MDU Resources (MDU) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Cover page

Cover page - shares	6 Months Ended
	Jun. 30, 2020	Jul. 30, 2020
Document Information [Line Items]
Document type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
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		200,522,277
Entity Central Index Key	0000067716
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues:
Operating revenues:	$ 1,362,928	$ 1,303,573	$ 2,560,302	$ 2,394,764
Operating expenses:
Operation and maintenance:	1,029,171	1,021,031	1,850,171	1,723,945
Purchased natural gas sold	56,844	54,866	222,256	238,695
Depreciation, depletion and amortization	71,508	63,019	140,747	122,916
Taxes, other than income	52,584	47,953	116,696	101,982
Electric fuel and purchased power	14,567	19,393	35,107	45,696
Total operating expenses	1,224,674	1,206,262	2,364,977	2,233,234
Operating income	138,254	97,311	195,325	161,530
Other income	10,063	1,615	9,058	9,208
Interest expense	24,818	25,429	49,371	48,836
Income before income taxes	123,499	73,497	155,012	121,902
Income taxes	23,657	10,352	29,631	17,668
Income from continuing operations	99,842	63,145	125,381	104,234
Loss from discontinued operations, net of tax	(139)	(1,320)	(548)	(1,483)
Net income	$ 99,703	$ 61,825	$ 124,833	$ 102,751
Earnings per share - basic:
Income from continuing operations	$ 0.50	$ 0.32	$ 0.62	$ 0.53
Discontinued operations, net of tax	0	(0.01)	0	(0.01)
Earnings per share - basic	0.50	0.31	0.62	0.52
Earnings per share - diluted:
Income from continuing operations	0.50	0.32	0.62	0.53
Discontinued operations, net of tax	0	(0.01)	0	(0.01)
Earnings per share - diluted	$ 0.50	$ 0.31	$ 0.62	$ 0.52
Weighted average common shares outstanding - basic	200,522	198,270	200,481	197,341
Weighted average common shares outstanding - diluted	200,539	198,287	200,497	197,356
Regulated operation
Operating revenues:
Operating revenues:	$ 241,353	$ 236,247	$ 660,035	$ 675,864
Operating expenses:
Operation and maintenance:	83,103	88,415	170,712	176,186
Income from continuing operations	19,878	7,597	71,007	66,606
Nonregulated operation
Operating revenues:
Operating revenues:	1,121,575	1,067,326	1,900,267	1,718,900
Operating expenses:
Operation and maintenance:	946,068	932,616	1,679,459	1,547,759
Income from continuing operations	$ 79,964	$ 55,548	$ 54,374	$ 37,628

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income	$ 99,703	$ 61,825	$ 124,833	$ 102,751
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, tax	36	36	72	(213)
Reclassification adjustment for loss on derivative instruments included in net income, net of tax	112	111	223	508
Postretirement liability adjustment:
Amortization of postretirement liability losses included in net periodic benefit cost, tax	155	89	304	189
Amortization of postretirement liability losses included in net periodic benefit cost, net of tax	480	276	942	586
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	(4)	21	32	31
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax	(13)	79	122	118
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	2	3	2	10
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax	7	12	6	40
Net unrealized gain (loss) on available-for-sale investments	(6)	91	128	158
Other comprehensive income	586	478	1,293	1,252
Comprehensive income attributable to common stockholders	$ 100,289	$ 62,303	$ 126,126	$ 104,003

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Current assets:
Cash and cash equivalents	$ 64,358	$ 66,459	$ 71,966
Receivables, net	920,824	836,605	890,579
Inventories	302,837	278,407	325,944
Current regulatory assets	60,557	63,613	80,661
Prepayments and other current assets	48,194	52,617	75,660
Total current assets	1,396,770	1,297,701	1,444,810
Noncurrent assets:
Property, plant and equipment	8,063,435	7,908,628	7,625,654
Less accumulated depreciation, depletion and amortization	3,064,833	2,991,486	2,903,274
Net property, plant and equipment	4,998,602	4,917,142	4,722,380
Goodwill	708,664	681,358	679,395
Other intangible assets, net	31,515	15,246	11,323
Regulatory assets	351,025	353,784	327,164
Investments	154,779	148,656	145,746
Operating lease right-of-use assets	115,751	115,323	118,795
Other	154,026	153,849	141,880
Total noncurrent assets	6,514,362	6,385,358	6,146,683
Total assets	7,911,132	7,683,059	7,591,493
Current liabilities:
Short-term borrowings	75,000	0	89,983
Long-term debt due within one year	16,560	16,540	51,822
Accounts payable	433,362	403,391	356,059
Taxes payable	80,882	48,970	46,731
Dividends payable	41,608	41,580	40,225
Accrued compensation	85,525	99,269	71,508
Regulatory liabilities due within one year	48,000	42,935	49,974
Operating lease liabilities due within one year	31,985	31,664	31,615
Asset retirement obligations due within one year	4,200	4,277	4,994
Other accrued liabilities	182,597	177,801	169,691
Total current liabilities	999,719	866,427	912,602
Noncurrent liabilities:
Long-term debt	2,265,316	2,226,567	2,327,984
Deferred income taxes	516,760	506,583	457,588
Regulatory liabilities	438,652	447,370	455,864
Asset retirement obligations	422,169	413,298	380,493
Operating lease liabilities	84,302	83,742	87,172
Other	286,527	291,826	309,489
Total noncurrent liabilities	4,013,726	3,969,386	4,018,590
Commitments and contingencies
Stockholders' equity:
Common stock	201,061	200,923	199,539
Other paid-in capital	1,363,182	1,355,404	1,315,511
Retained earnings	1,377,879	1,336,647	1,185,967
Accumulated other comprehensive loss	(40,809)	(42,102)	(37,090)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)	(3,626)
Total stockholders' equity	2,897,687	2,847,246	2,660,301
Total liabilities and stockholders' equity	$ 7,911,132	$ 7,683,059	$ 7,591,493
Common Stock, Shares Authorized	500,000,000	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1	$ 1	$ 1
Common Stock, Shares, Issued	201,061,198	200,922,790	199,539,110
Treasury Stock, Common, Shares	538,921	538,921	538,921

