10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2021

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from _____________ to ______________

Commission file number 1-03480

MDU RESOURCES GROUP INC

(Exact name of registrant as specified in its charter)

Delaware	30-1133956
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)

1200 West Century Avenue

P.O. Box 5650

Bismarck, North Dakota 58506-5650

(Address of principal executive offices)

(Zip Code)

(701) 530-1000

(Registrant's telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading symbol(s)	Name of each exchange on which registered
Common Stock, par value $1.00 per share	MDU	New York Stock Exchange

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐.

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐.

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large Accelerated Filer	☒	Accelerated Filer	☐
Non-Accelerated Filer	☐	Smaller Reporting Company	☐
		Emerging Growth Company	☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒.

Indicate the number of shares outstanding of each of the issuer's classes of common stock, as of July 29, 2021: 202,430,930 shares.

1

Index
	Page
Definitions	3
Introduction	5
Part I -- Financial Information
Item 1. Financial Statements	6
Consolidated Statements of Income -- Three and Six Months Ended June 30, 2021 and 2020	6
Consolidated Statements of Comprehensive Income -- Three and Six Months Ended June 30, 2021 and 2020	7
Consolidated Balance Sheets -- June 30, 2021 and 2020, and December 31, 2020	8
Consolidated Statements of Equity -- Six Months Ended June 30, 2021 and 2020	9
Consolidated Statements of Cash Flows -- Six Months Ended June 30, 2021 and 2020	10
Notes to Consolidated Financial Statements	11
1. Basis of presentation	11
2. New accounting standards	11
3. Seasonality of operations	12
4. Receivables and allowance for expected credit losses	12
5. Inventories and natural gas in storage	13
6. Earnings per share	13
7. Equity	13
8. Accumulated other comprehensive loss	14
9. Revenue from contracts with customers	15
10. Business combinations	18
11. Leases	19
12. Goodwill and other intangible assets	19
13. Regulatory assets and liabilities	20
14. Fair value measurements	21
15. Debt	23
16. Cash flow information	24
17. Business segment data	24
18. Employee benefit plans	27
19. Regulatory matters	27
20. Contingencies	28
Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations	31
Item 3. Quantitative and Qualitative Disclosures About Market Risk	51
Item 4. Controls and Procedures	51
Part II -- Other Information
Item 1. Legal Proceedings	53
Item 1A. Risk Factors	53
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds	55
Item 4. Mine Safety Disclosures	55
Item 5. Other Information	55
Item 6. Exhibits	55
Exhibits Index	56
Signatures	57

2

Definitions

The following abbreviations and acronyms used in this Form 10-Q are defined below:

Abbreviation or Acronym
2020 Annual Report	Company's Annual Report on Form 10-K for the year ended December 31, 2020
AFUDC	Allowance for funds used during construction
ASC	FASB Accounting Standards Codification
ASU	FASB Accounting Standards Update
Brazilian Transmission Lines	Company's former investment in companies owning three electric transmission lines in Brazil
Cascade	Cascade Natural Gas Corporation, an indirect wholly owned subsidiary of MDU Energy Capital
Centennial	Centennial Energy Holdings, Inc., a direct wholly owned subsidiary of the Company
Centennial Capital	Centennial Holdings Capital LLC, a direct wholly owned subsidiary of Centennial
Centennial Resources	Centennial Energy Resources LLC, a former direct wholly owned subsidiary of Centennial
Company	MDU Resources Group, Inc.
COVID-19	Coronavirus disease 2019. In March 2020, the World Health Organization declared the COVID-19 outbreak a pandemic and the President of the United States declared the COVID-19 outbreak a national emergency.
Coyote Creek	Coyote Creek Mining Company, LLC, a subsidiary of The North American Coal Corporation
Coyote Station	427-MW coal-fired electric generating facility near Beulah, North Dakota (25 percent ownership)
dk	Decatherm
Dodd-Frank Act	Dodd-Frank Wall Street Reform and Consumer Protection Act
EPA	United States Environmental Protection Agency
Exchange Act	Securities Exchange Act of 1934, as amended
FASB	Financial Accounting Standards Board
FERC	Federal Energy Regulatory Commission
Fidelity	Fidelity Exploration & Production Company, a direct wholly owned subsidiary of WBI Holdings (previously referred to as the Company's exploration and production segment)
GAAP	Accounting principles generally accepted in the United States of America
GHG	Greenhouse gas
Great Plains	Great Plains Natural Gas Co., a public utility division of Montana-Dakota
IBEW	International Brotherhood of Electrical Workers
ICWU	International Chemical Workers Union
Intermountain	Intermountain Gas Company, an indirect wholly owned subsidiary of MDU Energy Capital
IPUC	Idaho Public Utilities Commission
Knife River	Knife River Corporation, a direct wholly owned subsidiary of Centennial
kWh	Kilowatt-hour
LIBOR	London Inter-bank Offered Rate
MD&A	Management's Discussion and Analysis of Financial Condition and Results of Operations
MDU Construction Services	MDU Construction Services Group, Inc., a direct wholly owned subsidiary of Centennial
MDU Energy Capital	MDU Energy Capital, LLC, a direct wholly owned subsidiary of the Company
MISO	Midcontinent Independent System Operator, Inc.
MMcf	Million cubic feet
MMdk	Million dk
MNPUC	Minnesota Public Utilities Commission
Montana-Dakota	Montana-Dakota Utilities Co., a direct wholly owned subsidiary of MDU Energy Capital
MW	Megawatt
NDDEQ	North Dakota Department of Environmental Quality

3

NDPSC	North Dakota Public Service Commission
NERC	North American Electricity Reliability Corporation
Non-GAAP	Not in accordance with GAAP
Oil	Includes crude oil and condensate
PHMSA	Pipeline and Hazardous Materials Safety Administration
Regional Haze Rule	The EPA developed the Regional Haze Rule requiring states to develop and implement comprehensive plans to reduce human-caused regional haze in designated areas such as national parks and wilderness areas.
SDPUC	South Dakota Public Utilities Commission
SEC	United States Securities and Exchange Commission
Securities Act	Securities Act of 1933, as amended
SOFR	Secured Overnight Financing Rate
SPP	Southwest Power Pool, the organization that manages the electric grid and wholesale power market for the central United States.
TSA	Transportation Security Administration
VIE	Variable interest entity
WBI Holdings	WBI Holdings, Inc., a direct wholly owned subsidiary of Centennial
WUTC	Washington Utilities and Transportation Commission

4

Introduction

The Company is a regulated energy delivery and construction materials and services business. The organizational entity was originally incorporated as Montana-Dakota under the state laws of Delaware in 1924. Pursuant to an internal holding company reorganization completed on January 1, 2019, the Company was incorporated under the state laws of Delaware. Its principal executive offices are located at 1200 West Century Avenue, P.O. Box 5650, Bismarck, North Dakota 58506-5650, telephone (701) 530-1000.

The Company's strategy is to deliver superior value with a two-platform model, regulated energy delivery and construction materials and services businesses, while also pursuing organic growth opportunities and using a disciplined approach to strategic acquisitions of well-managed companies and properties.

The Company focuses on infrastructure and is Building a Strong America® by providing essential products and services through its regulated energy delivery and construction materials and services platforms, which are both comprised of different operating segments. Most of these segments experience seasonality related to the industries in which they operate. The two-platform approach helps balance this seasonality and the risk associated with each type of industry. Through its regulated energy delivery platform, the Company generates, transmits and distributes electricity and provides natural gas distribution, transportation and storage services. These businesses are regulated by state public service commissions and/or the FERC. The construction materials and services platform provides construction services to a variety of industries, including commercial, industrial and governmental customers, and provides construction materials through aggregate mining and marketing of related products, such as ready-mixed concrete, asphalt and asphalt oil.

The Company is organized into five reportable business segments. These business segments include: electric, natural gas distribution, pipeline, construction materials and contracting, and construction services. The Company's business segments are determined 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 segments is defined based on the reporting and review process used by the Company's chief executive officer.

The Company, through its wholly owned subsidiary, MDU Energy Capital, owns Montana-Dakota, Cascade and Intermountain. The electric segment is comprised of Montana-Dakota while the natural gas distribution segment is comprised of Montana-Dakota, Cascade and Intermountain.

The Company, through its wholly owned subsidiary, Centennial, owns WBI Holdings, Knife River, MDU Construction Services and Centennial Capital. WBI Holdings is the pipeline segment, Knife River is the construction materials and contracting segment, MDU Construction Services is the construction services segment and Centennial Capital is reflected in the Other category.

For more information on the Company's business segments, see Note 17 of the Notes to Consolidated Financial Statements.

5

Part I -- Financial Information

Item 1. Financial Statements

MDU Resources Group, Inc.
Consolidated Statements of Income
(Unaudited)
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands, except per share amounts)
Operating revenues:
Electric, natural gas distribution and regulated pipeline	$	260,568	$	241,353	$	702,951	$	660,035
Non-regulated pipeline, construction materials and contracting, construction services and other	1,163,089		1,121,575		1,948,644		1,900,267
Total operating revenues	1,423,657		1,362,928		2,651,595		2,560,302
Operating expenses:
Operation and maintenance:
Electric, natural gas distribution and regulated pipeline	89,404		83,103		183,737		170,712
Non-regulated pipeline, construction materials and contracting, construction services and other	988,392		946,068		1,705,717		1,679,459
Total operation and maintenance	1,077,796		1,029,171		1,889,454		1,850,171
Purchased natural gas sold	63,213		56,844		239,450		222,256
Depreciation, depletion and amortization	73,661		71,508		147,384		140,747
Taxes, other than income	53,189		52,584		115,724		116,696
Electric fuel and purchased power	18,109		14,567		36,730		35,107
Total operating expenses	1,285,968		1,224,674		2,428,742		2,364,977
Operating income	137,689		138,254		222,853		195,325
Other income	9,027		10,063		12,381		9,058
Interest expense	23,381		24,818		46,835		49,371
Income before income taxes	123,335		123,499		188,399		155,012
Income taxes	23,164		23,657		36,112		29,631
Income from continuing operations	100,171		99,842		152,287		125,381
Income (loss) from discontinued operations, net of tax	19		(139)		34		(548)
Net income	$	100,190	$	99,703	$	152,321	$	124,833
Earnings per share - basic:
Income from continuing operations	$	.50	$	.50	$	.76	$	.62
Discontinued operations, net of tax	—		—		—		—
Earnings per share - basic	$	.50	$	.50	$	.76	$	.62
Earnings per share - diluted:
Income from continuing operations	$	.50	$	.50	$	.76	$	.62
Discontinued operations, net of tax	—		—		—		—
Earnings per share - diluted	$	.50	$	.50	$	.76	$	.62
Weighted average common shares outstanding - basic	201,345		200,522		201,028		200,481
Weighted average common shares outstanding - diluted	201,693		200,539		201,328		200,497

The accompanying notes are an integral part of these consolidated financial statements.

6

MDU Resources Group, Inc.
Consolidated Statements of Comprehensive Income
(Unaudited)
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Net income	$	100,190	$	99,703	$	152,321	$	124,833
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, net of tax of $36 and $36 for the three months ended and $73 and $72 for the six months ended in 2021 and 2020, respectively	112		112		223		223
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax of $160 and $155 for the three months ended and $311 and $304 for the six months ended in 2021 and 2020, respectively	457		480		923		942
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax of $(13) and $(4) for the three months ended and $(25) and $32 for the six months ended in 2021 and 2020, respectively	(52)		(13)		(96)		122
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax of $6 and $2 for the three months ended and $15 and $2 for the six months ended in 2021 and 2020, respectively	25		7		60		6
Net unrealized gain (loss) on available-for-sale investments	(27)		(6)		(36)		128
Other comprehensive income	542		586		1,110		1,293
Comprehensive income attributable to common stockholders	$	100,732	$	100,289	$	153,431	$	126,126

The accompanying notes are an integral part of these consolidated financial statements.

7

MDU Resources Group, Inc.
Consolidated Balance Sheets
(Unaudited)
	June 30, 2021		June 30, 2020		December 31, 2020
Assets	(In thousands, except shares and per share amounts)
Current assets:
Cash and cash equivalents	$	57,946	$	64,358	$	59,547
Receivables, net	903,831		920,824		873,986
Inventories	316,328		302,837		291,167
Current regulatory assets	109,581		60,557		68,527
Prepayments and other current assets	74,259		48,194		44,120
Total current assets	1,461,945		1,396,770		1,337,347
Noncurrent assets:
Property, plant and equipment	8,417,559		8,063,435		8,300,770
Less accumulated depreciation, depletion and amortization	3,129,717		3,064,833		3,133,831
Net property, plant and equipment	5,287,842		4,998,602		5,166,939
Goodwill	717,863		708,664		714,963
Other intangible assets, net	23,401		31,515		25,496
Regulatory assets	376,913		351,025		379,381
Investments	173,157		154,779		165,022
Operating lease right-of-use assets	112,437		115,751		120,113
Other	144,653		154,026		144,111
Total noncurrent assets	6,836,266		6,514,362		6,716,025
Total assets	$	8,298,211	$	7,911,132	$	8,053,372
Liabilities and Stockholders' Equity
Current liabilities:
Short-term borrowings	$	50,000	$	75,000	$	50,000
Long-term debt due within one year	1,549		16,560		1,555
Accounts payable	431,878		433,362		426,264
Taxes payable	78,805		80,882		88,844
Dividends payable	42,791		41,608		42,611
Accrued compensation	95,909		85,525		90,629
Regulatory liabilities due within one year	23,454		48,000		31,450
Operating lease liabilities due within one year	31,787		31,985		33,655
Other accrued liabilities	188,187		186,797		198,514
Total current liabilities	944,360		999,719		963,522
Noncurrent liabilities:
Long-term debt	2,335,500		2,265,316		2,211,575
Deferred income taxes	538,633		516,760		516,098
Asset retirement obligations	450,620		422,169		440,356
Regulatory liabilities	428,467		438,652		428,075
Operating lease liabilities	81,052		84,302		86,868
Other	320,777		286,527		327,773
Total noncurrent liabilities	4,155,049		4,013,726		4,010,745
Commitments and contingencies
Stockholders' equity:
Common stock Authorized - 500,000,000 shares, $1.00 par value Shares issued - 202,822,301 at June 30, 2021, 201,061,198 at June 30, 2020 and 201,061,198 at December 31, 2020	202,822		201,061		201,061
Other paid-in capital	1,422,169		1,363,182		1,371,385
Retained earnings	1,624,405		1,377,879		1,558,363
Accumulated other comprehensive loss	(46,968)		(40,809)		(48,078)
Treasury stock at cost - 538,921 shares	(3,626)		(3,626)		(3,626)
Total stockholders' equity	3,198,802		2,897,687		3,079,105
Total liabilities and stockholders' equity	$	8,298,211	$	7,911,132	$	8,053,372

The accompanying notes are an integral part of these consolidated financial statements.

8

MDU Resources Group, Inc.
Consolidated Statements of Equity
(Unaudited)
				Other Paid-in Capital		Retained Earnings		Accumu-lated Other Compre-hensive Loss
	Common Stock									Treasury Stock
	Shares	Amount								Shares	Amount		Total
	(In thousands, except shares)
At December 31, 2020	201,061,198	$	201,061	$	1,371,385	$	1,558,363	$	(48,078)	(538,921)	$	(3,626)	$	3,079,105
Net income	—	—		—		52,131		—		—	—		52,131
Other comprehensive income	—	—		—		—		568		—	—		568
Dividends declared on common stock	—	—		—		(42,943)		—		—	—		(42,943)
Stock-based compensation	—	—		2,574		—		—		—	—		2,574
Repurchase of common stock	—	—		—		—		—		(392,294)	(6,701)		(6,701)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	—	—		(10,828)		—		—		392,294	6,701		(4,127)
Issuance of common stock	672,260	672		19,027		—		—		—	—		19,699
At March 31, 2021	201,733,458	$	201,733	$	1,382,158	$	1,567,551	$	(47,510)	(538,921)	$	(3,626)	$	3,100,306
Net income	—	—		—		100,190		—		—	—		100,190
Other comprehensive income	—	—		—		—		542		—	—		542
Dividends declared on common stock	—	—		—		(43,336)		—		—	—		(43,336)
Stock-based compensation	—	—		6,150		—		—		—	—		6,150
Issuance of common stock	1,088,843	1,089		33,861		—		—		—	—		34,950
At June 30, 2021	202,822,301	$	202,822	$	1,422,169	$	1,624,405	$	(46,968)	(538,921)	$	(3,626)	$	3,198,802

				Other Paid-in Capital		Retained Earnings		Accumu-lated Other Compre-hensive Loss
	Common Stock									Treasury Stock
	Shares	Amount								Shares	Amount		Total
	(In thousands, except shares)
At December 31, 2019	200,922,790	$	200,923	$	1,355,404	$	1,336,647	$	(42,102)	(538,921)	$	(3,626)	$	2,847,246
Net income	—	—		—		25,130		—		—	—		25,130
Other comprehensive income	—	—		—		—		707		—	—		707
Dividends declared on common stock	—	—		—		(41,789)		—		—	—		(41,789)
Stock-based compensation	—	—		2,250		—		—		—	—		2,250
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	26,406	26		(388)		—		—		—	—		(362)
Issuance of common stock	112,002	112		3,298		—		—		—	—		3,410
At March 31, 2020	201,061,198	$	201,061	$	1,360,564	$	1,319,988	$	(41,395)	(538,921)	$	(3,626)	$	2,836,592
Net income	—	—		—		99,703		—		—	—		99,703
Other comprehensive income	—	—		—		—		586		—	—		586
Dividends declared on common stock	—	—		—		(41,812)		—		—	—		(41,812)
Stock-based compensation	—	—		2,618		—		—		—	—		2,618
At June 30, 2020	201,061,198	$	201,061	$	1,363,182	$	1,377,879	$	(40,809)	(538,921)	$	(3,626)	$	2,897,687

The accompanying notes are an integral part of these consolidated financial statements.

9

MDU Resources Group, Inc.
Consolidated Statements of Cash Flows
(Unaudited)
	Six Months Ended
	June 30,
	2021		2020
	(In thousands)
Operating activities:
Net income	$	152,321	$	124,833
Income (loss) from discontinued operations, net of tax	34		(548)
Income from continuing operations	152,287		125,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	147,384		140,747
Deferred income taxes	14,498		2,881
Changes in current assets and liabilities, net of acquisitions:
Receivables	(18,516)		(40,801)
Inventories	(25,330)		(26,276)
Other current assets	(52,768)		30,790
Accounts payable	(3,845)		13,387
Other current liabilities	(22,605)		26,612
Other noncurrent changes	(8,236)		(10,923)
Net cash provided by continuing operations	182,869		261,798
Net cash used in discontinued operations	(58)		(396)
Net cash provided by operating activities	182,811		261,402
Investing activities:
Capital expenditures	(261,937)		(248,800)
Acquisitions, net of cash acquired	(13,721)		(70,729)
Net proceeds from sale or disposition of property and other	12,402		22,968
Investments	(3,244)		23
Net cash used in investing activities	(266,500)		(296,538)
Financing activities:
Issuance of short-term borrowings	50,000		75,000
Repayment of short-term borrowings	(50,000)		—
Issuance of long-term debt	171,769		200,400
Repayment of long-term debt	(48,151)		(162,225)
Proceeds from issuance of common stock	54,649		3,410
Dividends paid	(85,351)		(83,188)
Repurchase of common stock	(6,701)		—
Tax withholding on stock-based compensation	(4,127)		(362)
Net cash provided by financing activities	82,088		33,035
Decrease in cash and cash equivalents	(1,601)		(2,101)
Cash and cash equivalents -- beginning of year	59,547		66,459
Cash and cash equivalents -- end of period	$	57,946	$	64,358

The accompanying notes are an integral part of these consolidated financial statements.

10

MDU Resources Group, Inc.

Notes to Consolidated

Financial Statements

June 30, 2021 and 2020

(Unaudited)

Note 1 - Basis of presentation

The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2020 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses.

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 our country and our communities and, as a result, operations have generally continued throughout 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 six months ended June 30, 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. 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.

Management has also evaluated the impact of events occurring after June 30, 2021, up to the date of the issuance of these consolidated interim financial statements on August 5, 2021, that would require recognition or disclosure in the financial statements.

Note 2 - New accounting standards

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, clarified 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 effect a one percentage point change in assumed health care cost trend rates would have on certain benefit components. The Company adopted the guidance on January 1, 2021, on a retrospective basis. The Company determined the new guidance will 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. The Company adopted the guidance on January 1, 2021, and determined it did not have a material impact on 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 applied 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. LIBOR is expected to be retired with a full phase-out by the end of 2021 and replaced by a new reference rate, which includes SOFR. The guidance can be applied beginning in the interim period that includes March 12, 2020, and cannot be applied to contract modifications or hedging relationships entered into or evaluated after 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.

11

Note 3 - Seasonality of operations

Some of the Company's operations are highly seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Accordingly, the interim results for particular businesses, and for the Company as a whole, may not be indicative of results for the full fiscal year.

Note 4 - Receivables and allowance for expected credit losses

Receivables consists primarily of trade receivables from the sale of goods and services, which are recorded at the invoiced amount, and contract assets, net of expected credit losses. For more information on contract assets, see Note 9. The Company's trade receivables are all due in 12 months or less. The total balance of receivables past due 90 days or more was $34.2 million, $45.1 million and $43.9 million at June 30, 2021 and 2020, and December 31, 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, general economic conditions of the various local economies and impacts of COVID-19, among others. Specific account balances are written off when management determines the amounts to be uncollectible. Management has reviewed the balance reserved through the allowance for expected credit losses and believes it is reasonable.

Details of the Company's expected credit losses were as follows:

	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Total
	(In thousands)
At December 31, 2020	$	899	$	2,571	$	2	$	6,164	$	5,722	$	15,358
Current expected credit loss provision	538		1,273		—		(1,049)		(1,079)		(317)
Less write-offs charged against the allowance	888		1,107		—		273		401		2,669
Credit loss recoveries collected	129		213		—		—		—		342
At March 31, 2021	$	678	$	2,950	$	2	$	4,842	$	4,242	$	12,714
Current expected credit loss provision	(110)		(103)		—		11		(639)		(841)
Less write-offs charged against the allowance	341		787		—		232		64		1,424
Credit loss recoveries collected	100		199		—		—		—		299
At June 30, 2021	$	327	$	2,259	$	2	$	4,621	$	3,539	$	10,748

	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	555		1,156		—		694		1,150		3,555
Less write-offs charged against the allowance	500		624		—		68		73		1,265
Credit loss recoveries collected	109		229		—		—		—		338
At March 31, 2020	$	492	$	1,817	$	—	$	5,983	$	2,833	$	11,125
Current expected credit loss provision	303		190		—		(314)		896		1,075
Less write-offs charged against the allowance	224		677		—		44		454		1,399
Credit loss recoveries collected	88		201		—		—		—		289
At June 30, 2020	$	659	$	1,531	$	—	$	5,625	$	3,275	$	11,090

12

Note 5 - Inventories and natural gas in storage

Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method. The portion of the cost of natural gas in storage expected to be used within 12 months was included in inventories. Inventories on the Consolidated Balance Sheets were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Aggregates held for resale	$	183,977	$	165,357	$	175,782
Asphalt oil	51,500		57,207		28,238
Materials and supplies	27,969		27,805		25,142
Merchandise for resale	26,871		22,974		21,087
Natural gas in storage (current)	10,824		11,776		21,919
Other	15,187		17,718		18,999
Total	$	316,328	$	302,837	$	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 June 30, 2021 and December 31, 2020, and $48.3 million at June 30, 2020.

Note 6 - Earnings per share

Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands, except per share amounts)
Weighted average common shares outstanding - basic	201,345		200,522		201,028		200,481
Effect of dilutive performance share awards and restricted stock units	348		17		300		16
Weighted average common shares outstanding - diluted	201,693		200,539		201,328		200,497
Shares excluded from the calculation of diluted earnings per share	—		187		—		191
Dividends declared per common share	$	.2125	$	.2075	$	.4250	$	.4150

Note 7 - Equity

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.

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 this agreement. As of June 30, 2021, the Company had capacity to issue up to 4.6 million additional shares of common stock under the "at-the-market" offering program.

13

Details of the Company's "at-the-market" offering activity was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Shares issued	1.1		—		1.8		—
Net proceeds *	$	34.9	$	—	$	54.6	$	—
Issuance costs	$	.4	$	—	$	.7	$	—

*    Net proceeds were used for capital expenditures.

Note 8 - Accumulated other comprehensive loss

The after-tax changes in the components of accumulated other comprehensive loss were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  Liability Adjustment		Net Unrealized Gain (Loss) on Available-for-sale Investments		Total Accumulated  Other Comprehensive  Loss
	(In thousands)
At December 31, 2020	$	(984)	$	(47,207)	$	113	$	(48,078)
Other comprehensive loss before reclassifications	—		—		(44)		(44)
Amounts reclassified from accumulated other comprehensive loss	111		466		35		612
Net current-period other comprehensive income (loss)	111		466		(9)		568
At March 31, 2021	$	(873)	$	(46,741)	$	104	$	(47,510)
Other comprehensive loss before reclassifications	—		—		(52)		(52)
Amounts reclassified from accumulated other comprehensive loss	112		457		25		594
Net current-period other comprehensive income (loss)	112		457		(27)		542
At June 30, 2021	$	(761)	$	(46,284)	$	77	$	(46,968)

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  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 income before reclassifications	—		—		135		135
Amounts reclassified from (to) accumulated other comprehensive loss	111		462		(1)		572
Net current-period other comprehensive income	111		462		134		707
At March 31, 2020	$	(1,319)	$	(40,272)	$	196	$	(41,395)
Other comprehensive loss before reclassifications	—		—		(13)		(13)
Amounts reclassified from accumulated other comprehensive loss	112		480		7		599
Net current-period other comprehensive income (loss)	112		480		(6)		586
At June 30, 2020	$	(1,207)	$	(39,792)	$	190	$	(40,809)

14

The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows:

	Three Months Ended				Six Months Ended				Location on Consolidated Statements of Income
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Reclassification adjustment for loss on derivative instruments included in net income	$	(148)	$	(148)	$	(296)	$	(295)	Interest expense
	36		36		73		72		Income taxes
	(112)		(112)		(223)		(223)
Amortization of postretirement liability losses included in net periodic benefit cost	(617)		(635)		(1,234)		(1,246)		Other income
	160		155		311		304		Income taxes
	(457)		(480)		(923)		(942)
Reclassification adjustment on available-for-sale investments included in net income	(31)		(9)		(75)		(8)		Other income
	6		2		15		2		Income taxes
	(25)		(7)		(60)		(6)
Total reclassifications	$	(594)	$	(599)	$	(1,206)	$	(1,171)

Note 9 - 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.

Disaggregation

In the following tables, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 17.

Three Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	29,258	$	83,480	$	—	$	—	$	—	$	—	$	112,738
Commercial utility sales	33,834		47,612		—		—		—		—		81,446
Industrial utility sales	10,354		6,180		—		—		—		—		16,534
Other utility sales	1,825		—		—		—		—		—		1,825
Natural gas transportation	—		11,451		27,685		—		—		—		39,136
Natural gas storage	—		—		3,094		—		—		—		3,094
Contracting services	—		—		—		280,834		—		—		280,834
Construction materials	—		—		—		498,762		—		—		498,762
Intrasegment eliminations	—		—		—		(145,780)		—		—		(145,780)
Inside specialty contracting	—		—		—		—		347,702		—		347,702
Outside specialty contracting	—		—		—		—		165,123		—		165,123
Other	9,465		2,794		4,810		—		57		3,389		20,515
Intersegment eliminations	(136)		(142)		(7,862)		(142)		(797)		(3,361)		(12,440)
Revenues from contracts with customers	84,600		151,375		27,727		633,674		512,085		28		1,409,489
Revenues out of scope	(950)		2,413		46		—		12,659		—		14,168
Total external operating revenues	$	83,650	$	153,788	$	27,773	$	633,674	$	524,744	$	28	$	1,423,657

15

Three Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	27,954	$	78,653	$	—	$	—	$	—	$	—	$	106,607
Commercial utility sales	29,877		41,027		—		—		—		—		70,904
Industrial utility sales	8,072		5,658		—		—		—		—		13,730
Other utility sales	1,591		—		—		—		—		—		1,591
Natural gas transportation	—		10,350		27,965		—		—		—		38,315
Natural gas gathering	—		—		1,181		—		—		—		1,181
Natural gas storage	—		—		3,104		—		—		—		3,104
Contracting services	—		—		—		303,356		—		—		303,356
Construction materials	—		—		—		482,498		—		—		482,498
Intrasegment eliminations	—		—		—		(164,719)		—		—		(164,719)
Inside specialty contracting	—		—		—		—		324,921		—		324,921
Outside specialty contracting	—		—		—		—		160,696		—		160,696
Other	7,717		2,711		3,363		—		412		2,861		17,064
Intersegment eliminations	(196)		(185)		(7,999)		(90)		(779)		(2,973)		(12,222)
Revenues from contracts with customers	75,015		138,214		27,614		621,045		485,250		(112)		1,347,026
Revenues out of scope	1,423		3,280		44		—		11,155		—		15,902
Total external operating revenues	$	76,438	$	141,494	$	27,658	$	621,045	$	496,405	$	(112)	$	1,362,928

Six Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	62,694	$	286,617	$	—	$	—	$	—	$	—	$	349,311
Commercial utility sales	66,762		167,664		—		—		—		—		234,426
Industrial utility sales	20,383		14,992		—		—		—		—		35,375
Other utility sales	3,391		—		—		—		—		—		3,391
Natural gas transportation	—		23,903		57,102		—		—		—		81,005
Natural gas storage	—		—		7,123		—		—		—		7,123
Contracting services	—		—		—		376,859		—		—		376,859
Construction materials	—		—		—		715,174		—		—		715,174
Intrasegment eliminations	—		—		—		(192,496)		—		—		(192,496)
Inside specialty contracting	—		—		—		—		702,892		—		702,892
Outside specialty contracting	—		—		—		—		316,486		—		316,486
Other	19,238		5,803		7,470		—		93		6,730		39,334
Intersegment eliminations	(271)		(284)		(34,092)		(204)		(1,839)		(6,685)		(43,375)
Revenues from contracts with customers	172,197		498,695		37,603		899,333		1,017,632		45		2,625,505
Revenues out of scope	(3,873)		5,299		82		—		24,582		—		26,090
Total external operating revenues	$	168,324	$	503,994	$	37,685	$	899,333	$	1,042,214	$	45	$	2,651,595

16

Six Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	60,303	$	265,354	$	—	$	—	$	—	$	—	$	325,657
Commercial utility sales	63,464		156,023		—		—		—		—		219,487
Industrial utility sales	18,439		14,179		—		—		—		—		32,618
Other utility sales	3,239		—		—		—		—		—		3,239
Natural gas transportation	—		22,148		55,397		—		—		—		77,545
Natural gas gathering	—		—		3,271		—		—		—		3,271
Natural gas storage	—		—		6,150		—		—		—		6,150
Contracting services	—		—		—		401,757		—		—		401,757
Construction materials	—		—		—		690,408		—		—		690,408
Intrasegment eliminations	—		—		—		(208,823)		—		—		(208,823)
Inside specialty contracting	—		—		—		—		697,130		—		697,130
Outside specialty contracting	—		—		—		—		290,846		—		290,846
Other	16,167		5,209		6,604		—		763		5,852		34,595
Intersegment eliminations	(391)		(370)		(33,198)		(152)		(3,249)		(5,946)		(43,306)
Revenues from contracts with customers	161,221		462,543		38,224		883,190		985,490		(94)		2,530,574
Revenues out of scope	1,125		5,394		89		—		23,120		—		29,728
Total external operating revenues	$	162,346	$	467,937	$	38,313	$	883,190	$	1,008,610	$	(94)	$	2,560,302

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:

	June 30, 2021		December 31, 2020		Change		Location on Consolidated Balance Sheets
	(In thousands)
Contract assets	$	147,033	$	104,345	$	42,688	Receivables, net
Contract liabilities - current	(146,116)		(158,603)		12,487		Accounts payable
Contract liabilities - noncurrent	(160)		(52)		(108)		Noncurrent liabilities - other
Net contract assets (liabilities)	$	757	$	(54,310)	$	55,067

The Company recognized $21.9 million and $145.3 million in revenue for the three and six months ended June 30, 2021, respectively, which was previously included in contract liabilities at December 31, 2020. The Company recognized $32.3 million and $121.7 million in revenue for the three and six months ended June 30, 2020, respectively, which was previously included in contract liabilities at December 31, 2019.

