Cover page - USD ($)	12 Months Ended
Cover page - USD ($)	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	12 Months Ended
Audit Information	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Minneapolis, Minnesota

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 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 - 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	$ 1.00	$ 1.00
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	$ 1.00	$ 1.00
Common Stock, Shares, Issued	203,889,661	201,061,198
Treasury Stock, Common, Shares	538,921	538,921

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 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	12 Months Ended
Basis of Presentation	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

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 distribution		Pipeline		Construction materials and contracting		Construction services		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 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 per share

Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the 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. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows:


	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

Income taxes

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.

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

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 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.

At December 31, 2021, the Company's remaining performance obligations were $2.5 billion. The Company expects to recognize the following revenue amounts in future periods related to these remaining performance obligations: $1.8 billion within the next 12 months or less; $278.6 million within the next 13 to 24 months; and $411.9 million in 25 months or more.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Business Combinations	12 Months Ended
Business Combinations	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

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 Average Depreciable Life in Years
	(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 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 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 Acquired During the Year		Measurement Period Adjustments		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 During the Year		Measurement Period Adjustments		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

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 Unrealized Gains		Gross Unrealized Losses		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 Unrealized Gains		Gross Unrealized Losses		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 at December 31, 2021, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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 at December 31, 2020, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Debt

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

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 Limit			Amount Outstanding at December 31, 2021		Amount Outstanding at December 31, 2020		Letters of Credit at December 31, 2021			Expiration Date
		(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

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

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+ Details

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

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

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.

The Company currently has 2.0 million shares of preferred stock authorized to be issued with a $100 par value. At December 31, 2021 and 2020, there were no shares outstanding.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

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 Period	Target Grant of Shares
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 Shares	Weighted Average Grant-Date Fair Value
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 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 Unrealized Loss on Derivative Instruments Qualifying as Hedges		Post- retirement Liability Adjustment		Net Unrealized Gain (Loss) on Available- for-sale Investments		Total Accumulated Other Comprehensive Loss
	(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 Statements of Income
	(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

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.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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

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).

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Employee benefit plans

12 Months Ended

Dec. 31, 2021

Retirement Benefits [Abstract]

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 Postretirement Benefits
	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 Postretirement Benefits
	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 Postretirement Benefits
	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 Postretirement Benefits
	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 Benefits		Other Postretirement Benefits		Expected Medicare Part D Subsidy
			(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 at December 31, 2021, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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 at December 31, 2020, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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 at December 31, 2021, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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 at December 31, 2020, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		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 of Collective Bargaining Agreement
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 of Total Contributions (as of December 31 of the Plan's Year-End)
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.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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	12 Months Ended
Regulatory matters	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

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 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 Financial Information of Registrant (Unconsolidated)

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 Financial Information of Registrant (Unconsolidated)

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)	12 Months Ended
Basis of Presentation (Policies)	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)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

New accounting standards

The following table provides a brief description of the accounting pronouncements applicable to the Company and the potential impact on its 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.