) from Equity Method Investments	892	(32)
Joint Venture, Proportionate Consolidation
Schedule of Equity Method Investments [Line Items]
Revenues	14,700	69,700
Operating income	4,700	20,600
Receivables	$ 1,200	$ 1,800
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	33.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%

Accounting Policies - Derivativ

Accounting Policies - Derivatives (Details 11) - MMBTU	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commodity Contract [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure	450,000	1,400,000

Accounting Policies - EPS (Deta

Accounting Policies - EPS (Details 12) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Weighted average common shares outstanding - basic	202,076	200,502	198,612
Effect of dilutive performance share awards	307	69	14
Weighted average common shares outstanding - diluted	202,383	200,571	198,626
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	164	164

Accounting Policies - Income Ta

Accounting Policies - Income Taxes (Details 13)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Threshold of likelihood of tax positions being realized upon ultimate settlement with a taxing authority	50.00%

Disaggregation of revenue (Deta

Disaggregation of revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Operating revenues	$ 5,680,733	$ 5,532,750	$ 5,336,776
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(77,606)	(76,969)	(77,149)
Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(501,044)	(550,815)	(525,749)
Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues	162,409	157,232	147,114
Natural gas gathering
Disaggregation of Revenue [Line Items]
Operating revenues		4,865	9,164
Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues	14,680	14,918	11,708
Contracting services
Disaggregation of Revenue [Line Items]
Operating revenues	1,017,471	1,069,665	1,088,633
Construction materials
Disaggregation of Revenue [Line Items]
Operating revenues	1,712,503	1,659,152	1,627,833
Electrical & mechanical specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues	1,324,419	1,397,124	1,266,196
Transmission & distribution specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues	677,074	649,486	531,882
Other
Disaggregation of Revenue [Line Items]
Operating revenues	81,407	68,865	82,669
Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	5,628,488	5,471,545	5,281,621
Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	52,245	61,205	55,155
Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	671,562	599,051	608,821
Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	465,841	409,350	438,431
Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	72,721	62,987	64,660
Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	7,051	6,634	7,408
Electric
Disaggregation of Revenue [Line Items]
Operating revenues	349,039	331,538	351,725
Electric | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(543)	(491)	0
Electric | Other
Disaggregation of Revenue [Line Items]
Operating revenues	42,902	32,452	35,574
Electric | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	355,564	329,479	347,712
Electric | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	(6,525)	2,059	4,013
Electric | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	126,841	122,663	125,369
Electric | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	137,556	131,477	141,596
Electric | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	41,757	36,744	37,765
Electric | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	7,051	6,634	7,408
Natural gas distribution
Disaggregation of Revenue [Line Items]
Operating revenues	971,364	847,651	865,222
Natural gas distribution | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(576)	(534)	0
Natural gas distribution | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues	48,408	45,546	45,449
Natural gas distribution | Other
Disaggregation of Revenue [Line Items]
Operating revenues	10,567	10,753	12,726
Natural gas distribution | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	962,369	836,269	865,357
Natural gas distribution | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	8,995	11,382	(135)
Natural gas distribution | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	544,721	476,388	483,452
Natural gas distribution | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	328,285	277,873	296,835
Natural gas distribution | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	30,964	26,243	26,895
Natural gas distribution | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Pipeline
Disaggregation of Revenue [Line Items]
Operating revenues	82,858	85,346	84,192
Pipeline | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(59,678)	(58,531)	(56,252)
Pipeline | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues	114,001	111,686	101,665
Pipeline | Natural gas gathering
Disaggregation of Revenue [Line Items]
Operating revenues		4,865	9,164
Pipeline | Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues	14,680	14,918	11,708
Pipeline | Other
Disaggregation of Revenue [Line Items]
Operating revenues	13,667	12,216	17,687
Pipeline | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	82,670	85,154	83,972
Pipeline | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	188	192	220
Construction materials and contracting
Disaggregation of Revenue [Line Items]
Operating revenues	2,228,306	2,177,585	2,189,651
Construction materials and contracting | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(624)	(417)	(1,066)
Construction materials and contracting | Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(501,044)	(550,815)	(525,749)
Construction materials and contracting | Contracting services
Disaggregation of Revenue [Line Items]
Operating revenues	1,017,471	1,069,665	1,088,633
Construction materials and contracting | Construction materials
Disaggregation of Revenue [Line Items]
Operating revenues	1,712,503	1,659,152	1,627,833
Construction materials and contracting | Other
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Construction materials and contracting | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	2,228,306	2,177,585	2,189,651
Construction materials and contracting | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	0	0	0
Construction services
Disaggregation of Revenue [Line Items]
Operating revenues	2,049,082	2,090,685	1,845,896
Construction services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(2,555)	(5,038)	(3,370)
Construction services | Electrical & mechanical specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues	1,324,419	1,397,124	1,266,196
Construction services | Transmission & distribution specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues	677,074	649,486	531,882
Construction services | Other
Disaggregation of Revenue [Line Items]
Operating revenues	557	1,541	131
Construction services | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	1,999,495	2,043,113	1,794,839
Construction services | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	49,587	47,572	51,057
Other
Disaggregation of Revenue [Line Items]
Operating revenues	84	(55)	90
Other | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(13,630)	(11,958)	(16,461)
Other | Other
Disaggregation of Revenue [Line Items]
Operating revenues	13,714	11,903	16,551
Other | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues	84	(55)	90
Other | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues	$ 0	$ 0	$ 0

Contract balances (Details 2)

Contract balances (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract assets	$ 125,742	$ 104,345	$ 109,078
Change in contract assets	21,397	(4,733)
Contract liabilities - current	(179,140)	(158,603)	(142,768)
Change in contract liabilities - current	(20,537)	(15,835)
Contract liabilities - noncurrent	(118)	(52)	(19)
Change in contract liabilities - noncurrent	(66)	(33)
Net contract liabilities	(53,516)	(54,310)	$ (33,709)
Change in net contract assets (liabilities)	794	(20,601)
Amounts included in contract liability at the beginning of the period	155,000	138,200
Amounts from performance obligations satisfied in prior periods	$ 66,300	$ 58,800

Revenue from contracts with c_2

Revenue from contracts with customers Remaining performance obligations (Details 3) $ in Millions	Dec. 31, 2021USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 2,500
Remaining performance obligation, expected timing of satisfaction, start date: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 1,800
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Remaining performance obligation, expected timing of satisfaction, start date: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 278.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	13 months
Remaining performance obligation, expected timing of satisfaction, start date: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 411.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	25 months

Business Combinations (Details)

Business Combinations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 765,386,000	$ 714,963,000	$ 681,358,000
2021 Acquisition
Business Acquisition [Line Items]
Gross Aggregate Consideration	236,100,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	900,000
Business Combination, Consideration Transferred	235,200,000
Business Combination, Current Assets	17,000,000
Business Combination, Property, Plant, and Equipment	179,800,000
Goodwill	50,600,000
Business Combination, Other Intangible Assets	2,200,000
Business Combination, Current Liabilities	8,700,000
Business Combination, Noncurrent Liabilities	2,500,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	$ 3,200,000

Business Combinations - Assets

Business Combinations - Assets Acquired & Liabilities Assumed (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 765,386,000	$ 714,963,000	$ 681,358,000
Asset Retirement Obligation	468,686,000	446,919,000	$ 417,575,000
2020 Acquisition [Member]
Business Acquisition [Line Items]
Gross Aggregate Consideration		110,200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		1,700,000
Business Combination, Consideration Transferred		106,000,000
Business Combination, Consideration Transferred, Liabilities Incurred	$ 2,500,000	2,500,000
Business Combination, Current Assets		54,800,000
Business Combination, Property, Plant, and Equipment		27,100,000
Goodwill		33,600,000
Business Combination, Other Intangible Assets		19,000,000
Business Combination, Current Liabilities		22,600,000
Business Combination, Noncurrent Liabilities		300,000
Asset Retirement Obligation		$ 1,400,000