The Company recognized a net increase in revenues of $27.3 million and $54.6 million for the three and six months ended June 30, 2021, respectively, from performance obligations satisfied in prior periods. The Company recognized a net increase in revenues of $31.9 million and $42.9 million for the three and six months ended June 30, 2020, respectively, from performance obligations satisfied in prior periods.

17

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, which does not require additional disclosures for contracts with an original duration of less than 12 months, to certain firm transportation and non-regulated contracts. The Company's firm transportation and firm storage contracts included in the remaining performance obligations have weighted average remaining durations of approximately five and one years, respectively.

At June 30, 2021, the Company's remaining performance obligations were $2.4 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; $339.5 million within the next 13 to 24 months; and $225.9 million in 25 months or more.

Note 10 - Business combinations

The following acquisitions were accounted for as business combinations in accordance with ASC 805 - Business Combinations. The results of the acquired businesses have been included in the 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:

•Mt. Hood Rock, a construction aggregates business in Oregon, was acquired in April 2021. At June 30, 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, were acquired in December 2020. At June 30, 2021, the purchase price allocation was preliminary and will be finalized within 12 months of the acquisition date. In the second quarter of 2021, the Company made a purchase price adjustment, which was not material, to the provisional accounting and is reflected in the 2021 allocated amounts below.

•The assets of Oldcastle Infrastructure Spokane, a prestressed-concrete business in Washington, were 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.

In 2021, the total purchase price for acquisitions was $13.8 million, subject to certain adjustments, with cash acquired totaling $100,000. The purchase price includes consideration paid of $13.7 million. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2021 were as follows: $700,000 to current assets; $13.0 million to property, plant and equipment; $2.9 million to goodwill; $600,000 to other intangible assets; $200,000 to current liabilities; $100,000 to noncurrent liabilities and $3.2 million to deferred tax liabilities. The Company issued debt to finance the acquisitions.

In 2020, the total purchase price for acquisitions 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 Company issued debt to finance the acquisitions.

Costs incurred for acquisitions are included in operation and maintenance expense on the Consolidated Statements of Income and were not material for the six months ended June 30, 2021 and 2020.

18

Note 11 - Leases

The Company's leases primarily include operating leases for equipment, buildings, easements and vehicles. The Company leases certain equipment to third parties through its utility and construction services segments, which are considered short-term operating leases with terms of less than 12 months.

The Company recognized revenue from operating leases of $12.8 million and $24.8 million for the three and six months ended June 30, 2021, respectively. The Company recognized revenue from operating leases of $11.2 million and $23.3 million for the three and six months ended June 30, 2020, respectively. At June 30, 2021, the Company had $9.8 million of lease receivables with a majority due within 12 months.

Note 12 - 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 June 30, 2021
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	226,003		2,900		—		228,903
Construction services	143,224		—		—		143,224
Total	$	714,963	$	2,900	$	—	$	717,863

	Balance at January 1, 2020		Goodwill Acquired During the Year		Measurement Period Adjustments		Balance at June 30, 2020
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	217,234		6,483		—		223,717
Construction services	118,388		24,436		(3,613)		139,211
Total	$	681,358	$	30,919	$	(3,613)	$	708,664

	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 were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Customer relationships	$	29,423	$	30,087	$	28,836
Less accumulated amortization	8,765		5,239		6,887
	20,658		24,848		21,949
Noncompete agreements	3,991		4,229		3,941
Less accumulated amortization	2,576		2,084		2,309
	1,415		2,145		1,632
Other	11,957		13,060		12,927
Less accumulated amortization	10,629		8,538		11,012
	1,328		4,522		1,915
Total	$	23,401	$	31,515	$	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 10.

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Amortization expense for amortizable intangible assets for the three and six months ended June 30, 2021, was $1.2 million and $2.7 million, respectively. Amortization expense for amortizable intangible assets for the three and six months ended June 30, 2020, was $2.7 million and $4.7 million, respectively. Estimated amortization expense for identifiable intangible assets as of June 30, 2021, was:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Amortization expense	$	2,381	$	4,678	$	4,329	$	3,957	$	2,060	$	5,996

Note 13 - Regulatory assets and liabilities

The following table summarizes the individual components of unamortized regulatory assets and liabilities:

	Estimated Recovery or Refund Period as of June 30, 2021	*	June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Regulatory assets:
Current:
Natural gas costs recoverable through rate adjustments	Up to 1 year		$	85,045	$	42,582	$	42,481
Conservation programs	Up to 1 year		7,580		7,256		7,117
Cost recovery mechanisms	Up to 1 year		5,692		7,781		10,645
Other	Up to 1 year		11,264		2,938		8,284
			109,581		60,557		68,527
Noncurrent:
Pension and postretirement benefits	**		155,906		157,033		155,942
Plant costs/asset retirement obligations	Over plant lives		72,853		68,191		71,740
Plant retirement	-		46,061		49,185		65,919
Cost recovery mechanisms	Up to 10 years		44,415		13,140		16,245
Manufactured gas plant site remediation	-		26,155		14,826		26,429
Taxes recoverable from customers	Over plant lives		10,929		10,890		10,785
Natural gas costs recoverable through rate adjustments	Up to 3 years		8,389		27,184		21,539
Long-term debt refinancing costs	Up to 39 years		4,110		3,980		4,426
Other	Up to 18 years		8,095		6,596		6,356
			376,913		351,025		379,381
Total regulatory assets			$	486,494	$	411,582	$	447,908
Regulatory liabilities:
Current:
Natural gas costs refundable through rate adjustments	Up to 1 year		$	8,935	$	29,557	$	18,565
Electric fuel and purchased power deferral	Up to 1 year		5,431		7,799		3,667
Taxes refundable to customers	Up to 1 year		3,434		4,012		3,557
Other	Up to 1 year		5,654		6,632		5,661
			23,454		48,000		31,450
Noncurrent:
Taxes refundable to customers	Over plant lives		222,098		236,142		227,850
Plant removal and decommissioning costs	Over plant lives		171,381		173,399		167,171
Pension and postretirement benefits	**		16,940		18,015		16,989
Other	Up to 21 years		18,048		11,096		16,065
			428,467		438,652		428,075
Total regulatory liabilities			$	451,921	$	486,652	$	459,525
Net regulatory position			$	34,573	$	(75,070)	$	(11,617)

*Estimated recovery or refund period for amounts currently being recovered or refunded in rates charged to customers.

**    Recovered as expense is incurred or cash contributions are made.

At June 30, 2021 and 2020, and December 31, 2020, approximately $317.0 million, $296.6 million and $332.5 million, respectively, of regulatory assets were not earning a rate of return; however, these regulatory assets are expected to be recovered from customers in future rates. These assets are largely comprised of the unfunded portion of pension and postretirement benefits,

20

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 February 2021 in order to maintain services for its customers. These extraordinary gas costs were recorded as regulatory assets as they are expected to be recovered from customers. The Company has filed out-of-cycle purchased gas adjustment requests in four out of five jurisdictions affected by this cold-weather event and has received approval in three jurisdictions. The Company will continue to engage with its regulators to determine the appropriate recovery periods over which to recover the associated natural gas costs. For a discussion of the Company's most recent cases by jurisdiction, see Note 19.

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 has 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 in the second quarter of 2021, the Company began amortizing plant retirement and closure costs related to this facility. Requests have been filed with the NDPSC and SDPUC to offset the savings associated with the cessation of operations of this unit with the amortization of the deferred regulatory assets. In the second quarter of 2021, the Company moved the costs being recovered for this facility from plant retirement to cost recovery mechanisms in the previous table. The remaining two units are expected to be retired in early 2022. The Company expects to recover the regulatory assets related to the plant retirements in future rates. For a discussion of the Company's most recent cases by jurisdiction, see Note 19.

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 income (loss) in the period in which the discontinuance of regulatory accounting occurs.

Note 14 - Fair value measurements

The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of insurance contracts, to satisfy its obligations under its unfunded, nonqualified defined benefit and defined contribution plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $105.7 million, $92.4 million and $100.1 million, at June 30, 2021 and 2020, and December 31, 2020, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gains on these investments were $3.8 million and $3.9 million for the three and six months ended June 30, 2021, respectively. The net unrealized gains on these investments were $9.1 million and $5.4 million for the three and six months ended June 30, 2020, 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 income (loss). Details of available-for-sale securities were as follows:

June 30, 2021	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	8,278	$	127	$	9	$	8,396
U.S. Treasury securities	2,893		—		21		2,872
Total	$	11,171	$	127	$	30	$	11,268

June 30, 2020	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	9,812	$	239	$	6	$	10,045
U.S. Treasury securities	1,170		7		—		1,177
Total	$	10,982	$	246	$	6	$	11,222

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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

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's money market funds are valued at the net asset value of shares held at the end of the quarter, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the Company's mortgage-backed securities and U.S. Treasury securities are based on comparable market transactions, other observable inputs or other sources, including pricing from outside sources. The estimated fair value of the Company's insurance contracts are based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data.

Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value.

The Company's assets measured at fair value on a recurring basis were as follows:

	Fair Value Measurements at June 30, 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 June 30, 2021
	(In thousands)
Assets:
Money market funds	$	—	$	12,234	$	—	$	12,234
Insurance contracts*	—		105,684				105,684
Available-for-sale securities:
Mortgage-backed securities	—		8,396		—		8,396
U.S. Treasury securities	—		2,872		—		2,872
Total assets measured at fair value	$	—	$	129,186	$	—	$	129,186

*    The insurance contracts invest approximately 53 percent in fixed-income investments, 20 percent in common stock of large-cap companies, 10 percent in common stock of mid-cap companies, 9 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents.

	Fair Value Measurements at June 30, 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 June 30, 2020
	(In thousands)
Assets:
Money market funds	$	—	$	8,478	$	—	$	8,478
Insurance contract*	—		92,413		—		92,413
Available-for-sale securities:
Mortgage-backed securities	—		10,045		—		10,045
U.S. Treasury securities	—		1,177		—		1,177
Total assets measured at fair value	$	—	$	112,113	$	—	$	112,113

*    The insurance contract invests approximately 38 percent in fixed-income investments, 23 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, 4 percent in target date investments and 17 percent in cash equivalents.

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	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 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 fair value assessments of the assets acquired and liabilities assumed in the business combinations that occurred during 2021 and 2020. The fair value of these assets and liabilities were determined based on Level 2 and Level 3 inputs.

The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was categorized as Level 2 in the fair value hierarchy and was based on discounted future cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Carrying amount	$	2,337,049	$	2,281,876	$	2,213,130
Fair value	$	2,616,232	$	2,563,734	$	2,537,289

The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values.

Note 15 - Debt

Certain debt instruments of the Company's subsidiaries 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 June 30, 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.

Montana-Dakota's and Centennial's 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 the 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.

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Long-term debt

Long-term Debt Outstanding Long-term debt outstanding was as follows:

	Weighted Average Interest Rate at June 30, 2021		June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Senior Notes due on dates ranging from October 22, 2022 to October 30, 2060	4.40	%	$	1,950,000	$	1,900,000	$	1,950,000
Commercial paper supported by revolving credit agreements	.32	%	297,400		290,100		125,600
Credit agreements due on June 7, 2024	3.25	%	48,550		11,200		95,900
Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029	7.32	%	35,000		50,000		35,000
Term Loan Agreement due on September 3, 2032	2.00	%	8,400		9,100		8,400
Other notes due on dates ranging from July 15, 2021 to January 1, 2061	.83	%	3,232		28,342		4,034
Less unamortized debt issuance costs			5,505		6,668		5,803
Less discount			28		198		1
Total long-term debt			2,337,049		2,281,876		2,213,130
Less current maturities			1,549		16,560		1,555
Net long-term debt			$	2,335,500	$	2,265,316	$	2,211,575

Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at June 30, 2021, were as follows:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Long-term debt maturities	$	752	$	148,021	$	77,921	$	407,372	$	177,802	$	1,530,714

Note 16 - Cash flow information

Cash expenditures for interest and income taxes were as follows:

	Six Months Ended
	June 30,
	2021		2020
	(In thousands)
Interest, net*	$	45,870	$	47,769
Income taxes paid, net	$	46,734	$	735

*    AFUDC - borrowed was $816,000 and $1.3 million for the six months ended June 30, 2021 and 2020, respectively.

Noncash investing and financing transactions were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Right-of-use assets obtained in exchange for new operating lease liabilities	$	17,224	$	24,181	$	54,356
Property, plant and equipment additions in accounts payable	$	31,886	$	36,493	$	26,082
Accrual for holdback payment related to a business combination	$	—	$	5,000	$	2,500

Note 17 - 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.

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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. In 2020, the pipeline segment divested its regulated and non-regulated natural gas gathering assets. With the completion of these sales, the segment exited the natural gas gathering business.

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-mixed 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, liquid asphalt 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, as well as Alaska and Hawaii.

The construction services segment provides inside and outside specialty contracting services in 43 states plus Washington D.C. Its inside services include design, construction and maintenance of electrical and communication wiring and infrastructure, fire suppression systems, and mechanical piping and services. Its outside services include design, construction and maintenance of overhead and underground electrical distribution and transmission lines, substations, external lighting, traffic signalization, and gas pipelines, as well as utility excavation and the manufacture and distribution of transmission line construction equipment. This segment also constructs and maintains renewable energy projects. These specialty contracting services are provided to utilities and large manufacturing, commercial, industrial, institutional and governmental customers.

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. The Other category also includes Centennial Resources' former investment in Brazil.

Discontinued operations include the results and supporting activities of Fidelity other than certain general and administrative costs and interest expense as described above.

The information below follows the same accounting policies as described in Note 2 of the Notes to Consolidated Financial Statements in the 2020 Annual Report. Information on the Company's segments was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
External operating revenues:
Regulated operations:
Electric	$	83,650	$	76,438	$	168,324	$	162,346
Natural gas distribution	153,788		141,494		503,994		467,937
Pipeline	23,130		23,421		30,633		29,752
	260,568		241,353		702,951		660,035
Non-regulated operations:
Pipeline	4,643		4,237		7,052		8,561
Construction materials and contracting	633,674		621,045		899,333		883,190
Construction services	524,744		496,405		1,042,214		1,008,610
Other	28		(112)		45		(94)
	1,163,089		1,121,575		1,948,644		1,900,267
Total external operating revenues	$	1,423,657	$	1,362,928	$	2,651,595	$	2,560,302

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	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Intersegment operating revenues:
Regulated operations:
Electric	$	136	$	196	$	271	$	391
Natural gas distribution	142		185		284		370
Pipeline	7,695		7,857		33,685		33,040
	7,973		8,238		34,240		33,801
Non-regulated operations:
Pipeline	167		142		407		158
Construction materials and contracting	142		90		204		152
Construction services	797		779		1,839		3,249
Other	3,361		2,973		6,685		5,946
	4,467		3,984		9,135		9,505
Intersegment eliminations	(12,440)		(12,222)		(43,375)		(43,306)
Total intersegment operating revenues	$	—	$	—	$	—	$	—
Operating income (loss):
Electric	$	12,806	$	12,810	$	26,672	$	27,669
Natural gas distribution	3,601		678		57,173		50,677
Pipeline	11,076		12,225		23,612		23,644
Construction materials and contracting	72,452		74,741		37,563		31,472
Construction services	37,774		37,882		78,051		61,678
Other	(20)		(82)		(218)		185
Total operating income	$	137,689	$	138,254	$	222,853	$	195,325
Net income (loss):
Regulated operations:
Electric	$	10,304	$	12,153	$	21,054	$	23,527
Natural gas distribution	(707)		(959)		35,471		31,410
Pipeline	8,089		8,684		17,283		16,070
	17,686		19,878		73,808		71,007
Non-regulated operations:
Pipeline	1,106		268		810		255
Construction materials and contracting	51,396		53,020		20,584		14,806
Construction services	28,885		27,932		58,709		44,755
Other	1,098		(1,256)		(1,624)		(5,442)
	82,485		79,964		78,479		54,374
Income from continuing operations	100,171		99,842		152,287		125,381
Income (loss) from discontinued operations, net of tax	19		(139)		34		(548)
Net income	$	100,190	$	99,703	$	152,321	$	124,833

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Note 18 - Employee benefit plans

Pension and other postretirement plans

The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit credit for the Company's pension and other postretirement benefit plans were as follows:

	Pension Benefits				Other Postretirement Benefits
Three Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	400	$	414
Interest cost	2,455		3,074		466		627
Expected return on assets	(4,894)		(5,214)		(1,275)		(1,401)
Amortization of prior service credit	—		—		(349)		(402)
Amortization of net actuarial loss	2,004		1,723		6		142
Net periodic benefit credit, including amount capitalized	(435)		(417)		(752)		(620)
Less amount capitalized	—		—		44		35
Net periodic benefit credit	$	(435)	$	(417)	$	(796)	$	(655)

	Pension Benefits				Other Postretirement Benefits
Six Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	800	$	766
Interest cost	4,910		6,047		932		1,218
Expected return on assets	(9,788)		(9,975)		(2,550)		(2,649)
Amortization of prior service credit	—		—		(698)		(699)
Amortization of net actuarial loss	4,008		3,586		12		144
Net periodic benefit credit, including amount capitalized	(870)		(342)		(1,504)		(1,220)
Less amount capitalized	—		—		83		67
Net periodic benefit credit	$	(870)	$	(342)	$	(1,587)	$	(1,287)

The components of net periodic benefit credit, other than the service cost component, are included in other income on the Consolidated Statements of Income. The service cost component is included in operation and maintenance expense on the Consolidated Statements of Income.

Nonqualified defined benefit plans

In addition to the qualified defined benefit pension plans reflected in the table at the beginning of this note, the Company also has unfunded, nonqualified defined benefit plans for executive officers and certain key management employees. The Company's net periodic benefit cost for these plans was $769,000 and $1.5 million for the three and six months ended June 30, 2021, respectively. The Company's net periodic benefit cost for these plans for the three and six months ended June 30, 2020 was $900,000 and $1.9 million, respectively. The components of net periodic benefit cost for these plans are included in other income on the Consolidated Statements of Income.

Note 19 - Regulatory matters

The Company regularly reviews the need for electric and natural gas rate changes in each of the jurisdictions in which service is provided. The Company files for rate adjustments to seek recovery of operating costs and capital investments, as well as reasonable returns as allowed by regulators. Certain regulatory proceedings and cases may also contain recurring mechanisms that can have an annual true-up. Examples of these recurring mechanisms include: infrastructure riders, transmission trackers, renewable resource cost adjustment riders, as well as weather normalization and decoupling mechanisms. The following paragraphs summarize the Company's significant open regulatory proceedings and cases by jurisdiction including updates to those reported in the 2020 Annual Report. 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.

IPUC

On January 12, 2021, Intermountain filed an application with the IPUC for a decrease in its depreciation and amortization rates of approximately $2.9 million annually or a decrease from a combined rate of 3.0 percent to 2.6 percent. On June 3, 2021, Intermountain filed a joint settlement agreement with the IPUC Staff reflecting a revised annual decrease of approximately $3.8 million or approximately 2.4 percent. Intermountain and the IPUC Staff have requested the rates be retroactive to January 1, 2021. This matter is pending before the IPUC.

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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 March 30, 2021, Great Plains filed an out-of-cycle cost of gas adjustment with the MNPUC for the recovery of approximately $11.1 million. 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 length of recovery was requested at 28 months with a rate structure that is higher in the summer and lower in the winter due to the lower gas usage in the summer to mitigate the impact on customers. On June 8, 2021, the Company's request was denied; however, the MNPUC initiated its own investigation into the impact of severe weather in February 2021 on Minnesota's natural gas utility companies and consumers. The investigation will address the recovery of the extraordinary gas costs resulting from the February 2021 extreme cold weather event. MNPUC deliberations on this matter are scheduled for August 5, 2021. This matter is pending before the MNPUC.

NDPSC

Montana-Dakota defers the difference between the actual cost of gas spent to serve customers and that recovered from customers on a monthly basis. Annually, Montana-Dakota prepares a true-up pursuant to the purchased gas adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the NDPSC for approximately $13.5 million. 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 filing was made to expedite recovery of these costs and maintain the timing of annual purchased gas adjustment filings. On May 27, 2021, the NDPSC approved the requested increase with a recovery period of 16 months effective June 1, 2021.

On July 15, 2021, Montana-Dakota filed an annual update to its transmission cost adjustment rider with the NDPSC requesting to recover revenues of approximately $14.5 million, which includes a true-up of the prior period adjustment, resulting in a decrease of approximately $1.1 million from current rates. This filing includes approximately $5.1 million related to transmission capital projects. This matter is pending before the NDPSC.

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. This matter is pending before the SDPUC.

WUTC

On June 19, 2020, Cascade filed an application with the WUTC for a natural gas rate increase of approximately $13.8 million annually or approximately 5.3 percent above current rates. The requested increase was primarily to recover investments made in infrastructure upgrades, as well as increased operation and maintenance costs. Cascade updated its filing on July 24, 2020, to approximately $14.3 million annually or approximately 5.5 percent. Cascade filed a rebuttal case on January 8, 2021, supporting an increase of approximately $7.4 million annually or approximately 2.8 percent. The revised revenue within the rebuttal case reflects several adjustments including depreciation, reduction to return on equity, delays on certain projects, adjustments to income taxes and updates to wages. On May 18, 2021, the WUTC issued a final order reflecting an overall revenue decrease of approximately $391,000 or approximately 0.2 percent. On May 25, 2021, Cascade filed a petition for reconsideration with the WUTC. On June 18, 2021, the WUTC denied Cascade's petition for reconsideration. Final rates were effective July 1, 2021.

On June 1, 2021, Cascade filed its annual pipeline cost recovery mechanism requesting an increase in annual revenue of approximately $2.1 million or approximately 0.8 percent. The filing includes a proposed effective date of November 1, 2021. This filing will be updated to more accurate data prior to the effective date. This matter is pending before the WUTC.

Note 20 - 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 June 30, 2021 and 2020, and December 31, 2020, the Company accrued liabilities which have not been discounted, including liabilities held for sale, of $30.8 million, $34.5 million and $41.5 million, respectively. At June 30, 2021 and 2020, and December 31, 2020, the Company also recorded corresponding insurance receivables of $6.9 million, $21.1 million and

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$17.5 million, respectively, and regulatory assets of $21.2 million, $10.4 million and $21.3 million, respectively, related to the accrued liabilities. The accruals are for contingencies, including 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

The Company is a party to claims for the cleanup of environmental contamination at certain manufactured gas plant sites, as well as a superfund site. There were no material changes to the Company's environmental matters that were previously reported in the 2020 Annual Report.

Guarantees

In 2009, multiple sale agreements were signed to sell the Company's ownership interests in the Brazilian Transmission Lines. In connection with the sale, Centennial agreed to guarantee payment of any indemnity obligations of certain of the Company's indirect wholly owned subsidiaries. The remaining guarantee is expected to expire in 2021. The guarantees were required by the buyers as a condition to the sale of the Brazilian Transmission Lines.

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 June 30, 2021, the fixed maximum amounts guaranteed under these agreements aggregated $171.2 million. Certain of the guarantees also have no fixed maximum amounts specified. At June 30, 2021, the amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $37.2 million in 2021; $67.7 million in 2022; $55.6 million in 2023; $500,000 in 2024; $500,000 in 2025; $700,000 thereafter; and $9.0 million, which has no scheduled maturity date. There were no amounts outstanding under the previously mentioned guarantees at June 30, 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 June 30, 2021, the fixed maximum amounts guaranteed under these letters of credit aggregated $25.5 million. At June 30, 2021, the amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $23.4 million in 2021 and $2.1 million in 2022. There were no amounts outstanding under the previously mentioned letters of credit at June 30, 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 June 30, 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 June 30, 2021, approximately $1.1 billion of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet.

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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 June 30, 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 $32.6 million.

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Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations

The Company focuses on infrastructure and is Building a Strong America® by providing essential products and services through its regulated energy delivery and construction materials and services businesses. The Company and its employees work hard to keep the economy of the United States moving with the products and services provided, which include powering, heating and connecting homes, factories, offices and stores; and building roads, highways, data infrastructure and airports.

The Company's two-platform business model, regulated energy delivery and construction materials and services, are each comprised of different operating segments. Most of these segments experience seasonality related to the industries in which they operate. The two-platform approach helps balance this seasonality and the risks associated with each type of industry. The Company is authorized to conduct business in 46 states and during peak times has employed over 15,600 employees. The Company's organic investments are strong drivers of high-quality earnings and continue to be an important part of the Company's growth. Management believes the Company is well positioned in the industries and markets in which it operates.

The Company continues to effectively execute its strategy while managing the ongoing effects of the COVID-19 pandemic. In early 2020, the Company implemented its business continuity plans as well as a task force to monitor developments related to the pandemic allowing the Company to continue to provide safe and reliable services during the pandemic. Most of the Company's products and services are considered essential to our country and our communities and, as a result, operations have generally continued throughout the pandemic and reopening of the economy.

In March 2020, the Company took measures to mitigate the risk of COVID-19 transmission by requiring employees that had the capacity to do so to work from home. The Company also enacted additional physical and cybersecurity measures to safeguard systems for remote work locations. As of July 2021, many of these employees have returned to their office; however, some employees have transitioned to a permanent remote work environment.

Certain of the Company's supply vendors are facing production and staffing challenges as they work to achieve production capacity and lead times consistent with pre-pandemic levels. Coupled with other challenges of the pandemic, these vendors are also experiencing strong demand from the residential construction market, some industrial segments and some utility infrastructure investments. In addition, freight markets continue to have challenges with driver shortages; strong demand for consumer goods; extended lead times; and costs for vehicles, driver retention and recruitment. The Company has implemented measures to proactively order supplies and work with additional suppliers to ensure work continues without delays; however, the Company has experienced some price increases, disruptions and delays on delivery of certain materials.

The situation surrounding COVID-19 remains fluid. There has been a trend in many parts of the world of increasing availability and administration of vaccines against COVID-19, as well as an easing of restrictions on individual, business and government activities. The easing of restrictions and the potential for a resurgence in COVID-19 cases due to variants of the virus entering the United States, could prompt a return to tighter restrictions in certain areas of the country. Due to the uncertainty of the economic outlook resulting from the COVID-19 pandemic, the Company continues to monitor the situation closely. Although there have been logistical and other challenges as a result of COVID-19, there were no material adverse impacts on the Company's results of operations for the six months ended June 30, 2021 or 2020. The Company will continue to adjust its business in response to the pandemic while positioning for potential opportunities to enhance its competitive position. For more information specific to each of the Company's business segments, see the following discussions in each business segment's Outlook section. For more information on the possible impacts, see Part II, Item 1A. Risk Factors in this Form 10-Q.

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Forward-Looking Statements

The following sections contain forward-looking statements within the meaning of Section 21E of the Exchange Act. Forward-looking statements are all statements other than statements of historical fact, including without limitation those statements that are identified by the words "anticipates," "estimates," "expects," "intends," "plans," "predicts" and similar expressions, and include statements concerning plans, trends, objectives, goals, strategies, future events or performance, and underlying assumptions (many of which are based, in turn, upon further assumptions) and other statements that are other than statements of historical facts. From time to time, the Company may publish or otherwise make available forward-looking statements of this nature, including statements contained within Business Segment Financial and Operating Data.

Forward-looking statements involve risks and uncertainties, which could cause actual results or outcomes to differ materially from those expressed. The Company's expectations, beliefs and projections are expressed in good faith and are believed by the Company to have a reasonable basis, including without limitation, the impact of COVID-19 on the Company's business, management's examination of historical operating trends, data contained in the Company's records and other data available from third parties. Nonetheless, the Company's expectations, beliefs or projections may not be achieved or accomplished and changes in such assumptions and factors could cause actual future results to differ materially.

Any forward-looking statement contained in this document speaks only as of the date on which the statement is made, and the Company undertakes no obligation to update any forward-looking statement or statements to reflect events or circumstances that occur after the date on which the statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for management to predict all the factors, nor can it assess the effect of each factor on the Company's business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statement. All forward-looking statements, whether written or oral and whether made by or on behalf of the Company, are expressly qualified by the risk factors and cautionary statements reported in Part II, Item 1A. Risk Factors in this Form 10-Q, Part I, Item 1A. Risk Factors in the 2020 Annual Report and subsequent filings with the SEC.

Consolidated Earnings Overview

The following table summarizes the contribution to the consolidated income by each of the Company's business segments.

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions, except per share amounts)
Electric	$	10.3	$	12.2	$	21.0	$	23.5
Natural gas distribution	(.7)		(1.0)		35.5		31.4
Pipeline	9.2		9.0		18.1		16.3
Construction materials and contracting	51.4		53.0		20.6		14.8
Construction services	28.9		27.9		58.7		44.8
Other	1.1		(1.3)		(1.6)		(5.5)
Income from continuing operations	100.2		99.8		152.3		125.3
Loss from discontinued operations, net of tax	—		(.1)		—		(.5)
Net income	$	100.2	$	99.7	$	152.3	$	124.8
Earnings per share - basic:
Income from continuing operations	$	.50	$	.50	$	.76	$	.62
Discontinued operations, net of tax	—		—		—		—
Earnings per share - basic	$	.50	$	.50	$	.76	$	.62
Earnings per share - diluted:
Income from continuing operations	$	.50	$	.50	$	.76	$	.62
Discontinued operations, net of tax	—		—		—		—
Earnings per share - diluted	$	.50	$	.50	$	.76	$	.62

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 The Company's consolidated earnings increased $500,000.

Positively impacting the Company's earnings were favorable income tax adjustments related to the Company's consolidated annualized estimated tax rate included in Other. The construction services business experienced higher inside specialty contracting workloads as a result of increased demand for manufacturing projects as well as increased equipment sales and leasing of power line equipment. The natural gas distribution business benefited from approved rate relief in certain jurisdictions, partially offset by higher operation and maintenance expenses, and the pipeline business benefited from higher non-regulated project revenues. Partially offsetting these increases were higher payroll-related costs, largely stock-based compensation expense and health care costs, across all of the Company's businesses.

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Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 The Company's consolidated earnings increased $27.5 million or 22 percent.

The Company's earnings were positively impacted by increased earnings across most of the Company's businesses. The construction services business experienced an increase in gross margin as a result of higher inside specialty contracting workloads resulting from increased demand for manufacturing projects as well as increased equipment sales and leasing of power line equipment. In addition, the absence of an out-of-period adjustment in 2021 of approximately $6.7 million, net of tax, to correct the revenue recognition on a construction contract during 2020 at the construction services business contributed to the increase in earnings. The construction materials and contracting business experienced an increase in gross margin as well, resulting from higher realized material revenues and margins and higher contracting bid margins. The natural gas distribution business benefited from approved rate relief in certain jurisdictions, partially offset by higher operation and maintenance expenses. The pipeline business also experienced increased storage-related and non-regulated project revenues resulting in a positive impact to earnings. Favorable income tax adjustments related to the Company's consolidated annualized estimated tax rate had a positive impact on Other. Partially offsetting these increases were decreased earnings at the electric business, largely resulting from higher operation and maintenance expenses and depreciation, depletion and amortization costs, and increased payroll-related costs across all of the Company's businesses, largely stock-based compensation expense and health care costs.

A discussion of key financial data from the Company's business segments follows.

Business Segment Financial and Operating Data

The following sections include key financial and operating data for each of the Company's business segments. Also included are highlights on key growth strategies, projections and certain assumptions for the Company and its subsidiaries and other matters of the Company's business segments.

For information pertinent to various commitments and contingencies, see the Notes to Consolidated Financial Statements. For a summary of the Company's business segments, see Note 17 of the Notes to Consolidated Financial Statements.

Electric and Natural Gas Distribution

Strategy and challenges The electric and natural gas distribution segments provide electric and natural gas distribution services to customers, as discussed in Note 17. Both segments strive to be top performing utility companies measured by integrity, employee safety and satisfaction, customer service and shareholder return, while providing safe, environmentally responsible, reliable and competitively priced energy and related services to customers. The Company is focused on cultivating organic growth while managing operating costs and monitoring opportunities for these segments to retain, grow and expand their customer base through extensions of existing operations, including building and upgrading electric generation, transmission and distribution, and natural gas systems, and through selected acquisitions of companies and properties with similar operating and growth objectives at prices that will provide stable cash flows and an opportunity to earn a competitive return on investment. The continued efforts to create operational improvements and efficiencies across both segments promotes the Company's business integration strategy. The primary factors that impact the results of these segments are the ability to earn authorized rates of return, the cost of natural gas, cost of electric fuel and purchased power, weather, competitive factors in the energy industry, population growth and economic conditions in the segments' service areas.