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common stock	Other paid-in capital	Retained earnings	Accumulated other comprehensive loss	Treasury stock
Common stock balance (in shares) at Dec. 31, 2018		196,564,907
Treasury stock (in shares) at Dec. 31, 2018						(538,921)
Balance at Dec. 31, 2018	$ 2,566,775	$ 196,565	$ 1,248,576	$ 1,163,602	$ (38,342)	$ (3,626)
Net income	40,926			40,926
Other comprehensive income	774				774
Dividends declared on common stock	(40,019)			(40,019)
Stock-based compensation	1,617		1,617
Share Based Compensation, Shares, Shares Issued Net Of Tax Withholdings		246,214
Share Based Compensation, Value, Shares Issued Net Of Tax Withholdings		$ 246
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(3,261)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(3,015)
Issuance of common stock (shares)		1,505,687
Issuance of common stock	38,634	$ 1,506	37,128
Common stock balance (in shares) at Mar. 31, 2019		198,316,808
Treasury stock (in shares) at Mar. 31, 2019						(538,921)
Balance at Mar. 31, 2019	2,605,692	$ 198,317	1,284,060	1,164,509	(37,568)	$ (3,626)
Common stock balance (in shares) at Dec. 31, 2018		196,564,907
Treasury stock (in shares) at Dec. 31, 2018						(538,921)
Balance at Dec. 31, 2018	2,566,775	$ 196,565	1,248,576	1,163,602	(38,342)	$ (3,626)
Net income	102,751
Other comprehensive income	1,252
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	$ (3,015)
Common stock balance (in shares) at Jun. 30, 2019	199,539,110	199,539,110
Treasury stock (in shares) at Jun. 30, 2019						(538,921)
Balance at Jun. 30, 2019	$ 2,660,301	$ 199,539	1,315,511	1,185,967	(37,090)	$ (3,626)
Common stock balance (in shares) at Mar. 31, 2019		198,316,808
Treasury stock (in shares) at Mar. 31, 2019						(538,921)
Balance at Mar. 31, 2019	2,605,692	$ 198,317	1,284,060	1,164,509	(37,568)	$ (3,626)
Net income	61,825			61,825
Other comprehensive income	478				478
Dividends declared on common stock	(40,367)			(40,367)
Stock-based compensation	1,742		1,742
Issuance of common stock (shares)		1,222,302
Issuance of common stock	$ 30,931	$ 1,222	29,709
Common stock balance (in shares) at Jun. 30, 2019	199,539,110	199,539,110
Treasury stock (in shares) at Jun. 30, 2019						(538,921)
Balance at Jun. 30, 2019	$ 2,660,301	$ 199,539	1,315,511	1,185,967	(37,090)	$ (3,626)
Common stock balance (in shares) at Dec. 31, 2019	200,922,790	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
Share Based Compensation, Shares, Shares Issued Net Of Tax Withholdings		26,406
Share Based Compensation, Value, Shares Issued Net Of Tax Withholdings		$ 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	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)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net income	$ 124,833	$ 102,751
Loss from discontinued operations, net of tax	(548)	(1,483)
Income from continuing operations	125,381	104,234
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	140,747	122,916
Deferred income taxes	2,881	22,753
Changes in current assets and liabilities, net of acquisitions:
Receivables	(40,801)	(171,304)
Inventories	(26,276)	(36,302)
Other current assets	30,790	(32,088)
Accounts payable	13,387	1,398
Other current liabilities	26,612	15,585
Other noncurrent changes	(10,923)	(50,822)
Net cash provided by (used in) continuing operations	261,798	(23,630)
Net cash provided by (used in) discontinued operations	(396)	735
Net cash provided by (used in) operating activities	261,402	(22,895)
Investing activities:
Capital expenditures	(248,800)	(281,674)
Acquisitions, net of cash acquired	(70,729)	(30,868)
Net proceeds from sale or disposition of property and other	22,968	8,197
Investments	23	(713)
Net cash used in investing activities	(296,538)	(305,058)
Financing activities:
Issuance of short-term borrowings	75,000	119,977
Repayment of short-term borrowings	0	(30,000)
Issuance of long-term debt	200,400	368,975
Repayment of long-term debt	(162,225)	(99,961)
Proceeds from issuance of common stock	3,410	69,565
Dividends paid	(83,188)	(79,570)
Tax withholding on stock-based compensation	(362)	(3,015)
Net cash provided by financing activities	33,035	345,971
Increase (decrease) in cash and cash equivalents	(2,101)	18,018
Cash and cash equivalents -- beginning of year	66,459	53,948
Cash and cash equivalents -- end of period	$ 64,358	$ 71,966

Basis of presentation

Basis of presentation	6 Months Ended
	Jun. 30, 2020
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 2019 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. In March 2020, the World Health Organization declared the outbreak of COVID-19 a pandemic, and the President of the United States declared the COVID-19 outbreak as a national emergency. 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 and accordingly operations have been generally allowed to continue. The Company has experienced some inefficiency impacts, including operation suspensions and interruptions at some locations to carry out preventive measures or in response to instances of positive tests. The Company has assessed the impacts of the COVID-19 pandemic on its results of operations for the three and six months ended June 30, 2020, and determined there were no material adverse impacts. In the first quarter of 2020, the Company recorded an out-of-period adjustment to correct the recognition of revenue on a construction contract, which was the result of an overstatement of operating revenue and receivables of $7.7 million and an understatement of operating expense and accounts payable of $1.2 million in the year ended December 31, 2019. This adjustment resulted in an after-tax reduction to net income of $6.7 million in the first quarter of 2020. The Company evaluated the impact of the out-of-period adjustment and concluded it was not material to any previously issued interim and annual consolidated financial statements and the adjustment was not material to the three months ended March 31, 2020, and the six months ended June 30, 2020. Effective January 1, 2020, the Company adopted the requirements of the ASU on the measurement of credit losses on certain financial instruments following a modified retrospective approach, as further discussed in Notes 2 and 4. As such, results for reporting periods beginning on January 1, 2020, are presented under the new guidance, while prior period amounts are not adjusted and continue to be reported in accordance with historic accounting. The Company's adoption of this guidance did not have a material impact on its financial reporting. 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.

New accounting standards

New accounting standards	6 Months Ended
	Jun. 30, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
New accounting standards	New accounting standards Recently adopted accounting standards ASU 2016-13 - Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued guidance on the measurement of credit losses on certain financial instruments. The guidance introduced a new impairment model known as the current expected credit loss model that replaced the incurred loss impairment methodology previously included under GAAP. This guidance required entities to present certain investments in debt securities, trade accounts receivable and other financial assets at their net carrying value of the amount expected to be collected on the financial statements. The Company adopted the guidance on January 1, 2020, using a modified retrospective approach. The Company formed an implementation team to review and assess existing financial assets to identify and evaluate the financial assets subject to the new current expected credit loss model. The Company assessed the impact of the guidance on its processes and internal controls and identified and updated existing internal controls and processes to ensure compliance with the new guidance; such modifications were deemed insignificant. During the assessment phase, the Company identified the complete portfolio of assets subject to the current expected credit loss model. The Company determined the guidance did not have a material impact on its results of operations, financial position, cash flows or disclosures and did not record a material cumulative effect adjustment upon adoption. See Note 4 for additional information regarding the Company's expected credit losses. ASU 2018-13 - Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the FASB issued guidance on modifying the disclosure requirements on fair value measurements as part of the disclosure framework project. The guidance modified, among other things, the disclosures required for Level 3 fair value measurements, including the range and weighted average of significant unobservable inputs. The guidance removed, among other things, the disclosure requirement to disclose transfers between Levels 1 and 2. The Company adopted the guidance on January 1, 2020, and determined the guidance did not have a material impact on its disclosures. Recently issued accounting standards not yet adopted 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 removes disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and adds disclosure requirements identified as relevant. The guidance adds, 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 removes, among other things, the disclosure requirement to disclose the amount of net periodic benefit costs to be amortized over the next fiscal year from accumulated other comprehensive income (loss) and the effects a one percentage point change in assumed health care cost trend rates will have on certain benefit components. The guidance will be effective for the Company on January 1, 2021, and must be applied on a retrospective basis with early adoption permitted. The Company is evaluating the effects the adoption of the new guidance will have on its 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 removes exceptions on intraperiod tax allocations and reporting and provides simplification on accounting for franchise taxes, tax basis goodwill and tax law changes. The guidance will be effective for the Company on January 1, 2021, with early adoption permitted. Transition requirements vary among the exceptions and amendments which include retrospective, modified retrospective and prospective application. The Company is currently evaluating the effects of the new guidance and does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures. ASU 2020-04 - Reference Rate Reform In March 2020, the FASB issued optional guidance to ease the facilitation of the effects of reference rate reform on financial reporting. The guidance applies to certain contract modifications, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. 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 is currently updating its credit agreements to include language regarding the successor or alternate rate to LIBOR. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures.