Property, Plant, and Equipmen_2

Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 8,972,849	$ 8,300,770
Less accumulated depreciation, depletion and amortization	3,216,461	3,133,831	$ 2,991,486
Net property, plant and equipment	5,756,388	5,166,939	4,917,142
Electric
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	2,295,646	2,323,403	2,227,145
Natural gas distribution
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	3,015,164	2,868,853	2,688,123
Pipeline
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	1,051,868	821,697	834,215
Construction materials and contracting
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	2,347,696	2,028,476	1,910,562
Construction services
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	225,758	220,796	213,370
Other
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	36,717	37,545	$ 35,213
Regulated Operation | Electric | Electric Generation Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,056,632	1,133,390
Weighted average depreciable life in years	48 years
Regulated Operation | Electric | Electric Distribution
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 474,037	464,442
Weighted average depreciable life in years	47 years
Regulated Operation | Electric | Electric Transmission
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 562,080	524,155
Weighted average depreciable life in years	65 years
Regulated Operation | Electric | Construction in Progress
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 62,781	61,766
Regulated Operation | Electric | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 140,117	139,650
Weighted average depreciable life in years	14 years
Regulated Operation | Natural gas distribution | Construction in Progress
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 21,741	16,836
Regulated Operation | Natural gas distribution | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 225,272	213,976
Weighted average depreciable life in years	14 years
Regulated Operation | Natural gas distribution | Gas Distribution [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,427,779	2,302,121
Weighted average depreciable life in years	50 years
Regulated Operation | Natural gas distribution | Gas Transmission [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 107,721	104,695
Weighted average depreciable life in years	60 years
Regulated Operation | Natural gas distribution | Natural gas storage
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 34,997	33,014
Weighted average depreciable life in years	39 years
Regulated Operation | Natural gas distribution | General
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 197,653	198,211
Weighted average depreciable life in years	14 years
Regulated Operation | Pipeline | Construction in Progress
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 263,640	46,690
Regulated Operation | Pipeline | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 50,477	49,640
Weighted average depreciable life in years	17 years
Regulated Operation | Pipeline | Gas Transmission [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 673,344	665,567
Weighted average depreciable life in years	46 years
Regulated Operation | Pipeline | Gas Storage [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 57,670	52,632
Weighted average depreciable life in years	53 years
Nonregulated Operation | Pipeline | Construction in Progress
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 18	4
Nonregulated Operation | Pipeline | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,719	7,164
Weighted average depreciable life in years	10 years
Nonregulated Operation | Construction materials and contracting | Construction in Progress
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 50,425	23,803
Nonregulated Operation | Construction materials and contracting | Land [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	149,066	132,948
Nonregulated Operation | Construction materials and contracting | Building and Building Improvements [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 149,262	130,417
Weighted average depreciable life in years	21 years
Nonregulated Operation | Construction materials and contracting | Machinery, vehicles and equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,414,260	1,284,604
Weighted average depreciable life in years	12 years
Nonregulated Operation | Construction materials and contracting | Aggregate reserves [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 584,683	456,704
Nonregulated Operation | Construction services | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 13,467	8,824
Weighted average depreciable life in years	2 years
Nonregulated Operation | Construction services | Land [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,513	7,218
Nonregulated Operation | Construction services | Building and Building Improvements [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 39,039	41,674
Weighted average depreciable life in years	24 years
Nonregulated Operation | Construction services | Machinery, vehicles and equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 166,739	163,080
Weighted average depreciable life in years	7 years
Nonregulated Operation | Other | Other Capitalized Property Plant and Equipment
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 34,069	34,897
Weighted average depreciable life in years	7 years
Nonregulated Operation | Other | Land [Member]
Property, plant and equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,648	$ 2,648

Regulatory assets (Details)

Regulatory assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Feb. 28, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Current regulatory assets	$ 118,691		$ 68,527
Regulatory assets	357,851		379,381
Total regulatory assets	476,542		447,908
Regulatory assets not earning a rate of return	296,600		332,500
Natural gas costs recoverable through rate adjustments
Regulatory Assets [Line Items]
Current regulatory assets	86,371		42,481
Regulatory assets	$ 5,186		21,539
Total regulatory assets		$ 44,000
Natural gas costs recoverable through rate adjustments | Minimum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 1 year
Natural gas costs recoverable through rate adjustments | Maximum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 2 years
Decoupling
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 1 year
Current regulatory assets	$ 9,131		703
Conservation programs
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 1 year
Current regulatory assets	$ 8,225		7,117
Cost recovery mechanisms
Regulatory Assets [Line Items]
Current regulatory assets	4,536		10,645
Regulatory assets	$ 44,870		16,245
Cost recovery mechanisms | Minimum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 1 year
Cost recovery mechanisms | Maximum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 10 years
Other regulatory assets
Regulatory Assets [Line Items]
Current regulatory assets	$ 10,428		7,581
Regulatory assets	$ 9,742		6,356
Other regulatory assets | Minimum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 1 year
Other regulatory assets | Maximum
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 17 years
Pension and postretirement benefits
Regulatory Assets [Line Items]
Regulatory asset, recovery period	**
Regulatory assets	$ 142,681		155,942
Plant costs/asset retirement obligation costs
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Over plant lives
Regulatory assets	$ 63,116		71,740
Plants to be retired
Regulatory Assets [Line Items]
Regulatory asset, recovery period	-
Regulatory assets	$ 50,070		65,919
Manufactured gas plant sites remediation
Regulatory Assets [Line Items]
Regulatory asset, recovery period	-
Regulatory assets	$ 26,053		26,429
Taxes recoverable from customers
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Over plant lives
Regulatory assets	$ 12,339		10,785
Long-term debt refinancing costs
Regulatory Assets [Line Items]
Regulatory asset, recovery period	Up to 39 years
Regulatory assets	$ 3,794		$ 4,426

Regulatory liabilities (Details

Regulatory liabilities (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	$ 16,303	$ 31,450
Regulatory liabilities	428,790	428,075
Total regulatory liabilities	445,093	459,525
Net Regulatory Position	$ 31,449	(11,617)
Natural gas costs refundable through rate adjustments
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Up to 1 year
Regulatory liabilities due within one year	$ 6,700	18,565
Taxes refundable to customers
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	3,841	3,557
Regulatory liabilities	$ 215,421	227,850
Taxes refundable to customers | Minimum
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Up to 1 year
Taxes refundable to customers | Maximum
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Over plant lives
Electric fuel and purchased power deferral
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Up to 1 year
Regulatory liabilities due within one year	$ 0	3,667
Other regulatory liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	5,762	5,661
Regulatory liabilities	$ 24,783	16,065
Other regulatory liabilities | Minimum
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Up to 1 year
Other regulatory liabilities | Maximum
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Up to 20 years
Plant removal and decommissioning costs
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	Over plant lives
Regulatory liabilities	$ 168,152	167,171
Pension and postretirement benefits
Regulatory Liabilities [Line Items]
Regulatory liability, refund period	**
Regulatory liabilities	$ 20,434	$ 16,989

Goodwill rollforward (Details)

Goodwill rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Balance at beginning of period	$ 714,963	$ 681,358
Goodwill acquired during the year	50,640	33,214
Measurement period adjustments	(217)	391
Balance at end of period	765,386	714,963
Natural gas distribution
Goodwill [Roll Forward]
Balance at beginning of period	345,736	345,736
Goodwill acquired during the year	0	0
Measurement period adjustments	0	0
Balance at end of period	345,736	345,736
Construction materials and contracting
Goodwill [Roll Forward]
Balance at beginning of period	226,003	217,234
Goodwill acquired during the year	50,640	8,778
Measurement period adjustments	(217)	(9)
Balance at end of period	276,426	226,003
Construction services
Goodwill [Roll Forward]
Balance at beginning of period	143,224	118,388
Goodwill acquired during the year	0	24,436
Measurement period adjustments	0	400
Balance at end of period	$ 143,224	$ 143,224

Other intangible assets (Detail

Other intangible assets (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 22,578	$ 25,496
Amortization of intangible assets	5,100	9,000	$ 2,400
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	29,740	28,836
Intangible assets, less accumulated amortization	10,650	6,887
Intangible assets, net (excluding goodwill)	19,090	21,949
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	4,591	3,941
Intangible assets, less accumulated amortization	2,856	2,309
Intangible assets, net (excluding goodwill)	1,735	1,632
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	12,601	12,927
Intangible assets, less accumulated amortization	10,848	11,012
Intangible assets, net (excluding goodwill)	$ 1,753	$ 1,915

Future amortization expense (De

Future amortization expense (Details 3) $ in Thousands	Dec. 31, 2021USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2022	$ 4,928
2023	4,578
2024	4,308
2025	2,314
2026	1,693
Thereafter	$ 4,757

Fair value measurements insuran

Fair value measurements insurance contracts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 109.6	$ 100.1
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	$ 7.2	$ 13.1	$ 13.2

Available-for-sale securities (

Available-for-sale securities (Details 2) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Abstract]
Cost	$ 11,109	$ 11,185
Gross Unrealized Gains	51	156
Gross Unrealized Losses	58	14
Fair Value	11,102	11,327
Mortgage-backed securities
Debt Securities, Available-for-sale [Abstract]
Cost	8,702	9,799
Gross Unrealized Gains	51	156
Gross Unrealized Losses	47	9
Fair Value	8,706	9,946
U.S. Treasury securities
Debt Securities, Available-for-sale [Abstract]
Cost	2,407	1,386
Gross Unrealized Gains	0	0
Gross Unrealized Losses	11	5
Fair Value	$ 2,396	$ 1,381

Fair value measurements (Detail

Fair value measurements (Details 3) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Concentration risks, percentage [Abstract]
Percentage in fixed-income investments	61.00%	57.00%
Percentage investment in common stock of large-cap companies	17.00%	18.00%
Percentage investment in common stock of mid-cap companies	8.00%	9.00%
Percentage investment in common stock of small-cap companies	7.00%	9.00%
Percentage investment in target date investments	5.00%	5.00%
Percentage investment in cash and cash equivalents	2.00%	2.00%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 130,895	$ 120,348
Fair value, measurements, recurring | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	10,190	8,917
Fair value, measurements, recurring | Insurance contract*
Fair value measurements [Line Items]
Assets, fair value disclosure	109,603	100,104
Fair value, measurements, recurring | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	8,706	9,946
Fair value, measurements, recurring | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	2,396	1,381
Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	130,895	120,348
Fair value, inputs, level 2 | Fair value, measurements, recurring | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	10,190	8,917
Fair value, inputs, level 2 | Fair value, measurements, recurring | Insurance contract*
Fair value measurements [Line Items]
Assets, fair value disclosure	109,603	100,104
Fair value, inputs, level 2 | Fair value, measurements, recurring | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	8,706	9,946
Fair value, inputs, level 2 | Fair value, measurements, recurring | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 2,396	$ 1,381