The electric and natural gas distribution segments are subject to extensive regulation in the jurisdictions where they conduct operations with respect to costs, timely recovery of investments and permitted returns on investment, as well as certain operational, environmental and system integrity regulations. To date, many states have enacted, and others are considering, mandatory clean energy standards requiring utilities to meet certain thresholds of renewable energy generation. Federal legislation for clean energy standards and GHG emissions has been considered and may be implemented in the near future. The current presidential administration has also made climate change a focus during the first half of 2021. Over the long-term, the Company expects overall electric demand to be positively impacted by higher demand resulting from increased electrification trends, including electric vehicle adoption, as a means to address economy-wide carbon emission concerns and changing customer conservation patterns. These initiatives could result in increased costs to produce electricity and procure natural gas. To date, the impact of these initiatives on the Company is unknown. The Company will continue to monitor the progress of these initiatives and assess the potential impacts they may have on its stakeholders, business processes, results of operations, cash flows and disclosures.

The Company is focused on modernizing utility infrastructure to meet the varied energy needs of both its customers and communities while ensuring the delivery of safe, environmentally responsible, reliable and affordable energy. The segments continue to invest in facility upgrades to be in compliance with existing and known future regulations. To assist in the reduction of regulatory lag in obtaining revenue increases to align with increased investments, tracking mechanisms have been implemented in certain jurisdictions, as further discussed in Note 19 and the 2020 Annual Report.

In September 2019, the PHMSA issued a rule for additional regulations to strengthen the safety of natural gas transmission and storage facilities and hazardous liquid pipelines. The natural gas segment has implemented procedure changes for both the initial requirements and the additional requirements effective July 1, 2021.

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State implementation of pollution control plans to improve visibility at Class I areas, such as national parks, under the EPA's Regional Haze Rule could require the owners of Coyote Station to incur significant new costs. If the owners decide to incur such costs, the costs could, dependent on determination by state regulatory commissions on approval to recover such costs from customers, negatively impact the Company's results of operations, financial position and cash flows. The NDDEQ plans to draft a state implementation plan and share its controls selection with federal land managers of the National Park Service, the United States Fish and Wildlife Service and the United States Forest Service prior to submitting the plan to the EPA. The emissions modeling being conducted for the combined western state agencies affected by the Regional Haze Rule was delayed and has subsequently delayed the NDDEQ drafting of a state implementation plan. Therefore, the NDDEQ's state implementation plan, which was due to the EPA by July 2021, is anticipated to be submitted during the second half of 2021. Additionally, the Company is one of four owners of Coyote Station and cannot make a unilateral decision on the plant's future. The Company could be negatively impacted by the decisions of the other owners.

Revenues are impacted by both customer growth and usage, the latter of which is primarily impacted by weather, as well as impacts associated with commercial and industrial slow-downs, including economic recessions, and energy efficiencies. During 2020, the Company experienced higher usage from residential customers and lower usage from commercial customers as a result of the COVID-19 pandemic. Customer usage has started to shift back to pre-pandemic levels in 2021. Very cold winters increase demand for natural gas and to a lesser extent, electricity, while warmer than normal summers increase demand for electricity, especially among residential and commercial customers. Average consumption among both electric and natural gas customers has tended to decline as more efficient appliances and furnaces are installed, and as the Company has implemented conservation programs. Natural gas weather normalization and decoupling mechanisms in certain jurisdictions have been implemented to largely mitigate the effect that would otherwise be caused by variations in volumes sold to these customers due to weather and changing consumption patterns on the Company's distribution margins.

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. The Company's transmission settlement process with SPP helped offset the increased energy costs to electric customers during the cold weather event. Further, in some jurisdictions the Company utilized natural gas in storage to lessen the impact of high natural gas costs. Overall, Montana-Dakota and Great Plains incurred approximately $44.0 million in increased natural gas costs in February 2021 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 filed out-of-cycle purchased gas adjustment requests in four out of five jurisdictions affected by this cold-weather event and have received approval in three jurisdictions. The Company will continue to engage with its regulators to determine the appropriate recovery periods over which to recover the associated natural gas costs. For a discussion of the Company's most recent cases by jurisdiction, see Note 19.

The electric and natural gas distribution segments are facing increased lead times on delivery of certain raw materials and equipment used in electric transmission and natural gas pipeline projects. Long lead times are attributable to increased demand for steel products from pipeline companies as they continue pipeline system safety and integrity replacement projects driven by PHMSA regulations, as well as delays in the manufacturing of electrical equipment as a result of the COVID-19 pandemic, including delays in trucking times and issuance of permits for large and heavy loads. The Company continues to monitor the material lead times and is working with manufacturers to proactively order such materials to help mitigate the risk of any delays due to extended lead times.

The ability to grow through acquisitions is subject to significant competition and acquisition premiums. In addition, the ability of the segments to grow their service territory and customer base is affected by regulatory constraints, the economic environment of the markets served and competition from other energy providers and fuels. The construction of any new electric generating facilities, transmission lines and other service facilities is subject to increasing costs and lead times, extensive permitting procedures, and federal and state legislative and regulatory initiatives, which will likely necessitate increases in electric energy prices.

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Earnings overview - The following information summarizes the performance of the electric segment.

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	83.8	$	76.6	9	%	$	168.6	$	162.7	4	%
Electric fuel and purchased power	18.1		14.6		24	%	36.7		35.1		5	%
Taxes, other than income	.2		.1		100	%	.4		.3		33	%
Adjusted gross margin	65.5		61.9		6	%	131.5		127.3		3	%
Operating expenses:
Operation and maintenance	31.3		29.0		8	%	62.6		59.7		5	%
Depreciation, depletion and amortization	16.9		15.7		8	%	33.0		31.3		5	%
Taxes, other than income	4.5		4.4		2	%	9.2		8.7		6	%
Total operating expenses	52.7		49.1		7	%	104.8		99.7		5	%
Operating income	12.8		12.8		—	%	26.7		27.6		(3)	%
Other income	1.6		2.5		(36)	%	2.2		2.1		5	%
Interest expense	6.6		6.8		(3)	%	13.2		13.6		(3)	%
Income before income taxes	7.8		8.5		(8)	%	15.7		16.1		(2)	%
Income tax benefit	(2.5)		(3.7)		32	%	(5.3)		(7.4)		28	%
Net income	$	10.3	$	12.2	(15)	%	$	21.0	$	23.5	(11)	%

Operating statistics	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
Retail sales (million kWh):
Residential	254.1		257.7		589.0		588.3
Commercial	347.1		323.7		708.9		699.5
Industrial	144.1		115.9		288.6		268.9
Other	22.1		20.4		41.3		40.8
	767.4		717.7		1,627.8		1,597.5
Average cost of electric fuel and purchased power per kWh	$	.022	$	.019	$	.021	$	.020

Adjusted gross margin is a non-GAAP financial measure. For additional information and reconciliation of the non-GAAP adjusted gross margin attributable to the electric segment, see the Non-GAAP Financial Measures section later in this Item.

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Electric earnings decreased $1.9 million as a result of:

Adjusted gross margin: Increase of $3.6 million, partially due to higher retail sales volumes of 6.9 percent as a result of increased industrial and commercial sales volumes, offset in part by lower residential sales volumes as the impacts of the COVID-19 pandemic begin to reverse and individuals return to the office and businesses reopen, and higher demand revenues of $1.2 million. Also positively impacting adjusted gross margin were higher revenues associated with transmission interconnect upgrades of $1.0 million and higher renewable tracker revenues resulting from lower production tax credits, as discussed later.

Operation and maintenance: Increase of $2.3 million, largely resulting from increased payroll-related costs of $800,000, largely stock-based compensation expense and health care costs; contract services of $600,000; expenses for new software of $400,000 and other miscellaneous expenses. Partially offsetting these increases were decreased bad debt expense of $400,000 as a result of the collection process and arrears balances being largely back to pre-pandemic levels and decreased operating costs associated with the electric generating unit retired on March 31, 2021, as discussed in Note 13.

Depreciation, depletion and amortization: Increase of $1.2 million due in part to the amortization of plant retirement and closure costs, as discussed in Note 13.

Taxes, other than income: Comparable to the same period in the prior year.

Other income: Decrease of $900,000 directly resulting from lower returns on certain of the Company's benefit plan investments.

Interest expense: Comparable to the same period in the prior year.

Income tax benefit: Decrease of $1.2 million, primarily lower production tax credits related to less wind generation and the expiration of a 10-year credit-qualifying period on certain facilities.

35

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 Electric earnings decreased $2.5 million as a result of:

Adjusted gross margin: Increase of $4.2 million, primarily due to an increase in revenues. The revenue increase was driven by transmission interconnect upgrades of $1.5 million; $1.2 million higher transmission revenues, due equally to increased revenues from SPP as the result of a FERC settlement and higher tracker revenues as a result of more transmission assets; higher demand revenue of $800,000; and higher renewable tracker revenues of $400,000 as a result of lower production tax credits, as discussed later. Adjusted gross margin was also positively impacted by an increase in retail sales volumes of 1.9 percent due to increased industrial and commercial retail sales volumes as the impacts of the COVID-19 pandemic begin to reverse and businesses reopen.

Operation and maintenance: Increase of $2.9 million, resulting from increased payroll-related costs of $1.9 million, largely stock-based compensation expense and health care costs, higher expenses for new software of $300,000 and other miscellaneous expenses. Partially offsetting these increases were decreased bad debt expense of $400,000 as a result of the collection process and arrears balances being largely back to pre-pandemic levels and decreased operating costs associated with the electric generating unit retired on March 31, 2021, as discussed in Note 13.

Depreciation, depletion and amortization: Increase of $1.7 million largely resulting from increased property, plant and equipment balances primarily related to transmission projects placed in service and the amortization of plant retirement and closure costs, as discussed in Note 13.

Taxes, other than income: Increase of $500,000, driven by higher property taxes in certain jurisdictions of $400,000 and higher payroll taxes resulting from increased payroll-related costs.

Other income: Comparable to the same period in the prior year.

Interest expense: Decrease of $400,000, due to lower interest rates.

Income tax benefit: Decrease of $2.1 million, primarily lower production tax credits related to the expiration of a 10-year credit-qualifying period on certain facilities and less wind generation.

Earnings overview - The following information summarizes the performance of the natural gas distribution segment.

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	153.9	$	141.7	9	%	$	504.3	$	468.3	8	%
Purchased natural gas sold	70.9		64.6		10	%	273.1		255.2		7	%
Taxes, other than income	6.4		6.3		2	%	20.3		19.4		5	%
Adjusted gross margin	76.6		70.8		8	%	210.9		193.7		9	%
Operating expenses:
Operation and maintenance	46.0		43.1		7	%	97.2		89.1		9	%
Depreciation, depletion and amortization	20.3		21.0		(3)	%	42.7		41.8		2	%
Taxes, other than income	6.7		6.0		12	%	13.8		12.1		14	%
Total operating expenses	73.0		70.1		4	%	153.7		143.0		7	%
Operating income	3.6		.7		NM		57.2		50.7		13	%
Other income	2.4		4.1		(41)	%	4.0		4.4		(9)	%
Interest expense	9.1		9.0		1	%	18.2		18.1		1	%
Income (loss) before income taxes	(3.1)		(4.2)		26	%	43.0		37.0		16	%
Income tax (benefit) expense	(2.4)		(3.2)		25	%	7.5		5.6		34	%
Net income (loss)	$	(.7)	$	(1.0)	26	%	$	35.5	$	31.4	13	%

*NM - not meaningful

36

Operating statistics	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
Volumes (MMdk)
Retail sales:
Residential	9.0		9.7		37.8		37.4
Commercial	6.5		6.3		25.1		25.1
Industrial	1.1		1.0		2.6		2.5
	16.6		17.0		65.5		65.0
Transportation sales:
Commercial	.4		.4		1.1		1.1
Industrial	38.9		30.2		82.8		75.8
	39.3		30.6		83.9		76.9
Total throughput	55.9		47.6		149.4		141.9
Average cost of natural gas per dk	$	4.26	$	3.81	$	4.17	$	3.93

Adjusted gross margin is a non-GAAP financial measure. For additional information and reconciliation of the non-GAAP adjusted gross margin attributable to the natural gas distribution segment, see the Non-GAAP Financial Measures section later in this Item.

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Natural gas distribution's seasonal loss decreased $300,000 as a result of:

Adjusted gross margin: Increase of $5.8 million, as a result of approved rate relief in certain jurisdictions of $3.3 million, increased transportation revenues of $1.0 million due to higher volumes to electric generation customers and higher basic service charge of $500,000 due to customer growth. Lower retail sales volumes of approximately 2.1 percent, primarily to residential customers, were offset by weather normalization and decoupling mechanisms.

Operation and maintenance: Increase of $2.9 million, primarily due to higher payroll-related costs of $2.6 million, largely stock-based compensation expense and health care costs, and higher expenses for new software.

Depreciation, depletion and amortization: Decrease of $700,000, resulting from decreased depreciation rates in certain jurisdictions of $2.0 million, partially offset by increased property, plant and equipment balances from growth and replacement projects placed in service.

Taxes, other than income: Increase of $700,000, driven by higher property taxes in certain jurisdictions.

Other income: Decrease of $1.7 million, as a result of lower returns on certain of the Company's benefit plan investments of $1.4 million and decreased interest income related to the recovery of purchased gas adjustment balances.

Interest expense: Comparable to the same period in the prior year.

Income tax benefit: Decrease of $800,000, due to lower permanent tax adjustments and a decrease in the seasonal loss before income taxes.

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 Natural gas distribution earnings increased $4.1 million as a result of:

Adjusted gross margin: Increase of $17.2 million, as a result of approved rate relief in certain jurisdictions of $9.0 million; $4.6 million due to increased retail sales volumes of approximately 0.8 percent across all customer classes, including the benefit of weather normalization and decoupling mechanisms in certain jurisdictions; increased transportation revenues of $1.6 million due to higher volumes to electric generation customers; and higher non-regulated revenues.

Operation and maintenance: Increase of $8.1 million, primarily due to higher payroll-related costs of $5.4 million, largely stock-based compensation expense and health care costs; decreased credits for costs associated with the installation of meters partially from delaying meter replacements for safety measures implemented as a result of the COVID-19 pandemic of $1.4 million; and higher expenses for new software.

Depreciation, depletion and amortization: Increase of $900,000, resulting from increased property, plant and equipment balances from growth and replacement projects placed in service, partially offset by decreased depreciation rates in certain jurisdictions of $2.0 million.

Taxes, other than income: Increase of $1.7 million, due in part to higher property taxes in certain jurisdictions of $1.2 million, as well as higher payroll taxes driven by increased payroll-related costs.

Other income: Decrease of $400,000 driven by decreased interest income related to the recovery of purchased gas adjustment balances of $1.0 million, partially offset by higher returns on certain of the Company's benefit plan investments.

37

Interest expense: Comparable to the same period in the prior year.

Income tax expense: Increase of $1.9 million, primarily due to an increase in income before income taxes.

Outlook The Company continues to assess the impacts of the COVID-19 pandemic on its operations and is committed to providing safe and reliable service while ensuring the health and safety of its employees, customers and the communities in which it operates. In 2020, the Company instituted certain measures to help protect its employees from exposure to COVID-19 and to curb potential spread of the virus in customer homes and facilities, including suspension of disconnects due to nonpayment of bills, and continues to adjust and reduce these measures in 2021. In April 2020, the Company waived late payment fees to help customers experiencing financial hardships. As of January 1, 2021, the Company reinstated disconnects and late payment fees to certain customer classes in seven of its eight states of operation. The disconnect process for the remaining customers is expected to resume in the second half of 2021. As a consequence of the suspended disconnects and waived late fees, the Company's cash flows and collection of receivables have been affected but impacts have not been material. The Company experienced some impacts to its commercial and industrial electric and natural gas loads associated with reduced economic activity due to the COVID-19 pandemic and oil price impacts, as further discussed below, which has begun to transition back to historic levels. In 2021, the Company started to scale back certain restrictions put in place in response to the COVID-19 pandemic, including employee travel and temporary delays in non-essential training for employees. The Company filed requests for the use of deferred accounting for costs related to the COVID-19 pandemic in all of the jurisdictions in which it operates and has since withdrawn its applications in two of those jurisdictions. The Company has deferred an immaterial amount of costs related to the pandemic to date.

The Company expects these segments will grow rate base by approximately 5 percent annually over the next five years on a compound basis. Operations are spread across eight states where the Company expects customer growth to be higher than the national average. In 2020, these segments experienced retail customer growth of approximately 1.8 percent and the Company expects customer growth to continue to average 1 percent to 2 percent per year. This customer growth, along with system upgrades and replacements needed to supply safe and reliable service, will require investments in new and replacement electric and natural gas systems. On July 1, 2021, the Company filed in North Dakota, and provided a courtesy copy to South Dakota, an integrated resource plan for the electric segment, which included the Company's plans for future resources to meet customer demand.

These segments are exposed to energy price volatility and may be impacted by changes in oil and natural gas exploration and production activity. Rate schedules in the jurisdictions in which the Company's natural gas distribution segment operates contain clauses that permit the Company to file for rate adjustments for changes in the cost of purchased gas. Although changes in the price of natural gas are passed through to customers and have minimal impact on the Company's earnings, the natural gas distribution segment's customers benefit from lower natural gas prices through the Company's utilization of storage and fixed price contracts. The Company continues to monitor natural gas prices, as well as oil and natural gas production levels.

In February 2019, the Company announced the retirement of three aging coal-fired electric generating units, resulting from the Company's analysis showing that the plants are no longer expected to be cost competitive for customers. The Company ceased operations on March 31, 2021, of Unit 1 at Lewis & Clark Station in Sidney, Montana. The Company has completed pre-decommissioning activities and commenced decommissioning of Unit 1 at Lewis & Clark in July 2021. The retirement of Units 1 and 2 at Heskett Station near Mandan, North Dakota, is expected in early 2022. In addition, the Company announced that it intends to construct Heskett Unit 4, an 88-MW simple-cycle natural gas-fired combustion turbine peaking unit at the existing Heskett Station near Mandan, North Dakota. Heskett Unit 4 production costs coupled with the MISO market purchases are expected to be about half the total cost of continuing to run the coal-fired electric generating units at Heskett and Lewis & Clark stations.

The Company continues to monitor legislation related to clean energy standards that may impact its segments. In Oregon, an executive order issued in March 2020 requires the state to reduce GHG emissions 45 percent below 1990 levels by 2035 and 80 percent below 1990 levels by 2050. State agencies impacted by the order will continue to work through the end of 2021 on the rule-making necessary for compliance. Until the rule-making is completed, compliance impacts to the Company remain uncertain. In Washington, the Climate Commitment Act signed into law in May 2021 requires natural gas distribution companies to reduce overall GHG emissions 45 percent below 1990 levels by 2030, 70 percent below 1990 levels by 2040 and 95 percent below 1990 levels by 2050, which may be achieved through increased energy efficiency and conservation measures, purchased emission allowances and offsets, and purchase of renewable natural gas. The Company has begun reviewing compliance options and expects the compliance costs for these legislated actions will be recovered through customer rates.

The Company continues to be focused on the regulatory recovery of its investments by filing for rate adjustments to seek recovery of operating costs and capital investments, as well as reasonable returns as allowed by regulators. The Company's most recent cases by jurisdiction are discussed in Note 19.

The labor contract at Cascade with the ICWU has been ratified and is effective through March 31, 2024. The labor contract at Montana-Dakota with the IBEW was extended through August 31, 2021, and is currently in negotiations.

38

Pipeline

Strategy and challenges The pipeline segment provides natural gas transportation, underground storage and energy-related services, as discussed in Note 17. The segment focuses on utilizing its extensive expertise in the design, construction and operation of energy infrastructure and related services to increase market share and profitability through optimization of existing operations, organic growth and investments in energy-related assets within or in close proximity to its current operating areas. The segment focuses on the continual safety and reliability of its systems, which entails building, operating and maintaining safe natural gas pipelines and facilities. The segment continues to evaluate growth opportunities including the expansion of natural gas facilities; incremental pipeline projects; and expansion of energy-related services leveraging on its core competencies. In support of this strategy, the Company completed the following organic growth projects in 2020:

•In September 2020, Phase II of the Line Section 22 Expansion project in the Billings, Montana, area was placed in service. The completion of Phase I and II increased capacity by 22.5 MMcf per day.

•In February 2020, the Demicks Lake Expansion project in McKenzie County, North Dakota, was placed in service and increased capacity by 175 MMcf per day.

The segment is exposed to energy price volatility which is impacted by the fluctuations in pricing, production and basis differentials of the energy market's commodities. Legislative and regulatory initiatives on increased pipeline safety regulations and environmental matters such as the reduction of methane emissions could also impact the price and demand for natural gas. In February 2021, the FERC issued a revised notice of inquiry seeking new information and stakeholder perspectives regarding the certification of new interstate natural gas facilities. The FERC issued the original notice of inquiry seeking stakeholder perspectives on this topic in April 2018. The FERC also took a step toward reforming the way in which it analyzes GHG emissions for purposes of natural gas pipeline certificates by including a quantitative analysis of the GHG emissions associated with a pipeline replacement project. At this time, no accepted methodology for a GHG significance calculation has been established. The Company is monitoring the progress of these initiatives and is assessing the potential impacts they may have on its business processes, current and future projects, results of operations and disclosures.

The pipeline segment is also subject to extensive regulation including certain operational compliance, permit terms and system integrity. The Company continues to actively evaluate cybersecurity processes and procedures, including recent changes in the industry's cybersecurity regulations, for opportunities to further strengthen its cybersecurity protections. Implementation of enhancements and additional requirements is ongoing. In September 2019, the PHMSA issued a rule for additional regulations to strengthen the safety of natural gas transmission and storage facilities and hazardous liquid pipelines. The segment has implemented procedure changes and physical modifications to existing facilities necessary for new requirements including those that became effective July 1, 2021. The segment reviews and secures existing permits and easements, as well as new permits and easements as necessary to meet current demand and future growth opportunities on an ongoing basis. Groups opposing natural gas pipelines could also cause negative impacts on the segment with increased costs, potential delays to project completion, or cancellation of prospective projects.

In April 2020 and November 2020, the Company completed the sales of its regulated and non-regulated natural gas gathering assets, respectively. With the completion of these sales, the Company has exited the natural gas gathering business.

The segment regularly experiences extended lead times on raw materials that are critical to the segment's construction and maintenance work. Long lead times on materials could delay maintenance work and construction projects potentially causing lost revenues and/or increased costs. The Company proactively monitors and plans for material lead times and works with manufacturers and suppliers to help mitigate the risk of delays due to extended lead times.

The segment focuses on the recruitment and retention of a skilled workforce to remain competitive and provide services to its customers. The industry in which it operates relies on a skilled workforce to construct energy infrastructure and operate existing infrastructure in a safe manner. A shortage of skilled personnel can create a competitive labor market which could increase costs incurred by the segment. Competition from other pipeline companies can also have a negative impact on the segment.

39

Earnings overview - The following information summarizes the performance of the pipeline segment.

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	35.6	$	35.7	—	%	$	71.8	$	71.5	—	%
Operating expenses:
Operation and maintenance	16.1		15.1		7	%	31.3		30.1		4	%
Depreciation, depletion and amortization	5.2		5.3		(2)	%	10.3		11.2		(8)	%
Taxes, other than income	3.2		3.1		3	%	6.6		6.6		—	%
Total operating expenses	24.5		23.5		4	%	48.2		47.9		1	%
Operating income	11.1		12.2		(9)	%	23.6		23.6		—	%
Other income	1.9		1.0		90	%	2.8		1.0		180	%
Interest expense	1.9		1.9		—	%	3.9		3.9		—	%
Income before income taxes	11.1		11.3		(2)	%	22.5		20.7		9	%
Income tax expense	1.9		2.3		(17)	%	4.4		4.4		—	%
Net income	$	9.2	$	9.0	3	%	$	18.1	$	16.3	11	%

Operating statistics	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2021	2020	2021	2020
Transportation volumes (MMdk)	118.7	95.6	229.5	207.3
Natural gas gathering volumes (MMdk)	—	2.1	—	5.4
Customer natural gas storage balance (MMdk):
Beginning of period	5.2	3.8	25.5	16.2
Net injection (withdrawal)	10.8	15.3	(9.5)	2.9
End of period	16.0	19.1	16.0	19.1

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Pipeline earnings increased $200,000 as a result of:

Revenues: Comparable to the same period in the prior year. Revenues were positively impacted by higher non-regulated project revenues. Offsetting the increase were decreased gathering revenues of $1.2 million due to the sales of the Company's natural gas gathering assets in 2020 and decreased storage-related revenues.

Operation and maintenance: Increase of $1.0 million, primarily due to higher non-regulated project costs of $600,000 associated with higher non-regulated project revenues, as previously discussed, and higher payroll-related costs, largely stock-based compensation expense and health care costs.

Depreciation, depletion and amortization: Comparable to the same period in the prior year.

Taxes, other than income: Comparable to the same period in the prior year.

Other income: Increase of $900,000, primarily the result of higher AFUDC.

Interest expense: Comparable to the same period in the prior year.

Income tax expense: Decrease of $400,000, primarily resulting from an energy efficiency tax benefit.

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 Pipeline earnings increased $1.8 million as a result of:

Revenues: Comparable to the same period in the prior year. Revenues were positively impacted by an increase to storage-related revenues of $1.8 million and higher non-regulated project revenues. These increases were largely offset by lower gathering revenues of $3.3 million due to the sales of the Company's natural gas gathering assets in 2020.

Operation and maintenance: Increase of $1.2 million, primarily due to higher payroll-related costs of $1.1 million, largely stock-based compensation expense and health care costs, and higher non-regulated project costs associated with higher non-regulated project revenue, as previously discussed.

Depreciation, depletion and amortization: Decrease of $900,000, largely resulting from the absence of natural gas gathering assets, as previously discussed, offset in part by higher property, plant and equipment balances related to organic growth projects.

Taxes, other than income: Comparable to the same period in the prior year.

40

Other income: Increase of $1.8 million, primarily the result of higher AFUDC.

Interest expense: Comparable to the same period in the prior year.

Income taxes: Comparable to the same period in the prior year. Income tax expense was higher due to increased income before income taxes which was largely offset by an energy efficiency tax benefit.

Outlook The Company continues to manage the impacts of the COVID-19 pandemic on its operations and is committed to providing safe, reliable and compliant service while ensuring the health and safety of its employees, customers and the communities in which it operates. Overall, the pipeline business has had minimal impacts due to COVID-19 and does not expect delays to its regulatory filings or projects due to the pandemic.

The Company has continued to experience the effect of associated natural gas production in the Bakken, which has provided opportunities for organic growth projects and increased demand. The completion of organic growth projects has contributed to the volumes of natural gas the Company transports through its system. Although low oil prices slowed 2020 drilling activities and led to the shut-in of certain wells, the recovery of oil prices has allowed producers to bring wells back online and associated natural gas production in the Bakken has returned to near pre-pandemic levels.

The Company continues to focus on growth and improving existing operations through organic projects in all areas in which it operates. The national record levels of natural gas supply over the last few years has moderated the pressure on natural gas prices and continues to minimize price volatility. While the Company believes there will continue to be varying pressures on natural gas production levels and prices due to these circumstances, low natural gas prices provide growth opportunity for industrial supply related projects and seasonal pricing differentials provide opportunities for storage services.

In January 2019, the Company announced the North Bakken Expansion project, which includes construction of a new pipeline, compression and ancillary facilities to transport natural gas from core Bakken production areas near Tioga, North Dakota, to a new connection with Northern Border Pipeline in McKenzie County, North Dakota. Long-term take or pay customer contracts support the project at an amended design capacity of 250 MMcf per day, which can be readily expanded to meet forecasted natural gas growth levels and customer needs. In February 2020, the Company filed with the FERC its application for this project. In June 2021, the Company received a FERC order issuing a certificate of public convenience and necessity for the project and in July 2021, the FERC granted the Company a notice to proceed with construction. Construction began in July 2021 and is expected to be completed by the end of 2021 assuming favorable weather conditions.

In July 2021, the Company announced plans for a natural gas pipeline expansion project in eastern North Dakota. The Wahpeton Expansion project consists of 60 miles of pipe and ancillary facilities and is designed to increase capacity by 20 MMcf per day which is supported by long term customer agreements with Montana-Dakota and its utility customers. Construction is expected to begin in early 2024, depending on regulatory approvals, with a completion date later in 2024.

Construction Materials and Contracting

Strategy and challenges The construction materials and contracting segment provides an integrated set of aggregate-based construction services, as discussed in Note 17. The segment focuses on high-growth strategic markets located near major transportation corridors and desirable mid-sized metropolitan areas; strengthening the long-term, strategic aggregate reserve position through available purchase and/or lease opportunities; enhancing profitability through cost containment, margin discipline and vertical integration of the segment's operations; development and recruitment of talented employees; and continued growth through organic and acquisition opportunities.

A key element of the Company's long-term strategy for this business is to further expand its market presence in the higher-margin materials business (rock, sand, gravel, liquid asphalt, asphalt concrete, ready-mixed concrete and related products), complementing and expanding on the segment's expertise. The Company's continued acquisition activity supports this strategy.

As one of the country's largest sand and gravel producers, the segment continues to strategically manage its approximately 1.1 billion tons of aggregate reserves in all its markets, as well as take further advantage of being vertically integrated. The segment's vertical integration allows the segment to manage operations from aggregate mining to final lay-down of concrete and asphalt, with control of and access to permitted aggregate reserves being significant. The Company's aggregate reserves are naturally declining and as a result, the Company seeks acquisition opportunities to replace the reserves. During 2020, the Company made strategic asset purchases that contributed approximately 115 million tons of aggregate reserves. In the first quarter of 2021, the Company received the necessary permitting to expand its operation capabilities at its Honey Creek quarry near Austin, Texas. Honey Creek contains an estimated 40-year supply of aggregates.

The construction materials and contracting segment faces challenges that are not under the direct control of the business. The segment operates in geographically diverse and highly competitive markets. Competition can put negative pressure on the segment's operating margins. The segment is also subject to volatility in the cost of raw materials such as diesel fuel, gasoline, liquid asphalt, cement and steel. Such volatility can have an impact on the segment's margins, including fixed-price construction contracts that are particularly vulnerable to the volatility of energy and material prices. Other variables that can impact the segment's margins include adverse weather conditions, the timing of project starts or completion and declines or delays in new and

41

existing projects due to the cyclical nature of the construction industry and governmental infrastructure spending. Accordingly, operating results in any particular period may not be indicative of the results that can be expected for any other period.

The segment also faces challenges in the recruitment and retention of employees. Trends in the labor market include an aging workforce and availability issues. The segment continues to face increasing pressure to control costs, as well as recruit and train a skilled workforce to meet the needs of increasing demand and seasonal work.

Earnings overview - The following information summarizes the performance of the construction materials and contracting segment.

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	633.8	$	621.1	2	%	$	899.5	$	883.3	2	%
Cost of sales:
Operation and maintenance	497.0		487.9		2	%	740.2		738.7		—	%
Depreciation, depletion and amortization	24.3		21.2		15	%	46.7		40.8		14	%
Taxes, other than income	13.9		13.6		2	%	23.6		23.0		3	%
Total cost of sales	535.2		522.7		2	%	810.5		802.5		1	%
Gross margin	98.6		98.4		—	%	89.0		80.8		10	%
Selling, general and administrative expense:
Operation and maintenance	24.2		21.6		12	%	46.0		43.8		5	%
Depreciation, depletion and amortization	1.0		1.3		(23)	%	2.1		2.3		(9)	%
Taxes, other than income	1.0		.8		25	%	3.4		3.2		6	%
Total selling, general and administrative expense	26.2		23.7		11	%	51.5		49.3		4	%
Operating income	72.4		74.7		(3)	%	37.5		31.5		19	%
Other income	1.2		1.9		(37)	%	1.1		.7		57	%
Interest expense	4.8		5.7		(16)	%	9.5		10.9		(13)	%
Income before income taxes	68.8		70.9		(3)	%	29.1		21.3		37	%
Income tax expense	17.4		17.9		(3)	%	8.5		6.5		31	%
Net income	$	51.4	$	53.0	(3)	%	$	20.6	$	14.8	39	%

Operating statistics	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2021	2020	2021	2020
Sales (000's):
Aggregates (tons)	9,533	8,739	14,341	12,956
Asphalt (tons)	2,091	2,166	2,385	2,393
Ready-mixed concrete (cubic yards)	1,201	1,119	1,933	1,823

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Construction materials and contracting's earnings decreased $1.6 million as a result of:

Revenues: Increase of $12.7 million, primarily the result of higher material revenues for aggregates and ready-mixed concrete due to strong demand and large projects in certain regions. The increase was partially offset by decreased contracting services of $22.5 million due to less favorable weather conditions in certain regions in 2021 and delays in the start of some project work.