Seasonality of operations

Seasonality of operations	6 Months Ended
	Jun. 30, 2020
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.

Receivables and allowance for e

Receivables and allowance for expected credit losses	6 Months Ended
	Jun. 30, 2020
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 8. The Company's trade accounts receivable are all due in 12 months or less. The total balance of receivables past due 90 days or more was $45.1 million, $47.2 million and $46.7 million at June 30, 2020 and 2019, and December 31, 2019, respectively. The Company's expected credit losses are determined through a review using historical credit loss experience, changes in asset specific characteristics, current conditions and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. The Company develops and documents its methodology to determine its allowance for expected credit losses at each of its reportable business segments. Risk characteristics used by the business segments may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible. Details of the Company's expected credit losses were as follows: Electric Natural gas Construction Construction 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 The Company's allowance for doubtful accounts at June 30, 2019 and December 31, 2019, was $8.2 million and $8.5 million, respectively.

Inventories and natural gas in

Inventories and natural gas in storage	6 Months Ended
	Jun. 30, 2020
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, 2020 June 30, 2019 December 31, 2019 (In thousands) Aggregates held for resale $ 165,357 $ 147,030 $ 147,723 Asphalt oil 57,207 80,418 41,912 Materials and supplies 27,805 28,746 22,512 Merchandise for resale 22,974 27,167 22,232 Natural gas in storage (current) 11,776 15,841 22,058 Other 17,718 26,742 21,970 Total $ 302,837 $ 325,944 $ 278,407 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 $48.3 million, $48.2 million and $48.4 million at June 30, 2020 and 2019, and December 31, 2019, respectively.

Earnings per common share

Earnings per common share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Earnings per common 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 nonvested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury. Net income was the same for both the basic and diluted earnings per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings per share calculations follows: Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 200,522 198,270 200,481 197,341 Effect of dilutive performance share awards and restricted stock units 17 17 16 15 Weighted average common shares outstanding - diluted 200,539 198,287 200,497 197,356 Shares excluded from the calculation of diluted earnings per share 187 — 191 93 Dividends declared per common share $ .2075 $ .2025 $ .4150 $ .4050

Accumulated other comprehensive

Accumulated other comprehensive income (loss)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Comprehensive income (loss)	Accumulated other comprehensive income (loss) The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 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) Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2018 $ (2,161) $ (36,069) $ (112) $ (38,342) Other comprehensive income before reclassifications — — 39 39 Amounts reclassified from accumulated other comprehensive loss 397 310 28 735 Net current-period other comprehensive income 397 310 67 774 At March 31, 2019 $ (1,764) $ (35,759) $ (45) $ (37,568) Other comprehensive income before reclassifications — — 79 79 Amounts reclassified from accumulated other comprehensive loss 111 276 12 399 Net current-period other comprehensive income 111 276 91 478 At June 30, 2019 $ (1,653) $ (35,483) $ 46 $ (37,090) The following amounts were reclassified between accumulated other comprehensive loss and 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 June 30, June 30, 2020 2019 2020 2019 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (148) $ (147) $ (295) $ (295) Interest expense 36 36 72 (213) Income taxes (112) (111) (223) (508) Amortization of postretirement liability losses included in net periodic benefit cost (635) (365) (1,246) (775) Other income 155 89 304 189 Income taxes (480) (276) (942) (586) Reclassification adjustment on available-for-sale investments included in net income (9) (15) (8) (50) Other income 2 3 2 10 Income taxes (7) (12) (6) (40) Total reclassifications $ (599) $ (399) $ (1,171) $ (1,134)

Revenue from contracts with cus

Revenue from contracts with customers	6 Months Ended
	Jun. 30, 2020
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 16. Three Months Ended June 30, 2020 Electric Natural gas Pipeline Construction Construction 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 Three Months Ended June 30, 2019 Electric Natural gas Pipeline Construction Construction Other Total (In thousands) Residential utility sales $ 26,437 $ 71,010 $ — $ — $ — $ — $ 97,447 Commercial utility sales 33,231 41,250 — — — — 74,481 Industrial utility sales 9,344 5,577 — — — — 14,921 Other utility sales 1,879 — — — — — 1,879 Natural gas transportation — 10,706 24,804 — — — 35,510 Natural gas gathering — — 2,396 — — — 2,396 Natural gas storage — — 2,623 — — — 2,623 Contracting services — — — 297,124 — — 297,124 Construction materials — — — 444,768 — — 444,768 Intrasegment eliminations — — — (145,925) — — (145,925) Inside specialty contracting — — — — 319,276 — 319,276 Outside specialty contracting — — — — 133,288 — 133,288 Other 8,417 2,923 6,293 — 9 2,903 20,545 Intersegment eliminations — — (7,513) (168) (721) (2,879) (11,281) Revenues from contracts with customers 79,308 131,466 28,603 595,799 451,852 24 1,287,052 Revenues out of scope 1,703 2,401 77 — 12,340 — 16,521 Total external operating revenues $ 81,011 $ 133,867 $ 28,680 $ 595,799 $ 464,192 $ 24 $ 1,303,573 Six Months Ended June 30, 2020 Electric Natural gas Pipeline Construction Construction 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 Six Months Ended June 30, 2019 Electric Natural gas Pipeline Construction Construction Other Total (In thousands) Residential utility sales $ 62,993 $ 271,619 $ — $ — $ — $ — $ 334,612 Commercial utility sales 68,902 163,043 — — — — 231,945 Industrial utility sales 18,228 14,188 — — — — 32,416 Other utility sales 3,678 — — — — — 3,678 Natural gas transportation — 22,276 49,862 — — — 72,138 Natural gas gathering — — 4,517 — — — 4,517 Natural gas storage — — 5,269 — — — 5,269 Contracting services — — — 380,164 — — 380,164 Construction materials — — — 624,077 — — 624,077 Intrasegment eliminations — — — (181,066) — — (181,066) Inside specialty contracting — — — — 618,805 — 618,805 Outside specialty contracting — — — — 240,686 — 240,686 Other 17,538 6,836 8,989 — 26 10,747 44,136 Intersegment eliminations — — (31,468) (264) (849) (10,704) (43,285) Revenues from contracts with customers 171,339 477,962 37,169 822,911 858,668 43 2,368,092 Revenues out of scope 2,239 (1,948) 124 — 26,257 — 26,672 Total external operating revenues $ 173,578 $ 476,014 $ 37,293 $ 822,911 $ 884,925 $ 43 $ 2,394,764 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, 2020 December 31, 2019 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 136,514 $ 109,078 $ 27,436 Receivables, net Contract liabilities - current (158,272) (142,768) (15,504) Accounts payable Contract liabilities - noncurrent (72) (19) (53) Noncurrent liabilities - other Net contract liabilities $ (21,830) $ (33,709) $ 11,879 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 $22.6 million and $79.0 million in revenue for the three and six months ended June 30, 2019, respectively, which was previously included in contract liabilities at December 31, 2018. 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. The Company recognized a net increase in revenues of $20.6 million and $32.5 million for the three and six months ended June 30, 2019, 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 remaining performance obligations at the pipeline segment include firm transportation and storage contracts with fixed pricing and fixed volumes. At June 30, 2020, the Company's remaining performance obligations were $2.3 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; $296.0 million within the next 13 to 24 months; and $239.6 million in 25 months or more.