Fair value measurements (Deta_2

Fair value measurements (Details 5) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,741,900	$ 2,213,130
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,741,900	2,213,130
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 2,984,866	$ 2,537,289

Credit facilities (Details)

Credit facilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Line of credit facility and other debt [Abstract]
Letters of credit at end of period	$ 0
Long-term debt | Commercial paper revolving credit agreement | Montana-Dakota Utilities Co. [Member]
Line of credit facility and other debt [Abstract]
Facility limit, maximum borrowing capacity	175,000,000
Amount outstanding, end of period	64,900,000	$ 87,700,000
Letters of credit at end of period	$ 0
Expiration date	Dec. 19, 2024
Long-term debt | Commercial paper revolving credit agreement | Centennial Energy Holdings, Inc.
Line of credit facility and other debt [Abstract]
Facility limit, maximum borrowing capacity	$ 600,000,000
Amount outstanding, end of period	385,400,000	37,900,000
Letters of credit at end of period	$ 0
Expiration date	Dec. 19, 2024
Long-term debt | Revolving credit facility | Montana-Dakota Utilities Co. [Member]
Line of credit facility and other debt [Abstract]
Amount outstanding, end of period	$ 0
Option to increase borrowings, maximum amount	225,000,000
Long-term debt | Revolving credit facility | Cascade Natural Gas Corporation
Line of credit facility and other debt [Abstract]
Facility limit, maximum borrowing capacity	100,000,000
Amount outstanding, end of period	71,000,000	54,000,000
Letters of credit at end of period	$ 2,200,000
Expiration date	Jun. 7, 2024
Option to increase borrowings, maximum amount	$ 125,000,000
Long-term debt | Revolving credit facility | Intermountain Gas Company
Line of credit facility and other debt [Abstract]
Facility limit, maximum borrowing capacity	85,000,000
Amount outstanding, end of period	56,500,000	$ 41,900,000
Letters of credit at end of period	$ 0
Expiration date	Jun. 7, 2024
Option to increase borrowings, maximum amount	$ 110,000,000
Long-term debt | Revolving credit facility | Centennial Energy Holdings, Inc.
Line of credit facility and other debt [Abstract]
Amount outstanding, end of period	0
Option to increase borrowings, maximum amount	$ 700,000,000

Short-term Debt (Details 2)

Short-term Debt (Details 2) - USD ($) $ in Thousands	Dec. 31, 2021	Mar. 08, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Short-term borrowings	$ 0		$ 50,000
Term Loan Agreement [Member] | Montana-Dakota Utilities Co. [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 0	$ 50,000
Ratio of total debt to total capitalization as specified in debt covenants	65.00%

Long-term debt outstanding (Det

Long-term debt outstanding (Details 3) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,741,900	$ 2,213,130
Long-term debt due within one year	148,053	1,555
Long-term debt	$ 2,593,847	2,211,575
Senior Notes
Long-term debt outstanding [Line Items]
Weighted average interest rate	4.32%
Long-term debt	$ 2,125,000	1,950,000
Commercial paper
Long-term debt outstanding [Line Items]
Weighted average interest rate	0.40%
Long-term debt	$ 450,300	125,600
Credit Agreements
Long-term debt outstanding [Line Items]
Weighted average interest rate	1.94%
Long-term debt	$ 127,500	95,900
Medium-term notes
Long-term debt outstanding [Line Items]
Weighted average interest rate	7.32%
Long-term debt	$ 35,000	35,000
Term Loan Agreements
Long-term debt outstanding [Line Items]
Weighted average interest rate	2.00%
Long-term debt	$ 7,700	8,400
Other notes
Long-term debt outstanding [Line Items]
Weighted average interest rate	1.03%
Long-term debt	$ 2,564	4,034
Long-term debt
Long-term debt outstanding [Line Items]
Unamortized debt issuance costs	6,090	5,803
Discount	$ 74	$ 1

Long-term borrowings (Details 4

Long-term borrowings (Details 4) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 23, 2021	Dec. 15, 2021	Sep. 15, 2021	Dec. 31, 2020
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,741,900				$ 2,213,130
Montana-Dakota Utilities Co. [Member]
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization	51.00%
Cascade Natural Gas [Member]
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization	51.00%
Intermountain Gas Company
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization	50.00%
Centennial Energy Holdings, Inc.
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization	43.00%
WBI Energy Transmission, Inc.
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization	38.00%
Senior Notes
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,125,000				$ 1,950,000
Weighted average interest rate	4.32%
Senior Notes | Montana-Dakota Utilities Co. [Member]
Long-term debt outstanding [Line Items]
Long-term debt			$ 50,000
Weighted average interest rate				3.23%
Ratio of total debt to total capitalization as specified in debt covenants				65.00%
Senior Notes | Montana-Dakota Utilities Co. [Member] | Minimum
Long-term debt outstanding [Line Items]
Long-term debt				$ 75,000
Senior Notes | Montana-Dakota Utilities Co. [Member] | Maximum
Long-term debt outstanding [Line Items]
Long-term debt				$ 125,000
Senior Notes | WBI Energy Transmission, Inc.
Long-term debt outstanding [Line Items]
Long-term debt	$ 195,000	$ 50,000
Weighted average interest rate		3.67%
Ratio of total debt to total capitalization as specified in debt covenants	55.00%	55.00%
Long-term private shelf agreement issuance capacity	$ 300,000
Remaining capacity under uncommitted private shelf agreement	$ 105,000
Revolving credit facility | Montana-Dakota Utilities Co. [Member]
Long-term debt outstanding [Line Items]
Ratio of funded debt to total capitalization as specified in debt covenants	65.00%
Revolving credit facility | Cascade Natural Gas [Member]
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization as specified in debt covenants	65.00%
Revolving credit facility | Intermountain Gas Company
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization as specified in debt covenants	65.00%
Revolving credit facility | Centennial Energy Holdings, Inc.
Long-term debt outstanding [Line Items]
Ratio of total debt to total capitalization as specified in debt covenants	65.00%

Schedule of debt maturities (De

Schedule of debt maturities (Details 5) $ in Thousands	Dec. 31, 2021USD ($)
Long-term debt maturities [Line Items]
2022	$ 148,053
2023	77,925
2024	638,604
2025	177,802
2026	140,802
Thereafter	$ 1,564,878

Lease costs (Details)

Lease costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Short-term lease cost	$ 132,449	$ 135,376
Operating lease cost	46,622	45,319
Variable lease cost	1,516	1,319
Total lease costs	$ 180,587	$ 182,014
Weighted average remaining lease term	2 years 8 months 1 day	2 years 8 months 23 days
Weighted average discount rate	3.54%	4.03%
Cash paid for amounts included in the measurement of lease liabilities	$ 43,489	$ 45,043

Operating lease liabilities und

Operating lease liabilities undiscounted cash flows maturity schedule (Details 2) $ in Thousands	Dec. 31, 2021USD ($)
Leases [Abstract]
2022	$ 38,605
2023	27,460
2024	19,732
2025	12,278
2026	6,681
Thereafter	44,039
Total	148,795
Less discount	24,174
Total operating lease liabilities	$ 124,621

Lessor accounting (Details 3)

Lessor accounting (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating Lease, Lease Income	$ 50.1	$ 48
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	$ 9.2

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Asset retirement obligation [Roll Forward]
Balance at beginning of year	$ 446,919	$ 417,575
Liabilities incurred	12,454	11,560
Liabilities acquired	1,805	1,378
Liabilities settled	(15,155)	(5,369)
Accretion expense*	21,214	21,668
Revisions in estimates	1,449	107
Balance at end of year	468,686	446,919
Plant costs/asset retirement obligation costs
Asset retirement obligation [Roll Forward]
Accretion expense, including asset retirement obligations	$ 19,600	$ 20,100

Common stock (Details)

Common stock (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Dividends declared per common share	$ 0.8550	$ 0.8350	$ 0.8150
Dividends declared to common stockholders	$ 174,084	$ 168,489	$ 162,408
Credit agreement limitation on company's subsidiaries ratio of funded debt to capitalization	65.00%
Company's subsidiaries net assets restricted from use for dividend payments	$ 1,700,000
Common stock
Dividends declared to common stockholders	$ 173,000	$ 167,400	$ 162,100
Centennial [Member]
Maximum distributions to the company as a ratio of average consolidated indebtedness to consolidated EBITDA	350.00%

Common stock Common stock issua

Common stock Common stock issuance (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	203,889,661	201,061,198
Proceeds from Issuance of Common Stock	$ 88,767	$ 3,385	$ 106,848
At-the-market offering
Class of Stock [Line Items]
Common Stock, Shares Authorized	6,400,000
Common Stock, Shares, Issued	2,800,000	0
Proceeds from Issuance of Common Stock	$ 88,800	$ 0
Payments of Stock Issuance Costs	$ 1,200	$ 0
Common Stock, Authorized Shares Remaining	3,600,000
K-Plan
Class of Stock [Line Items]
Common Stock, Authorized Shares Remaining	7,200,000

Preferred Stock (Details 3)

Preferred Stock (Details 3) - Preferred Stock [Member] - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Preferred stock, shares authorized	2,000,000
Preferred stock, par value per share	$ 100
Preferred stock, shares oustanding	0	0