Gross margin: Comparable to the same period in the prior year. Gross margin was positively impacted by increased revenues, which was mostly offset by higher depreciation expense.

Selling, general and administrative expense: Increase of $2.5 million driven by higher payroll-related costs, largely stock-based compensation expense and health care costs.

Other income: Decrease of $700,000, largely due to lower returns on the Company's benefit plan investments.

Interest expense: Decrease of $900,000 due to lower average interest rates.

Income tax expense: Comparable to the same period in the prior year.

42

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 Construction materials and contracting's earnings increased $5.8 million as a result of:

Revenues: Increase of $16.2 million, primarily the result of higher material revenues for aggregates and ready-mixed concrete due to strong demand, large projects and higher realized prices in certain regions. The increase was partially offset by decreased contracting services of $24.9 million due to less favorable weather conditions in certain regions in 2021 and delays in the start of some project work.

Gross margin: Increase of $8.2 million, largely due to higher revenues, as previously discussed, and higher realized materials margins, primarily aggregates and ready-mixed concrete, and higher contracting bid margins. Partially offsetting these increases was higher depreciation expense.

Selling, general and administrative expense: Increase of $2.2 million, primarily due to higher payroll-related costs of $4.2 million, largely stock-based compensation expense and health care costs. Partially offsetting the increase was the recovery of prior bad debt expense of $1.3 million and lower professional services.

Other income: Increase of $400,000 as a result of higher returns on the Company's benefit plan investments.

Interest expense: Decrease of $1.4 million, mainly due to lower average interest rates.

Income tax expense: Increase of $2.0 million, largely due to an increase in income before income taxes.

Outlook The Company continues to assess the impacts of the COVID-19 pandemic on its operations and is committed to the health and safety of its employees, customers and the communities in which it operates. In 2021, the Company continues to implement safety measures developed in 2020 for its employees that were not able to work from home and has experienced some inefficiencies and additional costs in relation to these measures, including delays in the ability to obtain permits from government agencies and, for the most part, has been able to continue business processes with minimal interruptions. The Company also continues to monitor job progress and service work and at this time has not experienced significant delays, cancellations or disruptions due to the pandemic. The American Rescue Plan Act approved by the United States Congress in the first quarter of 2021 provides $1.9 trillion in COVID-19 relief funding for states, schools and local governments. Because of limited guidance currently available to states on how the funds can be spent, there is uncertainty regarding whether the funds will be made available for infrastructure projects that could positively impact the segment. Additionally, the current presidential administration and the United States Congress continue working toward an agreement on a comprehensive infrastructure proposal that, if adopted, could positively impact the segment. The Company continues to monitor the progress of these legislative items.

The segment's vertically integrated aggregate-based business model provides the Company with the ability to capture margin throughout the sales delivery process. The aggregate products are sold internally and externally for use in other products such as ready-mixed concrete, asphaltic concrete and public and private construction markets. The contracting services and construction materials are sold in connection with street, highway and other public infrastructure projects, as well as private commercial, industrial and residential development projects. The public infrastructure projects have traditionally been more stable markets as public funding is more secure during periods of economic decline. The public projects are, however, dependent on federal and state funding such as appropriations to the Federal Highway Administration. Spending on private development is highly dependent on both local and national economic cycles, providing additional sales during times of strong economic cycles.

During 2021 and 2020, the Company made strategic purchases that support the Company's long-term strategy to expand its market presence. In April 2021, the Company acquired Mt. Hood Rock, a construction aggregates business located in Portland, Oregon. The Company continues to evaluate additional acquisition opportunities that would be accretive to earnings of the Company. For more information on the Company's business combinations, see Note 10.

The construction materials and contracting segment's backlog at June 30, 2021, was $912.1 million, which is up slightly from backlog of $875.1 million at June 30, 2020. The Company continues to monitor bidding activity as it moves into the third quarter of 2021. The Company expects to complete a significant amount of backlog at June 30, 2021, during the next 12 months.

One of the labor contracts that the construction materials and contracting segment was negotiating at December 31, 2020, as reported in Items 1 and 2 - Business Properties - General in the 2020 Annual Report, has been ratified.

Construction Services

Strategy and challenges The construction services segment provides inside and outside specialty contracting, as discussed in Note 17. The construction services segment focuses on safely executing projects; providing a superior return on investment by building new and strengthening existing customer relationships; ensuring quality service; effectively controlling costs; retaining, developing and recruiting talented employees; growing through organic and strategic acquisition opportunities; and focusing efforts on projects that will permit higher margins while properly managing risk. The growth experienced by the segment in recent years is due in part to its ability to support national customers in most of the regions in which it operates.

The construction services segment faces challenges, which are not under direct control of the business, in the highly competitive markets in which it operates. Competitive pricing environments, project delays, changes in management's estimates of variable

43

consideration and the effects from restrictive regulatory requirements have negatively impacted revenues and margins in the past and could affect revenues and margins in the future. Additionally, margins may be negatively impacted on a quarterly basis due to adverse weather conditions, as well as timing of project starts or completions; disruptions to the supply chain due to transportation delays, raw material cost increases and shortages, and closures of businesses or facilities; declines or delays in new projects due to the cyclical nature of the construction industry; and other factors. These challenges may also impact the risk of loss on certain projects. Accordingly, operating results in any particular period may not be indicative of the results that can be expected for any other period.

The need to ensure available specialized labor resources for projects also drives strategic relationships with customers and project margins. These trends include an aging workforce and labor availability issues, increasing pressure to reduce costs and improve reliability, and increasing duration and complexity of customer capital programs. Due to these and other factors, the Company believes overall customer and competitor demand for labor resources will continue to increase, possibly surpassing the supply of industry resources.

Earnings overview - The following information summarizes the performance of the construction services segment.

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	525.6	$	497.2	6	%	$	1,044.1	$	1,011.9	3	%
Cost of sales:
Operation and maintenance	442.0		411.1		8	%	869.2		847.3		3	%
Depreciation, depletion and amortization	3.9		4.0		(3)	%	7.9		7.9		—	%
Taxes, other than income	16.3		17.2		(5)	%	35.7		40.6		(12)	%
Total cost of sales	462.2		432.3		7	%	912.8		895.8		2	%
Gross margin	63.4		64.9		(2)	%	131.3		116.1		13	%
Selling, general and administrative expense:
Operation and maintenance	23.6		23.5		—	%	48.2		47.4		2	%
Depreciation, depletion and amortization	1.0		2.4		(58)	%	2.3		4.2		(45)	%
Taxes, other than income	1.0		1.1		(9)	%	2.7		2.8		(4)	%
Total selling, general and administrative expense	25.6		27.0		(5)	%	53.2		54.4		(2)	%
Operating income	37.8		37.9		—	%	78.1		61.7		27	%
Other income	1.6		.5		NM		1.8		.7		NM
Interest expense	.9		1.1		(18)	%	1.8		2.3		(22)	%
Income before income taxes	38.5		37.3		3	%	78.1		60.1		30	%
Income tax expense	9.6		9.4		2	%	19.4		15.3		27	%
Net income	$	28.9	$	27.9	3	%	$	58.7	$	44.8	31	%

*NM - not meaningful

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Construction services earnings increased $1.0 million as a result of:

Revenues: Increase of $28.4 million, primarily resulting from higher inside specialty contracting workloads of $24.4 million, or 7.5% more compared to the same period in the prior year, as a result of increased customer demand for manufacturing projects and continued hospitality demand. Outside specialty contracting workloads contributed 2.8% more compared to the same period in the prior year as a result of strong demand for utility projects. An increase in equipment sales and leasing of the power line equipment the Company manufactures also had a positive impact of $2.1 million in the second quarter of 2021.

Gross margin: Decrease of $1.5 million, mainly resulting from contracting margins as a result of higher employee costs in certain regions associated with a shortage of available labor and the absence of higher margin work compared to the second quarter of 2020.

Selling, general and administrative expense: Decrease of $1.4 million, resulting from the recovery of prior bad debt expense of $1.6 million and lower amortization expense of $1.2 million, offset in part by higher office expense and higher payroll-related costs of $300,000, largely stock-based compensation expense and health care costs.

Other income: Increase of $1.1 million, largely due to increased earnings on investments.

Interest expense: Comparable to the same period in the prior year.

Income tax expense: Comparable to the same period in the prior year.

44

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 Construction services earnings increased $13.9 million as a result of:

Revenues: Increase of $32.2 million, primarily resulting from higher outside specialty contracting workloads of $24.3 million, or 8.8% more compared to the same period in the prior year, as a result of strong demand for utility projects. Inside specialty contracting workloads contributed 1.1% more compared to the same period in the prior year as a result of increased customer demand for manufacturing projects, continued hospitality demand and the absence in 2021 of an out-of-period adjustment in the first quarter of 2020 to correct an overstatement of operating revenues of $7.7 million. An increase in equipment sales and leasing of the power line equipment the Company manufactures also had a positive impact of $2.4 million in 2021.

Gross margin: Increase of $15.2 million, primarily due to the higher volume of work resulting in an increase in revenues, as previously discussed, partially offset by an increase in operation and maintenance expense as a direct result of the expenses related to the increased workloads. Also contributing to the increase was the absence in 2021 of an out-of-period adjustment in the first quarter of 2020 to correct an overstatement of operating revenues of $7.7 million and an understatement of operation and maintenance expense of $1.2 million previously recognized on a construction contract.

Selling, general and administrative expense: Decrease of $1.2 million due in part to the recovery of bad debt expense of $3.7 million and lower amortization expense of $1.8 million, offset in part by higher payroll-related costs, largely stock-based compensation expense and health care costs.

Other income: Increase of $1.1 million, largely related to increased earnings on investments.

Interest expense: Decrease of $500,000, driven by lower debt balances as a result of collections on customer accounts during the construction season.

Income taxes: Increase of $4.1 million, directly resulting from an increase in income before income taxes.

Outlook The Company continues to assess the impacts of the COVID-19 pandemic on its operations and is committed to the health and safety of its employees, customers and the communities in which it operates. In 2021, the Company continues to implement safety measures developed in 2020 for its employees that were not able to work from home and has experienced some inefficiencies in relation to these measures but, for the most part, has been able to continue pre-pandemic business processes. The Company continues to monitor job progress and service work for delays, cancellations and disruptions due to the pandemic but expects minimal disruptions the remainder of 2021. Despite the challenges presented by the COVID-19 pandemic, the Company believes there are long-term growth opportunities and demand for construction services. The American Rescue Plan Act approved by the United States Congress in the first quarter of 2021 provides $1.9 trillion in COVID-19 relief funding for states, schools and local government including broadband infrastructure. Because of limited guidance currently available to states on how the funds can be spent, there is uncertainty regarding whether the funds will be made available for infrastructure projects that could impact the segment. Additionally, the current presidential administration and the United States Congress continue working toward an agreement on a comprehensive infrastructure proposal that, if adopted, could positively impact the segment. The Company will continue to monitor the progress of these legislative items.

The Company continues to have bidding opportunities for both inside and outside specialty contracting work in 2021 as evidenced by the segment's backlog. Although bidding remains highly competitive in all areas, the Company expects the segment's relationship with existing customers, skilled workforce, quality of service and effective cost management will continue to provide a benefit in securing and executing profitable projects.

The construction services segment's backlog at June 30, was as follows:

	Three Months Ended
	June 30,
	2021		2020
	(In millions)
Inside specialty contracting	$	1,059	$	1,106
Outside specialty contracting	261		200
	$	1,320	$	1,306

The increase in backlog was largely attributable to the new project opportunities that the Company continues to be awarded across its diverse operations, particularly outside specialty contracting from increased utility demand. The Company continues to have strong inside specialty contracting backlog related to commercial industries and public projects. The Company expects to complete a significant amount of the backlog at June 30, 2021, during the next 12 months. Additionally, the Company continues to further evaluate potential acquisition opportunities that would be accretive to earnings of the Company and continue to grow the segment's backlog.

45

Other

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2021		2020		Variance		2021		2020		Variance
	(In millions)
Operating revenues	$	3.4	$	2.9	17	%	$	6.7	$	5.9	14	%
Operating expenses:
Operation and maintenance	2.3		2.3		—	%	4.5		4.4		2	%
Depreciation, depletion and amortization	1.1		.6		83	%	2.4		1.3		85	%
Total operating expenses	3.4		2.9		17	%	6.9		5.7		21	%
Operating income (loss)	—		—		NM		(.2)		.2		NM
Other income	.3		—		NM		.4		.2		100	%
Interest expense	.1		.3		(67)	%	.2		.6		(67)	%
Income (loss) before income taxes	.2		(.3)		NM		—		(.2)		NM
Income tax (benefit) expense	(.9)		1.0		NM		1.6		5.3		(70)	%
Net income (loss)	$	1.1	$	(1.3)	NM		$	(1.6)	$	(5.5)	70	%

*NM - not meaningful

Three Months Ended June 30, 2021, Compared to Three Months Ended June 30, 2020 Other was positively impacted in the second quarter of 2021 by lower income tax adjustments related to the Company's consolidated annualized estimated tax rate, partially offset by higher depreciation, depletion and amortization expense for software placed in service. General and administrative costs and interest expense previously allocated to the exploration and production and refining businesses that do not meet the criteria for income (loss) from discontinued operations are also included in Other.

Six Months Ended June 30, 2021, Compared to Six Months Ended June 30, 2020 During the first six months of 2021, Other was positively impacted by lower income tax adjustments related to the Company's consolidated annualized estimated tax rate, partially offset by higher depreciation, depletion and amortization expense for software placed in service. General and administrative costs and interest expense previously allocated to the exploration and production and refining businesses that do not meet the criteria for income (loss) from discontinued operations are also included in Other.

Intersegment Transactions

Amounts presented in the preceding tables will not agree with the Consolidated Statements of Income due to the Company's elimination of intersegment transactions. The amounts related to these items were as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Intersegment transactions:
Operating revenues	$	12.4	$	12.3	$	43.4	$	43.3
Operation and maintenance	4.7		4.5		9.8		10.3
Purchased natural gas sold	7.7		7.8		33.6		33.0

For more information on intersegment eliminations, see Note 17.

Liquidity and Capital Commitments

At June 30, 2021, the Company had cash and cash equivalents of $58.0 million and available borrowing capacity of $611.8 million under the outstanding credit facilities of the Company's subsidiaries. The Company expects to meet its obligations for debt maturing within one year and its other operating and capital requirements from various sources, including internally generated funds; credit facilities and commercial paper of the Company's subsidiaries, as described in Capital resources; and issuance of debt and equity securities.

46

Cash flows

	Six Months Ended
	June 30,
	2021		2020
	(In millions)
Net cash provided by (used in):
Operating activities	$	182.8	$	261.4
Investing activities	(266.5)		(296.5)
Financing activities	82.1		33.0
Decrease in cash and cash equivalents	(1.6)		(2.1)
Cash and cash equivalents -- beginning of year	59.6		66.5
Cash and cash equivalents -- end of period	$	58.0	$	64.4

Operating activities 

	Six Months Ended
	June 30,
	2021		2020		Variance
Components of net cash provided by operating activities:	(In millions)
Income from continuing operations	$	152.3	$	125.3	$	27.0
Depreciation, depletion and amortization	147.4		140.8		6.6
Deferred income taxes	14.5		2.9		11.6
Receivables	(18.5)		(40.8)		22.3
Inventories	(25.3)		(26.3)		1.0
Other current assets	(52.8)		30.8		(83.6)
Accounts payable	(3.9)		13.4		(17.3)
Other current liabilities	(22.6)		26.6		(49.2)
Other noncurrent changes	(8.2)		(10.9)		2.7
Net cash used in discontinued operations	(.1)		(.4)		.3
Net cash provided by operating activities	$	182.8	$	261.4	$	(78.6)

The changes in cash flows from operating activities generally follow the results of operations, as discussed in Business Segment Financial and Operating Data, and are affected by changes in working capital. The decrease in cash flows provided by operating activities in the previous table was largely driven by an increase in natural gas purchases, as discussed in Note 13, partially offset by the associated deferred taxes. Also contributing to the decrease was higher working capital requirements at the construction services and construction materials and contracting businesses. Both businesses experienced increased estimated tax payments due to the timing of the payment of quarterly income tax estimates and the deferral of payroll taxes as a result of the COVID-19 pandemic during 2020, and the construction services business experienced an increase in accounts payable from the fluctuation in job activity, which were slightly offset by the stronger collection of accounts receivable at the construction materials and contracting business. Partially offsetting the net decrease in cash flows provided by operating activities was higher earnings at all businesses during the first half of 2021.

Investing activities

	Six Months Ended
	June 30,
	2021		2020		Variance
Components of net cash used in investing activities:	(In millions)
Capital expenditures	$	(261.9)	$	(248.8)	$	(13.1)
Acquisitions, net of cash acquired	(13.7)		(70.7)		57.0
Net proceeds from sale or disposition of property and other	12.4		23.0		(10.6)
Investments	(3.3)		—		(3.3)
Net cash used in investing activities	$	(266.5)	$	(296.5)	$	30.0

The decrease in cash used in investing activities in the previous table was primarily due to lower cash used in acquisition activity in 2021 compared to 2020 at the construction services and construction materials and contracting businesses. Partially offsetting the decrease in cash used in investing activities were increased capital expenditures in 2021 at the pipeline business, largely related to the North Bakken Expansion project as discussed previously, and at the construction materials and contracting business related to increased operating projects, partially offset by lower capital expenditures at the electric business related to reduced electric transmission projects. The pipeline business also experienced lower proceeds from asset sales as a result of the sale of its natural gathering assets during 2020.

47

Financing activities

	Six Months Ended
	June 30,
	2021		2020		Variance
Components of net cash provided by financing activities:	(In millions)
Issuance of short-term borrowings	$	50.0	$	75.0	$	(25.0)
Repayment of short-term borrowings	(50.0)		—		(50.0)
Issuance of long-term debt	171.8		200.4		(28.6)
Repayment of long-term debt	(48.1)		(162.2)		114.1
Proceeds from issuance of common stock	54.6		3.4		51.2
Dividends paid	(85.3)		(83.2)		(2.1)
Repurchase of common stock	(6.7)		—		(6.7)
Tax withholding on stock-based compensation	(4.2)		(.4)		(3.8)
Net cash provided by financing activities	$	82.1	$	33.0	$	49.1

The increase in cash provided by financing activities in the previous table was largely the result of lower repayments on commercial paper and revolving credit agreements at Montana-Dakota during 2021. During 2021, the Company received increased net proceeds of $51.2 million from the issuance of common stock under the Company's "at-the-market" offering. Partially offsetting the increase in cash provided by financing activities were decreased long-term borrowings during 2021 at the natural gas distribution business, partially offset by an increase in long-term borrowings at the construction materials and contracting business for acquisitions. In addition, Montana-Dakota issued and repaid $50 million in short term borrowings during the first quarter of 2021. The issuance was related to financing the higher natural gas purchases, as previously discussed, and the repayment was related to short-term borrowings completed during 2020.

Defined benefit pension plans

There were no material changes to the Company's qualified noncontributory defined benefit pension plans from those reported in the 2020 Annual Report. For more information, see Note 18 and Part II, Item 7 in the 2020 Annual Report.

Capital expenditures

Capital expenditures for the first six months of 2021 were $283.2 million, which includes the completed business combination of a construction aggregates business at the construction materials and contracting business. Capital expenditures for the first six months of 2020 were $310.6 million, which includes the completed business combinations at the construction materials and contracting and construction services businesses. Capital expenditures allocated to the Company's business segments are estimated to be approximately $805.9 million for 2021. Capital expenditures have been updated from what was previously reported in the 2020 Annual Report to accommodate project timeline and scope changes made throughout the first half of 2021. The Company will continue to monitor capital expenditures for project delays and changes in economic viability related to COVID-19.

The Company has included in the estimated capital expenditures for 2021 the completed business combination of a construction aggregates business and the North Bakken Expansion project, as previously discussed Business Segment Financial and Operating Data, as well as system upgrades; service extensions; routine equipment maintenance and replacements; buildings, land and building improvements; pipeline and natural gas storage projects; power generation and transmission opportunities, including certain costs for additional electric generating capacity; environmental upgrades; and other growth opportunities.

The Company continues to evaluate potential future acquisitions and other growth opportunities that would be incremental to the outlined capital program; however, such growth is dependent upon the availability of economic opportunities and, as a result, capital expenditures may vary significantly from the estimate previously discussed. It is anticipated that all of the funds required for capital expenditures for 2021 will be met from various sources, including internally generated funds; credit facilities and commercial paper of the Company's subsidiaries, as described later; and issuance of debt and equity securities.

Capital resources

Certain debt instruments of the Company's subsidiaries contain restrictive and financial covenants and cross-default provisions. In order to borrow under the respective debt instruments, 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 June 30, 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. For more information on the covenants, certain other conditions and cross-default provisions, see Part II, Item 8 in the 2020 Annual Report.

48

The following table summarizes the outstanding revolving credit facilities of the Company's subsidiaries at June 30, 2021:

Company	Facility		Facility Limit			Amount Outstanding		Letters of Credit			Expiration Date
			(In millions)
Montana-Dakota Utilities Co.	Commercial paper/Revolving credit agreement	(a)	$	175.0		$	97.6	$	—		12/19/24
Cascade Natural Gas Corporation	Revolving credit agreement		$	100.0	(b)	$	25.5	$	2.2	(c)	6/7/24
Intermountain Gas Company	Revolving credit agreement		$	85.0	(d)	$	23.1	$	—		6/7/24
Centennial Energy Holdings, Inc.	Commercial paper/Revolving credit agreement	(e)	$	600.0		$	199.8	$	—		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). At June 30, 2021, 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). At June 30, 2021, 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 the 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.

Total equity as a percent of total capitalization was 57 percent, 55 percent and 58 percent at June 30, 2021 and 2020, and December 31, 2020, respectively. This ratio is calculated as the Company's total equity, divided by the Company's total capital. Total capital is the Company's total debt, including short-term borrowings and long-term debt due within one year, plus total equity. This ratio is an indicator of how a company is financing its operations, as well as its financial strength.

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.

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 this agreement. As of June 30, 2021, the Company had capacity to issue up to 4.6 million additional shares of common stock under the "at-the-market" offering program. Proceeds from the sale of shares of common stock under this agreement have been and are expected to be used for general corporate purposes, which may include, among other things, working capital, capital expenditures, debt repayment and the financing of acquisitions.

Details of the Company's "at-the-market" offering activity was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Shares issued	1.1		—		1.8		—
Net proceeds *	$	34.9	$	—	$	54.6	$	—
Issuance costs	$	.4	$	—	$	.7	$	—

*    Net proceeds were used for capital expenditures.

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. 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.

49

Off balance sheet arrangements

At June 30, 2021, the Company had no material off balance sheet arrangements.

Contractual obligations and commercial commitments

There were no material changes in the Company's contractual obligations relating to estimated interest payments, asset retirement obligations, uncertain tax positions and minimum funding requirements for its defined benefit plans for 2021 from those reported in the 2020 Annual Report.

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 commitments under these contracts as of June 30, 2021, were:

	Less than 1 year		1-3 years		3-5 years		More than 5 years		Total
	(In millions)
Purchase commitments	$	615.0	$	392.2	$	208.7	$	799.4	$	2,015.3

For more information on contractual obligations and commercial commitments, see Part II, Item 7 in the 2020 Annual Report.

New Accounting Standards

For information regarding new accounting standards, see Note 2, which is incorporated by reference.

Critical Accounting Estimates

The Company's critical accounting estimates include impairment testing of goodwill; fair values of acquired assets and liabilities under the acquisition method of accounting; regulatory assets expected to be recovered in rates charged to customers; revenue recognized using the cost-to-cost measure of progress for contracts; actuarially determined benefit costs; and tax provisions. There were no material changes in the Company's critical accounting estimates from those reported in the 2020 Annual Report. For more information on critical accounting estimates, see Part II, Item 7 in the 2020 Annual Report.

Non-GAAP Financial Measures

The Business Segment Financial and Operating Data includes financial information prepared in accordance with GAAP, as well as another financial measure, adjusted gross margin, that is considered a non-GAAP financial measure as it relates to the Company's electric and natural gas distribution segments. The presentation of adjusted gross margin is intended to be a useful supplemental financial measure for investors’ understanding of the segments' operating performance. This non-GAAP financial measure should not be considered as an alternative to, or more meaningful than, GAAP financial measures such as operating income (loss) or net income (loss). The Company's non-GAAP financial measure, adjusted gross margin, is not standardized; therefore, it may not be possible to compare this financial measure with other companies’ gross margin measures having the same or similar names.

In addition to operating revenues and operating expenses, management also uses the non-GAAP financial measure of adjusted gross margin when evaluating the results of operations for the electric and natural gas distribution segments. Adjusted gross margin for the electric and natural gas distribution segments is calculated by adding back adjustments to operating income (loss). These add-back adjustments include: operation and maintenance expense; depreciation, depletion and amortization expense; and certain taxes, other than income.

Adjusted gross margin includes operating revenues less the cost of electric fuel and purchased power, purchased natural gas sold and certain taxes, other than income. These taxes, other than income, included as a reduction to adjusted gross margin relate to revenue taxes. These segments pass on to their customers the increases and decreases in the wholesale cost of power purchases, natural gas and other fuel supply costs in accordance with regulatory requirements. As such, the segments' revenues are directly impacted by the fluctuations in such commodities. Revenue taxes, which are passed back to customers, fluctuate with revenues as they are calculated as a percentage of revenues. For these reasons, period over period, the segments' operating income (loss) is generally not impacted. The Company's management believes the adjusted gross margin is a useful supplemental financial measure as these items are included in both operating revenues and operating expenses. The Company's management also believes that adjusted gross margin and the remaining operating expenses that calculate operating income (loss) are useful in assessing the Company's utility performance as management has the ability to influence control over the remaining operating expenses.

50

The following information reconciles operating income to adjusted gross margin for the electric segment.

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Operating income	$	12.8	$	12.8	$	26.7	$	27.6
Adjustments:
Operating expenses:
Operation and maintenance	31.3		29.0		62.6		59.7
Depreciation, depletion and amortization	16.9		15.7		33.0		31.3
Taxes, other than income	4.5		4.4		9.2		8.7
Total adjustments	52.7		49.1		104.8		99.7
Adjusted gross margin	$	65.5	$	61.9	$	131.5	$	127.3

The following information reconciles operating income to adjusted gross margin for the natural gas distribution segment.

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Operating income	$	3.6	$	.7	$	57.2	$	50.7
Adjustments:
Operating expenses:
Operation and maintenance	46.0		43.1		97.2		89.1
Depreciation, depletion and amortization	20.3		21.0		42.7		41.8
Taxes, other than income	6.7		6.0		13.8		12.1
Total adjustments	73.0		70.1		153.7		143.0
Adjusted gross margin	$	76.6	$	70.8	$	210.9	$	193.7

Item 3. Quantitative and Qualitative Disclosures About Market Risk

The Company is exposed to the impact of market fluctuations associated with interest rates and commodity prices. The Company has policies and procedures to assist in controlling these market risks and from time to time has utilized derivatives to manage a portion of its risk.

Interest rate risk

There were no material changes to interest rate risk faced by the Company from those reported in the 2020 Annual Report.

At June 30, 2021, the Company had no outstanding interest rate hedges.

Commodity price risk

There were no material changes to commodity price risk faced by the Company from those reported in the 2020 Annual Report.

Item 4. Controls and Procedures

Evaluation of disclosure controls and procedures

The term "disclosure controls and procedures" is defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act. The Company's disclosure controls and other procedures are designed to provide reasonable assurance that information required to be disclosed in the reports that the Company files or submits under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the SEC's rules and forms. The Company's disclosure controls and other procedures are designed to provide reasonable assurance that information required to be disclosed is accumulated and communicated to management, including the Company's chief executive officer and chief financial officer, to allow timely decisions regarding required disclosure. The Company's management, with the participation of the Company's chief executive officer and chief financial officer, has evaluated the effectiveness of the Company's disclosure controls and other procedures as of the end of the period covered by this report. Based upon that evaluation, the chief executive officer and the chief financial officer have concluded that, as of the end of the period covered by this report, such controls and procedures were effective at a reasonable assurance level.

51

Changes in internal controls

No change in the Company's internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the three months ended June 30, 2021, that has materially affected, or is reasonably likely to materially affect, the Company's internal control over financial reporting.

52

Part II -- Other Information

Item 1. Legal Proceedings

There were no material changes to the Company's legal proceedings in Part 1, Item 3 - Legal Proceedings in the 2020 Annual Report.

Item 1A. Risk Factors

Please refer to the Company's risk factors that are disclosed in Part I, Item 1A. Risk Factors in the 2020 Annual Report that could be materially harmful to the Company's business, prospects, financial condition or financial results if they occur. At June 30, 2021, there were no material changes to the Company's risk factors provided in Part I, Item 1A. Risk Factors in the 2020 Annual Report other than as set forth below.

Technology disruptions or cyberattacks could adversely impact the Company's operations.

The Company uses technology in substantially all aspects of its business operations and requires uninterrupted operation of information technology and operation technology systems, including disaster recovery and backup systems and network infrastructure. While the Company has policies, procedures and processes in place designed to strengthen and protect these systems, they may be vulnerable to physical and cybersecurity failures or unauthorized access, due to:

•hacking,

•human error,

•theft,

•sabotage,

•malicious software,

•ransomware,

•third-party compromise,

•acts of terrorism,

•acts of war,

•acts of nature or

•other causes.

Although there are manual processes in place, should a compromise or system failure occur, interdependencies to technology may disrupt the Company's ability to fulfill critical business functions. This may include interruption of electric generation, transmission and distribution facilities, natural gas storage and pipeline facilities and facilities for delivery of construction materials or other products and services, any of which could adversely affect the Company's reputation, business, cash flows and results of operations or subject the Company to legal or regulatory liabilities and increased costs. Additionally, the Company's electric generation and transmission systems and natural gas pipelines are part of interconnected systems with other operators’ facilities; therefore, a cyber-related disruption in another operator’s system could negatively impact the Company's business.

The Company’s accounting systems and its ability to collect information and invoice customers for products and services could be disrupted. If the Company’s operations are disrupted, it could result in decreased revenues and remediation costs that could adversely affect the Company's results of operations and cash flows.

The Company is subject to cybersecurity and privacy laws and regulations of many government agencies, including TSA, FERC and NERC. NERC issues comprehensive regulations and standards surrounding the security of bulk power systems and continually updates these requirements, as well as establishing new requirements with which the utility industry must comply. As these regulations evolve, the Company may experience increased compliance costs and may be at higher risk for violating these standards. Experiencing a cybersecurity incident could cause the Company to be non-compliant with applicable laws and regulations, causing the Company to incur costs related to legal claims, proceedings and regulatory fines or penalties.

The Company, through the ordinary course of business, requires access to sensitive customer, employee and Company data. While the Company has implemented extensive security measures, including limiting the amount of sensitive information retained, a breach of its systems could compromise sensitive data and could go unnoticed for some time. Such an event could result in negative publicity and reputational harm, remediation costs, legal claims and fines that could have an adverse effect on the Company's financial results. Third-party service providers that perform critical business functions for the Company or have access to sensitive information within the Company also may be vulnerable to security breaches and information technology risks that could adversely affect the Company.

The Company’s information systems experience ongoing and often sophisticated cyberattacks by a variety of sources with the apparent aim to breach the Company's cyber-defenses. Although the incidents the Company has experienced to date have not had a material effect on its business, financial condition or results of operations, such incidents could have a material adverse effect in the future as cyberattacks continue to increase in frequency and sophistication. The Company is continuously reevaluating the need to upgrade and/or replace systems and network infrastructure. These upgrades and/or replacements could adversely impact

53

operations by imposing substantial capital expenditures, creating delays or outages, or experiencing difficulties transitioning to new systems. System disruptions, if not anticipated and appropriately mitigated, could adversely affect the Company.

The Company's participation in joint venture contracts may have a negative impact on its reputation, business operations, revenues, results of operations, liquidity and cash flows.

The Company enters into certain joint venture arrangements typically to bid and execute particular projects. Generally, these agreements are directly with a third-party client; however, services may be performed by the venture, the joint venture partners or a combination thereof. Engaging in joint venture contracts exposes the Company to risks and uncertainties, some of which are outside the Company's control.