Business Combinations

Business Combinations	6 Months Ended
	Jun. 30, 2020
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 were material to the Company's financial position or results of operations. For all business combinations, the Company preliminarily allocates the purchase price of the acquisitions to the assets acquired and liabilities assumed based on their estimated fair values as of the acquisition dates and are considered provisional until final fair values are determined or the measurement period has passed. The Company expects to record adjustments as it accumulates the information needed to estimate the fair value of assets acquired and liabilities assumed, including working capital balances; identifiable intangible assets; property, plant and equipment; total consideration and goodwill. The excess of the purchase price over the aggregate fair values is recorded as goodwill. The Company calculated the fair value of the assets acquired in 2020 and 2019 using a market or cost approach (or a combination of both). Fair values for some of the assets were determined based on Level 3 inputs including estimated future cash flows, discount rates, growth rates, sales projections, retention rates and terminal values, all of which require significant management judgment and are susceptible to change. The final fair value of the net assets acquired may result in adjustments to the assets and liabilities, including goodwill, and will be made as soon as practical, but no later than 12 months from the respective acquisition dates. Any subsequent measurement period adjustments are not expected to have a material impact on the Company's results of operations. 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. The following are the acquisitions made during 2020 and 2019 at the construction materials and contracting segment: • In February 2020, the Company acquired the assets of Oldcastle Infrastructure Spokane, a prestressed-concrete business in Washington. • In December 2019, the Company acquired the assets of Roadrunner Ready Mix, Inc., a provider of ready-mixed concrete in Idaho. • In March 2019, the Company acquired Viesko Redi-Mix, Inc., a provider of ready-mixed concrete in Oregon. The following are the acquisitions made during 2020 and 2019 at the construction services segment: • In February 2020, the Company acquired PerLectric, Inc., a leading electrical construction company in Virginia. • In September 2019, the Company purchased the assets of Pride Electric, Inc., an electrical construction company in Washington. The total purchase price for acquisitions that occurred in 2020 was $77.4 million, subject to certain adjustments, with cash acquired totaling $1.7 million. The purchase price includes consideration paid of $70.7 million and $5.0 million of indemnity holdback liabilities. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2020 were as follows: $46.1 million to current assets; $4.9 million to property, plant and equipment; $27.3 million to goodwill; $20.6 million to other intangible assets; $21.2 million to current liabilities and $300,000 to noncurrent liabilities. During the second quarter of 2020, measurement period adjustments of $3.6 million were made to the previously reported provisional amounts, which reduced goodwill. At June 30, 2020, the purchase price allocations for these acquisitions were preliminary and will be finalized within 12 months of the respective acquisition dates. The Company issued debt to finance these acquisitions. In 2019, the gross aggregate consideration for acquisitions was $56.8 million, subject to certain adjustments, and included $1.2 million of debt assumed. The amounts allocated to the aggregated assets acquired and liabilities assumed during 2019 were as follows: $15.8 million to current assets; $16.7 million to property, plant and equipment; $23.1 million to goodwill; $6.7 million to other intangible assets; $500,000 to other noncurrent assets; $5.9 million to current liabilities and $100,000 to noncurrent liabilities. At December 31, 2019, the purchase price adjustments for Viesko Redi-Mix, Inc. had been settled and no material adjustments were made to the provisional accounting. At June 30, 2020, the purchase price allocations for Pride Electric, Inc. and Roadrunner Ready Mix, Inc. were preliminary and will be finalized within 12 months of the respective acquisition dates. The Company issued debt and equity securities to finance these acquisitions. Costs incurred for acquisitions are included in operation and maintenance expense on the Consolidated Statements of Income and were not material for the six months ended June 30, 2020 and 2019.

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases of Lessor Disclosure	Leases The Company's leases primarily include operating leases for equipment, buildings, easements and vehicles. The Company leases certain equipment to third parties through its utility and construction services segments, which are considered short-term operating leases with terms of less than 12 months. The Company recognized revenue from operating leases of $11.2 million and $23.3 million for the three and six months ended June 30, 2020, respectively. The Company recognized revenue from operating leases of $12.5 million and $26.5 million for the three and six months ended June 30, 2019, respectively. At June 30, 2020, the Company had $10.4 million of lease receivables with a majority due within 12 months.