Stock based compensation plans

Stock based compensation plans (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-based compensation arrangement, number of shares available for grant	3.7
Share-based compensation expense, net of tax	$ 12	$ 10.8	$ 6.5
Share-based compensation nonvested awards total compensation cost not yet recognized	$ 10.9
Share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition	1 year 7 months 6 days

Stock awards (Details 2)

Stock awards (Details 2) - Board of Directors - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based compensation arrangement by share-based payment award [Line Items]
Share-based Compensation Arrangement Shares Issued in Period	41,925	45,273	41,644
Share-based Compensation Arrangement, Value	$ 1.2	$ 1.1	$ 1.2

Restricted stock awards (Detail

Restricted stock awards (Details 3) - Restricted Stock Units (RSUs) [Member]	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target grant of shares under performance awards | shares	93,700
Weighted average grant-date fair value | $ / shares	$ 27.35

Performance share awards (Detai

Performance share awards (Details 4) - Performance shares [Member] - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based compensation arrangement by share-based payment award [Line Items]
Weighted average grant-date fair value	$ 32.66
Fair value of vested shares	$ 13,700,000	$ 9,700,000	$ 9,700,000
Share-based compensation arrangement by share-based payment award, options, outstanding [Roll Forward]
Nonvested at beginning of period	613,174
Nonvested at beginning of period	$ 33.24
Granted	284,104
Weighted average grant-date fair value	$ 32.66
Additional performance shares earned	116,467
Additional performance shares earned	$ 22.68
Vested	443,661
Vested	$ 28.57
Forfeited	15,037
Forfeited	$ 35.49
Nonvested at end of period	555,047	613,174
Nonvested at end of period	$ 34.40	$ 33.24
Grant Date February 2020 [Member]
Share-based compensation arrangement by share-based payment award [Line Items]
Target grant of shares under performance awards	273,918
Grant Date February 2021
Share-based compensation arrangement by share-based payment award [Line Items]
Target grant of shares under performance awards	281,129
Market Condition [Member]
Share-based compensation arrangement by share-based payment award [Line Items]
Historical volatility rate	50.00%
Implied volatility rate	50.00%
Weighted average grant-date fair value	$ 37.96	$ 40.75	$ 35.07
Expected volatility rate, minimum	35.37%	15.30%	19.50%
Expected volatility rate, maximum	46.35%	15.97%	19.69%
Risk-free interest rate, minimum	0.02%	1.45%	2.46%
Risk-free interest rate, maximum	0.20%	1.62%	2.55%
Weighted average discounted dividends per share	$ 3.16	$ 2.91	$ 2.85
Share-based compensation arrangement by share-based payment award, options, outstanding [Roll Forward]
Weighted average grant-date fair value	$ 37.96	$ 40.75	$ 35.07
Market Condition [Member] | Minimum
Share-based compensation arrangement by share-based payment award [Line Items]
Participant target grant of shares, percentage rate range	0.00%
Market Condition [Member] | Maximum
Share-based compensation arrangement by share-based payment award [Line Items]
Participant target grant of shares, percentage rate range	200.00%
Performance Condition [Member]
Share-based compensation arrangement by share-based payment award [Line Items]
Weighted average grant-date fair value	$ 27.35	31.63	26.25
Share-based compensation arrangement by share-based payment award, options, outstanding [Roll Forward]
Weighted average grant-date fair value	$ 27.35	$ 31.63	$ 26.25
Performance Condition [Member] | Minimum
Share-based compensation arrangement by share-based payment award [Line Items]
Participant target grant of shares, percentage rate range	0.00%
Performance Condition [Member] | Maximum
Share-based compensation arrangement by share-based payment award [Line Items]
Participant target grant of shares, percentage rate range	200.00%

Accumulated other comprehensi_4

Accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated other comprehensive loss [Roll Forward]
Balance	$ 3,079,105
Other comprehensive income (loss)	7,074	$ (5,976)	$ (3,760)
Balance	3,382,874	3,079,105
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive loss [Roll Forward]
Balance	(984)	(1,430)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	446	446
Other comprehensive income (loss)	446	446
Balance	(538)	(984)	(1,430)
Postretirement liability adjustment
Accumulated other comprehensive loss [Roll Forward]
Balance	(47,207)	(40,734)
Other comprehensive income (loss) before reclassifications	4,876	(8,395)
Amounts reclassified from accumulated other comprehensive loss	1,870	1,922
Other comprehensive income (loss)	6,746	(6,473)
Balance	(40,461)	(47,207)	(40,734)
Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive loss [Roll Forward]
Balance	113	62
Other comprehensive income (loss) before reclassifications	(252)	(1)
Amounts reclassified from accumulated other comprehensive loss	134	52
Other comprehensive income (loss)	(118)	51
Balance	(5)	113	62
Total accumulated other comprehensive loss
Accumulated other comprehensive loss [Roll Forward]
Balance	(48,078)	(42,102)
Other comprehensive income (loss) before reclassifications	4,624	(8,396)
Amounts reclassified from accumulated other comprehensive loss	2,450	2,420
Other comprehensive income (loss)	7,074	(5,976)	(3,760)
Balance	$ (41,004)	$ (48,078)	$ (42,102)

Reclassification out of accumul

Reclassification out of accumulated other comprehensive loss (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Interest expense	$ (93,984)	$ (96,519)	$ (98,587)
Income taxes	(88,920)	(84,590)	(63,279)
Other income	26,416	26,711	15,812
Net income	378,131	390,205	$ 335,453
Reclassification out of accumulated other comprehensive loss
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Net income	(2,450)	(2,420)
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	(591)	(591)
Income taxes	145	145
Net income	(446)	(446)
Amortization of postretirement liability losses included in net periodic benefit cost | Reclassification out of accumulated other comprehensive loss
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Income taxes	615	630
Other income	(2,485)	(2,552)
Net income	(1,870)	(1,922)
Reclassification adjustment for loss 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]
Income taxes	36	14
Other income	(170)	(66)
Net income	$ (134)	$ (52)

Components of income before inc

Components of income before income taxes from continuing operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
United States	$ 466,651	$ 474,856	$ 398,532
Foreign	0	261	(87)
Income before income taxes	$ 466,651	$ 475,117	$ 398,445

Income tax expense (benefit) (D

Income tax expense (benefit) (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal	$ 17,121	$ 65,006	$ (3,502)
State	11,549	21,234	3,366
Foreign	0	151	0
Current income taxes	28,670	86,391	(136)
Deferred:
Federal	45,885	(3,735)	50,218
State	12,610	(625)	12,098
Investment tax credit - net	1,755	2,559	1,099
Deferred income taxes	60,250	(1,801)	63,415
Total income tax expense	$ 88,920	$ 84,590	$ 63,279

Components of deferred tax asse

Components of deferred tax assets and liabilities (Details 3) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Postretirement	$ 45,752	$ 51,495
Compensation-related	37,917	40,477
Operating lease liabilities	26,710	25,963
Asset retirement obligations	8,696	8,060
Legal and environmental contingencies	8,603	9,467
Customer advances	7,683	7,463
Payroll tax deferral	6,940	14,010
Other	39,960	37,944
Total deferred tax assets	182,261	194,879
Deferred tax liabilities:
Basis differences on property, plant and equipment	585,095	536,966
Postretirement	48,302	49,233
Operating lease right-of-use-assets	26,570	25,858
Intangible assets	21,074	19,514
Other	81,070	67,922
Total deferred tax liabilities	762,111	699,493
Valuation allowance	12,112	11,484
Net deferred income tax liability	$ 591,962	$ 516,098

Carryforwards (Details 4)

Carryforwards (Details 4) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
State and local jurisdiction
Carryforwards [Line Items]
Operating loss carryforwards	$ 164.8	$ 151.5
Investment tax credit carryforward, amount	35	36.3
Federal and State Taxing Authority
Carryforwards [Line Items]
Tax credit carryforward, amount	$ 35.6	$ 37.1

Deferred tax reconciliation (De

Deferred tax reconciliation (Details 5) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Change in net deferred income tax liability from the preceding table	$ 75,864
Deferred taxes associated with other comprehensive loss	(2,355)
Excess deferred income tax amortization	(10,295)
Other	(2,964)
Deferred income taxes	$ 60,250	$ (1,801)	$ 63,415

Income tax expense (benefit) st

Income tax expense (benefit) statutory rate versus actual rate (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Computed tax at federal statutory rate
Computed tax at federal statutory rate	$ 97,997	$ 99,775	$ 83,674
Federal statutory rate	21.00%	21.00%	21.00%
Increases (reductions) resulting from:
State income taxes, net of federal income tax	$ 19,496	$ 17,845	$ 14,029
State income tax, rate	4.20%	3.80%	3.50%
Federal renewable energy credit	$ (13,914)	$ (16,009)	$ (15,843)
Federal renewable energy credit, rate	(3.00%)	(3.40%)	(4.00%)
Tax compliance and uncertain tax positions	$ (477)	$ (3,543)	$ (2,739)
Tax compliance and uncertain tax positions, rate	(0.10%)	(0.70%)	(0.70%)
Excess deferred income tax amortization	$ (10,295)	$ (12,517)	$ (11,904)
Excess deferred income tax amortization, rate	(2.20%)	(2.60%)	(3.00%)
Other	$ (3,887)	$ (961)	$ (3,938)
Other, rate	(0.80%)	(0.30%)	(0.90%)
Income taxes	$ 88,920	$ 84,590	$ 63,279
Total income tax expense, rate	19.10%	17.80%	15.90%