The Company is reliant on joint venture partners to satisfy their contractual obligations, including obligations to commit working capital and equity, and to perform the work as outlined in the agreement. Failure to do so could result in the Company providing additional investments or services to address such performance issues. If the Company is unable to satisfactorily resolve any partner performance issues, the customer could terminate the contract opening the Company to legal liability which could negatively impact the Company's reputation, revenues, results of operations, liquidity and cash flows.

COVID-19 may have a negative impact on the Company's business operations, revenues, results of operations, liquidity and cash flows.

The ongoing COVID-19 pandemic has disrupted national, state and local economies. To the extent the COVID-19 pandemic adversely impacts the Company's businesses, operations, revenues, liquidity or cash flows, it could also have a heightening effect on other risks described in the 2020 Annual Report. The degree to which COVID-19 will impact the Company depends on future developments, including the resurgence and/or variants of the virus, actions taken by governmental authorities, effectiveness of vaccines being administered, and the pace and extent to which the economy recovers and returns to relatively normal operating conditions.

The Company’s businesses have generally been deemed essential service providers and have experienced some inefficiencies and interruptions on its businesses from the pandemic. The Company could be materially affected if its services were deemed no longer essential or if conditions worsen and new restrictions are imposed by national or local governmental authorities.

The Company's operations have experienced minor disruptions due to shortages of employees or third-party contractors and altered work operations. If a significant percentage of the Company's workforce are unable to work because of illness, quarantine or government restrictions in connection with the COVID-19 pandemic, the Company's operations may be negatively impacted, potentially adversely affecting its business, operations, revenues, liquidity and cash flows.

In response to the COVID-19 pandemic, the Company implemented a remote work environment for a portion of the Company's workforce. As of July 2021, many of these employees have returned to their office; however, some employees have transitioned to a permanent remote work environment. The increase in remote work and longevity of the pandemic may create increased vulnerability to cybersecurity incidents affecting the Company’s ability to maintain secure operations, communications and productivity. To date, the Company has not experienced any significant delays or information technology disruptions as a result of the COVID-19 pandemic.

Other factors associated with the COVID-19 pandemic that could impact the Company's businesses and future operating results, revenues and liquidity include impacts related to the health, safety, and availability of employees and contractors; extended rise in unemployment; public and private sector budget changes and constraints; continued flexible payment plans; counterparty credit; costs and availability of supplies; capital construction and infrastructure operation and maintenance programs; financing plans; pension valuations; travel restrictions; and legal and regulatory matters, including the potential for delayed regulatory filings, accounting for the impacts of the COVID-19 pandemic and recovery of invested capital. The economic and market disruptions resulting from COVID-19 could also lead to greater than normal uncertainty with respect to the realization of estimated amounts, including estimates for backlog, revenue recognition, intangible assets, other investments and provisions for credit losses.

54

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

The following table includes information with respect to the Company's purchase of equity securities:

ISSUER PURCHASES OF EQUITY SECURITIES
Period	(a) Total Number of Shares (or Units) Purchased (1)	(b) Average Price Paid per Share (or Unit)	(c) Total Number of Shares (or Units) Purchased as Part of Publicly Announced Plans or Programs (2)	(d) Maximum Number (or Approximate Dollar Value) of Shares (or Units) that May Yet Be Purchased Under the Plans or Programs (2)
April 1 through April 30, 2021	—	—	—	—
May 1 through May 31, 2021	—	—	—	—
June 1 through June 30, 2021	—	—	—	—
Total	—	—	—	—

(1)    Represents shares of common stock purchased on the open market in connection with the vesting of shares granted pursuant to the Long-Term Performance-Based Incentive Plan.

(2)    Not applicable. The Company does not currently have in place any publicly announced plans or programs to purchase equity securities.

Item 4. Mine Safety Disclosures

For information regarding mine safety violations or other regulatory matters required by Section 1503(a) of the Dodd-Frank Act and Item 104 of Regulation S-K, see Exhibit 95 to this Form 10-Q, which is incorporated herein by reference.

Item 5. Other Information

None.

Item 6. Exhibits

See the index to exhibits immediately preceding the signature page to this report.

55

Exhibits Index
			Incorporated by Reference
Exhibit Number	Exhibit Description	Filed Herewith	Form	Period Ended	Exhibit	Filing Date	File Number
3(a)	Amended and Restated Certificate of Incorporation of MDU Resources Group, Inc.		8-K		3.2	5/8/19	1-03480
3(b)	Amended and Restated Bylaws of MDU Resources Group, Inc.		8-K		3.1	2/15/19	1-03480
+10(b)	MDU Resources Group, Inc. Director Compensation Policy, as amended May 12, 2021	X
31(a)	Certification of Chief Executive Officer filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002	X
31(b)	Certification of Chief Financial Officer filed pursuant to Section 302 of the Sarbanes-Oxley Act of 2002	X
32	Certification of Chief Executive Officer and Chief Financial Officer furnished pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002	X
95	Mine Safety Disclosures	X
101.INS	XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document
101.SCH	XBRL Taxonomy Extension Schema Document
101.CAL	XBRL Taxonomy Extension Calculation Linkbase Document
101.DEF	XBRL Taxonomy Extension Definition Linkbase Document
101.LAB	XBRL Taxonomy Extension Label Linkbase Document
101.PRE	XBRL Taxonomy Extension Presentation Linkbase Document

+    Management contract, compensatory plan or arrangement.

56

Signatures

Pursuant to the requirements of the Exchange Act, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		MDU RESOURCES GROUP, INC.
DATE:	August 5, 2021	BY:	/s/ Jason L. Vollmer
			Jason L. Vollmer
			Vice President and Chief Financial Officer
		BY:	/s/ Stephanie A. Barth
			Stephanie A. Barth
			Vice President, Chief Accounting Officer and Controller

57

EX-10.B

MDU RESOURCES GROUP, INC.

DIRECTOR COMPENSATION POLICY

    Each director of MDU Resources Group, Inc. (the “Company”) who is not a full-time employee of the Company (a “Director”) shall receive compensation made up of annual cash retainers and shares of the Company’s common stock (“Common Stock”), as set forth in this policy.

Director Compensation

Annual Cash Retainers
	Base Retainer	$100,000*
	Additional Retainers:
	Non-Executive Chair of the Board	$112,500*
	Chair of Audit Committee	20,000*
	Chair of Compensation Committee	15,000*
	Chair of Environmental and Sustainability Committee	15,000*
	Chair of Nominating and Governance Committee	15,000*
	*Effective June 1, 2021.

    Such cash retainers shall be paid in monthly installments.

    The MDU Resources Group, Inc. Deferred Compensation Plan for Directors (as amended and restated effective May 15, 2008) (the “Plan”) permits a Director to defer all or any portion of the annual cash retainers. The amount deferred is recorded in each participant's deferred compensation account and credited with income in the manner prescribed in the Plan. For further details, reference is made to the Plan, a copy of which is attached.

Common Stock

    Each person, other than the Non-Executive Chair of the Board, who is a Director of the Company at any time during the calendar year shall receive a $140,000 stock payment, and any person who is the Non-Executive Chair of the Board shall receive a $165,000 stock payment, on or about the Wednesday following the Board of Directors’ regularly-scheduled November meeting, pursuant to the Non-Employee Director Long-Term Incentive Compensation Plan. The stock payment shall be made under the Non-Employee Director Long-Term Incentive Compensation Plan. The stock payment shall be made by providing the Director or Non-Executive Chair with the number of whole shares of Common Stock determined (i) if the shares are original issue or treasury stock, by dividing the amount of the applicable stock payment by the closing price of the Common Stock on the New York Stock Exchange on the grant date and (ii) if the shares are purchased on the open market, by dividing the amount of the applicable stock payment by the weighted average price paid to purchase shares for the Director or Non-Executive Chair for that stock payment, excluding any related brokerage commissions or other service fees. Any fractional shares shall be paid in cash. The stock payment shall be prorated for any Director or Non-Executive Chair who does not serve the entire calendar year by multiplying the

applicable stock payment by a fraction, the numerator of which is the number of actual or expected months (with a partial month counted as a full month) of service on the Board during the calendar year and the denominator of which is twelve.

    By written election a Director may reduce his or her annual cash retainers and have that amount applied to the purchase of additional shares of Common Stock under the Non-Employee Director Long-Term Incentive Compensation Plan. The annual election shall specify the percentage of the annual cash retainers to be applied toward the purchase of additional shares and must be received by the Company by the last business day of the year prior to the year in which the election is to be effective. No election may be changed or revoked for the current year, but may be changed for a subsequent year. The additional stock payments will be made on the last business day of March, June, September, and December. The stock payment shall be made by providing the Director with the number of whole shares of Common Stock determined (i) if the shares are original issue or treasury stock, by dividing the amount of the applicable stock payment by the closing price of the Common Stock on the New York Stock Exchange on the grant date or (ii) if the shares are purchased on the open market, by dividing the amount of the applicable stock payment by the weighted average price paid to purchase shares for the Director for that stock payment, excluding any related brokerage commissions or other service fees. No fractional shares shall be purchased and cash in lieu of any fractional shares shall be paid to the Director.

Travel Expense Reimbursement

All Directors will be reimbursed for reasonable travel expenses incurred while serving as a Director, including spouse’s expenses, in connection with attendance at meetings of the Company’s Board of Directors and its committees. If the travel expense is related to the reimbursement of airfare, such reimbursement will not exceed full-coach rate. Spousal travel expenses paid by the Company are treated as taxable income to the Director. See the paragraph below entitled "Code Section 409A" for further rules relating to travel expense reimbursements.

Directors' Liability

    Article Seven of the Company's Amended and Restated Certificate of Incorporation provides that no Director of the Company shall be liable to the Company or its stockholders for monetary damages for breach of fiduciary duty as a Director, except for liability: (i) for any breach of the Director’s duty of loyalty to the Company or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section-174 of the Delaware General Corporation Law (relating to unlawful declaration of dividends and unlawful purchase of the Company's stock), or (iv) for any transaction from which the Director derived an improper personal benefit.

    Section 7.07 of the Company’s Bylaws requires the Company to indemnify a Director, to the fullest extent permitted by applicable law, against expenses, attorneys fees, judgments, fines and amounts paid in settlement of any suit, action or proceeding, whether civil or criminal, arising from the fact that the Director was a Director of the Company.

    Additional protection is provided through individual indemnification agreements with each Director.

2

    The Company has and does maintain Directors' and Officers' liability insurance coverage with a $130 million limit.

Insurance Coverages

    The Company maintains the following insurance for protection of its Directors as they carry out the business of the Company, which shall be provided while serving as a Director: (i) general liability and automobile liability insurance, (ii) fiduciary and crime insurance, (iii) aircraft liability insurance, and (iv) business travel accident insurance.

    All outside Directors are protected by a non-contributory group life insurance policy with coverage of $100,000. The coverage begins the day the Director is elected to the Board of Directors and terminates when the Director ceases to be an outside Director. A Summary Plan Description (SPD) can be provided to the Director. The beneficiary of the insurance will be the beneficiary recorded on a beneficiary designation provided by the Company. The group life insurance policy is considered taxable compensation under current tax laws. Consequently, the Company will provide each Director annually on Form 1099 the amount of taxable income related to this coverage.

Hedging Stock Ownership

Directors are not permitted to hedge their ownership of Company common stock. Hedging strategies include but are not limited to zero-cost collars, equity swaps, straddles, prepaid variable forward contracts, security futures contracts, exchange funds, forward sale contracts and other financial transactions that allow the Director to benefit from devaluation of the Company's stock. Hedging strategies may allow Directors to own stock technically but without the full benefits and risks of such ownership. Therefore, Directors are prohibited from engaging in any such transactions.

Policy Regarding Margin Accounts and Pledging of Company Stock

Effective December 21, 2012, Directors and related persons are prohibited from holding Company common stock in a margin account or pledging Company securities as collateral for a loan, with certain exceptions. Company common stock may be held in a margin brokerage account only if the stock is explicitly excluded from any margin, pledge or security provisions of the customer agreement. Company common stock may be held in a cash account, which is a brokerage account that does not allow any extension of credit on securities. “Related person” means a Director’s spouse, minor child and any person (other than a tenant or domestic employee) sharing the household of a Director, as well as any entities over which a Director exercises control.

Code Section 409A

    To the extent any reimbursements or in-kind benefits provided to a Director pursuant to this policy constitute “deferred compensation” under Internal Revenue Code Section 409A, any such reimbursement or in-kind benefit shall be paid in a manner consistent with Treasury Regulation Section 1.409A-3(i)(1)(iv), including the requirements that the amount of reimbursable expenses or in-kind benefits provided during a year may not affect the expenses eligible for reimbursement or in-kind benefits provided in any other year and that any reimbursement be made on or before the last day of the calendar year following the calendar year in which the expense was incurred.

3

EX-31.A

CERTIFICATION

I, David L. Goodin, certify that:

1.I have reviewed this quarterly report on Form 10-Q of MDU Resources Group, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: August 5, 2021 

/s/ David L. Goodin

David L. Goodin

President and Chief Executive Officer

EX-31.B

CERTIFICATION

I, Jason L. Vollmer, certify that:

1.I have reviewed this quarterly report on Form 10-Q of MDU Resources Group, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date:  August 5, 2021

/s/ Jason L. Vollmer

Jason L. Vollmer

Vice President and Chief Financial Officer

EX-32

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906

OF THE SARBANES-OXLEY ACT OF 2002

    Each of the undersigned, David L. Goodin, the President and Chief Executive Officer, and Jason L. Vollmer, the Vice President and Chief Financial Officer of MDU Resources Group, Inc. (the "Company"), DOES HEREBY CERTIFY that:

    1.  The Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2021 (the "Report"), fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and

    2.  Information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

    IN WITNESS WHERE OF, each of the undersigned has executed this statement this 5th day of August, 2021.

/s/ David L. Goodin

David L. Goodin

President and Chief Executive Officer

/s/ Jason L. Vollmer

Jason L. Vollmer

Vice President and Chief Financial Officer

A signed original of this written statement required by Section 906 has been provided to MDU Resources Group, Inc. and will be retained by MDU Resources Group, Inc. and furnished to the Securities and Exchange Commission or its staff upon request.

EX-95

MDU RESOURCES GROUP, INC.

MINE SAFETY INFORMATION

The Dodd-Frank Wall Street Reform and Consumer Protection Act (Dodd-Frank Act) requires issuers to include in periodic reports filed with the SEC certain information relating to citations or orders for violations of standards under the Federal Mine Safety and Health Act of 1977 (Mine Act), as amended by the Mine Improvement and New Emergency Response Act of 2006 (Mine Safety Act). The Dodd-Frank Act requires reporting of the following types of citations or orders:

1.    Citations issued under Section 104 of the Mine Safety Act for violations that could significantly and substantially contribute to the cause and effect of a coal or other mine safety or health hazard.

2.    Orders issued under Section 104(b) of the Mine Safety Act. Orders are issued under this section when citations issued under Section 104 have not been totally abated within the time period allowed by the citation or subsequent extensions.

3.    Citations or orders issued under Section 104(d) of the Mine Safety Act. Citations or orders are issued under this section when it has been determined that the violation is caused by an unwarrantable failure of the mine operator to comply with the standards. An unwarrantable failure occurs when the mine operator is deemed to have engaged in aggravated conduct constituting more than ordinary negligence.

4.    Citations issued under Section 110(b)(2) of the Mine Safety Act for flagrant violations. Violations are considered flagrant for repeat or reckless failures to make reasonable efforts to eliminate a known violation of a mandatory health and safety standard that substantially and proximately caused, or reasonably could have been expected to cause, death or serious bodily injury.

5.    Imminent danger orders issued under Section 107(a) of the Mine Safety Act. An imminent danger is defined as the existence of any condition or practice in a coal or other mine which could reasonably be expected to cause death or serious physical harm before such condition or practice can be abated.

6.    Notice received under Section 104(e) of the Mine Safety Act of a pattern of violations or the potential to have such a pattern of violations that could significantly and substantially contribute to the cause and effect of mine health and safety standards.

During the three months ended June 30, 2021, none of the Company's operating subsidiaries received citations or orders under the following sections of the Mine Safety Act: 104(b), 104(d), 110(b)(2), 107(a) or 104(e). The Company did not have any mining-related fatalities during this period.

1

MSHA Identification Number/Contractor ID	Section 104 S&S Citations (#)	Total Dollar Value of MSHA Assessments Proposed ($)		Legal Actions Pending as of Last Day of Period (#)	Legal Actions Initiated During Period (#)	Legal Actions Resolved During Period (#)
04-01698	—	125		—	—	—
10-02088	—	—		—	—	1
21-03127	1	655		—	—	—
24-02022	1	1,030		—	—	—
32-00774	—	896		—	—	—
35-02382	3	2,448		—	—	—
35-00512	—	279		—	—	1
35-02968	—	—		1	1	2
35-03496	—	603		—	—	—
35-03527	—	125		—	—	—
35-03605	2	2,407		—	—	—
35-03667	1	—		—	—	—
39-00008	—	355		—	—	—
39-01478	—	125		—	—	—
41-05492	—	125		—	—	—
48-00715	—	125		—	—	—
48-01383	—	1,769		—	—	—
48-01670	—	699		—	—	—
51-00036	—	250		—	—	—
51-00242	—	125		—	—	—
	8	$	12,141	1	1	4

Legal actions pending before the Federal Mine Safety and Health Review Commission (the Commission) may involve, among other questions, challenges by operators to citations, orders and penalties they have received from the Federal Mine Safety and Health Administration (MSHA) or complaints of discrimination by miners under section 105 of the Mine Act. The following is a brief description of the types of legal actions that may be brought before the Commission.

•Contests of Citations and Orders - A contest proceeding may be filed with the Commission by operators, miners or miners' representatives to challenge the issuance of a citation or order issued by MSHA.

•Contests of Proposed Penalties (Petitions for Assessment of Penalties) - A contest of a proposed penalty is an administrative proceeding before the Commission challenging a civil penalty that MSHA has proposed for the alleged violation contained in a citation or order.

•Complaints for Compensation - A complaint for compensation may be filed with the Commission by miners entitled to compensation when a mine is closed by certain withdrawal orders issued by MSHA. The purpose of the proceeding is to determine the amount of compensation, if any, due miners idled by the orders.

•Complaints of Discharge, Discrimination or Interference - A discrimination proceeding is a case that involves a miner's allegation that he or she has suffered a wrong by the operator because he or she engaged in some type of activity protected under the Mine Act, such as making a safety complaint.

•Applications for Temporary Relief - Applications for temporary relief from any modification or termination of any order or from any order issued under section 104 of the Mine Act.

•Appeals of Judges' Decisions or Orders to the Commission - A filing with the Commission for discretionary review of a judge's decision or order by a person who has been adversely affected or aggrieved by such decision or order.

2

The following table reflects the types of legal actions pending before the Commission as of June 30, 2021:

MSHA Identification Number	Contests of Citations and Orders	Contests of Proposed Penalties	Complaints for Compensation	Complaints of Discharge, Discrimination or Interference	Applications for Temporary Relief	Appeals of Judges' Decisions or Orders to the Commission
35-02968	1	—	—	—	—	—

3

XML

Cover page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 29, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	1-03480
Entity Registrant Name	MDU RESOURCES GROUP INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	30-1133956
Entity Address, Address Line One	1200 West Century Avenue
Entity Address, Address Line Two	P.O. Box 5650
Entity Address, City or Town	Bismarck
Entity Address, State or Province	ND
Entity Address, Postal Zip Code	58506-5650
City Area Code	701
Local Phone Number	530-1000
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	MDU
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity common stock, shares outstanding		202,430,930
Entity Central Index Key	0000067716
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

XML

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating revenues:
Operating revenues:	$ 1,423,657	$ 1,362,928	$ 2,651,595	$ 2,560,302
Operating expenses:
Operation and maintenance:	1,077,796	1,029,171	1,889,454	1,850,171
Purchased natural gas sold	63,213	56,844	239,450	222,256
Depreciation, depletion and amortization	73,661	71,508	147,384	140,747
Taxes, other than income	53,189	52,584	115,724	116,696
Electric fuel and purchased power	18,109	14,567	36,730	35,107
Total operating expenses	1,285,968	1,224,674	2,428,742	2,364,977
Operating income	137,689	138,254	222,853	195,325
Other income	9,027	10,063	12,381	9,058
Interest expense	23,381	24,818	46,835	49,371
Income before income taxes	123,335	123,499	188,399	155,012
Income taxes	23,164	23,657	36,112	29,631
Income from continuing operations	100,171	99,842	152,287	125,381
Income (loss) from discontinued operations, net of tax	19	(139)	34	(548)
Net income	$ 100,190	$ 99,703	$ 152,321	$ 124,833
Earnings per share - basic:
Income from continuing operations	$ 0.50	$ 0.50	$ 0.76	$ 0.62
Discontinued operations, net of tax	0	0	0	0
Earnings per share - basic	0.50	0.50	0.76	0.62
Earnings per share - diluted:
Income from continuing operations	0.50	0.50	0.76	0.62
Discontinued operations, net of tax	0	0	0	0
Earnings per share - diluted	$ 0.50	$ 0.50	$ 0.76	$ 0.62
Weighted average common shares outstanding - basic	201,345	200,522	201,028	200,481
Weighted average common shares outstanding - diluted	201,693	200,539	201,328	200,497
Regulated operation
Operating revenues:
Operating revenues:	$ 260,568	$ 241,353	$ 702,951	$ 660,035
Operating expenses:
Operation and maintenance:	89,404	83,103	183,737	170,712
Income from continuing operations	17,686	19,878	73,808	71,007
Nonregulated operation
Operating revenues:
Operating revenues:	1,163,089	1,121,575	1,948,644	1,900,267
Operating expenses:
Operation and maintenance:	988,392	946,068	1,705,717	1,679,459
Income from continuing operations	$ 82,485	$ 79,964	$ 78,479	$ 54,374

XML

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net income	$ 100,190	$ 99,703	$ 152,321	$ 124,833
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, tax	36	36	73	72
Reclassification adjustment for loss on derivative instruments included in net income, net of tax	112	112	223	223
Postretirement liability adjustment:
Amortization of postretirement liability losses included in net periodic benefit cost, tax	160	155	311	304
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	457	480	923	942
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	(13)	(4)	(25)	32
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax	(52)	(13)	(96)	122
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	6	2	15	2
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax	25	7	60	6
Net unrealized gain (loss) on available-for-sale investments	(27)	(6)	(36)	128
Other comprehensive income	542	586	1,110	1,293
Comprehensive income attributable to common stockholders	$ 100,732	$ 100,289	$ 153,431	$ 126,126

XML

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Current assets:
Cash and cash equivalents	$ 57,946	$ 59,547	$ 64,358
Receivables, net	903,831	873,986	920,824
Inventories	316,328	291,167	302,837
Current regulatory assets	109,581	68,527	60,557
Prepayments and other current assets	74,259	44,120	48,194
Total current assets	1,461,945	1,337,347	1,396,770
Noncurrent assets:
Property, plant and equipment	8,417,559	8,300,770	8,063,435
Less accumulated depreciation, depletion and amortization	3,129,717	3,133,831	3,064,833
Net property, plant and equipment	5,287,842	5,166,939	4,998,602
Goodwill	717,863	714,963	708,664
Other intangible assets, net	23,401	25,496	31,515
Regulatory assets	376,913	379,381	351,025
Investments	173,157	165,022	154,779
Operating lease right-of-use assets	112,437	120,113	115,751
Other	144,653	144,111	154,026
Total noncurrent assets	6,836,266	6,716,025	6,514,362
Total assets	8,298,211	8,053,372	7,911,132
Current liabilities:
Short-term borrowings	50,000	50,000	75,000
Long-term debt due within one year	1,549	1,555	16,560
Accounts payable	431,878	426,264	433,362
Taxes payable	78,805	88,844	80,882
Dividends payable	42,791	42,611	41,608
Accrued compensation	95,909	90,629	85,525
Regulatory liabilities due within one year	23,454	31,450	48,000
Operating lease liabilities due within one year	31,787	33,655	31,985
Other accrued liabilities	188,187	198,514	186,797
Total current liabilities	944,360	963,522	999,719
Noncurrent liabilities:
Long-term debt	2,335,500	2,211,575	2,265,316
Deferred income taxes	538,633	516,098	516,760
Asset retirement obligations	450,620	440,356	422,169
Regulatory liabilities	428,467	428,075	438,652
Operating lease liabilities	81,052	86,868	84,302
Other	320,777	327,773	286,527
Total noncurrent liabilities	4,155,049	4,010,745	4,013,726
Commitments and contingencies
Stockholders' equity:
Common stock	202,822	201,061	201,061
Other paid-in capital	1,422,169	1,371,385	1,363,182
Retained earnings	1,624,405	1,558,363	1,377,879
Accumulated other comprehensive loss	(46,968)	(48,078)	(40,809)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)	(3,626)
Total stockholders' equity	3,198,802	3,079,105	2,897,687
Total liabilities and stockholders' equity	$ 8,298,211	$ 8,053,372	$ 7,911,132
Common Stock, Shares Authorized	500,000,000	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00	$ 1.00
Common Stock, Shares, Issued	202,822,301	201,061,198	201,061,198
Treasury Stock, Common, Shares	538,921	538,921	538,921

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Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common stock	Other paid-in capital	Retained earnings	Accumulated other comprehensive loss	Treasury stock
Common stock balance (in shares) at Dec. 31, 2019		200,922,790
Treasury stock (in shares) at Dec. 31, 2019						(538,921)
Balance at Dec. 31, 2019	$ 2,847,246	$ 200,923	$ 1,355,404	$ 1,336,647	$ (42,102)	$ (3,626)
Net income	25,130			25,130
Other comprehensive income	707				707
Dividends declared on common stock	(41,789)			(41,789)
Stock-based compensation	2,250		2,250
Issuance of common stock upon vesting of stock-based compensation, tax withholding shares		26,406
Issuance of common stock upon vesting of stock-based compensation, tax withholding shares value		$ 26
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 (shares)		112,002
Issuance of common stock	3,410	$ 112	3,298
Common stock balance (in shares) at Mar. 31, 2020		201,061,198
Treasury stock (in shares) at Mar. 31, 2020						(538,921)
Balance at Mar. 31, 2020	2,836,592	$ 201,061	1,360,564	1,319,988	(41,395)	$ (3,626)
Common stock balance (in shares) at Dec. 31, 2019		200,922,790
Treasury stock (in shares) at Dec. 31, 2019						(538,921)
Balance at Dec. 31, 2019	2,847,246	$ 200,923	1,355,404	1,336,647	(42,102)	$ (3,626)
Net income	124,833
Other comprehensive income	1,293
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	$ (362)
Common stock balance (in shares) at Jun. 30, 2020	201,061,198	201,061,198
Treasury stock (in shares) at Jun. 30, 2020						(538,921)
Balance at Jun. 30, 2020	$ 2,897,687	$ 201,061	1,363,182	1,377,879	(40,809)	$ (3,626)
Common stock balance (in shares) at Mar. 31, 2020		201,061,198
Treasury stock (in shares) at Mar. 31, 2020						(538,921)
Balance at Mar. 31, 2020	2,836,592	$ 201,061	1,360,564	1,319,988	(41,395)	$ (3,626)
Net income	99,703			99,703
Other comprehensive income	586				586
Dividends declared on common stock	(41,812)			(41,812)
Stock-based compensation	$ 2,618		2,618
Common stock balance (in shares) at Jun. 30, 2020	201,061,198	201,061,198
Treasury stock (in shares) at Jun. 30, 2020						(538,921)
Balance at Jun. 30, 2020	$ 2,897,687	$ 201,061	1,363,182	1,377,879	(40,809)	$ (3,626)
Common stock balance (in shares) at Dec. 31, 2020	201,061,198	201,061,198
Treasury stock (in shares) at Dec. 31, 2020						(538,921)
Balance at Dec. 31, 2020	$ 3,079,105	$ 201,061	1,371,385	1,558,363	(48,078)	$ (3,626)
Net income	52,131			52,131
Other comprehensive income	568				568
Dividends declared on common stock	(42,943)			(42,943)
Stock-based compensation	2,574		2,574
Repurchase of common stock						(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						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 (shares)		672,260
Issuance of common stock	19,699	$ 672	19,027
Common stock balance (in shares) at Mar. 31, 2021		201,733,458
Treasury stock (in shares) at Mar. 31, 2021						(538,921)
Balance at Mar. 31, 2021	$ 3,100,306	$ 201,733	1,382,158	1,567,551	(47,510)	$ (3,626)
Common stock balance (in shares) at Dec. 31, 2020	201,061,198	201,061,198
Treasury stock (in shares) at Dec. 31, 2020						(538,921)
Balance at Dec. 31, 2020	$ 3,079,105	$ 201,061	1,371,385	1,558,363	(48,078)	$ (3,626)
Net income	152,321
Other comprehensive income	1,110
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	$ (4,127)
Common stock balance (in shares) at Jun. 30, 2021	202,822,301	202,822,301
Treasury stock (in shares) at Jun. 30, 2021						(538,921)
Balance at Jun. 30, 2021	$ 3,198,802	$ 202,822	1,422,169	1,624,405	(46,968)	$ (3,626)
Common stock balance (in shares) at Mar. 31, 2021		201,733,458
Treasury stock (in shares) at Mar. 31, 2021						(538,921)
Balance at Mar. 31, 2021	3,100,306	$ 201,733	1,382,158	1,567,551	(47,510)	$ (3,626)
Net income	100,190			100,190
Other comprehensive income	542				542
Dividends declared on common stock	(43,336)			(43,336)
Stock-based compensation	6,150		6,150
Issuance of common stock (shares)		1,088,843
Issuance of common stock	$ 34,950	$ 1,089	33,861
Common stock balance (in shares) at Jun. 30, 2021	202,822,301	202,822,301
Treasury stock (in shares) at Jun. 30, 2021						(538,921)
Balance at Jun. 30, 2021	$ 3,198,802	$ 202,822	$ 1,422,169	$ 1,624,405	$ (46,968)	$ (3,626)

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Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net income	$ 152,321	$ 124,833
Income (loss) from discontinued operations, net of tax	34	(548)
Income from continuing operations	152,287	125,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	147,384	140,747
Deferred income taxes	14,498	2,881
Changes in current assets and liabilities, net of acquisitions:
Receivables	(18,516)	(40,801)
Inventories	(25,330)	(26,276)
Other current assets	(52,768)	30,790
Accounts payable	(3,845)	13,387
Other current liabilities	(22,605)	26,612
Other noncurrent changes	(8,236)	(10,923)
Net cash provided by continuing operations	182,869	261,798
Net cash used in discontinued operations	(58)	(396)
Net cash provided by operating activities	182,811	261,402
Investing activities:
Capital expenditures	(261,937)	(248,800)
Acquisitions, net of cash acquired	(13,721)	(70,729)
Net proceeds from sale or disposition of property and other	12,402	22,968
Investments	(3,244)	23
Net cash used in investing activities	(266,500)	(296,538)
Financing activities:
Issuance of short-term borrowings	50,000	75,000
Repayment of short-term borrowings	(50,000)	0
Issuance of long-term debt	171,769	200,400
Repayment of long-term debt	(48,151)	(162,225)
Proceeds from issuance of common stock	54,649	3,410
Dividends paid	(85,351)	(83,188)
Repurchase of common stock	(6,701)	0
Tax withholding on stock-based compensation	(4,127)	(362)
Net cash provided by financing activities	82,088	33,035
Decrease in cash and cash equivalents	(1,601)	(2,101)
Cash and cash equivalents -- beginning of year	59,547	66,459
Cash and cash equivalents -- end of period	$ 57,946	$ 64,358

XML

Basis of presentation

6 Months Ended

Jun. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of presentation

Basis of presentation

The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2020 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses.

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 our country and our communities and, as a result, operations have generally continued throughout 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 six months ended June 30, 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. 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.

Management has also evaluated the impact of events occurring after June 30, 2021, up to the date of the issuance of these consolidated interim financial statements on August 5, 2021, that would require recognition or disclosure in the financial statements.

XML

New accounting standards

6 Months Ended

Jun. 30, 2021

Accounting Standards Update and Change in Accounting Principle [Abstract]

New accounting standards

New accounting standards

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, clarified 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 effect a one percentage point change in assumed health care cost trend rates would have on certain benefit components. The Company adopted the guidance on January 1, 2021, on a retrospective basis. The Company determined the new guidance will 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. The Company adopted the guidance on January 1, 2021, and determined it did not have a material impact on 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 applied 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. LIBOR is expected to be retired with a full phase-out by the end of 2021 and replaced by a new reference rate, which includes SOFR. The guidance can be applied beginning in the interim period that includes March 12, 2020, and cannot be applied to contract modifications or hedging relationships entered into or evaluated after 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.