Goodwill and other intangible a

Goodwill and other intangible assets	6 Months Ended
	Jun. 30, 2020
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, 2020 Goodwill Measurement 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, 2019 Goodwill Measurement Balance at June 30, 2019 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 209,421 14,473 — 223,894 Construction services 109,765 — — 109,765 Total $ 664,922 $ 14,473 $ — $ 679,395 Balance at January 1, 2019 Goodwill Measurement Balance at December 31, 2019 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 209,421 14,482 (6,669) 217,234 Construction services 109,765 8,623 — 118,388 Total $ 664,922 $ 23,105 $ (6,669) $ 681,358 During 2020 and 2019, the Company completed two and three business combinations, respectively, and the results of these acquisitions have been included in the Company's construction materials and contracting and construction services segments. These business combinations increased the construction materials and contracting segment's goodwill balance at June 30, 2020 and 2019, and December 31, 2019, respectively, and increased the construction services segment's goodwill balance at June 30, 2020 and December 31, 2019, respectively, as noted in the previous tables. As a result of the business combinations, other intangible assets increased $21.0 million at June 30, 2020, compared to December 31, 2019. For more information related to these business combinations, see Note 9. Other amortizable intangible assets were as follows: June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Customer relationships $ 30,087 $ 14,601 $ 17,958 Less accumulated amortization 5,239 5,629 6,268 24,848 8,972 11,690 Noncompete agreements 4,229 3,179 3,439 Less accumulated amortization 2,084 1,798 1,957 2,145 1,381 1,482 Other 13,060 6,578 8,094 Less accumulated amortization 8,538 5,608 6,020 4,522 970 2,074 Total $ 31,515 $ 11,323 $ 15,246 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. Amortization expense for amortizable intangible assets for the three and six months ended June 30, 2019, was $500,000 and $1.1 million, respectively. Estimated amortization expense for identifiable intangible assets as of June 30, 2020, was: Remainder of 2021 2022 2023 2024 Thereafter (In thousands) Amortization expense $ 5,313 $ 5,199 $ 4,711 $ 4,490 $ 4,160 $ 7,642

Regulatory assets and liabiliti

Regulatory assets and liabilities	6 Months Ended
	Jun. 30, 2020
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 * June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 42,582 $ 65,448 $ 42,823 Cost recovery mechanisms Up to 1 year 7,781 7,484 6,288 Conservation programs Up to 1 year 7,256 6,529 6,963 Other Up to 1 year 2,938 1,200 7,539 60,557 80,661 63,613 Noncurrent: Pension and postretirement benefits ** 157,033 165,861 157,069 Asset retirement obligations Over plant lives 68,191 64,215 66,000 Plant to be retired - 49,185 16,933 32,931 Natural gas costs recoverable through rate adjustments Up to 3 years 27,184 29,095 46,381 Manufactured gas plant site remediation - 14,826 15,387 15,126 Cost recovery mechanisms Up to 10 years 13,140 11,004 13,108 Taxes recoverable from customers Over plant lives 10,890 11,755 11,486 Long-term debt refinancing costs Up to 17 years 3,980 4,592 4,286 Other Up to 19 years 6,596 8,322 7,397 351,025 327,164 353,784 Total regulatory assets $ 411,582 $ 407,825 $ 417,397 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments $ 29,557 $ 25,737 $ 23,825 Electric fuel and purchased power deferral 7,799 4,686 5,824 Taxes refundable to customers 4,012 7,104 3,472 Other 6,632 12,447 9,814 48,000 49,974 42,935 Noncurrent: Taxes refundable to customers 236,142 256,921 246,034 Plant removal and decommissioning costs 173,399 173,661 173,722 Pension and postretirement benefits 18,015 15,215 18,065 Other 11,096 10,067 9,549 438,652 455,864 447,370 Total regulatory liabilities $ 486,652 $ 505,838 $ 490,305 Net regulatory position $ (75,070) $ (98,013) $ (72,908) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. ** Recovered as expense is incurred or cash contributions are made. At June 30, 2020 and 2019, and December 31, 2019, approximately $296.6 million, $290.7 million and $276.5 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. 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 that it intends to retire three aging coal-fired electric generating units in early 2021 and early 2022. The Company has accelerated the depreciation related to these facilities in property, plant and equipment and has recorded the difference between the accelerated depreciation, in accordance with GAAP, and the depreciation approved for rate-making purposes as regulatory assets. The Company expects to recover the regulatory assets related to the plants to be retired in future rates. If, for any reason, the Company's regulated businesses cease to meet the criteria for application of regulatory accounting for all or part of their operations, the regulatory assets and liabilities relating to those portions ceasing to meet such criteria would be removed from the balance sheet and included in the statement of income or accumulated other comprehensive income (loss) in the period in which the discontinuance of regulatory accounting occurs.

Fair value measurements

Fair value measurements	6 Months Ended
	Jun. 30, 2020
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 an insurance contract, to satisfy its obligations under its unfunded, nonqualified defined benefit plans for executive officers and certain key management employees, and invests in these fixed-income and equity securities for the purpose of earning investment returns and capital appreciation. These investments, which totaled $92.4 million, $83.1 million and $87.0 million, at June 30, 2020 and 2019, and December 31, 2019, respectively, are classified as investments on the Consolidated Balance Sheets. 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 net unrealized gains on these investments were $2.9 million and $9.3 million for the three and six months ended June 30, 2019, 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, 2020 Cost Gross Gross 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 June 30, 2019 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 10,771 $ 94 $ 35 $ 10,830 U.S. Treasury securities 180 — — 180 Total $ 10,951 $ 94 $ 35 $ 11,010 December 31, 2019 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 9,804 $ 87 $ 10 $ 9,881 U.S. Treasury securities 1,228 1 — 1,229 Total $ 11,032 $ 88 $ 10 $ 11,110 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 Level 2 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 Level 2 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 Level 2 insurance contract is based on contractual cash surrender values that are determined primarily by investments in managed separate accounts of the insurer. These amounts approximate fair value. The managed separate accounts are valued based on other observable inputs or corroborated market data. Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. The Company's assets measured at fair value on a recurring basis were as follows: Fair Value Measurements at June 30, 2020, Using Quoted Prices in Significant Significant 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 June 30, 2019, Using Quoted Prices in Significant Significant Balance at June 30, 2019 (In thousands) Assets: Money market funds $ — $ 10,816 $ — $ 10,816 Insurance contract* — 83,134 — 83,134 Available-for-sale securities: Mortgage-backed securities — 10,830 — 10,830 U.S. Treasury securities — 180 — 180 Total assets measured at fair value $ — $ 104,960 $ — $ 104,960 * The insurance contract invests approximately 51 percent in fixed-income investments, 22 percent in common stock of large-cap companies, 12 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 4 percent in target date investments and 1 percent in cash equivalents. Fair Value Measurements at December 31, 2019, Using Quoted Prices in Significant Significant Balance at December 31, 2019 (In thousands) Assets: Money market funds $ — $ 8,440 $ — $ 8,440 Insurance contract* — 87,009 — 87,009 Available-for-sale securities: Mortgage-backed securities — 9,881 — 9,881 U.S. Treasury securities — 1,229 — 1,229 Total assets measured at fair value $ — $ 106,559 $ — $ 106,559 * The insurance contract invests approximately 51 percent in fixed-income investments, 23 percent in common stock of large-cap companies, 12 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 3 percent in target date investments and 1 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. In the second quarter of 2019, the Company reviewed a non-utility investment at its electric and natural gas distribution segments for impairment. This was a cost-method investment and was written down to zero using the income approach to determine its fair value, requiring the Company to record a write-down of $2.0 million, before tax. The fair value of this investment was categorized as Level 3 in the fair value hierarchy. This reduction is reflected in investments on the Company's Consolidated Balance Sheet, as well as within other income on the Consolidated Statements of Income. The Company performed a fair value assessment of the assets acquired and liabilities assumed in the business combinations that have occurred during 2020 and 2019. For more information on these Level 2 and Level 3 fair value measurements, see Note 9. 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, 2020 June 30, 2019 December 31, 2019 (In thousands) Carrying amount $ 2,281,876 $ 2,379,806 $ 2,243,107 Fair value $ 2,563,734 $ 2,521,325 $ 2,418,631 The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values .