Cash flow information (Details)

Cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest, net*	$ 91,165	$ 88,681	$ 93,414
Income taxes paid (refunded), net**	71,079	65,536	(8,475)
AFUDC borrowed	2,800	2,600	2,800
Property, plant and equipment additions in accounts payable	57,605	26,082	46,119
Right-of-use assets obtained in exchange for new operating lease liabilities	55,987	54,356	54,880
Debt assumed in connection with a business combination	10	0	1,163
Accrual for holdback payment related to a business combination	0	2,500	0
Continuing and discontinued operations
Income taxes paid (refunded), net**	$ 70,900	$ 59,400	$ (9,400)

Business segment data (Details)

Business segment data (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business segment data [Line Items]
Operating revenues	$ 5,680,733	$ 5,532,750	$ 5,336,776
Depreciation, depletion and amortization	299,214	285,100	256,017
Operating income (loss)	534,219	544,925	481,220
Interest expense	93,984	96,519	98,587
Income taxes	88,920	84,590	63,279
Income from continuing operations	377,731	390,527	335,166
Income (loss) from discontinued operations, net of tax	400	(322)	287
Net income	378,131	390,205	335,453
Capital expenditures	935,806	648,279	636,498
Total assets	8,910,435	8,053,372	7,683,059
Property, Plant and Equipment, Gross	8,972,849	8,300,770
Less accumulated depreciation, depletion and amortization	3,216,461	3,133,831	2,991,486
Net property, plant and equipment	5,756,388	5,166,939	4,917,142
Additional information [Abstract]
Net noncash acquisitions, capital expenditure-related accounts payable and AFUDC	38,700	(15,700)	4,800
Electric
Business segment data [Line Items]
Operating revenues	349,039	331,538	351,725
Depreciation, depletion and amortization	66,750	62,998	58,721
Operating income (loss)	66,335	63,434	64,039
Interest expense	26,712	26,699	25,334
Income taxes	(7,626)	(11,636)	(12,650)
Capital expenditures	82,427	114,676	99,449
Total assets	1,810,695	2,123,693	1,680,194
Property, Plant and Equipment, Gross	2,295,646	2,323,403	2,227,145
Natural gas distribution
Business segment data [Line Items]
Operating revenues	971,364	847,651	865,222
Depreciation, depletion and amortization	86,065	84,580	79,564
Operating income (loss)	89,173	73,082	69,188
Interest expense	37,265	36,798	35,488
Income taxes	8,366	5,746	1,405
Capital expenditures	170,411	193,048	206,799
Total assets	2,929,519	2,302,770	2,574,965
Property, Plant and Equipment, Gross	3,015,164	2,868,853	2,688,123
Pipeline
Business segment data [Line Items]
Operating revenues	82,858	85,346	84,192
Depreciation, depletion and amortization	20,569	21,669	21,220
Operating income (loss)	48,078	49,436	42,796
Interest expense	7,010	7,622	7,198
Income taxes	9,594	7,650	7,219
Capital expenditures	234,803	62,224	71,477
Total assets	913,945	703,377	677,482
Property, Plant and Equipment, Gross	1,051,868	821,697	834,215
Construction materials and contracting
Business segment data [Line Items]
Operating revenues	2,228,306	2,177,585	2,189,651
Depreciation, depletion and amortization	100,974	89,626	77,450
Operating income (loss)	191,077	214,498	179,955
Interest expense	19,218	20,577	23,792
Income taxes	43,459	47,431	37,389
Capital expenditures	417,524	191,635	190,092
Total assets	2,161,653	1,798,493	1,684,161
Property, Plant and Equipment, Gross	2,347,696	2,028,476	1,910,562
Construction services
Business segment data [Line Items]
Operating revenues	2,049,082	2,090,685	1,845,896
Depreciation, depletion and amortization	20,270	23,523	17,038
Operating income (loss)	145,754	147,644	126,426
Interest expense	3,540	4,095	5,331
Income taxes	35,426	35,797	29,973
Capital expenditures	29,140	83,651	60,500
Total assets	845,262	818,662	761,127
Property, Plant and Equipment, Gross	225,758	220,796	213,370
Other
Business segment data [Line Items]
Operating revenues	84	(55)	90
Depreciation, depletion and amortization	4,586	2,704	2,024
Operating income (loss)	(6,198)	(3,169)	(1,184)
Interest expense	342	883	1,859
Income taxes	(299)	(398)	(57)
Capital expenditures	1,501	3,045	8,181
Total assets	248,489	305,157	303,279
Property, Plant and Equipment, Gross	36,717	37,545	35,213
Assets held for sale
Business segment data [Line Items]
Total assets	872	1,220	1,851
Intersegment eliminations
Business segment data [Line Items]
Operating revenues	(77,606)	(76,969)	(77,149)
Interest expense	(103)	(155)	(415)
Intersegment eliminations | Electric
Business segment data [Line Items]
Operating revenues	(543)	(491)	0
Intersegment eliminations | Natural gas distribution
Business segment data [Line Items]
Operating revenues	(576)	(534)	0
Intersegment eliminations | Pipeline
Business segment data [Line Items]
Operating revenues	(59,678)	(58,531)	(56,252)
Intersegment eliminations | Construction materials and contracting
Business segment data [Line Items]
Operating revenues	(624)	(417)	(1,066)
Intersegment eliminations | Construction services
Business segment data [Line Items]
Operating revenues	(2,555)	(5,038)	(3,370)
Intersegment eliminations | Other
Business segment data [Line Items]
Operating revenues	(13,630)	(11,958)	(16,461)
Total intersegment operating revenues
Business segment data [Line Items]
Operating revenues	0	0	0
Regulated Operation
Business segment data [Line Items]
Operating revenues	1,390,343	1,249,146	1,279,304
Income from continuing operations	143,085	135,103	122,535
Regulated Operation | Electric
Business segment data [Line Items]
Operating revenues	349,039	331,538	351,725
Income from continuing operations	51,906	55,601	54,763
Regulated Operation | Natural gas distribution
Business segment data [Line Items]
Operating revenues	971,364	847,651	865,222
Income from continuing operations	51,596	44,049	39,517
Regulated Operation | Pipeline
Business segment data [Line Items]
Operating revenues	69,940	69,957	62,357
Income from continuing operations	39,583	35,453	28,255
Regulated Operation | Intersegment eliminations
Business segment data [Line Items]
Operating revenues	60,108	59,002	56,037
Regulated Operation | Intersegment eliminations | Electric
Business segment data [Line Items]
Operating revenues	543	491	0
Regulated Operation | Intersegment eliminations | Natural gas distribution
Business segment data [Line Items]
Operating revenues	576	534	0
Regulated Operation | Intersegment eliminations | Pipeline
Business segment data [Line Items]
Operating revenues	58,989	57,977	56,037
Nonregulated Operation
Business segment data [Line Items]
Operating revenues	4,290,390	4,283,604	4,057,472
Income from continuing operations	234,646	255,424	212,631
Nonregulated Operation | Pipeline
Business segment data [Line Items]
Operating revenues	12,918	15,389	21,835
Income from continuing operations	1,313	1,559	1,348
Nonregulated Operation | Construction materials and contracting
Business segment data [Line Items]
Operating revenues	2,228,306	2,177,585	2,189,651
Income from continuing operations	129,755	147,325	120,371
Nonregulated Operation | Construction services
Business segment data [Line Items]
Operating revenues	2,049,082	2,090,685	1,845,896
Income from continuing operations	109,402	109,721	92,998
Nonregulated Operation | Other
Business segment data [Line Items]
Operating revenues	84	(55)	90
Income from continuing operations	(5,824)	(3,181)	(2,086)
Nonregulated Operation | Intersegment eliminations
Business segment data [Line Items]
Operating revenues	17,498	17,967	21,112
Nonregulated Operation | Intersegment eliminations | Pipeline
Business segment data [Line Items]
Operating revenues	689	554	215
Nonregulated Operation | Intersegment eliminations | Construction materials and contracting
Business segment data [Line Items]
Operating revenues	624	417	1,066
Nonregulated Operation | Intersegment eliminations | Construction services
Business segment data [Line Items]
Operating revenues	2,555	5,038	3,370
Nonregulated Operation | Intersegment eliminations | Other
Business segment data [Line Items]
Operating revenues	$ 13,630	$ 11,958	$ 16,461