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Seasonality of operations	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Seasonality of operations	Seasonality of operations Some of the Company's operations are highly seasonal and revenues from, and certain expenses for, such operations may fluctuate significantly among quarterly periods. Accordingly, the interim results for particular businesses, and for the Company as a whole, may not be indicative of results for the full fiscal year.

XML

Receivables and allowance for expected credit losses

6 Months Ended

Jun. 30, 2021

Credit Loss [Abstract]

Receivables and allowance for expected credit loss

Receivables and allowance for expected credit losses

Receivables consists primarily of trade receivables from the sale of goods and services, which are recorded at the invoiced amount, and contract assets, net of expected credit losses. For more information on contract assets, see Note 9. The Company's trade receivables are all due in 12 months or less. The total balance of receivables past due 90 days or more was $34.2 million, $45.1 million and $43.9 million at June 30, 2021 and 2020, and December 31, 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, general economic conditions of the various local economies and impacts of COVID-19, among others. Specific account balances are written off when management determines the amounts to be uncollectible. Management has reviewed the balance reserved through the allowance for expected credit losses and believes it is reasonable.

Details of the Company's expected credit losses were as follows:

	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Total
	(In thousands)
At December 31, 2020	$	899	$	2,571	$	2	$	6,164	$	5,722	$	15,358
Current expected credit loss provision	538		1,273		—		(1,049)		(1,079)		(317)
Less write-offs charged against the allowance	888		1,107		—		273		401		2,669
Credit loss recoveries collected	129		213		—		—		—		342
At March 31, 2021	$	678	$	2,950	$	2	$	4,842	$	4,242	$	12,714
Current expected credit loss provision	(110)		(103)		—		11		(639)		(841)
Less write-offs charged against the allowance	341		787		—		232		64		1,424
Credit loss recoveries collected	100		199		—		—		—		299
At June 30, 2021	$	327	$	2,259	$	2	$	4,621	$	3,539	$	10,748

	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	555		1,156		—		694		1,150		3,555
Less write-offs charged against the allowance	500		624		—		68		73		1,265
Credit loss recoveries collected	109		229		—		—		—		338
At March 31, 2020	$	492	$	1,817	$	—	$	5,983	$	2,833	$	11,125
Current expected credit loss provision	303		190		—		(314)		896		1,075
Less write-offs charged against the allowance	224		677		—		44		454		1,399
Credit loss recoveries collected	88		201		—		—		—		289
At June 30, 2020	$	659	$	1,531	$	—	$	5,625	$	3,275	$	11,090

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Inventories and natural gas in storage

6 Months Ended

Jun. 30, 2021

Inventory Disclosure [Abstract]

Inventories and natural gas in storage

Inventories and natural gas in storage

Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method. The portion of the cost of natural gas in storage expected to be used within 12 months was included in inventories. Inventories on the Consolidated Balance Sheets were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Aggregates held for resale	$	183,977	$	165,357	$	175,782
Asphalt oil	51,500		57,207		28,238
Materials and supplies	27,969		27,805		25,142
Merchandise for resale	26,871		22,974		21,087
Natural gas in storage (current)	10,824		11,776		21,919
Other	15,187		17,718		18,999
Total	$	316,328	$	302,837	$	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 June 30, 2021 and December 31, 2020, and $48.3 million at June 30, 2020.

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Earnings per share

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Earnings per share

Earnings per share

Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands, except per share amounts)
Weighted average common shares outstanding - basic	201,345		200,522		201,028		200,481
Effect of dilutive performance share awards and restricted stock units	348		17		300		16
Weighted average common shares outstanding - diluted	201,693		200,539		201,328		200,497
Shares excluded from the calculation of diluted earnings per share	—		187		—		191
Dividends declared per common share	$	.2125	$	.2075	$	.4250	$	.4150

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Equity

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Equity

Equity

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.

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 this agreement. As of June 30, 2021, the Company had capacity to issue up to 4.6 million additional shares of common stock under the "at-the-market" offering program.

Details of the Company's "at-the-market" offering activity was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Shares issued	1.1		—		1.8		—
Net proceeds *	$	34.9	$	—	$	54.6	$	—
Issuance costs	$	.4	$	—	$	.7	$	—

*    Net proceeds were used for capital expenditures.

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Accumulated other comprehensive income (loss)

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Accumulated other comprehensive income (loss)

Accumulated other comprehensive loss

The after-tax changes in the components of accumulated other comprehensive loss were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  Liability Adjustment		Net Unrealized Gain (Loss) on Available-for-sale Investments		Total Accumulated  Other Comprehensive  Loss
	(In thousands)
At December 31, 2020	$	(984)	$	(47,207)	$	113	$	(48,078)
Other comprehensive loss before reclassifications	—		—		(44)		(44)
Amounts reclassified from accumulated other comprehensive loss	111		466		35		612
Net current-period other comprehensive income (loss)	111		466		(9)		568
At March 31, 2021	$	(873)	$	(46,741)	$	104	$	(47,510)
Other comprehensive loss before reclassifications	—		—		(52)		(52)
Amounts reclassified from accumulated other comprehensive loss	112		457		25		594
Net current-period other comprehensive income (loss)	112		457		(27)		542
At June 30, 2021	$	(761)	$	(46,284)	$	77	$	(46,968)

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  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 income before reclassifications	—		—		135		135
Amounts reclassified from (to) accumulated other comprehensive loss	111		462		(1)		572
Net current-period other comprehensive income	111		462		134		707
At March 31, 2020	$	(1,319)	$	(40,272)	$	196	$	(41,395)
Other comprehensive loss before reclassifications	—		—		(13)		(13)
Amounts reclassified from accumulated other comprehensive loss	112		480		7		599
Net current-period other comprehensive income (loss)	112		480		(6)		586
At June 30, 2020	$	(1,207)	$	(39,792)	$	190	$	(40,809)

The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows:

	Three Months Ended				Six Months Ended				Location on Consolidated Statements of Income
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Reclassification adjustment for loss on derivative instruments included in net income	$	(148)	$	(148)	$	(296)	$	(295)	Interest expense
	36		36		73		72		Income taxes
	(112)		(112)		(223)		(223)
Amortization of postretirement liability losses included in net periodic benefit cost	(617)		(635)		(1,234)		(1,246)		Other income
	160		155		311		304		Income taxes
	(457)		(480)		(923)		(942)
Reclassification adjustment on available-for-sale investments included in net income	(31)		(9)		(75)		(8)		Other income
	6		2		15		2		Income taxes
	(25)		(7)		(60)		(6)
Total reclassifications	$	(594)	$	(599)	$	(1,206)	$	(1,171)

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Revenue from contracts with customers

6 Months Ended

Jun. 30, 2021

Revenue from Contract with Customer [Abstract]

Revenue from contracts with customers

Revenue from contracts with customers

Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes.

Disaggregation

In the following tables, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 17.

Three Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	29,258	$	83,480	$	—	$	—	$	—	$	—	$	112,738
Commercial utility sales	33,834		47,612		—		—		—		—		81,446
Industrial utility sales	10,354		6,180		—		—		—		—		16,534
Other utility sales	1,825		—		—		—		—		—		1,825
Natural gas transportation	—		11,451		27,685		—		—		—		39,136
Natural gas storage	—		—		3,094		—		—		—		3,094
Contracting services	—		—		—		280,834		—		—		280,834
Construction materials	—		—		—		498,762		—		—		498,762
Intrasegment eliminations	—		—		—		(145,780)		—		—		(145,780)
Inside specialty contracting	—		—		—		—		347,702		—		347,702
Outside specialty contracting	—		—		—		—		165,123		—		165,123
Other	9,465		2,794		4,810		—		57		3,389		20,515
Intersegment eliminations	(136)		(142)		(7,862)		(142)		(797)		(3,361)		(12,440)
Revenues from contracts with customers	84,600		151,375		27,727		633,674		512,085		28		1,409,489
Revenues out of scope	(950)		2,413		46		—		12,659		—		14,168
Total external operating revenues	$	83,650	$	153,788	$	27,773	$	633,674	$	524,744	$	28	$	1,423,657

Three Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	27,954	$	78,653	$	—	$	—	$	—	$	—	$	106,607
Commercial utility sales	29,877		41,027		—		—		—		—		70,904
Industrial utility sales	8,072		5,658		—		—		—		—		13,730
Other utility sales	1,591		—		—		—		—		—		1,591
Natural gas transportation	—		10,350		27,965		—		—		—		38,315
Natural gas gathering	—		—		1,181		—		—		—		1,181
Natural gas storage	—		—		3,104		—		—		—		3,104
Contracting services	—		—		—		303,356		—		—		303,356
Construction materials	—		—		—		482,498		—		—		482,498
Intrasegment eliminations	—		—		—		(164,719)		—		—		(164,719)
Inside specialty contracting	—		—		—		—		324,921		—		324,921
Outside specialty contracting	—		—		—		—		160,696		—		160,696
Other	7,717		2,711		3,363		—		412		2,861		17,064
Intersegment eliminations	(196)		(185)		(7,999)		(90)		(779)		(2,973)		(12,222)
Revenues from contracts with customers	75,015		138,214		27,614		621,045		485,250		(112)		1,347,026
Revenues out of scope	1,423		3,280		44		—		11,155		—		15,902
Total external operating revenues	$	76,438	$	141,494	$	27,658	$	621,045	$	496,405	$	(112)	$	1,362,928

Six Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	62,694	$	286,617	$	—	$	—	$	—	$	—	$	349,311
Commercial utility sales	66,762		167,664		—		—		—		—		234,426
Industrial utility sales	20,383		14,992		—		—		—		—		35,375
Other utility sales	3,391		—		—		—		—		—		3,391
Natural gas transportation	—		23,903		57,102		—		—		—		81,005
Natural gas storage	—		—		7,123		—		—		—		7,123
Contracting services	—		—		—		376,859		—		—		376,859
Construction materials	—		—		—		715,174		—		—		715,174
Intrasegment eliminations	—		—		—		(192,496)		—		—		(192,496)
Inside specialty contracting	—		—		—		—		702,892		—		702,892
Outside specialty contracting	—		—		—		—		316,486		—		316,486
Other	19,238		5,803		7,470		—		93		6,730		39,334
Intersegment eliminations	(271)		(284)		(34,092)		(204)		(1,839)		(6,685)		(43,375)
Revenues from contracts with customers	172,197		498,695		37,603		899,333		1,017,632		45		2,625,505
Revenues out of scope	(3,873)		5,299		82		—		24,582		—		26,090
Total external operating revenues	$	168,324	$	503,994	$	37,685	$	899,333	$	1,042,214	$	45	$	2,651,595

Six Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	60,303	$	265,354	$	—	$	—	$	—	$	—	$	325,657
Commercial utility sales	63,464		156,023		—		—		—		—		219,487
Industrial utility sales	18,439		14,179		—		—		—		—		32,618
Other utility sales	3,239		—		—		—		—		—		3,239
Natural gas transportation	—		22,148		55,397		—		—		—		77,545
Natural gas gathering	—		—		3,271		—		—		—		3,271
Natural gas storage	—		—		6,150		—		—		—		6,150
Contracting services	—		—		—		401,757		—		—		401,757
Construction materials	—		—		—		690,408		—		—		690,408
Intrasegment eliminations	—		—		—		(208,823)		—		—		(208,823)
Inside specialty contracting	—		—		—		—		697,130		—		697,130
Outside specialty contracting	—		—		—		—		290,846		—		290,846
Other	16,167		5,209		6,604		—		763		5,852		34,595
Intersegment eliminations	(391)		(370)		(33,198)		(152)		(3,249)		(5,946)		(43,306)
Revenues from contracts with customers	161,221		462,543		38,224		883,190		985,490		(94)		2,530,574
Revenues out of scope	1,125		5,394		89		—		23,120		—		29,728
Total external operating revenues	$	162,346	$	467,937	$	38,313	$	883,190	$	1,008,610	$	(94)	$	2,560,302

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:

	June 30, 2021		December 31, 2020		Change		Location on Consolidated Balance Sheets
	(In thousands)
Contract assets	$	147,033	$	104,345	$	42,688	Receivables, net
Contract liabilities - current	(146,116)		(158,603)		12,487		Accounts payable
Contract liabilities - noncurrent	(160)		(52)		(108)		Noncurrent liabilities - other
Net contract assets (liabilities)	$	757	$	(54,310)	$	55,067

The Company recognized $21.9 million and $145.3 million in revenue for the three and six months ended June 30, 2021, respectively, which was previously included in contract liabilities at December 31, 2020. The Company recognized $32.3 million and $121.7 million in revenue for the three and six months ended June 30, 2020, respectively, which was previously included in contract liabilities at December 31, 2019.

The Company recognized a net increase in revenues of $27.3 million and $54.6 million for the three and six months ended June 30, 2021, respectively, from performance obligations satisfied in prior periods. The Company recognized a net increase in revenues of $31.9 million and $42.9 million for the three and six months ended June 30, 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, which does not require additional disclosures for contracts with an original duration of less than 12 months, to certain firm transportation and non-regulated contracts. The Company's firm transportation and firm storage contracts included in the remaining performance obligations have weighted average remaining durations of approximately five and one years, respectively.

At June 30, 2021, the Company's remaining performance obligations were $2.4 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; $339.5 million within the next 13 to 24 months; and $225.9 million in 25 months or more.

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Business Combinations

6 Months Ended

Jun. 30, 2021

Business Combinations [Abstract]

Business Combinations

Business combinations

The following acquisitions were accounted for as business combinations in accordance with ASC 805 - Business Combinations. The results of the acquired businesses have been included in the 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:

•Mt. Hood Rock, a construction aggregates business in Oregon, was acquired in April 2021. At June 30, 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, were acquired in December 2020. At June 30, 2021, the purchase price allocation was preliminary and will be finalized within 12 months of the acquisition date. In the second quarter of 2021, the Company made a purchase price adjustment, which was not material, to the provisional accounting and is reflected in the 2021 allocated amounts below.

•The assets of Oldcastle Infrastructure Spokane, a prestressed-concrete business in Washington, were 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.

In 2021, the total purchase price for acquisitions was $13.8 million, subject to certain adjustments, with cash acquired totaling $100,000. The purchase price includes consideration paid of $13.7 million. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2021 were as follows: $700,000 to current assets; $13.0 million to property, plant and equipment; $2.9 million to goodwill; $600,000 to other intangible assets; $200,000 to current liabilities; $100,000 to noncurrent liabilities and $3.2 million to deferred tax liabilities. The Company issued debt to finance the acquisitions.

In 2020, the total purchase price for acquisitions 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 Company issued debt to finance the acquisitions.

Costs incurred for acquisitions are included in operation and maintenance expense on the Consolidated Statements of Income and were not material for the six months ended June 30, 2021 and 2020.

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Leases

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Leases

Leases

The Company's leases primarily include operating leases for equipment, buildings, easements and vehicles. The Company leases certain equipment to third parties through its utility and construction services segments, which are considered short-term operating leases with terms of less than 12 months.

The Company recognized revenue from operating leases of $12.8 million and $24.8 million for the three and six months ended June 30, 2021, respectively. The Company recognized revenue from operating leases of $11.2 million and $23.3 million for the three and six months ended June 30, 2020, respectively. At June 30, 2021, the Company had $9.8 million of lease receivables with a majority due within 12 months.

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Goodwill and other intangible assets

6 Months Ended

Jun. 30, 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 June 30, 2021
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	226,003		2,900		—		228,903
Construction services	143,224		—		—		143,224
Total	$	714,963	$	2,900	$	—	$	717,863

	Balance at January 1, 2020		Goodwill Acquired During the Year		Measurement Period Adjustments		Balance at June 30, 2020
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	217,234		6,483		—		223,717
Construction services	118,388		24,436		(3,613)		139,211
Total	$	681,358	$	30,919	$	(3,613)	$	708,664

	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 were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Customer relationships	$	29,423	$	30,087	$	28,836
Less accumulated amortization	8,765		5,239		6,887
	20,658		24,848		21,949
Noncompete agreements	3,991		4,229		3,941
Less accumulated amortization	2,576		2,084		2,309
	1,415		2,145		1,632
Other	11,957		13,060		12,927
Less accumulated amortization	10,629		8,538		11,012
	1,328		4,522		1,915
Total	$	23,401	$	31,515	$	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 10.

Amortization expense for amortizable intangible assets for the three and six months ended June 30, 2021, was $1.2 million and $2.7 million, respectively. Amortization expense for amortizable intangible assets for the three and six months ended June 30, 2020, was $2.7 million and $4.7 million, respectively. Estimated amortization expense for identifiable intangible assets as of June 30, 2021, was:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Amortization expense	$	2,381	$	4,678	$	4,329	$	3,957	$	2,060	$	5,996

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Regulatory assets and liabilities

6 Months Ended

Jun. 30, 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:

	Estimated Recovery or Refund Period as of June 30, 2021	*	June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Regulatory assets:
Current:
Natural gas costs recoverable through rate adjustments	Up to 1 year		$	85,045	$	42,582	$	42,481
Conservation programs	Up to 1 year		7,580		7,256		7,117
Cost recovery mechanisms	Up to 1 year		5,692		7,781		10,645
Other	Up to 1 year		11,264		2,938		8,284
			109,581		60,557		68,527
Noncurrent:
Pension and postretirement benefits	**		155,906		157,033		155,942
Plant costs/asset retirement obligations	Over plant lives		72,853		68,191		71,740
Plant retirement	-		46,061		49,185		65,919
Cost recovery mechanisms	Up to 10 years		44,415		13,140		16,245
Manufactured gas plant site remediation	-		26,155		14,826		26,429
Taxes recoverable from customers	Over plant lives		10,929		10,890		10,785
Natural gas costs recoverable through rate adjustments	Up to 3 years		8,389		27,184		21,539
Long-term debt refinancing costs	Up to 39 years		4,110		3,980		4,426
Other	Up to 18 years		8,095		6,596		6,356
			376,913		351,025		379,381
Total regulatory assets			$	486,494	$	411,582	$	447,908
Regulatory liabilities:
Current:
Natural gas costs refundable through rate adjustments	Up to 1 year		$	8,935	$	29,557	$	18,565
Electric fuel and purchased power deferral	Up to 1 year		5,431		7,799		3,667
Taxes refundable to customers	Up to 1 year		3,434		4,012		3,557
Other	Up to 1 year		5,654		6,632		5,661
			23,454		48,000		31,450
Noncurrent:
Taxes refundable to customers	Over plant lives		222,098		236,142		227,850
Plant removal and decommissioning costs	Over plant lives		171,381		173,399		167,171
Pension and postretirement benefits	**		16,940		18,015		16,989
Other	Up to 21 years		18,048		11,096		16,065
			428,467		438,652		428,075
Total regulatory liabilities			$	451,921	$	486,652	$	459,525
Net regulatory position			$	34,573	$	(75,070)	$	(11,617)

*Estimated recovery or refund period for amounts currently being recovered or refunded in rates charged to customers.

**    Recovered as expense is incurred or cash contributions are made.

At June 30, 2021 and 2020, and December 31, 2020, approximately $317.0 million, $296.6 million and $332.5 million, respectively, of regulatory assets were not earning a rate of return; however, these regulatory assets are expected to be recovered from customers in future rates. These assets are largely comprised of the unfunded portion of pension and postretirement benefits,

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 February 2021 in order to maintain services for its customers. These extraordinary gas costs were recorded as regulatory assets as they are expected to be recovered from customers. The Company has filed out-of-cycle purchased gas adjustment requests in four out of five jurisdictions affected by this cold-weather event and has received approval in three jurisdictions. The Company will continue to engage with its regulators to determine the appropriate recovery periods over which to recover the associated natural gas costs. For a discussion of the Company's most recent cases by jurisdiction, see Note 19.

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 has 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 in the second quarter of 2021, the Company began amortizing plant retirement and closure costs related to this facility. Requests have been filed with the NDPSC and SDPUC to offset the savings associated with the cessation of operations of this unit with the amortization of the deferred regulatory assets. In the second quarter of 2021, the Company moved the costs being recovered for this facility from plant retirement to cost recovery mechanisms in the previous table. The remaining two units are expected to be retired in early 2022. The Company expects to recover the regulatory assets related to the plant retirements in future rates. For a discussion of the Company's most recent cases by jurisdiction, see Note 19.

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 income (loss) in the period in which the discontinuance of regulatory accounting occurs.

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Fair value measurements

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Fair value measurements

Fair value measurements

The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income. The Company anticipates using these investments, which consist of insurance contracts, to satisfy its obligations under its unfunded, nonqualified defined benefit and defined contribution plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $105.7 million, $92.4 million and $100.1 million, at June 30, 2021 and 2020, and December 31, 2020, respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gains on these investments were $3.8 million and $3.9 million for the three and six months ended June 30, 2021, respectively. The net unrealized gains on these investments were $9.1 million and $5.4 million for the three and six months ended June 30, 2020, 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 income (loss). Details of available-for-sale securities were as follows:

June 30, 2021	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	8,278	$	127	$	9	$	8,396
U.S. Treasury securities	2,893		—		21		2,872
Total	$	11,171	$	127	$	30	$	11,268

June 30, 2020	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	9,812	$	239	$	6	$	10,045
U.S. Treasury securities	1,170		7		—		1,177
Total	$	10,982	$	246	$	6	$	11,222

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

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's money market funds are valued at the net asset value of shares held at the end of the quarter, based on published market quotations on active markets, or using other known sources including pricing from outside sources. The estimated fair value of the Company's mortgage-backed securities and U.S. Treasury securities are based on comparable market transactions, other observable inputs or other sources, including pricing from outside sources. The estimated fair value of the Company's insurance contracts are based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data.

Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value.

The Company's assets measured at fair value on a recurring basis were as follows:

	Fair Value Measurements at June 30, 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 June 30, 2021
	(In thousands)
Assets:
Money market funds	$	—	$	12,234	$	—	$	12,234
Insurance contracts*	—		105,684				105,684
Available-for-sale securities:
Mortgage-backed securities	—		8,396		—		8,396
U.S. Treasury securities	—		2,872		—		2,872
Total assets measured at fair value	$	—	$	129,186	$	—	$	129,186

*    The insurance contracts invest approximately 53 percent in fixed-income investments, 20 percent in common stock of large-cap companies, 10 percent in common stock of mid-cap companies, 9 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents.

	Fair Value Measurements at June 30, 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 June 30, 2020
	(In thousands)
Assets:
Money market funds	$	—	$	8,478	$	—	$	8,478
Insurance contract*	—		92,413		—		92,413
Available-for-sale securities:
Mortgage-backed securities	—		10,045		—		10,045
U.S. Treasury securities	—		1,177		—		1,177
Total assets measured at fair value	$	—	$	112,113	$	—	$	112,113

*    The insurance contract invests approximately 38 percent in fixed-income investments, 23 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, 4 percent in target date investments and 17 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 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 fair value assessments of the assets acquired and liabilities assumed in the business combinations that occurred during 2021 and 2020. The fair value of these assets and liabilities were determined based on Level 2 and Level 3 inputs.

The Company's long-term debt is not measured at fair value on the Consolidated Balance Sheets and the fair value is being provided for disclosure purposes only. The fair value was categorized as Level 2 in the fair value hierarchy and was based on discounted future cash flows using current market interest rates. The estimated fair value of the Company's Level 2 long-term debt was as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Carrying amount	$	2,337,049	$	2,281,876	$	2,213,130
Fair value	$	2,616,232	$	2,563,734	$	2,537,289

The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values.

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Debt

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Debt

Debt

Certain debt instruments of the Company's subsidiaries 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 June 30, 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.

Montana-Dakota's and Centennial's 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 the 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.

Long-term debt

Long-term Debt Outstanding Long-term debt outstanding was as follows:

	Weighted Average Interest Rate at June 30, 2021		June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Senior Notes due on dates ranging from October 22, 2022 to October 30, 2060	4.40	%	$	1,950,000	$	1,900,000	$	1,950,000
Commercial paper supported by revolving credit agreements	.32	%	297,400		290,100		125,600
Credit agreements due on June 7, 2024	3.25	%	48,550		11,200		95,900
Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029	7.32	%	35,000		50,000		35,000
Term Loan Agreement due on September 3, 2032	2.00	%	8,400		9,100		8,400
Other notes due on dates ranging from July 15, 2021 to January 1, 2061	.83	%	3,232		28,342		4,034
Less unamortized debt issuance costs			5,505		6,668		5,803
Less discount			28		198		1
Total long-term debt			2,337,049		2,281,876		2,213,130
Less current maturities			1,549		16,560		1,555
Net long-term debt			$	2,335,500	$	2,265,316	$	2,211,575

Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at June 30, 2021, were as follows:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Long-term debt maturities	$	752	$	148,021	$	77,921	$	407,372	$	177,802	$	1,530,714

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Cash flow information

6 Months Ended

Jun. 30, 2021

Supplemental Cash Flow Information [Abstract]

Cash flow information

Cash flow information

Cash expenditures for interest and income taxes were as follows:

	Six Months Ended
	June 30,
	2021		2020
	(In thousands)
Interest, net*	$	45,870	$	47,769
Income taxes paid, net	$	46,734	$	735

*    AFUDC - borrowed was $816,000 and $1.3 million for the six months ended June 30, 2021 and 2020, respectively.

Noncash investing and financing transactions were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Right-of-use assets obtained in exchange for new operating lease liabilities	$	17,224	$	24,181	$	54,356
Property, plant and equipment additions in accounts payable	$	31,886	$	36,493	$	26,082
Accrual for holdback payment related to a business combination	$	—	$	5,000	$	2,500

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Business segment data

6 Months Ended

Jun. 30, 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. In 2020, the pipeline segment divested its regulated and non-regulated natural gas gathering assets. With the completion of these sales, the segment exited the natural gas gathering business.

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-mixed 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, liquid asphalt 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, as well as Alaska and Hawaii.

The construction services segment provides inside and outside specialty contracting services in 43 states plus Washington D.C. Its inside services include design, construction and maintenance of electrical and communication wiring and infrastructure, fire suppression systems, and mechanical piping and services. Its outside services include design, construction and maintenance of overhead and underground electrical distribution and transmission lines, substations, external lighting, traffic signalization, and gas pipelines, as well as utility excavation and the manufacture and distribution of transmission line construction equipment. This segment also constructs and maintains renewable energy projects. These specialty contracting services are provided to utilities and large manufacturing, commercial, industrial, institutional and governmental customers.

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. The Other category also includes Centennial Resources' former investment in Brazil.

Discontinued operations include the results and supporting activities of Fidelity other than certain general and administrative costs and interest expense as described above.

The information below follows the same accounting policies as described in Note 2 of the Notes to Consolidated Financial Statements in the 2020 Annual Report. Information on the Company's segments was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
External operating revenues:
Regulated operations:
Electric	$	83,650	$	76,438	$	168,324	$	162,346
Natural gas distribution	153,788		141,494		503,994		467,937
Pipeline	23,130		23,421		30,633		29,752
	260,568		241,353		702,951		660,035
Non-regulated operations:
Pipeline	4,643		4,237		7,052		8,561
Construction materials and contracting	633,674		621,045		899,333		883,190
Construction services	524,744		496,405		1,042,214		1,008,610
Other	28		(112)		45		(94)
	1,163,089		1,121,575		1,948,644		1,900,267
Total external operating revenues	$	1,423,657	$	1,362,928	$	2,651,595	$	2,560,302

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Intersegment operating revenues:
Regulated operations:
Electric	$	136	$	196	$	271	$	391
Natural gas distribution	142		185		284		370
Pipeline	7,695		7,857		33,685		33,040
	7,973		8,238		34,240		33,801
Non-regulated operations:
Pipeline	167		142		407		158
Construction materials and contracting	142		90		204		152
Construction services	797		779		1,839		3,249
Other	3,361		2,973		6,685		5,946
	4,467		3,984		9,135		9,505
Intersegment eliminations	(12,440)		(12,222)		(43,375)		(43,306)
Total intersegment operating revenues	$	—	$	—	$	—	$	—
Operating income (loss):
Electric	$	12,806	$	12,810	$	26,672	$	27,669
Natural gas distribution	3,601		678		57,173		50,677
Pipeline	11,076		12,225		23,612		23,644
Construction materials and contracting	72,452		74,741		37,563		31,472
Construction services	37,774		37,882		78,051		61,678
Other	(20)		(82)		(218)		185
Total operating income	$	137,689	$	138,254	$	222,853	$	195,325
Net income (loss):
Regulated operations:
Electric	$	10,304	$	12,153	$	21,054	$	23,527
Natural gas distribution	(707)		(959)		35,471		31,410
Pipeline	8,089		8,684		17,283		16,070
	17,686		19,878		73,808		71,007
Non-regulated operations:
Pipeline	1,106		268		810		255
Construction materials and contracting	51,396		53,020		20,584		14,806
Construction services	28,885		27,932		58,709		44,755
Other	1,098		(1,256)		(1,624)		(5,442)
	82,485		79,964		78,479		54,374
Income from continuing operations	100,171		99,842		152,287		125,381
Income (loss) from discontinued operations, net of tax	19		(139)		34		(548)
Net income	$	100,190	$	99,703	$	152,321	$	124,833

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Employee benefit plans

6 Months Ended

Jun. 30, 2021

Retirement Benefits [Abstract]

Employee benefit plans

Employee benefit plans

Pension and other postretirement plans

The Company has noncontributory qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit credit for the Company's pension and other postretirement benefit plans were as follows:

	Pension Benefits				Other Postretirement Benefits
Three Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	400	$	414
Interest cost	2,455		3,074		466		627
Expected return on assets	(4,894)		(5,214)		(1,275)		(1,401)
Amortization of prior service credit	—		—		(349)		(402)
Amortization of net actuarial loss	2,004		1,723		6		142
Net periodic benefit credit, including amount capitalized	(435)		(417)		(752)		(620)
Less amount capitalized	—		—		44		35
Net periodic benefit credit	$	(435)	$	(417)	$	(796)	$	(655)

	Pension Benefits				Other Postretirement Benefits
Six Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	800	$	766
Interest cost	4,910		6,047		932		1,218
Expected return on assets	(9,788)		(9,975)		(2,550)		(2,649)
Amortization of prior service credit	—		—		(698)		(699)
Amortization of net actuarial loss	4,008		3,586		12		144
Net periodic benefit credit, including amount capitalized	(870)		(342)		(1,504)		(1,220)
Less amount capitalized	—		—		83		67
Net periodic benefit credit	$	(870)	$	(342)	$	(1,587)	$	(1,287)

The components of net periodic benefit credit, other than the service cost component, are included in other income on the Consolidated Statements of Income. The service cost component is included in operation and maintenance expense on the Consolidated Statements of Income.

Nonqualified defined benefit plans

In addition to the qualified defined benefit pension plans reflected in the table at the beginning of this note, the Company also has unfunded, nonqualified defined benefit plans for executive officers and certain key management employees. The Company's net periodic benefit cost for these plans was $769,000 and $1.5 million for the three and six months ended June 30, 2021, respectively. The Company's net periodic benefit cost for these plans for the three and six months ended June 30, 2020 was $900,000 and $1.9 million, respectively. The components of net periodic benefit cost for these plans are included in other income on the Consolidated Statements of Income.

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Regulatory matters

6 Months Ended

Jun. 30, 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 including updates to those reported in the 2020 Annual Report. 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.

IPUC

On January 12, 2021, Intermountain filed an application with the IPUC for a decrease in its depreciation and amortization rates of approximately $2.9 million annually or a decrease from a combined rate of 3.0 percent to 2.6 percent. On June 3, 2021, Intermountain filed a joint settlement agreement with the IPUC Staff reflecting a revised annual decrease of approximately $3.8 million or approximately 2.4 percent. Intermountain and the IPUC Staff have requested the rates be retroactive to January 1, 2021. This matter is pending before the IPUC.

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 March 30, 2021, Great Plains filed an out-of-cycle cost of gas adjustment with the MNPUC for the recovery of approximately $11.1 million. 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 length of recovery was requested at 28 months with a rate structure that is higher in the summer and lower in the winter due to the lower gas usage in the summer to mitigate the impact on customers. On June 8, 2021, the Company's request was denied; however, the MNPUC initiated its own investigation into the impact of severe weather in February 2021 on Minnesota's natural gas utility companies and consumers. The investigation will address the recovery of the extraordinary gas costs resulting from the February 2021 extreme cold weather event. MNPUC deliberations on this matter are scheduled for August 5, 2021. This matter is pending before the MNPUC.