Debt

Debt	6 Months Ended
	Jun. 30, 2020
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, 2020. In the event the Company's 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. Due to the impacts of the COVID-19 pandemic on the short-term capital markets, the Company temporarily borrowed under its revolving credit agreements in addition to accessing the commercial paper markets in the first half of 2020 . At June 30, 2020, all borrowings under the revolving credit agreements for Montana-Dakota and Centennial had been repaid. Long-term debt Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Senior Notes due on dates ranging from October 22, 2022 to June 15, 2060 4.43 % $ 1,900,000 $ 1,656,000 $ 1,850,000 Commercial paper supported by revolving credit agreements 1.02 % 290,100 433,350 222,900 Term Loan Agreement due on September 3, 2032 2.00 % 9,100 209,800 9,100 Credit agreements due on June 7, 2024 3.25 % 11,200 11,075 89,050 Medium-Term Notes due on dates ranging from September 1, 2020 to March 16, 2029 6.68 % 50,000 50,000 50,000 Other notes due on dates ranging from July 15, 2021 to November 30, 2038 4.59 % 28,342 26,105 29,117 Less unamortized debt issuance costs 6,668 6,164 7,010 Less discount 198 360 50 Total long-term debt 2,281,876 2,379,806 2,243,107 Less current maturities 16,560 51,822 16,540 Net long-term debt $ 2,265,316 $ 2,327,984 $ 2,226,567 Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at June 30, 2020, were as follows: Remainder of 2021 2022 2023 2024 Thereafter (In thousands) Long-term debt maturities $ 15,762 $ 1,522 $ 148,021 $ 77,921 $ 362,722 $ 1,682,794

Cash flow information

Cash flow information	6 Months Ended
	Jun. 30, 2020
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, 2020 2019 (In thousands) Interest, net* $ 47,769 $ 45,702 Income taxes paid, net** $ 735 $ 4,124 * AFUDC - borrowed was $1.3 million and $1.2 million for the six months ended June 30, 2020 and 2019, respectively. ** Income taxes paid, including discontinued operations, were $882,000 and $2.0 million for the six months ended June 30, 2020 and 2019, respectively. Noncash investing and financing transactions were as follows: June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 24,181 $ 24,990 $ 54,880 Property, plant and equipment additions in accounts payable $ 36,493 $ 27,312 $ 46,119 Accrual for holdback payment related to a business combination $ 5,000 $ — $ — Debt assumed in connection with a business combination $ — $ 1,163 $ 1,163

Business segment data

Business segment data	6 Months Ended
	Jun. 30, 2020
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 vast majority of 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, underground storage and gathering services through regulated and nonregulated pipeline systems primarily in the Rocky Mountain and northern Great Plains regions of the United States. This segment also provides cathodic protection and other energy-related services. The construction materials and contracting segment mines, processes and sells construction aggregates (crushed stone, sand and gravel); produces and sells asphalt mix; and supplies ready-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, including Alaska and Hawaii. The construction services segment provides inside and outside specialty contracting services. 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 government 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 1 of the Notes to Consolidated Financial Statements in the 2019 Annual Report. Information on the Company's segments was as follows: Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (In thousands) External operating revenues: Regulated operations: Electric $ 76,438 $ 81,011 $ 162,346 $ 173,578 Natural gas distribution 141,494 133,867 467,937 476,014 Pipeline 23,421 21,369 29,752 26,272 241,353 236,247 660,035 675,864 Nonregulated operations: Pipeline 4,237 7,311 8,561 11,021 Construction materials and contracting 621,045 595,799 883,190 822,911 Construction services 496,405 464,192 1,008,610 884,925 Other (112) 24 (94) 43 1,121,575 1,067,326 1,900,267 1,718,900 Total external operating revenues $ 1,362,928 $ 1,303,573 $ 2,560,302 $ 2,394,764 Intersegment operating revenues: Regulated operations: Electric $ 196 $ — $ 391 $ — Natural gas distribution 185 — 370 — Pipeline 7,857 7,426 33,040 31,349 8,238 7,426 33,801 31,349 Nonregulated operations: Pipeline 142 87 158 119 Construction materials and contracting 90 168 152 264 Construction services 779 721 3,249 849 Other 2,973 2,879 5,946 10,704 3,984 3,855 9,505 11,936 Intersegment eliminations (12,222) (11,281) (43,306) (43,285) Total intersegment operating revenues $ — $ — $ — $ — Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (In thousands) Operating income (loss): Electric $ 12,810 $ 9,791 $ 27,669 $ 27,779 Natural gas distribution 678 (2,621) 50,677 47,696 Pipeline 12,225 10,698 23,644 20,602 Construction materials and contracting 74,741 46,178 31,472 4,597 Construction services 37,882 31,966 61,678 59,431 Other (82) 1,299 185 1,425 Total operating income $ 138,254 $ 97,311 $ 195,325 $ 161,530 Net income (loss): Regulated operations: Electric $ 12,153 $ 7,471 $ 23,527 $ 22,976 Natural gas distribution (959) (6,252) 31,410 30,248 Pipeline 8,684 6,378 16,070 13,382 19,878 7,597 71,007 66,606 Nonregulated operations: Pipeline 268 742 255 579 Construction materials and contracting 53,020 29,166 14,806 (5,283) Construction services 27,932 22,845 44,755 42,869 Other (1,256) 2,795 (5,442) (537) 79,964 55,548 54,374 37,628 Income from continuing operations 99,842 63,145 125,381 104,234 Loss from discontinued operations, net of tax (139) (1,320) (548) (1,483) Net income $ 99,703 $ 61,825 $ 124,833 $ 102,751

Employee benefit plans

Employee benefit plans	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Pension and other postretirement 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 cost (credit) for the Company's pension and other postretirement benefit plans were as follows: Pension Benefits Other Three Months Ended June 30, 2020 2019 2020 2019 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 414 $ 227 Interest cost 3,074 3,840 627 713 Expected return on assets (5,214) (3,998) (1,401) (1,182) Amortization of prior service credit — — (402) (228) Amortization of net actuarial (gain) loss 1,723 1,418 142 (42) Net periodic benefit cost (credit), including amount capitalized (417) 1,260 (620) (512) Less amount capitalized — — 35 27 Net periodic benefit cost (credit) $ (417) $ 1,260 $ (655) $ (539) Pension Benefits Other Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 766 $ 571 Interest cost 6,047 7,613 1,218 1,493 Expected return on assets (9,975) (9,118) (2,649) (2,402) Amortization of prior service credit — — (699) (577) Amortization of net actuarial loss 3,586 2,773 144 55 Net periodic benefit cost (credit), including amount capitalized (342) 1,268 (1,220) (860) Less amount capitalized — — 67 58 Net periodic benefit cost (credit) $ (342) $ 1,268 $ (1,287) $ (918) The components of net periodic benefit cost (credit), other than the service cost component, are included in other income on the Consolidated Statements of Income. 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 for the three and six months ended June 30, 2020, was $900,000 and $1.9 million, respectfully. The Company's net periodic benefit cost for these plans for the three and six months ended June 30, 2019, was $1.1 million and $2.2 million, respectfully. The components of net periodic benefit cost for these plans are included in other income on the Consolidated Statements of Income.