Change in benefit obligations a

Change in benefit obligations and plan assets (Details) - Qualified Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Underfunded Plan | Pension Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	$ 437,360	$ 421,166
Service cost	0	0	$ 0
Interest cost	9,819	12,093	15,225
Plan participants' contributions	0	0
Actuarial (gain) loss	(12,140)	27,737
Benefits paid	(23,542)	(23,636)
Benefit obligation at end of year	411,497	437,360	421,166
Change in net plan assets:
Fair value of plan assets at beginning of year	383,834	365,264
Actual return on plan assets	12,817	42,206
Employer contribution	0	0
Plan participants' contributions	0	0
Benefits paid	(23,542)	(23,636)
Fair value of net plan assets at end of year	373,109	383,834	365,264
Funded status - over (under)	(38,388)	(53,526)
Amounts recognized in the Consolidated Balance Sheets at December 31:
Noncurrent assets - other	0	0
Other accrued liabilities	0	0
Noncurrent liabilities - other	38,388	53,526
Benefit obligation assets (liabilities) - net amount recognized	(38,388)	(53,526)
Amounts recognized in accumulated other comprehensive loss:
Actuarial loss	25,976	27,527
Prior service credit	0	0
Total	25,976	27,527
Amounts recognized in regulatory assets or liabilities:
Actuarial (gain) loss	142,166	154,013
Prior service credit	0	0
Total	142,166	154,013
Overfunded Plan | Other Postretirement Benefits
Change in benefit obligation:
Benefit obligation at beginning of year	86,155	83,614
Service cost	1,600	1,532	1,142
Interest cost	1,862	2,437	2,986
Plan participants' contributions	641	752
Actuarial (gain) loss	(12,802)	2,203
Benefits paid	(3,996)	(4,383)
Benefit obligation at end of year	73,460	86,155	83,614
Change in net plan assets:
Fair value of plan assets at beginning of year	101,639	94,587
Actual return on plan assets	1,398	10,249
Employer contribution	476	434
Plan participants' contributions	641	752
Benefits paid	(3,996)	(4,383)
Fair value of net plan assets at end of year	100,158	101,639	$ 94,587
Funded status - over (under)	26,698	15,484
Amounts recognized in the Consolidated Balance Sheets at December 31:
Noncurrent assets - other	45,863	36,769
Other accrued liabilities	544	622
Noncurrent liabilities - other	18,621	20,663
Benefit obligation assets (liabilities) - net amount recognized	26,698	15,484
Amounts recognized in accumulated other comprehensive loss:
Actuarial loss	2,367	5,557
Prior service credit	(290)	(634)
Total	2,077	4,923
Amounts recognized in regulatory assets or liabilities:
Actuarial (gain) loss	(14,727)	(8,228)
Prior service credit	(5,193)	(6,808)
Total	$ (19,920)	$ (15,036)

Benefit obligations in excess o

Benefit obligations in excess of plan assets (Details 2) - Qualified Plan - Pension Benefits - Underfunded Plan - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 411,497	$ 437,360
Accumulated benefit obligation	411,497	437,360
Fair value of plan assets	$ 373,109	$ 383,834

Components of net periodic bene

Components of net periodic benefit cost (Details 3) - Qualified Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Underfunded Plan | Pension Benefits
Components of net periodic benefit cost (credit):
Service cost	$ 0	$ 0	$ 0
Interest cost	9,819	12,093	15,225
Expected return on assets	(19,576)	(19,949)	(18,236)
Amortization of prior service credit	0	0	0
Recognized net actuarial loss	8,017	7,172	5,548
Net periodic benefit cost (credit), including amount capitalized	(1,740)	(684)	2,537
Less amount capitalized	0	0	0
Net periodic benefit cost (credit)	(1,740)	(684)	2,537
Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss:
Net (gain) loss	(265)	934	(144)
Amortization of actuarial loss	(1,286)	(1,155)	(904)
Amortization of prior service credit	0	0	0
Total recognized in accumulated other comprehensive loss	(1,551)	(221)	(1,048)
Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities:
Net (gain) loss	(5,116)	4,546	189
Amortization of actuarial gain (loss)	(6,731)	(6,017)	(4,644)
Amortization of prior service credit	0	0	0
Total recognized in regulatory assets or liabilities	(11,847)	(1,471)	(4,455)
Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities	(15,138)	(2,376)	(2,966)
Overfunded Plan | Other Postretirement Benefits
Components of net periodic benefit cost (credit):
Service cost	1,600	1,532	1,142
Interest cost	1,862	2,437	2,986
Expected return on assets	(5,098)	(5,019)	(4,804)
Amortization of prior service credit	(1,398)	(1,398)	(1,398)
Recognized net actuarial loss	24	287	353
Net periodic benefit cost (credit), including amount capitalized	(3,010)	(2,161)	(1,721)
Less amount capitalized	150	156	113
Net periodic benefit cost (credit)	(3,160)	(2,317)	(1,834)
Other changes in plan assets and benefit obligations recognized in accumulated comprehensive loss:
Net (gain) loss	(2,811)	(259)	(127)
Amortization of actuarial loss	(135)	(306)	(110)
Amortization of prior service credit	100	101	100
Total recognized in accumulated other comprehensive loss	(2,846)	(464)	(137)
Other changes in plan assets and benefit obligations recognized in regulatory assets or liabilities:
Net (gain) loss	(6,292)	(3,793)	(8,168)
Amortization of actuarial gain (loss)	110	19	(242)
Amortization of prior service credit	1,298	1,297	1,297
Total recognized in regulatory assets or liabilities	(4,884)	(2,477)	(7,113)
Total recognized in net periodic benefit cost (credit), accumulated other comprehensive loss and regulatory assets or liabilities	$ (10,890)	$ (5,258)	$ (9,084)

Weighted average assumptions (D

Weighted average assumptions (Details 4) - Qualified Plan	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Underfunded Plan | Pension Benefits
Used to determine benefit obligation
Discount rate	2.64%	2.30%
Expected return on plan assets	6.00%	6.00%
Used to determine benefit cost
Discount rate	2.30%	2.96%
Expected return on plan assets	6.00%	6.25%
Overfunded Plan | Other Postretirement Benefits
Used to determine benefit obligation
Discount rate	2.66%	2.30%
Expected return on plan assets	5.50%	5.50%
Rate of compensation increase	3.00%	3.00%
Used to determine benefit cost
Discount rate	2.30%	3.00%
Expected return on plan assets	5.50%	5.75%
Rate of compensation increase	3.00%	3.00%

Investment Allocations (Details

Investment Allocations (Details 5) - Qualified Plan	Dec. 31, 2021
Underfunded Plan | Minimum | Equity securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	35.00%
Underfunded Plan | Minimum | Fixed Income Securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	55.00%
Underfunded Plan | Maximum | Equity securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	45.00%
Underfunded Plan | Maximum | Fixed Income Securities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	65.00%
Overfunded Plan | Equity securities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	10.00%
Overfunded Plan | Fixed Income Securities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, target allocation, percentage	90.00%

Health care rate assumptions an

Health care rate assumptions and cost trend rate (Details 6) - Overfunded Plan - Qualified Plan - Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Health care trend rate assumed for next year	7.00%	7.00%
Health care cost trend rate - ultimate	4.50%	4.50%
Year in which ultimate trend rate achieved	2031	2031

Estimated future benefit paymen

Estimated future benefit payments and subsidies (Details 7) - Qualified Plan - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021
Underfunded Plan | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		$ 0
Defined Benefit Plan, Plan Assets, Additional Contributions by Employer	$ 20,000,000
2022		24,644,000
2023		24,766,000
2024		24,897,000
2025		24,739,000
2026		24,571,000
2027-2031		117,413,000
Overfunded Plan | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		601,000
2022		4,393,000
2023		4,522,000
2024		4,572,000
2025		4,612,000
2026		4,642,000
2027-2031		17,867,000
2022		70,000
2023		65,000
2024		58,000
2025		52,000
2026		46,000
2027-2031		$ 157,000

Fair value - pension (Details 8

Fair value - pension (Details 8) - Qualified Plan - Underfunded Plan - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 373,109	$ 383,834	$ 365,264
Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 4,637	$ 7,841
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage		8.00%
Pension investments in insurance contracts	100.00%
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 7,483	$ 12,844
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 1,279	$ 1,727
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	19.00%	24.00%
Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 208,476	$ 233,185
Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 125,167	$ 92,809
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	37.00%	36.00%
Municipal bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 7,507	$ 10,126
U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 9,015	$ 13,872
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	9.00%	5.00%
Pooled Separate Accounts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 3,088
Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 373,109	$ 383,834
Defined Benefit Plan, Equity Securities, US, Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	16.00%	18.00%
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Percentage	19.00%	9.00%
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 7,483	$ 12,844
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	167,093	177,397
Quoted Prices in Active Markets for Identical Assets  (Level 1) | U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	7,113	11,177
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	181,689	201,418
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	4,637	7,841
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1,279	1,727
Significant Other Observable Inputs  (Level 2) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	41,383	55,788
Significant Other Observable Inputs  (Level 2) | Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	125,167	92,809
Significant Other Observable Inputs  (Level 2) | Municipal bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	7,507	10,126
Significant Other Observable Inputs  (Level 2) | U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1,902	2,695
Significant Other Observable Inputs  (Level 2) | Pooled Separate Accounts
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	3,088
Significant Other Observable Inputs  (Level 2) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	184,963	170,986
Fair Value Measured at Net Asset Value Per Share | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 6,457	$ 11,430