NDPSC

Montana-Dakota defers the difference between the actual cost of gas spent to serve customers and that recovered from customers on a monthly basis. Annually, Montana-Dakota prepares a true-up pursuant to the purchased gas adjustment tariff. On March 31, 2021, Montana-Dakota filed an out-of-cycle cost of gas adjustment with the NDPSC for approximately $13.5 million. 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 filing was made to expedite recovery of these costs and maintain the timing of annual purchased gas adjustment filings. On May 27, 2021, the NDPSC approved the requested increase with a recovery period of 16 months effective June 1, 2021.

On July 15, 2021, Montana-Dakota filed an annual update to its transmission cost adjustment rider with the NDPSC requesting to recover revenues of approximately $14.5 million, which includes a true-up of the prior period adjustment, resulting in a decrease of approximately $1.1 million from current rates. This filing includes approximately $5.1 million related to transmission capital projects. This matter is pending before the NDPSC.

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. This matter is pending before the SDPUC.

WUTC

On June 19, 2020, Cascade filed an application with the WUTC for a natural gas rate increase of approximately $13.8 million annually or approximately 5.3 percent above current rates. The requested increase was primarily to recover investments made in infrastructure upgrades, as well as increased operation and maintenance costs. Cascade updated its filing on July 24, 2020, to approximately $14.3 million annually or approximately 5.5 percent. Cascade filed a rebuttal case on January 8, 2021, supporting an increase of approximately $7.4 million annually or approximately 2.8 percent. The revised revenue within the rebuttal case reflects several adjustments including depreciation, reduction to return on equity, delays on certain projects, adjustments to income taxes and updates to wages. On May 18, 2021, the WUTC issued a final order reflecting an overall revenue decrease of approximately $391,000 or approximately 0.2 percent. On May 25, 2021, Cascade filed a petition for reconsideration with the WUTC. On June 18, 2021, the WUTC denied Cascade's petition for reconsideration. Final rates were effective July 1, 2021.

On June 1, 2021, Cascade filed its annual pipeline cost recovery mechanism requesting an increase in annual revenue of approximately $2.1 million or approximately 0.8 percent. The filing includes a proposed effective date of November 1, 2021. This filing will be updated to more accurate data prior to the effective date. This matter is pending before the WUTC.

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Contingencies

6 Months Ended

Jun. 30, 2021

Commitments and Contingencies Disclosure [Abstract]

Contingencies

Contingencies

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

At June 30, 2021 and 2020, and December 31, 2020, the Company accrued liabilities which have not been discounted, including liabilities held for sale, of $30.8 million, $34.5 million and $41.5 million, respectively. At June 30, 2021 and 2020, and December 31, 2020, the Company also recorded corresponding insurance receivables of $6.9 million, $21.1 million and

$17.5 million, respectively, and regulatory assets of $21.2 million, $10.4 million and $21.3 million, respectively, related to the accrued liabilities. The accruals are for contingencies, including 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

The Company is a party to claims for the cleanup of environmental contamination at certain manufactured gas plant sites, as well as a superfund site. There were no material changes to the Company's environmental matters that were previously reported in the 2020 Annual Report.

Guarantees

In 2009, multiple sale agreements were signed to sell the Company's ownership interests in the Brazilian Transmission Lines. In connection with the sale, Centennial agreed to guarantee payment of any indemnity obligations of certain of the Company's indirect wholly owned subsidiaries. The remaining guarantee is expected to expire in 2021. The guarantees were required by the buyers as a condition to the sale of the Brazilian Transmission Lines.

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 June 30, 2021, the fixed maximum amounts guaranteed under these agreements aggregated $171.2 million. Certain of the guarantees also have no fixed maximum amounts specified. At June 30, 2021, the amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $37.2 million in 2021; $67.7 million in 2022; $55.6 million in 2023; $500,000 in 2024; $500,000 in 2025; $700,000 thereafter; and $9.0 million, which has no scheduled maturity date. There were no amounts outstanding under the previously mentioned guarantees at June 30, 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 June 30, 2021, the fixed maximum amounts guaranteed under these letters of credit aggregated $25.5 million. At June 30, 2021, the amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $23.4 million in 2021 and $2.1 million in 2022. There were no amounts outstanding under the previously mentioned letters of credit at June 30, 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 June 30, 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 June 30, 2021, approximately $1.1 billion 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 June 30, 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 $32.6 million.

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Basis of presentation (Policies)	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying consolidated interim financial statements were prepared in accordance with GAAP for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Interim financial statements do not include all disclosures provided in annual financial statements and, accordingly, these financial statements should be read in conjunction with those appearing in the 2020 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses.

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New accounting standards (Policies)

6 Months Ended

Jun. 30, 2021

Accounting Standards Update and Change in Accounting Principle [Abstract]

New accounting standards

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, clarified 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 effect a one percentage point change in assumed health care cost trend rates would have on certain benefit components. The Company adopted the guidance on January 1, 2021, on a retrospective basis. The Company determined the new guidance will 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. The Company adopted the guidance on January 1, 2021, and determined it did not have a material impact on 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 applied 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. LIBOR is expected to be retired with a full phase-out by the end of 2021 and replaced by a new reference rate, which includes SOFR. The guidance can be applied beginning in the interim period that includes March 12, 2020, and cannot be applied to contract modifications or hedging relationships entered into or evaluated after 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.

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Receivables and allowance for expected credit losses (Policies)	6 Months Ended
	Jun. 30, 2021
Credit Loss [Abstract]
Accounts receivable and allowance for doubtful accounts	Receivables consists primarily of trade receivables from the sale of goods and services, which are recorded at the invoiced amount, and contract assets, net of expected credit losses. For more information on contract assets, see Note 9. The Company's trade receivables are all due in 12 months or less.
Expected credit loss	The Company's expected credit losses are determined through a review using historical credit loss experience; changes in asset specific characteristics; current conditions; and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. The Company develops and documents its methodology to determine its allowance for expected credit losses at each of its reportable business segments. Risk characteristics used by the business segments may include customer mix, knowledge of customers, general economic conditions of the various local economies and impacts of COVID-19, among others. Specific account balances are written off when management determines the amounts to be uncollectible.

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Inventories and natural gas in storage (Policies)	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Inventories and natural gas in storage	Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method.

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Earnings per share (Policies)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Earnings per share	Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per share is computed by dividing net income by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of non-vested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury.

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Revenue from contracts with customers (Policies)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue from contracts with customers	Revenue is recognized when a performance obligation is satisfied by transferring control over a product or service to a customer. Revenue is measured based on consideration specified in a contract with a customer and excludes any sales incentives and amounts collected on behalf of third parties. The Company is considered an agent for certain taxes collected from customers. As such, the Company presents revenues net of these taxes at the time of sale to be remitted to governmental authorities, including sales and use taxes.

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Business Combinations (Policies)	6 Months Ended
	Jun. 30, 2021
Business Combinations [Abstract]
Business Combinations Policy	The following acquisitions were accounted for as business combinations in accordance with ASC 805 - Business Combinations. The results of the acquired businesses have been included in the 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.

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Fair value disclosures (Policies)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair value measurements	The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income.
Investments	The Company did not elect the fair value option, which records gains and losses in income, for its available-for-sale securities, which include mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as investments on the Consolidated Balance Sheets

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Business segment data (Policies)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Business segment data	The Company's reportable segments are those that are based on the Company's method of internal reporting, which generally segregates the strategic business units due to differences in products, services and regulation. The internal reporting of these operating segments is defined based on the reporting and review process used by the Company's chief executive officer.

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Contingencies (Policies)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Contingencies	The Company is party to claims and lawsuits arising out of its business and that of its consolidated subsidiaries, which may include, but are not limited to, matters involving property damage, personal injury, and environmental, contractual, statutory and regulatory obligations. The Company accrues a liability for those contingencies when the incurrence of a loss is probable and the amount can be reasonably estimated. If a range of amounts can be reasonably estimated and no amount within the range is a better estimate than any other amount, then the minimum of the range is accrued. The Company does not accrue liabilities when the likelihood that the liability has been incurred is probable but the amount cannot be reasonably estimated or when the liability is believed to be only reasonably possible or remote. For contingencies where an unfavorable outcome is probable or reasonably possible and which are material, the Company discloses the nature of the contingency and, in some circumstances, an estimate of the possible loss. Accruals are based on the best information available, but in certain situations management is unable to estimate an amount or range of a reasonably possible loss including, but not limited to when: (1) the damages are unsubstantiated or indeterminate, (2) the proceedings are in the early stages, (3) numerous parties are involved, or (4) the matter involves novel or unsettled legal theories.
Variable interest entity	The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary.

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Accounts receivable and allowance for doubtful accounts Receivables and allowance for expected credit losses (Tables)

6 Months Ended

Jun. 30, 2021

Credit Loss [Abstract]

Accounts Receivable, Allowance for Credit Loss [Table Text Block]

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 December 31, 2020	$	899	$	2,571	$	2	$	6,164	$	5,722	$	15,358
Current expected credit loss provision	538		1,273		—		(1,049)		(1,079)		(317)
Less write-offs charged against the allowance	888		1,107		—		273		401		2,669
Credit loss recoveries collected	129		213		—		—		—		342
At March 31, 2021	$	678	$	2,950	$	2	$	4,842	$	4,242	$	12,714
Current expected credit loss provision	(110)		(103)		—		11		(639)		(841)
Less write-offs charged against the allowance	341		787		—		232		64		1,424
Credit loss recoveries collected	100		199		—		—		—		299
At June 30, 2021	$	327	$	2,259	$	2	$	4,621	$	3,539	$	10,748

	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	555		1,156		—		694		1,150		3,555
Less write-offs charged against the allowance	500		624		—		68		73		1,265
Credit loss recoveries collected	109		229		—		—		—		338
At March 31, 2020	$	492	$	1,817	$	—	$	5,983	$	2,833	$	11,125
Current expected credit loss provision	303		190		—		(314)		896		1,075
Less write-offs charged against the allowance	224		677		—		44		454		1,399
Credit loss recoveries collected	88		201		—		—		—		289
At June 30, 2020	$	659	$	1,531	$	—	$	5,625	$	3,275	$	11,090

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Inventories and natural gas in storage (Tables)

6 Months Ended

Jun. 30, 2021

Inventory Disclosure [Abstract]

Inventories

Inventories on the Consolidated Balance Sheets were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Aggregates held for resale	$	183,977	$	165,357	$	175,782
Asphalt oil	51,500		57,207		28,238
Materials and supplies	27,969		27,805		25,142
Merchandise for resale	26,871		22,974		21,087
Natural gas in storage (current)	10,824		11,776		21,919
Other	15,187		17,718		18,999
Total	$	316,328	$	302,837	$	291,167

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Earnings per share (Tables)

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Weighted average common shares outstanding

A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands, except per share amounts)
Weighted average common shares outstanding - basic	201,345		200,522		201,028		200,481
Effect of dilutive performance share awards and restricted stock units	348		17		300		16
Weighted average common shares outstanding - diluted	201,693		200,539		201,328		200,497
Shares excluded from the calculation of diluted earnings per share	—		187		—		191
Dividends declared per common share	$	.2125	$	.2075	$	.4250	$	.4150

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Equity (Tables)

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Schedule of Stock by Class

Details of the Company's "at-the-market" offering activity was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In millions)
Shares issued	1.1		—		1.8		—
Net proceeds *	$	34.9	$	—	$	54.6	$	—
Issuance costs	$	.4	$	—	$	.7	$	—

*    Net proceeds were used for capital expenditures.

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Accumulated other comprehensive income (loss) (Tables)

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Accumulated comprehensive loss

The after-tax changes in the components of accumulated other comprehensive loss were as follows:

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  Liability Adjustment		Net Unrealized Gain (Loss) on Available-for-sale Investments		Total Accumulated  Other Comprehensive  Loss
	(In thousands)
At December 31, 2020	$	(984)	$	(47,207)	$	113	$	(48,078)
Other comprehensive loss before reclassifications	—		—		(44)		(44)
Amounts reclassified from accumulated other comprehensive loss	111		466		35		612
Net current-period other comprehensive income (loss)	111		466		(9)		568
At March 31, 2021	$	(873)	$	(46,741)	$	104	$	(47,510)
Other comprehensive loss before reclassifications	—		—		(52)		(52)
Amounts reclassified from accumulated other comprehensive loss	112		457		25		594
Net current-period other comprehensive income (loss)	112		457		(27)		542
At June 30, 2021	$	(761)	$	(46,284)	$	77	$	(46,968)

	Net Unrealized Gain (Loss) on Derivative  Instruments  Qualifying as Hedges		Postretirement  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 income before reclassifications	—		—		135		135
Amounts reclassified from (to) accumulated other comprehensive loss	111		462		(1)		572
Net current-period other comprehensive income	111		462		134		707
At March 31, 2020	$	(1,319)	$	(40,272)	$	196	$	(41,395)
Other comprehensive loss before reclassifications	—		—		(13)		(13)
Amounts reclassified from accumulated other comprehensive loss	112		480		7		599
Net current-period other comprehensive income (loss)	112		480		(6)		586
At June 30, 2020	$	(1,207)	$	(39,792)	$	190	$	(40,809)

Reclassification out of accumulated other comprehensive loss

The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows:

	Three Months Ended				Six Months Ended				Location on Consolidated Statements of Income
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Reclassification adjustment for loss on derivative instruments included in net income	$	(148)	$	(148)	$	(296)	$	(295)	Interest expense
	36		36		73		72		Income taxes
	(112)		(112)		(223)		(223)
Amortization of postretirement liability losses included in net periodic benefit cost	(617)		(635)		(1,234)		(1,246)		Other income
	160		155		311		304		Income taxes
	(457)		(480)		(923)		(942)
Reclassification adjustment on available-for-sale investments included in net income	(31)		(9)		(75)		(8)		Other income
	6		2		15		2		Income taxes
	(25)		(7)		(60)		(6)
Total reclassifications	$	(594)	$	(599)	$	(1,206)	$	(1,171)

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Revenue from contracts with customers (Tables)

6 Months Ended

Jun. 30, 2021

Revenue from Contract with Customer [Abstract]

Disaggregation of revenue

In the following tables, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 17.

Three Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	29,258	$	83,480	$	—	$	—	$	—	$	—	$	112,738
Commercial utility sales	33,834		47,612		—		—		—		—		81,446
Industrial utility sales	10,354		6,180		—		—		—		—		16,534
Other utility sales	1,825		—		—		—		—		—		1,825
Natural gas transportation	—		11,451		27,685		—		—		—		39,136
Natural gas storage	—		—		3,094		—		—		—		3,094
Contracting services	—		—		—		280,834		—		—		280,834
Construction materials	—		—		—		498,762		—		—		498,762
Intrasegment eliminations	—		—		—		(145,780)		—		—		(145,780)
Inside specialty contracting	—		—		—		—		347,702		—		347,702
Outside specialty contracting	—		—		—		—		165,123		—		165,123
Other	9,465		2,794		4,810		—		57		3,389		20,515
Intersegment eliminations	(136)		(142)		(7,862)		(142)		(797)		(3,361)		(12,440)
Revenues from contracts with customers	84,600		151,375		27,727		633,674		512,085		28		1,409,489
Revenues out of scope	(950)		2,413		46		—		12,659		—		14,168
Total external operating revenues	$	83,650	$	153,788	$	27,773	$	633,674	$	524,744	$	28	$	1,423,657

Three Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	27,954	$	78,653	$	—	$	—	$	—	$	—	$	106,607
Commercial utility sales	29,877		41,027		—		—		—		—		70,904
Industrial utility sales	8,072		5,658		—		—		—		—		13,730
Other utility sales	1,591		—		—		—		—		—		1,591
Natural gas transportation	—		10,350		27,965		—		—		—		38,315
Natural gas gathering	—		—		1,181		—		—		—		1,181
Natural gas storage	—		—		3,104		—		—		—		3,104
Contracting services	—		—		—		303,356		—		—		303,356
Construction materials	—		—		—		482,498		—		—		482,498
Intrasegment eliminations	—		—		—		(164,719)		—		—		(164,719)
Inside specialty contracting	—		—		—		—		324,921		—		324,921
Outside specialty contracting	—		—		—		—		160,696		—		160,696
Other	7,717		2,711		3,363		—		412		2,861		17,064
Intersegment eliminations	(196)		(185)		(7,999)		(90)		(779)		(2,973)		(12,222)
Revenues from contracts with customers	75,015		138,214		27,614		621,045		485,250		(112)		1,347,026
Revenues out of scope	1,423		3,280		44		—		11,155		—		15,902
Total external operating revenues	$	76,438	$	141,494	$	27,658	$	621,045	$	496,405	$	(112)	$	1,362,928

Six Months Ended June 30, 2021	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	62,694	$	286,617	$	—	$	—	$	—	$	—	$	349,311
Commercial utility sales	66,762		167,664		—		—		—		—		234,426
Industrial utility sales	20,383		14,992		—		—		—		—		35,375
Other utility sales	3,391		—		—		—		—		—		3,391
Natural gas transportation	—		23,903		57,102		—		—		—		81,005
Natural gas storage	—		—		7,123		—		—		—		7,123
Contracting services	—		—		—		376,859		—		—		376,859
Construction materials	—		—		—		715,174		—		—		715,174
Intrasegment eliminations	—		—		—		(192,496)		—		—		(192,496)
Inside specialty contracting	—		—		—		—		702,892		—		702,892
Outside specialty contracting	—		—		—		—		316,486		—		316,486
Other	19,238		5,803		7,470		—		93		6,730		39,334
Intersegment eliminations	(271)		(284)		(34,092)		(204)		(1,839)		(6,685)		(43,375)
Revenues from contracts with customers	172,197		498,695		37,603		899,333		1,017,632		45		2,625,505
Revenues out of scope	(3,873)		5,299		82		—		24,582		—		26,090
Total external operating revenues	$	168,324	$	503,994	$	37,685	$	899,333	$	1,042,214	$	45	$	2,651,595

Six Months Ended June 30, 2020	Electric		Natural gas distribution		Pipeline		Construction materials and contracting		Construction services		Other		Total
	(In thousands)
Residential utility sales	$	60,303	$	265,354	$	—	$	—	$	—	$	—	$	325,657
Commercial utility sales	63,464		156,023		—		—		—		—		219,487
Industrial utility sales	18,439		14,179		—		—		—		—		32,618
Other utility sales	3,239		—		—		—		—		—		3,239
Natural gas transportation	—		22,148		55,397		—		—		—		77,545
Natural gas gathering	—		—		3,271		—		—		—		3,271
Natural gas storage	—		—		6,150		—		—		—		6,150
Contracting services	—		—		—		401,757		—		—		401,757
Construction materials	—		—		—		690,408		—		—		690,408
Intrasegment eliminations	—		—		—		(208,823)		—		—		(208,823)
Inside specialty contracting	—		—		—		—		697,130		—		697,130
Outside specialty contracting	—		—		—		—		290,846		—		290,846
Other	16,167		5,209		6,604		—		763		5,852		34,595
Intersegment eliminations	(391)		(370)		(33,198)		(152)		(3,249)		(5,946)		(43,306)
Revenues from contracts with customers	161,221		462,543		38,224		883,190		985,490		(94)		2,530,574
Revenues out of scope	1,125		5,394		89		—		23,120		—		29,728
Total external operating revenues	$	162,346	$	467,937	$	38,313	$	883,190	$	1,008,610	$	(94)	$	2,560,302

Contract balances

The changes in contract assets and liabilities were as follows:

	June 30, 2021		December 31, 2020		Change		Location on Consolidated Balance Sheets
	(In thousands)
Contract assets	$	147,033	$	104,345	$	42,688	Receivables, net
Contract liabilities - current	(146,116)		(158,603)		12,487		Accounts payable
Contract liabilities - noncurrent	(160)		(52)		(108)		Noncurrent liabilities - other
Net contract assets (liabilities)	$	757	$	(54,310)	$	55,067

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Goodwill and other intangible assets (Tables)

6 Months Ended

Jun. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying amount of goodwill

The changes in the carrying amount of goodwill were as follows:

	Balance at January 1, 2021		Goodwill Acquired During  the Year		Measurement Period Adjustments		Balance at June 30, 2021
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	226,003		2,900		—		228,903
Construction services	143,224		—		—		143,224
Total	$	714,963	$	2,900	$	—	$	717,863

	Balance at January 1, 2020		Goodwill Acquired During the Year		Measurement Period Adjustments		Balance at June 30, 2020
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	217,234		6,483		—		223,717
Construction services	118,388		24,436		(3,613)		139,211
Total	$	681,358	$	30,919	$	(3,613)	$	708,664

	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

Other amortizable intangible assets were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Customer relationships	$	29,423	$	30,087	$	28,836
Less accumulated amortization	8,765		5,239		6,887
	20,658		24,848		21,949
Noncompete agreements	3,991		4,229		3,941
Less accumulated amortization	2,576		2,084		2,309
	1,415		2,145		1,632
Other	11,957		13,060		12,927
Less accumulated amortization	10,629		8,538		11,012
	1,328		4,522		1,915
Total	$	23,401	$	31,515	$	25,496

Estimated amortization expense

Estimated amortization expense for identifiable intangible assets as of June 30, 2021, was:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Amortization expense	$	2,381	$	4,678	$	4,329	$	3,957	$	2,060	$	5,996

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Regulatory assets and liabilities (Tables)

6 Months Ended

Jun. 30, 2021

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

The following table summarizes the individual components of unamortized regulatory assets and liabilities:

	Estimated Recovery or Refund Period as of June 30, 2021	*	June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Regulatory assets:
Current:
Natural gas costs recoverable through rate adjustments	Up to 1 year		$	85,045	$	42,582	$	42,481
Conservation programs	Up to 1 year		7,580		7,256		7,117
Cost recovery mechanisms	Up to 1 year		5,692		7,781		10,645
Other	Up to 1 year		11,264		2,938		8,284
			109,581		60,557		68,527
Noncurrent:
Pension and postretirement benefits	**		155,906		157,033		155,942
Plant costs/asset retirement obligations	Over plant lives		72,853		68,191		71,740
Plant retirement	-		46,061		49,185		65,919
Cost recovery mechanisms	Up to 10 years		44,415		13,140		16,245
Manufactured gas plant site remediation	-		26,155		14,826		26,429
Taxes recoverable from customers	Over plant lives		10,929		10,890		10,785
Natural gas costs recoverable through rate adjustments	Up to 3 years		8,389		27,184		21,539
Long-term debt refinancing costs	Up to 39 years		4,110		3,980		4,426
Other	Up to 18 years		8,095		6,596		6,356
			376,913		351,025		379,381
Total regulatory assets			$	486,494	$	411,582	$	447,908
Regulatory liabilities:
Current:
Natural gas costs refundable through rate adjustments	Up to 1 year		$	8,935	$	29,557	$	18,565
Electric fuel and purchased power deferral	Up to 1 year		5,431		7,799		3,667
Taxes refundable to customers	Up to 1 year		3,434		4,012		3,557
Other	Up to 1 year		5,654		6,632		5,661
			23,454		48,000		31,450
Noncurrent:
Taxes refundable to customers	Over plant lives		222,098		236,142		227,850
Plant removal and decommissioning costs	Over plant lives		171,381		173,399		167,171
Pension and postretirement benefits	**		16,940		18,015		16,989
Other	Up to 21 years		18,048		11,096		16,065
			428,467		438,652		428,075
Total regulatory liabilities			$	451,921	$	486,652	$	459,525
Net regulatory position			$	34,573	$	(75,070)	$	(11,617)

Regulatory Liabilities

The following table summarizes the individual components of unamortized regulatory assets and liabilities:

	Estimated Recovery or Refund Period as of June 30, 2021	*	June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Regulatory assets:
Current:
Natural gas costs recoverable through rate adjustments	Up to 1 year		$	85,045	$	42,582	$	42,481
Conservation programs	Up to 1 year		7,580		7,256		7,117
Cost recovery mechanisms	Up to 1 year		5,692		7,781		10,645
Other	Up to 1 year		11,264		2,938		8,284
			109,581		60,557		68,527
Noncurrent:
Pension and postretirement benefits	**		155,906		157,033		155,942
Plant costs/asset retirement obligations	Over plant lives		72,853		68,191		71,740
Plant retirement	-		46,061		49,185		65,919
Cost recovery mechanisms	Up to 10 years		44,415		13,140		16,245
Manufactured gas plant site remediation	-		26,155		14,826		26,429
Taxes recoverable from customers	Over plant lives		10,929		10,890		10,785
Natural gas costs recoverable through rate adjustments	Up to 3 years		8,389		27,184		21,539
Long-term debt refinancing costs	Up to 39 years		4,110		3,980		4,426
Other	Up to 18 years		8,095		6,596		6,356
			376,913		351,025		379,381
Total regulatory assets			$	486,494	$	411,582	$	447,908
Regulatory liabilities:
Current:
Natural gas costs refundable through rate adjustments	Up to 1 year		$	8,935	$	29,557	$	18,565
Electric fuel and purchased power deferral	Up to 1 year		5,431		7,799		3,667
Taxes refundable to customers	Up to 1 year		3,434		4,012		3,557
Other	Up to 1 year		5,654		6,632		5,661
			23,454		48,000		31,450
Noncurrent:
Taxes refundable to customers	Over plant lives		222,098		236,142		227,850
Plant removal and decommissioning costs	Over plant lives		171,381		173,399		167,171
Pension and postretirement benefits	**		16,940		18,015		16,989
Other	Up to 21 years		18,048		11,096		16,065
			428,467		438,652		428,075
Total regulatory liabilities			$	451,921	$	486,652	$	459,525
Net regulatory position			$	34,573	$	(75,070)	$	(11,617)

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Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Available-for-sale securities

Details of available-for-sale securities were as follows:

June 30, 2021	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	8,278	$	127	$	9	$	8,396
U.S. Treasury securities	2,893		—		21		2,872
Total	$	11,171	$	127	$	30	$	11,268

June 30, 2020	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	9,812	$	239	$	6	$	10,045
U.S. Treasury securities	1,170		7		—		1,177
Total	$	10,982	$	246	$	6	$	11,222

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

Assets and liabilities measured at fair value on a recurring basis

The Company's assets measured at fair value on a recurring basis were as follows:

	Fair Value Measurements at June 30, 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 June 30, 2021
	(In thousands)
Assets:
Money market funds	$	—	$	12,234	$	—	$	12,234
Insurance contracts*	—		105,684				105,684
Available-for-sale securities:
Mortgage-backed securities	—		8,396		—		8,396
U.S. Treasury securities	—		2,872		—		2,872
Total assets measured at fair value	$	—	$	129,186	$	—	$	129,186

*    The insurance contracts invest approximately 53 percent in fixed-income investments, 20 percent in common stock of large-cap companies, 10 percent in common stock of mid-cap companies, 9 percent in common stock of small-cap companies, 6 percent in target date investments and 2 percent in cash equivalents.

	Fair Value Measurements at June 30, 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 June 30, 2020
	(In thousands)
Assets:
Money market funds	$	—	$	8,478	$	—	$	8,478
Insurance contract*	—		92,413		—		92,413
Available-for-sale securities:
Mortgage-backed securities	—		10,045		—		10,045
U.S. Treasury securities	—		1,177		—		1,177
Total assets measured at fair value	$	—	$	112,113	$	—	$	112,113

*    The insurance contract invests approximately 38 percent in fixed-income investments, 23 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, 4 percent in target date investments and 17 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.

Fair value of long term debt outstanding

The estimated fair value of the Company's Level 2 long-term debt was as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Carrying amount	$	2,337,049	$	2,281,876	$	2,213,130
Fair value	$	2,616,232	$	2,563,734	$	2,537,289

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Debt (Tables)

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Long-term debt outstanding

Long-term debt outstanding was as follows:

	Weighted Average Interest Rate at June 30, 2021		June 30, 2021		June 30, 2020		December 31, 2020
			(In thousands)
Senior Notes due on dates ranging from October 22, 2022 to October 30, 2060	4.40	%	$	1,950,000	$	1,900,000	$	1,950,000
Commercial paper supported by revolving credit agreements	.32	%	297,400		290,100		125,600
Credit agreements due on June 7, 2024	3.25	%	48,550		11,200		95,900
Medium-Term Notes due on dates ranging from September 15, 2027 to March 16, 2029	7.32	%	35,000		50,000		35,000
Term Loan Agreement due on September 3, 2032	2.00	%	8,400		9,100		8,400
Other notes due on dates ranging from July 15, 2021 to January 1, 2061	.83	%	3,232		28,342		4,034
Less unamortized debt issuance costs			5,505		6,668		5,803
Less discount			28		198		1
Total long-term debt			2,337,049		2,281,876		2,213,130
Less current maturities			1,549		16,560		1,555
Net long-term debt			$	2,335,500	$	2,265,316	$	2,211,575

Schedule of debt maturities

Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at June 30, 2021, were as follows:

	Remainder of 2021		2022		2023		2024		2025		Thereafter
	(In thousands)
Long-term debt maturities	$	752	$	148,021	$	77,921	$	407,372	$	177,802	$	1,530,714

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Cash flow information (Tables)

6 Months Ended

Jun. 30, 2021

Supplemental Cash Flow Information [Abstract]

Cash expenditures for interest and income taxes and noncash investing and financing transactions

Cash expenditures for interest and income taxes were as follows:

	Six Months Ended
	June 30,
	2021		2020
	(In thousands)
Interest, net*	$	45,870	$	47,769
Income taxes paid, net	$	46,734	$	735

*    AFUDC - borrowed was $816,000 and $1.3 million for the six months ended June 30, 2021 and 2020, respectively.