Regulatory matters

Regulatory matters	6 Months Ended
	Jun. 30, 2020
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 regulatory proceedings and cases by jurisdiction, including the status of each open request, as well as updates to those reported in the 2019 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 May 4, 2020, Intermountain filed a request with the IPUC for authority to facilitate access for RNG producers to its distribution system to move RNG to the producers' buyers. Intermountain has executed contracts with three RNG producers to facilitate such access. Intermountain intends to completely insulate utility customers from all potential impacts of RNG production. If any startup or extraordinary expenses are incurred, the RNG producer will be billed for the actual expenses that are incurred. Additionally, Intermountain will be collecting an access fee that will be recorded as non-utility revenue. On June 12, 2020, the IPUC issued an accounting order approving this request. On May 12, 2020, Intermountain filed a request with the IPUC to use deferred accounting for costs related to the COVID-19 pandemic. On July 7, 2020, the IPUC approved this request with an accounting order to track expenses and revenues related to the COVID-19 pandemic. This order had an immediate effective date. MNPUC On September 27, 2019, Great Plains filed an application with the MNPUC for a natural gas rate increase of approximately $2.9 million annually or approximately 12.0 percent above current rates. The requested increase was primarily to recover investments in facilities to enhance safety and reliability and the depreciation and taxes associated with the increase in investment. On November 22, 2019, Great Plains received approval to implement an interim rate increase of approximately $2.6 million or approximately 11.0 percent, subject to refund, effective January 1, 2020. This matter is pending before the MNPUC. On April 20, 2020, Great Plains filed a request with the MNPUC to use deferred accounting for costs related to the COVID-19 pandemic. On May 22, 2020, the MNPUC approved this request with an accounting order to track expenses and revenues related to the COVID-19 pandemic. This order had an immediate effective date. MTPSC On November 1, 2019, Montana-Dakota submitted an application with the MTPSC requesting the use of deferred accounting for the treatment of costs related to the retirement of Lewis & Clark Station in Sidney, Montana, and Units 1 and 2 at Heskett Station near Mandan, North Dakota. On June 18, 2020, the MTPSC approved this request with an accounting order to allow Montana-Dakota to defer costs related to the retirement of the plants with an immediate effective date. On May 8, 2020, Montana-Dakota filed a request with the MTPSC to use deferred accounting for costs related to the COVID-19 pandemic. This matter is pending before the MTPSC. On June 22, 2020, Montana-Dakota filed an application with the MTPSC for a natural gas rate increase of approximately $8.6 million annually or approximately 13.4 percent above current rates. The requested increase was primarily to recover investments in facilities that were made to enhance system safety and reliability, as well as the depreciation, taxes and operation and maintenance costs associated with this increase in investment. The Company requested an interim rate increase of approximately $4.9 million or approximately 8.2 percent, subject to refund, to be effective February 1, 2021. This matter is pending before the MTPSC. NDPSC On August 28, 2019, Montana-Dakota filed an application with the NDPSC for an advanced determination of prudence and a certificate of public convenience and necessity to construct, own and operate Heskett Unit 4, an 88-MW simple-cycle natural gas-fired combustion turbine peaking unit at the existing Heskett Station near Mandan, North Dakota. On September 16, 2019, Montana-Dakota submitted an application with the NDPSC requesting the use of deferred accounting for the treatment of costs related to the retirement of Lewis & Clark Station in Sidney, Montana, and Units 1 and 2 at Heskett Station near Mandan, North Dakota. On April 2, 2020, a combined settlement, for the previously discussed matters, was filed with the NDPSC. The settlement recommended approval of the advanced determination of prudence and deferred accounting. A consolidated hearing was held on April 30, 2020. On July 23, 2020, a modified settlement agreement adjusting the amortization period of deferred costs was filed with the NDPSC. On August 5, 2020, the NDPSC approved the combined settlement. On April 24, 2020, Montana-Dakota filed a request with the NDPSC to use deferred accounting for costs related to the COVID-19 pandemic. This matter is pending before the NDPSC. On July 17, 2020, Montana-Dakota filed an annual update to its transmission cost adjustment rider with the NDPSC requesting to recover revenues of approximately $15.5 million, which includes a true-up of the prior period adjustment, resulting in an increase of approximately $6.3 million over current rates. This filing includes approximately $3.3 million related to transmission capital projects. This matter is pending before the NDPSC. OPUC On March 26, 2020, Cascade filed a request with the OPUC to use deferred accounting for costs related to the COVID-19 pandemic. This matter is pending before the OPUC. On March 31, 2020, Cascade filed a natural gas general rate case with the OPUC requesting an increase in annual revenue of approximately $4.9 million or approximately 7.2 percent, which included a request for an additional recovery of environmental remediation deferred costs of approximately $364,000. This matter is pending before the OPUC. SDPUC On May 1, 2020, Montana-Dakota filed a request with the SDPUC to use deferred accounting for costs related to the COVID-19 pandemic. This matter is pending before the SDPUC. WUTC On May 27, 2020, Cascade filed a request with the WUTC to use deferred accounting for costs related to the COVID-19 pandemic. This matter is pending before the WUTC. On May 29, 2020, Cascade filed its annual pipeline cost recovery mechanism requesting an increase in annual revenue of approximately $1.0 million or approximately 0.4 percent. The filing includes a proposed effective date of November 1, 2020. This matter is pending before the 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 WUTC has 11 months to render a final decision on the rate case. The requested increase was primarily to recover investments made in infrastructure upgrades, as well as increased operation and maintenance costs. This matter is pending before the WUTC. WYPSC On May 14, 2020, Montana-Dakota filed separate requests for its electric and natural gas services with the WYPSC to use deferred accounting for costs related to the COVID-19 pandemic. On June 1, 2020, the WYPSC approved these requests with an accounting order to track expenses and revenues related to the COVID-19 pandemic. This order had an immediate effective date.