Fair value - other postretireme

Fair value - other postretirement (Details 9) - Other Postretirement Benefits - Qualified Plan - Overfunded Plan - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 100,158	$ 101,639	$ 94,587
Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	4,281	$ 3,517
Postretirement Investments in Collective and Mutual Funds		8.00%
Postretirement Investments in Insurance Contracts		1.00%
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	2,332	$ 1,850
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 1	$ 2
Postretirement Investments in Collective and Mutual Funds	19.00%	24.00%
Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 94	$ 157
Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	93,447	96,103
Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 100,158	$ 101,639
Corporate debt securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	37.00%	36.00%
Postretirement Investments in Insurance Contracts	58.00%	67.00%
Defined Benefit Plan, Equity Securities, US, Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	16.00%	18.00%
Postretirement Investments in Insurance Contracts	13.00%	10.00%
Defined Benefit Plan, Equity Securities, US, Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Insurance Contracts	5.00%	4.00%
U.S. Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	9.00%	5.00%
Postretirement Investments in Insurance Contracts	13.00%	12.00%
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Postretirement Investments in Collective and Mutual Funds	19.00%	9.00%
Postretirement Investments in Insurance Contracts	11.00%	6.00%
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 2,332	$ 1,850
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	4	10
Quoted Prices in Active Markets for Identical Assets  (Level 1) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	2,336	1,860
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	4,281	3,517
Significant Other Observable Inputs  (Level 2) | Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	1	2
Significant Other Observable Inputs  (Level 2) | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	90	147
Significant Other Observable Inputs  (Level 2) | Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	93,447	96,103
Significant Other Observable Inputs  (Level 2) | Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	97,819	99,769
Fair Value Measured at Net Asset Value Per Share | Collective and mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 3	$ 10

Nonqualified Benefit Plans Bene

Nonqualified Benefit Plans Benefit Obligations (Details 10) - Unfunded Plan - Nonqualified Plan - Supplemental Employee Retirement Plan - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 92,918	$ 101,242
Accumulated benefit obligation	$ 92,918	$ 101,242

Nonqualified Benefit Plans Comp

Nonqualified Benefit Plans Components of NPBC (Details 11) - Unfunded Plan - Nonqualified Plan - Supplemental Employee Retirement Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 58	$ 109
Interest cost	1,912	2,606	3,473
Recognized net actuarial loss	1,164	1,192	764
Net periodic benefit cost	$ 3,076	$ 3,856	$ 4,346

Nonqualified Benefit Plans Weig

Nonqualified Benefit Plans Weighted Average Assumptions (Details 12) - Unfunded Plan - Nonqualified Plan - Supplemental Employee Retirement Plan	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation discount rate	2.39%	1.97%
Net periodic benefit cost discount rate	1.97%	2.73%

Nonqualified Benefit Plans Futu

Nonqualified Benefit Plans Future Benefit Payments (Details 13) - Unfunded Plan - Nonqualified Plan - Supplemental Employee Retirement Plan $ in Thousands	Dec. 31, 2021USD ($)
Defined Benefit Plan Disclosure [Line Items]
2022	$ 6,877
2023	6,890
2024	7,354
2025	7,537
2026	7,609
2027-2031	$ 31,983

Nonqualified Benefit Plans Cont

Nonqualified Benefit Plans Contributions (Details 14) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Unfunded Plan | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Nonqualified Defined Contribution Plan, Cost	$ 2.4	$ 1.8	$ 1.6

Nonqualified Benefit Plans Inve

Nonqualified Benefit Plans Investments (Details 15) - Unfunded Plan - Supplemental Employee Retirement Plan - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 158,149	$ 148,800
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	109,603	100,104
Life insurance carried on plan participants
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	38,356	39,779
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 10,190	$ 8,917

Defined Contribution Benefit Pl

Defined Contribution Benefit Plans Contribution (Details 16) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Nonqualified Defined Contribution Plan, Cost	$ 45.4	$ 50.1	$ 51.8

Multiemployer Plans Zones (Deta

Multiemployer Plans Zones (Details 17)	12 Months Ended
	Dec. 31, 2021
Maximum
Multiemployer Plans [Line Items]
Multiemployer plan red zone status funded percentage	65.00%
Mulitiemployer plan yellow status funded percentage	80.00%
Minimum
Multiemployer Plans [Line Items]
Multiemployer plan yellow zone status funded percentage	65.00%
Multiemployer plan green zone status funded percentage	80.00%

Multiemployer Plans Participati

Multiemployer Plans Participation by Plan (Details 18) - Pension Benefits - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Insignificant, Employer Contribution, Cost	$ 23,390	$ 23,722	$ 19,598
Multiemployer Plan, Employer Contribution, Cost	$ 82,388	$ 85,444	72,525
Edison Pension Plan
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	936061681
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 18,331	$ 16,121	12,252
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Dec. 31, 2023
IBEW Local 212 Pension Trust
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	316127280
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Certified Zone Status, Date	Apr. 30, 2021	Apr. 30, 2020
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 1,733	$ 1,521	1,110
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Jun. 1, 2025
IBEW Local 357 Pension Plan A
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	886023284
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 6,485	$ 9,913	10,162
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	May 31, 2024
IBEW Local 82 Pension Plan
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	316127268
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Certified Zone Status, Date	Jun. 30, 2021	Jun. 30, 2020
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 1,353	$ 1,373	1,662
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Dec. 3, 2023
Idaho Plumbers and Pipefitters Pension Plan
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	826010346
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Certified Zone Status, Date	May 31, 2021	May 31, 2020
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 1,528	$ 1,370	1,307
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Mar. 31, 2023
National Electrical Benefit Fund
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	530181657
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 14,361	$ 14,484	12,679
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
National Electrical Benefit Fund | Minimum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	May 31, 2021
National Electrical Benefit Fund | Maximum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	May 31, 2026
Pension and Retirement Plan of Plumbers and Pipefitters Local 525
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	886003864
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 4,345	$ 6,266	4,747
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Sep. 30, 2024
Pension Trust Fund for Operating Engineers
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	946090764
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Yellow	Yellow
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	Implemented
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 2,495	$ 2,680	2,598
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Pension Trust Fund for Operating Engineers | Minimum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Jun. 15, 2022
Pension Trust Fund for Operating Engineers | Maximum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Jun. 30, 2023
Sheet Metal Workers Pension Plan of Southern CA, AZ, and NV
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	956052257
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Yellow	Yellow
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	Implemented
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 2,615	$ 3,255	2,119
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Jun. 30, 2024
Southern California IBEW-NECA Pension Trust Fund
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	956392774
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Yellow	Yellow
Multiemployer Plan, Pension, Significant, Certified Zone Status, Date	Jun. 30, 2021	Jun. 30, 2020
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	Implemented
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 2,746	$ 1,714	1,477
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Southern California IBEW-NECA Pension Trust Fund | Minimum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Jun. 30, 2022
Southern California IBEW-NECA Pension Trust Fund | Maximum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	May 31, 2026
Western Conference of Teamsters Pension Plan
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Employer Identification Number	916145047
Multiemployer Plan, Pension, Significant, Plan Number	001
Multiemployer Plan, Pension, Significant, Certified Zone Status [Fixed List]	Green	Green
Multiemployer Plan, Pension, Significant, Funding Improvement or Rehabilitation Plan, Implementation Status [Fixed List]	No
Multiemployer Plan, Pension, Significant, Employer Contribution, Cost	$ 3,006	$ 3,025	$ 2,814
Multiemployer Plan, Pension, Significant, Surcharge [Fixed List]	No
Western Conference of Teamsters Pension Plan | Minimum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Dec. 31, 2023
Western Conference of Teamsters Pension Plan | Maximum
Multiemployer Plans [Line Items]
Multiemployer Plan, Pension, Significant, Collective-Bargaining Arrangement, Expiration Date	Dec. 31, 2025

Multiemployer Plan Contribution

Multiemployer Plan Contributions (Details 19) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Multiemployer Plans, Defined Contribution [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost	$ 54.8	$ 54.2	$ 49.2
Other Postretirement Benefits
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost	$ 66.1	$ 63.8	$ 59.5

Jointly owned facilities (Detai

Jointly owned facilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Jointly owned electricity generation plant | Big Stone Station
Jointly Owned Utility Plant Interests [Line Items]
Proportionate ownership share	22.70%
Utility plant in service	$ 157,259	$ 155,967
Construction work in progress	571	104
Less accumulated depreciation	47,293	45,435
Utility plant in services net	$ 110,537	110,636
Jointly owned electricity generation plant | Coyote Station
Jointly Owned Utility Plant Interests [Line Items]
Proportionate ownership share	25.00%
Utility plant in service	$ 157,764	159,784
Construction work in progress	784	323
Less accumulated depreciation	109,202	108,852
Utility plant in services net	$ 49,346	51,255
Jointly owned electricity generation plant | Wygen III
Jointly Owned Utility Plant Interests [Line Items]
Proportionate ownership share	25.00%
Utility plant in service	$ 66,357	66,101
Construction work in progress	108	232
Less accumulated depreciation	11,383	10,038
Utility plant in services net	$ 55,082	56,295
Jointly Owned Electricity Transmission and Distribution System | BSSE
Jointly Owned Utility Plant Interests [Line Items]
Proportionate ownership share	50.00%
Utility plant in service	$ 107,424	107,442
Construction work in progress	0	0
Less accumulated depreciation	4,506	2,682
Utility plant in services net	$ 102,918	$ 104,760

MNPUC (Details)

MNPUC (Details) $ in Millions	Sep. 01, 2021USD ($)
Pending Rate Case [Member] | MNPUC [Member] | Gas Distribution [Member] | Great Plains Natural Gas Co. [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 8.8

NDPSC (Details 2)

NDPSC (Details 2) - Electricity [Member] - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - Subsequent Event [Member] $ in Millions	Feb. 01, 2022USD ($)
Public Utilities, General Disclosures [Line Items]
Renewable Resource Cost Adjustment Rate Tariff	$ 12.4
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (2)

SDPUC (Details 3)

SDPUC (Details 3)	Nov. 15, 2021USD ($)
SDPUC | Montana-Dakota Utilities Co. [Member] | Electricity [Member]
Public Utilities, General Disclosures [Line Items]
Total Infrastructure Rider	$ 0