Noncash investing and financing transactions were as follows:

	June 30, 2021		June 30, 2020		December 31, 2020
	(In thousands)
Right-of-use assets obtained in exchange for new operating lease liabilities	$	17,224	$	24,181	$	54,356
Property, plant and equipment additions in accounts payable	$	31,886	$	36,493	$	26,082
Accrual for holdback payment related to a business combination	$	—	$	5,000	$	2,500

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Business segment data (Tables)

6 Months Ended

Jun. 30, 2021

Segment Reporting [Abstract]

Information on the Company's businesses

Information on the Company's segments was as follows:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
External operating revenues:
Regulated operations:
Electric	$	83,650	$	76,438	$	168,324	$	162,346
Natural gas distribution	153,788		141,494		503,994		467,937
Pipeline	23,130		23,421		30,633		29,752
	260,568		241,353		702,951		660,035
Non-regulated operations:
Pipeline	4,643		4,237		7,052		8,561
Construction materials and contracting	633,674		621,045		899,333		883,190
Construction services	524,744		496,405		1,042,214		1,008,610
Other	28		(112)		45		(94)
	1,163,089		1,121,575		1,948,644		1,900,267
Total external operating revenues	$	1,423,657	$	1,362,928	$	2,651,595	$	2,560,302

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2021		2020		2021		2020
	(In thousands)
Intersegment operating revenues:
Regulated operations:
Electric	$	136	$	196	$	271	$	391
Natural gas distribution	142		185		284		370
Pipeline	7,695		7,857		33,685		33,040
	7,973		8,238		34,240		33,801
Non-regulated operations:
Pipeline	167		142		407		158
Construction materials and contracting	142		90		204		152
Construction services	797		779		1,839		3,249
Other	3,361		2,973		6,685		5,946
	4,467		3,984		9,135		9,505
Intersegment eliminations	(12,440)		(12,222)		(43,375)		(43,306)
Total intersegment operating revenues	$	—	$	—	$	—	$	—
Operating income (loss):
Electric	$	12,806	$	12,810	$	26,672	$	27,669
Natural gas distribution	3,601		678		57,173		50,677
Pipeline	11,076		12,225		23,612		23,644
Construction materials and contracting	72,452		74,741		37,563		31,472
Construction services	37,774		37,882		78,051		61,678
Other	(20)		(82)		(218)		185
Total operating income	$	137,689	$	138,254	$	222,853	$	195,325
Net income (loss):
Regulated operations:
Electric	$	10,304	$	12,153	$	21,054	$	23,527
Natural gas distribution	(707)		(959)		35,471		31,410
Pipeline	8,089		8,684		17,283		16,070
	17,686		19,878		73,808		71,007
Non-regulated operations:
Pipeline	1,106		268		810		255
Construction materials and contracting	51,396		53,020		20,584		14,806
Construction services	28,885		27,932		58,709		44,755
Other	1,098		(1,256)		(1,624)		(5,442)
	82,485		79,964		78,479		54,374
Income from continuing operations	100,171		99,842		152,287		125,381
Income (loss) from discontinued operations, net of tax	19		(139)		34		(548)
Net income	$	100,190	$	99,703	$	152,321	$	124,833

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Employee benefit plans (Tables)

6 Months Ended

Jun. 30, 2021

Retirement Benefits [Abstract]

Schedule of net benefit costs

Components of net periodic benefit credit for the Company's pension and other postretirement benefit plans were as follows:

	Pension Benefits				Other Postretirement Benefits
Three Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	400	$	414
Interest cost	2,455		3,074		466		627
Expected return on assets	(4,894)		(5,214)		(1,275)		(1,401)
Amortization of prior service credit	—		—		(349)		(402)
Amortization of net actuarial loss	2,004		1,723		6		142
Net periodic benefit credit, including amount capitalized	(435)		(417)		(752)		(620)
Less amount capitalized	—		—		44		35
Net periodic benefit credit	$	(435)	$	(417)	$	(796)	$	(655)

	Pension Benefits				Other Postretirement Benefits
Six Months Ended June 30,	2021		2020		2021		2020
	(In thousands)
Components of net periodic benefit credit:
Service cost	$	—	$	—	$	800	$	766
Interest cost	4,910		6,047		932		1,218
Expected return on assets	(9,788)		(9,975)		(2,550)		(2,649)
Amortization of prior service credit	—		—		(698)		(699)
Amortization of net actuarial loss	4,008		3,586		12		144
Net periodic benefit credit, including amount capitalized	(870)		(342)		(1,504)		(1,220)
Less amount capitalized	—		—		83		67
Net periodic benefit credit	$	(870)	$	(342)	$	(1,587)	$	(1,287)

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Receivables and allowance for expected credit losses (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Credit Loss [Abstract]
Accounts Receivable, Noncurrent, 90 Days or More Past Due, Still Accruing	$ 34.2	$ 43.9	$ 45.1

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Accounts receivable and allowance for doubtful accounts Receivables and allowance for expected credit losses (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	$ 12,714	$ 15,358	$ 11,125	$ 8,497
Current expected credit loss provision	(841)	(317)	1,075	3,555
Less write-offs charged against the allowance	1,424	2,669	1,399	1,265
Credit loss recoveries collected	299	342	289	338
Balance	10,748	12,714	11,090	11,125
Electric
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	678	899	492	328
Current expected credit loss provision	(110)	538	303	555
Less write-offs charged against the allowance	341	888	224	500
Credit loss recoveries collected	100	129	88	109
Balance	327	678	659	492
Natural gas distribution
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,950	2,571	1,817	1,056
Current expected credit loss provision	(103)	1,273	190	1,156
Less write-offs charged against the allowance	787	1,107	677	624
Credit loss recoveries collected	199	213	201	229
Balance	2,259	2,950	1,531	1,817
Pipeline
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2	2	0	0
Current expected credit loss provision	0	0	0	0
Less write-offs charged against the allowance	0	0	0	0
Credit loss recoveries collected	0	0	0	0
Balance	2	2	0	0
Construction materials and contracting
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	4,842	6,164	5,983	5,357
Current expected credit loss provision	11	(1,049)	(314)	694
Less write-offs charged against the allowance	232	273	44	68
Credit loss recoveries collected	0	0	0	0
Balance	4,621	4,842	5,625	5,983
Construction services
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	4,242	5,722	2,833	1,756
Current expected credit loss provision	(639)	(1,079)	896	1,150
Less write-offs charged against the allowance	64	401	454	73
Credit loss recoveries collected	0	0	0	0
Balance	$ 3,539	$ 4,242	$ 3,275	$ 2,833

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Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Inventory Disclosure [Abstract]
Aggregates held for resale	$ 183,977	$ 175,782	$ 165,357
Asphalt oil	51,500	28,238	57,207
Materials and supplies	27,969	25,142	27,805
Merchandise for resale	26,871	21,087	22,974
Natural gas in storage (current)	10,824	21,919	11,776
Other	15,187	18,999	17,718
Total	316,328	291,167	302,837
Natural gas in storage noncurrent	$ 47,500	$ 47,500	$ 48,300

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Earnings per share (Details) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Weighted average common shares outstanding - basic	201,345	200,522	201,028	200,481
Effect of dilutive performance share awards and restricted stock units	348	17	300	16
Weighted average common shares outstanding - diluted	201,693	200,539	201,328	200,497
Shares excluded from the calculation of diluted earnings per share	0	187	0	191
Dividends declared per common share	$ 0.2125	$ 0.2075	$ 0.4250	$ 0.4150

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Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Class of Stock [Line Items]
Common Stock, Shares Authorized	500,000,000	500,000,000	500,000,000	500,000,000	500,000,000
Proceeds from issuance of common stock			$ 54,649	$ 3,410
At-the-market offering
Class of Stock [Line Items]
Common Stock, Shares Authorized	6,400,000		6,400,000
Common Stock, Capital Shares Reserved for Future Issuance	4,600,000		4,600,000
Issuance of common stock (shares)	1,100,000	0	1,800,000	0
Proceeds from issuance of common stock	$ 34,900	$ 0	$ 54,600	$ 0
Payments of Stock Issuance Costs	$ 400	$ 0	$ 700	$ 0

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Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	$ 3,100,306	$ 3,079,105	$ 2,836,592	$ 2,847,246	$ 3,079,105	$ 2,847,246
Other comprehensive income (loss)	542	568	586	707	1,110	1,293
Balance	3,198,802	3,100,306	2,897,687	2,836,592	3,198,802	2,897,687
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(873)	(984)	(1,319)	(1,430)	(984)	(1,430)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from (to) accumulated other comprehensive loss	112	111	112	111
Other comprehensive income (loss)	112	111	112	111
Balance	(761)	(873)	(1,207)	(1,319)	(761)	(1,207)
Postretirement liability adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(46,741)	(47,207)	(40,272)	(40,734)	(47,207)	(40,734)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from (to) accumulated other comprehensive loss	457	466	480	462
Other comprehensive income (loss)	457	466	480	462
Balance	(46,284)	(46,741)	(39,792)	(40,272)	(46,284)	(39,792)
Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	104	113	196	62	113	62
Other comprehensive income (loss) before reclassifications	(52)	(44)	(13)	135
Amounts reclassified from (to) accumulated other comprehensive loss	25	35	7	(1)
Other comprehensive income (loss)	(27)	(9)	(6)	134
Balance	77	104	190	196	77	190
Total accumulated other comprehensive loss
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(47,510)	(48,078)	(41,395)	(42,102)	(48,078)	(42,102)
Other comprehensive income (loss) before reclassifications	(52)	(44)	(13)	135
Amounts reclassified from (to) accumulated other comprehensive loss	594	612	599	572
Other comprehensive income (loss)	542	568	586	707
Balance	$ (46,968)	$ (47,510)	$ (40,809)	$ (41,395)	$ (46,968)	$ (40,809)

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Reclassification out of accumulated other comprehensive loss (Details 2) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	$ (23,381)		$ (24,818)		$ (46,835)	$ (49,371)
Income taxes	(23,164)		(23,657)		(36,112)	(29,631)
Other income	9,027		10,063		12,381	9,058
Net Income	100,190	$ 52,131	99,703	$ 25,130	152,321	124,833
Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Net Income	(594)		(599)		(1,206)	(1,171)
Reclassification adjustment for loss on derivative instruments included in net income | Reclassification out of accumulated other comprehensive loss | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Interest expense	(148)		(148)		(296)	(295)
Income taxes	36		36		73	72
Net Income	(112)		(112)		(223)	(223)
Amortization of postretirement liability losses included in net periodic benefit cost | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Income taxes	160		155		311	304
Other income	(617)		(635)		(1,234)	(1,246)
Net Income	(457)		(480)		(923)	(942)
Reclassification adjustment on available-for-sale investments included in net income | Reclassification out of accumulated other comprehensive loss
Reclassification adjustment out of accumulated other comprehensive loss [Line Items]
Income taxes	6		2		15	2
Other income	(31)		(9)		(75)	(8)
Net Income	$ (25)		$ (7)		$ (60)	$ (6)

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Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Operating revenues:	$ 1,423,657	$ 1,362,928	$ 2,651,595	$ 2,560,302
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(12,440)	(12,222)	(43,375)	(43,306)
Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(145,780)	(164,719)	(192,496)	(208,823)
Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	39,136	38,315	81,005	77,545
Natural gas gathering
Disaggregation of Revenue [Line Items]
Operating revenues:		1,181		3,271
Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues:	3,094	3,104	7,123	6,150
Contracting services
Disaggregation of Revenue [Line Items]
Operating revenues:	280,834	303,356	376,859	401,757
Construction materials
Disaggregation of Revenue [Line Items]
Operating revenues:	498,762	482,498	715,174	690,408
Inside specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	347,702	324,921	702,892	697,130
Outside specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	165,123	160,696	316,486	290,846
Other
Disaggregation of Revenue [Line Items]
Operating revenues:	20,515	17,064	39,334	34,595
Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	1,409,489	1,347,026	2,625,505	2,530,574
Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	14,168	15,902	26,090	29,728
Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	112,738	106,607	349,311	325,657
Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	81,446	70,904	234,426	219,487
Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	16,534	13,730	35,375	32,618
Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	1,825	1,591	3,391	3,239
Electric
Disaggregation of Revenue [Line Items]
Operating revenues:	83,650	76,438	168,324	162,346
Electric | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(136)	(196)	(271)	(391)
Electric | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	9,465	7,717	19,238	16,167
Electric | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	84,600	75,015	172,197	161,221
Electric | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	(950)	1,423	(3,873)	1,125
Electric | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	29,258	27,954	62,694	60,303
Electric | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	33,834	29,877	66,762	63,464
Electric | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	10,354	8,072	20,383	18,439
Electric | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	1,825	1,591	3,391	3,239
Natural gas distribution
Disaggregation of Revenue [Line Items]
Operating revenues:	153,788	141,494	503,994	467,937
Natural gas distribution | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(142)	(185)	(284)	(370)
Natural gas distribution | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	11,451	10,350	23,903	22,148
Natural gas distribution | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	2,794	2,711	5,803	5,209
Natural gas distribution | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	151,375	138,214	498,695	462,543
Natural gas distribution | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	2,413	3,280	5,299	5,394
Natural gas distribution | Residential utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	83,480	78,653	286,617	265,354
Natural gas distribution | Commercial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	47,612	41,027	167,664	156,023
Natural gas distribution | Industrial utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	6,180	5,658	14,992	14,179
Natural gas distribution | Other utility sales
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Pipeline
Disaggregation of Revenue [Line Items]
Operating revenues:	27,773	27,658	37,685	38,313
Pipeline | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(7,862)	(7,999)	(34,092)	(33,198)
Pipeline | Natural gas transportation
Disaggregation of Revenue [Line Items]
Operating revenues:	27,685	27,965	57,102	55,397
Pipeline | Natural gas gathering
Disaggregation of Revenue [Line Items]
Operating revenues:		1,181		3,271
Pipeline | Natural gas storage
Disaggregation of Revenue [Line Items]
Operating revenues:	3,094	3,104	7,123	6,150
Pipeline | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	4,810	3,363	7,470	6,604
Pipeline | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	27,727	27,614	37,603	38,224
Pipeline | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	46	44	82	89
Construction materials and contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	633,674	621,045	899,333	883,190
Construction materials and contracting | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(142)	(90)	(204)	(152)
Construction materials and contracting | Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(145,780)	(164,719)	(192,496)	(208,823)
Construction materials and contracting | Contracting services
Disaggregation of Revenue [Line Items]
Operating revenues:	280,834	303,356	376,859	401,757
Construction materials and contracting | Construction materials
Disaggregation of Revenue [Line Items]
Operating revenues:	498,762	482,498	715,174	690,408
Construction materials and contracting | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Construction materials and contracting | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	633,674	621,045	899,333	883,190
Construction materials and contracting | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	0	0	0	0
Construction services
Disaggregation of Revenue [Line Items]
Operating revenues:	524,744	496,405	1,042,214	1,008,610
Construction services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(797)	(779)	(1,839)	(3,249)
Construction services | Inside specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	347,702	324,921	702,892	697,130
Construction services | Outside specialty contracting
Disaggregation of Revenue [Line Items]
Operating revenues:	165,123	160,696	316,486	290,846
Construction services | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	57	412	93	763
Construction services | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	512,085	485,250	1,017,632	985,490
Construction services | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	12,659	11,155	24,582	23,120
Other
Disaggregation of Revenue [Line Items]
Operating revenues:	28	(112)	45	(94)
Other | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Operating revenues:	(3,361)	(2,973)	(6,685)	(5,946)
Other | Other
Disaggregation of Revenue [Line Items]
Operating revenues:	3,389	2,861	6,730	5,852
Other | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Operating revenues:	28	(112)	45	(94)
Other | Revenues out of scope
Disaggregation of Revenue [Line Items]
Operating revenues:	$ 0	$ 0	$ 0	$ 0

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Contract balances (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Contract assets	$ 147,033		$ 147,033		$ 104,345
Change in contract assets			42,688
Contract liabilities - current	(146,116)		(146,116)		(158,603)
Change in contract liabilities - current			12,487
Contract liabilities - noncurrent	(160)		(160)		(52)
Change in contract liabilities - noncurrent			(108)
Net contract assets (liabilities)	757		757		$ (54,310)
Change in net contract liabilities			55,067
Amounts included in contract liability at the beginning of the period	21,900	$ 32,300	145,300	$ 121,700
Amounts from performance obligations satisfied in prior periods	$ 27,300	$ 31,900	$ 54,600	$ 42,900

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Revenue from contracts with customers Remaining performance obligations (Details 3) $ in Millions	Jun. 30, 2021 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,400.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1,800.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 339.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	13 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 225.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	25 months

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Business Combinations (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 717,863,000	$ 714,963,000	$ 708,664,000	$ 681,358,000
2021 Acquisition
Business Acquisition [Line Items]
Gross Aggregate Consideration	13,800,000
Cash Assumed	100,000
Business Combination, Consideration Transferred	13,700,000
Current Assets	700,000
Property, Plant, and Equipment	13,000,000.0
Goodwill	2,900,000
Other Intangibles	600,000
Current Liabilities	200,000
Deferred Credits and Other Liabilities	100,000
Deferred Tax Liabilities	$ 3,200,000

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Business Combinations (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 714,963,000	$ 717,863,000	$ 708,664,000	$ 681,358,000
2020 Acquisition
Business Acquisition [Line Items]
Gross Aggregate Consideration	110,200,000
Cash Assumed	1,700,000
Business Combination, Consideration Transferred	106,000,000.0
Business Combination, Consideration Transferred, Liabilities Incurred	2,500,000
Current Assets	54,800,000
Property, Plant, and Equipment	27,100,000
Goodwill	33,600,000
Other Intangibles	19,000,000.0
Current Liabilities	22,600,000
Deferred Credits and Other Liabilities	300,000
Asset Retirement Obligation	$ 1,400,000

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Lessor accounting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating Lease, Lease Income	$ 12.8	$ 11.2	$ 24.8	$ 23.3
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	$ 9.8		$ 9.8

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Goodwill rollforward (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Goodwill [Roll Forward]
Balance at beginning of period	$ 714,963	$ 681,358	$ 681,358
Goodwill acquired during the year	2,900	30,919	33,214
Measurement period adjustments	0	(3,613)	391
Balance at end of period	717,863	708,664	714,963
Natural gas distribution
Goodwill [Roll Forward]
Balance at beginning of period	345,736	345,736	345,736
Goodwill acquired during the year	0	0	0
Measurement period adjustments	0	0	0
Balance at end of period	345,736	345,736	345,736
Construction materials and contracting
Goodwill [Roll Forward]
Balance at beginning of period	226,003	217,234	217,234
Goodwill acquired during the year	2,900	6,483	8,778
Measurement period adjustments	0	0	(9)
Balance at end of period	228,903	223,717	226,003
Construction services
Goodwill [Roll Forward]
Balance at beginning of period	143,224	118,388	118,388
Goodwill acquired during the year	0	24,436	24,436
Measurement period adjustments	0	(3,613)	400
Balance at end of period	$ 143,224	$ 139,211	$ 143,224

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Other intangible assets (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 23,401	$ 31,515	$ 23,401	$ 31,515	$ 25,496
Amortization of intangible assets	1,200	2,700	2,700	4,700
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	29,423	30,087	29,423	30,087	28,836
Intangible assets, less accumulated amortization	8,765	5,239	8,765	5,239	6,887
Intangible assets, net (excluding goodwill)	20,658	24,848	20,658	24,848	21,949
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	3,991	4,229	3,991	4,229	3,941
Intangible assets, less accumulated amortization	2,576	2,084	2,576	2,084	2,309
Intangible assets, net (excluding goodwill)	1,415	2,145	1,415	2,145	1,632
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	11,957	13,060	11,957	13,060	12,927
Intangible assets, less accumulated amortization	10,629	8,538	10,629	8,538	11,012
Intangible assets, net (excluding goodwill)	$ 1,328	$ 4,522	$ 1,328	$ 4,522	$ 1,915

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Future amortization expense (Details 3) $ in Thousands	Jun. 30, 2021 USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2021	$ 2,381
2022	4,678
2023	4,329
2024	3,957
2025	2,060
Thereafter	$ 5,996

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Regulatory assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Feb. 28, 2021	Dec. 31, 2020	Jun. 30, 2020
Regulatory Assets
Regulatory Assets, Current	$ 109,581		$ 68,527	$ 60,557
Regulatory Assets, Noncurrent	376,913		379,381	351,025
Total regulatory assets	486,494		447,908	411,582
Regulatory assets not earning a rate of return	317,000		332,500	296,600
Natural gas costs recoverable through rate adjustments
Regulatory Assets
Regulatory Assets, Current	85,045		42,481	42,582
Regulatory Assets, Noncurrent	$ 8,389		21,539	27,184
Natural gas costs recoverable through rate adjustments | Minimum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Natural gas costs recoverable through rate adjustments | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 3 years
Conservation programs
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Regulatory Assets, Current	$ 7,580		7,117	7,256
Cost recovery mechanisms
Regulatory Assets
Regulatory Assets, Current	5,692		10,645	7,781
Regulatory Assets, Noncurrent	$ 44,415		16,245	13,140
Cost recovery mechanisms | Minimum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Cost recovery mechanisms | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 10 years
Pension and postretirement benefits
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	**
Regulatory Assets, Noncurrent	$ 155,906		155,942	157,033
Plant costs/asset retirement obligations
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Over plant lives
Regulatory Assets, Noncurrent	$ 72,853		71,740	68,191
Plant retirement
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	-
Regulatory Assets, Noncurrent	$ 46,061		65,919	49,185
Manufactured gas plant site remediation
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	-
Regulatory Assets, Noncurrent	$ 26,155		26,429	14,826
Taxes recoverable from/refundable to customers
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Over plant lives
Regulatory Assets, Noncurrent	$ 10,929		10,785	10,890
Long-term debt refinancing costs
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 39 years
Regulatory Assets, Noncurrent	$ 4,110		4,426	3,980
Other regulatory assets/liabilities
Regulatory Assets
Regulatory Assets, Current	11,264		8,284	2,938
Regulatory Assets, Noncurrent	$ 8,095		$ 6,356	$ 6,596
Other regulatory assets/liabilities | Minimum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Other regulatory assets/liabilities | Maximum [Member]
Regulatory Assets
Estimated Recovery or Refund Period as of June 30, 2021	Up to 18 years
Increased Gas Costs
Regulatory Assets
Total regulatory assets		$ 44,000

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Regulatory liabilities (Details 2) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	$ 23,454	$ 31,450	$ 48,000
Regulatory liabilities	428,467	428,075	438,652
Total regulatory liabilities	451,921	459,525	486,652
Net regulatory position	$ 34,573	(11,617)	(75,070)
Natural gas costs refundable through rate adjustments
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Regulatory liabilities due within one year	$ 8,935	18,565	29,557
Electric fuel and purchased power deferral
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Regulatory liabilities due within one year	$ 5,431	3,667	7,799
Deferred Income Tax Charge [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	3,434	3,557	4,012
Regulatory liabilities	$ 222,098	227,850	236,142
Deferred Income Tax Charge [Member] | Minimum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Deferred Income Tax Charge [Member] | Maximum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Over plant lives
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities due within one year	$ 5,654	5,661	6,632
Regulatory liabilities	$ 18,048	16,065	11,096
Other Regulatory Liabilities | Minimum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Up to 1 year
Other Regulatory Liabilities | Maximum [Member]
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Up to 21 years
Plant retirement
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	Over plant lives
Regulatory liabilities	$ 171,381	167,171	173,399
Pension and postretirement benefits
Regulatory Liabilities [Line Items]
Estimated Recovery or Refund Period as of June 30, 2021	**
Regulatory liabilities	$ 16,940	$ 16,989	$ 18,015

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Fair value measurements Insurance contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 105.7	$ 92.4	$ 105.7	$ 92.4	$ 100.1
Net unrealized gain on investments used to satisfy obligations under nonqualified benefit plans	$ 3.8	$ 9.1	$ 3.9	$ 5.4

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Available-for-sale securities (Details 2) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Available-for-sale securities [Abstract]
Cost	$ 11,171	$ 11,185	$ 10,982
Gross Unrealized Gains	127	156	246
Gross Unrealized Losses	30	14	6
Fair Value	11,268	11,327	11,222
Mortgage-backed securities
Available-for-sale securities [Abstract]
Cost	8,278	9,799	9,812
Gross Unrealized Gains	127	156	239
Gross Unrealized Losses	9	9	6
Fair Value	8,396	9,946	10,045
U.S. Treasury securities
Available-for-sale securities [Abstract]
Cost	2,893	1,386	1,170
Gross Unrealized Gains	0	0	7
Gross Unrealized Losses	21	5	0
Fair Value	$ 2,872	$ 1,381	$ 1,177

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Fair value measurements (Details 3) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	53.00%	57.00%	38.00%
Percentage investment in common stock of large-cap companies	20.00%	18.00%	23.00%
Percentage investment in common stock of mid-cap companies	10.00%	9.00%	9.00%
Percentage investment in common stock of small-cap companies	9.00%	9.00%	9.00%
Percentage investment in target date investments	6.00%	5.00%	4.00%
Percentage investment in cash and cash equivalents	2.00%	2.00%	17.00%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 129,186	$ 120,348	$ 112,113
Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	129,186	120,348	112,113
Money market funds | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	12,234	8,917	8,478
Money market funds | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	12,234	8,917	8,478
Insurance contracts* | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	105,684	100,104	92,413
Insurance contracts* | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	105,684	100,104	92,413
Mortgage-backed securities | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	8,396	9,946	10,045
Mortgage-backed securities | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	8,396	9,946	10,045
U.S. Treasury securities | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	2,872	1,381	1,177
U.S. Treasury securities | Fair value, inputs, level 2 | Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 2,872	$ 1,381	$ 1,177

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Fair value measurements (Details 4) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,337,049	$ 2,213,130	$ 2,281,876
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,337,049	2,213,130	2,281,876
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 2,616,232	$ 2,537,289	$ 2,563,734

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Long-term debt outstanding (Details 1) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,337,049	$ 2,213,130	$ 2,281,876
Long-term debt due within one year	1,549	1,555	16,560
Long-term debt	$ 2,335,500	2,211,575	2,265,316
Senior Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	4.40%
Long-term debt	$ 1,950,000	1,950,000	1,900,000
Commercial Paper
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	0.32%
Long-term debt	$ 297,400	125,600	290,100
Credit Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	3.25%
Long-term debt	$ 48,550	95,900	11,200
Medium-term Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	7.32%
Long-term debt	$ 35,000	35,000	50,000
Term Loan Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	2.00%
Long-term debt	$ 8,400	8,400	9,100
Other Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	0.83%
Long-term debt	$ 3,232	4,034	28,342
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs	5,505	5,803	6,668
Discount	$ 28	$ 1	$ 198

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Schedule of debt maturities (Details 2) $ in Thousands	Jun. 30, 2021 USD ($)
Long-term debt maturities [Line Items]
Remainder of 2021	$ 752
2022	148,021
2023	77,921
2024	407,372
2025	177,802
Thereafter	$ 1,530,714

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Cash flow information (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Supplemental Cash Flow Information [Abstract]
Interest, net*	$ 45,870,000	$ 47,769,000
Income taxes paid, net	46,734,000	735,000
AFUDC borrowed	816,000	1,300,000
Right-of-use assets obtained in exchange for new operating lease liabilities	17,224,000	24,181,000	$ 54,356,000
Property, plant and equipment additions in accounts payable	31,886,000	36,493,000	26,082,000
Accrual for holdback payment related to a business combination	$ 0	$ 5,000,000	$ 2,500,000

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Business segment data (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,423,657		$ 1,362,928		$ 2,651,595	$ 2,560,302
Operating income	137,689		138,254		222,853	195,325
Income from continuing operations	100,171		99,842		152,287	125,381
Income (loss) from discontinued operations, net of tax	19		(139)		34	(548)
Net income	100,190	$ 52,131	99,703	$ 25,130	152,321	124,833
Electric
Segment Reporting Information [Line Items]
Revenues	83,650		76,438		168,324	162,346
Operating income	12,806		12,810		26,672	27,669
Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	153,788		141,494		503,994	467,937
Operating income	3,601		678		57,173	50,677
Pipeline
Segment Reporting Information [Line Items]
Revenues	27,773		27,658		37,685	38,313
Operating income	11,076		12,225		23,612	23,644
Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	633,674		621,045		899,333	883,190
Operating income	72,452		74,741		37,563	31,472
Construction services
Segment Reporting Information [Line Items]
Revenues	524,744		496,405		1,042,214	1,008,610
Operating income	37,774		37,882		78,051	61,678
Other
Segment Reporting Information [Line Items]
Revenues	28		(112)		45	(94)
Operating income	(20)		(82)		(218)	185
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	(12,440)		(12,222)		(43,375)	(43,306)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	(136)		(196)		(271)	(391)
Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	(142)		(185)		(284)	(370)
Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	(7,862)		(7,999)		(34,092)	(33,198)
Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	(142)		(90)		(204)	(152)
Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	(797)		(779)		(1,839)	(3,249)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	(3,361)		(2,973)		(6,685)	(5,946)
Total intersegment operating revenues
Segment Reporting Information [Line Items]
Revenues	0		0		0	0
Regulated operation
Segment Reporting Information [Line Items]
Revenues	260,568		241,353		702,951	660,035
Income from continuing operations	17,686		19,878		73,808	71,007
Regulated operation | Electric
Segment Reporting Information [Line Items]
Revenues	83,650		76,438		168,324	162,346
Income from continuing operations	10,304		12,153		21,054	23,527
Regulated operation | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	153,788		141,494		503,994	467,937
Income from continuing operations	(707)		(959)		35,471	31,410
Regulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	23,130		23,421		30,633	29,752
Income from continuing operations	8,089		8,684		17,283	16,070
Regulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	7,973		8,238		34,240	33,801
Regulated operation | Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	136		196		271	391
Regulated operation | Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	142		185		284	370
Regulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	7,695		7,857		33,685	33,040
Nonregulated operation
Segment Reporting Information [Line Items]
Revenues	1,163,089		1,121,575		1,948,644	1,900,267
Income from continuing operations	82,485		79,964		78,479	54,374
Nonregulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	4,643		4,237		7,052	8,561
Income from continuing operations	1,106		268		810	255
Nonregulated operation | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	633,674		621,045		899,333	883,190
Income from continuing operations	51,396		53,020		20,584	14,806
Nonregulated operation | Construction services
Segment Reporting Information [Line Items]
Revenues	524,744		496,405		1,042,214	1,008,610
Income from continuing operations	28,885		27,932		58,709	44,755
Nonregulated operation | Other
Segment Reporting Information [Line Items]
Revenues	28		(112)		45	(94)
Income from continuing operations	1,098		(1,256)		(1,624)	(5,442)
Nonregulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	4,467		3,984		9,135	9,505
Nonregulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	167		142		407	158
Nonregulated operation | Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	142		90		204	152
Nonregulated operation | Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	797		779		1,839	3,249
Nonregulated operation | Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	$ 3,361		$ 2,973		$ 6,685	$ 5,946

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Employee benefit plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Qualified plan | Underfunded plan | Pension benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	2,455,000	3,074,000	4,910,000	6,047,000
Expected return on assets	(4,894,000)	(5,214,000)	(9,788,000)	(9,975,000)
Amortization of prior service credit	0	0	0	0
Amortization of net actuarial loss	2,004,000	1,723,000	4,008,000	3,586,000
Net periodic benefit credit, including amount capitalized	(435,000)	(417,000)	(870,000)	(342,000)
Less amount capitalized	0	0	0	0
Net periodic benefit credit	(435,000)	(417,000)	(870,000)	(342,000)
Qualified plan | Overfunded Plan | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	400,000	414,000	800,000	766,000
Interest cost	466,000	627,000	932,000	1,218,000
Expected return on assets	(1,275,000)	(1,401,000)	(2,550,000)	(2,649,000)
Amortization of prior service credit	(349,000)	(402,000)	(698,000)	(699,000)
Amortization of net actuarial loss	6,000	142,000	12,000	144,000
Net periodic benefit credit, including amount capitalized	(752,000)	(620,000)	(1,504,000)	(1,220,000)
Less amount capitalized	44,000	35,000	83,000	67,000
Net periodic benefit credit	(796,000)	(655,000)	(1,587,000)	(1,287,000)
Nonqualified plan | Unfunded plan | Supplemental employee retirement plans
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Net periodic benefit credit	$ 769,000	$ 900,000	$ 1,500,000	$ 1,900,000

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IPUC (Details) - Pending Rate Case [Member] - IPUC - Intermountain Gas - Gas Distribution [Member] - USD ($) $ in Millions	Jun. 03, 2021	Jan. 12, 2021
Public Utilities, General Disclosures [Line Items]
Depreciation and Amortization Rate Case		$ (2.9)
Depreciation and Amortization, Rate, Percent		3.00%
Depreciation and Amortization, Requested Rate, Percent		2.60%
Depreciation and Amortization Requested Rate Increase (Decrease), Amended Amount	$ (3.8)
Depreciation and Amortization, Requested Rate, Amended, Percent	2.40%

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MNPUC (Details 2) $ in Millions	Mar. 30, 2021 USD ($)
MNPUC [Member] | Gas Distribution [Member] | Great Plains Natural Gas Co. [Member] | Pending Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 11.1

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NDPSC (Details 3) - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($) $ in Millions	Jul. 15, 2021	Jun. 01, 2021
Gas Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 13.5
Pending Rate Case [Member] | Electric | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Total Transmission Cost Adjustment Rider	$ 14.5
Public Utilities, Requested Rate Increase (Decrease), Amount	(1.1)
Transmission Capital Projects Increase (Decrease)	$ 5.1

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SDPUC (Details 4)	Mar. 11, 2021 USD ($)
SDPUC | Pending Rate Case [Member] | Electricity [Member] | Montana-Dakota Utilities Co. [Member]
Public Utilities, General Disclosures [Line Items]
Total Infrastructure Rider	$ 0

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WUTC (Details 5) - WUTC [Member] - Cascade Natural Gas [Member] - USD ($)	Jul. 01, 2021	Jun. 01, 2021	Jan. 08, 2021	Jul. 24, 2020	Jun. 19, 2020
Gas Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 13,800,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					5.30%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 7,400,000	$ 14,300,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Percentage			2.80%	5.50%
Gas Distribution [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (391,000)
Public Utilities, Approved Rate Increase (Decrease), Percentage	(0.20%)
Pending Rate Case [Member] | Pipeline Cost Recovery Mechanism [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 2,100,000
Public Utilities, Requested Rate Increase (Decrease), Percentage		0.80%

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Litigation (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 30.8	$ 41.5	$ 34.5
Insurance Receivable	6.9	17.5	21.1
Regulatory Assets	$ 21.2	$ 21.3	$ 10.4

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Guarantees (Details 2)	Jun. 30, 2021 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 171,200,000
Fixed maximum amounts guaranteed by year 2021	37,200,000
Fixed maximum amounts guaranteed by year 2022	67,700,000
Fixed maximum amounts guaranteed by year 2023	55,600,000
Fixed maximum amounts guaranteed by year 2024	500,000
Fixed maximum amounts guaranteed by year 2025	500,000
Fixed maximum amounts guaranteed, thereafter	700,000
No scheduled maturity date	9,000,000.0
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	25,500,000
Letters of credit set to expire - 2021	23,400,000
Letters of credit set to expire - 2022	2,100,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 1,100,000,000

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Variable interest entities (Details 3) $ in Millions	Jun. 30, 2021 USD ($)
Fuel contract
Variable Interest Entities [Line Items]
Variable interest entity, reporting entity involvement, maximum loss exposure, amount	$ 32.6