WUTC (Details 4)

WUTC (Details 4) - Pending Rate Case [Member] - Gas Distribution [Member] - WUTC [Member] - Cascade Natural Gas [Member] $ in Millions	Sep. 30, 2021USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 13.7
Public Utilities, Requested Rate Increase (Decrease), Percentage	5.10%

FERC (Details 5)

FERC (Details 5) $ in Millions	Jan. 01, 2022USD ($)
MISO [Member] | Montana-Dakota Utilities Co. [Member] | Electric | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Transmission Formula Revenue Requirement	$ 13.4

Litigation (Details)

Litigation (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 37	$ 41.5
Loss Contingency, Receivable	14.1	17.5
Loss Contingency, Regulated	$ 21.2	$ 21.3

Enviromental matters (Details 2

Enviromental matters (Details 2)	12 Months Ended
	Dec. 31, 2021USD ($)
Portland Harbor Site
Site Contingency [Line Items]
Environmental matters investigative costs	$ 115,000,000
Environmental matters, estimated costs	1,000,000,000
Missoula, MT manufactured gas plant site
Site Contingency [Line Items]
Total estimated costs for site remediation	560,000
Environmental Matters Estimated Investigative Costs	823,000
Environmental matters accrual for site remediation	419,000
Incurred Costs For Site Remedial Investigation	505,000
Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Environmental matters accrual for site remediation	17,500,000
Total estimated costs for site remedial investigation and feasibility study	7,600,000
Incurred costs for site remedial investigation and feasibility study	5,300,000
Environmental matters accrual of investigative costs	2,300,000
Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, preferred alternative estimate	9,300,000
Minimum | Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	13,600,000
Minimum | Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	8,000,000
Maximum | Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	71,000,000
Maximum | Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	$ 20,400,000

Purchase commitments (Details 3

Purchase commitments (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Long-term Purchase Commitment [Line Items]
Commitment term	38 years
Purchase commitments due
2022	$ 589,898
2023	200,667
2024	141,383
2025	99,545
2026	86,628
Purchase Obligation, to be Paid, after Year Five	731,679
Amounts purchased under various commitments	$ 849,300	$ 666,000	$ 686,500

Guarantees (Details 4)

Guarantees (Details 4)	Dec. 31, 2021USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 134,800,000
Fixed maximum amounts guaranteed by year 2022	28,600,000
Fixed maximum amounts guaranteed by year 2023	45,200,000
Fixed maximum amounts guaranteed by year 2024	50,200,000
Fixed maximum amounts guaranteed by year 2025	800,000
Fixed maximum amounts guaranteed by year 2026	800,000
Fixed maximum amounts guaranteed, thereafter	200,000
No scheduled maturity date	9,000,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	25,700,000
Letters of credit set to expire - 2022	25,200,000
Letters of credit set to expire - 2023	500,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 934,400,000

Variable interest entities (Det

Variable interest entities (Details 5) $ in Millions	Dec. 31, 2021USD ($)
Fuel contract
Variable Interest Entities [Line Items]
Variable interest entity, reporting entity involvement, maximum loss exposure, amount	$ 31.5

Condensed Statements of Income

Condensed Statements of Income and Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Income from continuing operations	$ 377,731	$ 390,527	$ 335,166
Comprehensive income	385,205	384,229	331,693
MDU Resources Group, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Equity in earnings of subsidiaries from continuing operations	377,731	390,527	335,166
Income from continuing operations	377,731	390,527	335,166
Equity in earnings (loss) of subsidiaries from discontinued operations	400	(322)	287
Net income	378,131	390,205	335,453
Comprehensive income	$ 385,205	$ 384,229	$ 331,693

Condensed Balance Sheets (Detai

Condensed Balance Sheets (Details 2) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 54,161,000	$ 59,547,000	$ 66,459,000	$ 53,948,000
Receivables, net	946,741,000	873,986,000
Prepayments and other current assets	95,741,000	44,120,000
Assets, Current	1,550,943,000	1,337,347,000
Noncurrent Assets
Investments	175,476,000	165,022,000
Operating lease right-of-use assets	124,138,000	120,113,000
Other	157,675,000	144,111,000
Total noncurrent assets	7,359,492,000	6,716,025,000
Total assets	8,910,435,000	8,053,372,000	7,683,059,000
Current liabilities:
Accounts payable	478,933,000	426,264,000
Taxes payable	80,372,000	88,844,000
Dividends payable	44,229,000	42,611,000
Accrued compensation	81,904,000	90,629,000
Operating lease liabilities due within one year	35,368,000	33,655,000
Other accrued liabilities	207,078,000	198,514,000
Total current liabilities	1,092,240,000	963,522,000
Noncurrent liabilities:
Operating lease liabilities	89,253,000	86,868,000
Other	273,408,000	327,773,000
Total noncurrent liabilities	4,435,321,000	4,010,745,000
Commitments and contingencies
Commitments and Contingencies
Stockholders' equity:
Common stock	203,889,000	201,061,000
Other paid-in capital	1,461,205,000	1,371,385,000
Retained earnings	1,762,410,000	1,558,363,000
Accumulated other comprehensive loss	(41,004,000)	(48,078,000)
Treasury stock at cost - 538,921 shares	(3,626,000)	(3,626,000)
Stockholders' Equity Attributable to Parent	3,382,874,000	3,079,105,000
Total liabilities and stockholders' equity	$ 8,910,435,000	$ 8,053,372,000
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921
MDU Resources Group, Inc. [Member]
Current assets:
Cash and cash equivalents	$ 6,159,000	$ 8,781,000	$ 12,326,000	$ 2,271,000
Receivables, net	6,120,000	4,865,000
Accounts receivable from subsidiaries	49,696,000	50,539,000
Prepayments and other current assets	2,528,000	1,612,000
Assets, Current	64,503,000	65,797,000
Noncurrent Assets
Investments	55,686,000	52,000,000
Investment in subsidiaries	3,368,537,000	3,069,956,000
Deferred income taxes	7,364,000	9,691,000
Operating lease right-of-use assets	114,000	56,000
Other	26,558,000	28,866,000
Total noncurrent assets	3,458,259,000	3,160,569,000
Total assets	3,522,762,000	3,226,366,000
Current liabilities:
Accounts payable	2,546,000	2,135,000
Accounts payable to subsidiaries	6,133,000	5,412,000
Taxes payable	1,672,000	4,056,000
Dividends payable	44,229,000	42,611,000
Accrued compensation	4,098,000	7,825,000
Operating lease liabilities due within one year	52,000	40,000
Other accrued liabilities	7,309,000	6,881,000
Total current liabilities	66,039,000	68,960,000
Noncurrent liabilities:
Operating lease liabilities	62,000	16,000
Other	73,787,000	78,285,000
Total noncurrent liabilities	73,849,000	78,301,000
Commitments and contingencies
Commitments and Contingencies
Stockholders' equity:
Common stock	203,889,000	201,061,000
Other paid-in capital	1,461,205,000	1,371,385,000
Retained earnings	1,762,410,000	1,558,363,000
Accumulated other comprehensive loss	(41,004,000)	(48,078,000)
Treasury stock at cost - 538,921 shares	(3,626,000)	(3,626,000)
Stockholders' Equity Attributable to Parent	3,382,874,000	3,079,105,000
Total liabilities and stockholders' equity	$ 3,522,762,000	$ 3,226,366,000
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 495,777	$ 768,374	$ 542,280
Capital expenditures	(659,425)	(558,007)	(576,065)
Net proceeds from sale or disposition of property and other	15,238	35,557	29,812
Investments	(3,973)	(1,814)	(2,011)
Net cash used in investing activities	(885,878)	(630,243)	(603,861)
Issuance of long-term debt	554,027	117,450	603,969
Repayment of long-term debt	(24,979)	(148,634)	(468,917)
Proceeds from issuance of common stock	88,767	3,385	106,848
Dividends paid	(171,354)	(166,405)	(160,256)
Repurchase of common stock	(6,701)	0	0
Tax withholding on stock-based compensation	(4,127)	(362)	(3,015)
Net cash used in financing activities	384,715	(145,043)	74,092
Cash and cash equivalents - beginning of year	59,547	66,459	53,948
Cash and cash equivalents - end of year	54,161	59,547	66,459
MDU Resources Group, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	187,297	226,642	168,520
Investments in and advances to subsidiaries	(102,000)	(67,000)	(120,000)
Advances from subsidiaries	0	0	17,000
Investments	(391)	(4)	(236)
Net cash used in investing activities	(102,391)	(67,004)	(103,236)
Proceeds from issuance of common stock	88,767	3,385	106,848
Dividends paid	(171,354)	(166,405)	(160,256)
Repurchase of common stock	(2,992)	0	0
Tax withholding on stock-based compensation	(1,949)	(163)	(1,821)
Net cash used in financing activities	(87,528)	(163,183)	(55,229)
Increase (decrease) in cash and cash equivalents	(2,622)	(3,545)	10,055
Cash and cash equivalents - beginning of year	8,781	12,326	2,271
Cash and cash equivalents - end of year	$ 6,159	$ 8,781	$ 12,326

Notes to Condensed Financial St

Notes to Condensed Financial Statements (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
MDU Resources Group, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Cash dividends paid to parent company by consolidated subsidiaries	$ 188.1	$ 228.4	$ 177.1