Contingencies

Contingencies	6 Months Ended
	Jun. 30, 2020
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, 2020 and 2019, and December 31, 2019, the Company accrued liabilities which have not been discounted, including liabilities held for sale, of $34.5 million, $32.1 million and $29.1 million, respectively. 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 2019 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, 2020, the fixed maximum amounts guaranteed under these agreements aggregated $272.7 million. Certain of the guarantees also have no fixed maximum amounts specified. At June 30, 2020, the amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $91.8 million in 2020; $169.4 million in 2021; $400,000 in 2022; $500,000 in 2023; $500,000 in 2024; $1.1 million thereafter; and $9.0 million, which has no scheduled maturity date. There were no amounts outstanding under the previously mentioned guarantees at June 30, 2020. 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, 2020, the fixed maximum amounts guaranteed under these letters of credit aggregated $23.9 million. At June 30, 2020, the amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $20.4 million in 2020 and $3.5 million in 2021. There were no amounts outstanding under the previously mentioned letters of credit at June 30, 2020. 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, 2020. 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, 2020, approximately $1.0 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, 2020, 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 $34.8 million.

Basis of presentation (Policies

Basis of presentation (Policies)	6 Months Ended
	Jun. 30, 2020
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 2019 Annual Report. The information is unaudited but includes all adjustments that are, in the opinion of management, necessary for a fair presentation of the accompanying consolidated interim financial statements and are of a normal recurring nature. Depreciation, depletion and amortization expense is reported separately on the Consolidated Statements of Income and therefore is excluded from the other line items within operating expenses.

New accounting standards (Polic

New accounting standards (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Standards Update and Change in Accounting Principle [Abstract]
New accounting standards	Recently adopted accounting standards ASU 2016-13 - Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued guidance on the measurement of credit losses on certain financial instruments. The guidance introduced a new impairment model known as the current expected credit loss model that replaced the incurred loss impairment methodology previously included under GAAP. This guidance required entities to present certain investments in debt securities, trade accounts receivable and other financial assets at their net carrying value of the amount expected to be collected on the financial statements. The Company adopted the guidance on January 1, 2020, using a modified retrospective approach. The Company formed an implementation team to review and assess existing financial assets to identify and evaluate the financial assets subject to the new current expected credit loss model. The Company assessed the impact of the guidance on its processes and internal controls and identified and updated existing internal controls and processes to ensure compliance with the new guidance; such modifications were deemed insignificant. During the assessment phase, the Company identified the complete portfolio of assets subject to the current expected credit loss model. The Company determined the guidance did not have a material impact on its results of operations, financial position, cash flows or disclosures and did not record a material cumulative effect adjustment upon adoption. See Note 4 for additional information regarding the Company's expected credit losses. ASU 2018-13 - Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the FASB issued guidance on modifying the disclosure requirements on fair value measurements as part of the disclosure framework project. The guidance modified, among other things, the disclosures required for Level 3 fair value measurements, including the range and weighted average of significant unobservable inputs. The guidance removed, among other things, the disclosure requirement to disclose transfers between Levels 1 and 2. The Company adopted the guidance on January 1, 2020, and determined the guidance did not have a material impact on its disclosures. Recently issued accounting standards not yet adopted 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 removes disclosures that are no longer considered cost beneficial, clarifies the specific requirements of disclosures and adds disclosure requirements identified as relevant. The guidance adds, 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 removes, among other things, the disclosure requirement to disclose the amount of net periodic benefit costs to be amortized over the next fiscal year from accumulated other comprehensive income (loss) and the effects a one percentage point change in assumed health care cost trend rates will have on certain benefit components. The guidance will be effective for the Company on January 1, 2021, and must be applied on a retrospective basis with early adoption permitted. The Company is evaluating the effects the adoption of the new guidance will have on its 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 removes exceptions on intraperiod tax allocations and reporting and provides simplification on accounting for franchise taxes, tax basis goodwill and tax law changes. The guidance will be effective for the Company on January 1, 2021, with early adoption permitted. Transition requirements vary among the exceptions and amendments which include retrospective, modified retrospective and prospective application. The Company is currently evaluating the effects of the new guidance and does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures. ASU 2020-04 - Reference Rate Reform In March 2020, the FASB issued optional guidance to ease the facilitation of the effects of reference rate reform on financial reporting. The guidance applies to certain contract modifications, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform. 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 is currently updating its credit agreements to include language regarding the successor or alternate rate to LIBOR. The Company does not expect the guidance to have a material impact on its results of operations, financial position, cash flows or disclosures.

Receivables and allowance for_2

Receivables and allowance for expected credit losses (Policies)	6 Months Ended
	Jun. 30, 2020
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 8. The Company's trade accounts receivable are all due in 12 months or less.
Expected credit loss	The Company's expected credit losses are determined through a review using historical credit loss experience, changes in asset specific characteristics, current conditions and reasonable and supportable future forecasts, among other specific account data, and is performed at least quarterly. The Company develops and documents its methodology to determine its allowance for expected credit losses at each of its reportable business segments. Risk characteristics used by the business segments may include customer mix, knowledge of customers and general economic conditions of the various local economies, among others. Specific account balances are written off when management determines the amounts to be uncollectible.

Inventories and natural gas i_2

Inventories and natural gas in storage (Policies)	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Inventories and natural gas in storage	Natural gas in storage for the Company's regulated operations is generally valued at lower of cost or market using the last-in, first-out method or lower of cost or net realizable value using the average cost or first-in, first-out method. The majority of all other inventories are valued at the lower of cost or net realizable value using the average cost method.

Earnings per common share (Poli

Earnings per common share (Policies)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Earnings per common share	Basic earnings per share is computed by dividing net income by the weighted average number of shares of common stock outstanding during the 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 nonvested performance share awards and restricted stock units. Common stock outstanding includes issued shares less shares held in treasury.

Revenue from contracts with c_2

Revenue from contracts with customers (Policies)	6 Months Ended
	Jun. 30, 2020
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.

Business Combinations (Policies

Business Combinations (Policies)	6 Months Ended
	Jun. 30, 2020
Business Combinations [Abstract]
Business Combinations Policy [Policy Text Block]	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 were material to the Company's financial position or results of operations. For all business combinations, the Company preliminarily allocates the purchase price of the acquisitions to the assets acquired and liabilities assumed based on their estimated fair values as of the acquisition dates and are considered provisional until final fair values are determined or the measurement period has passed. The Company expects to record adjustments as it accumulates the information needed to estimate the fair value of assets acquired and liabilities assumed, including working capital balances; identifiable intangible assets; property, plant and equipment; total consideration and goodwill. The excess of the purchase price over the aggregate fair values is recorded as goodwill. The Company calculated the fair value of the assets acquired in 2020 and 2019 using a market or cost approach (or a combination of both). Fair values for some of the assets were determined based on Level 3 inputs including estimated future cash flows, discount rates, growth rates, sales projections, retention rates and terminal values, all of which require significant management judgment and are susceptible to change. The final fair value of the net assets

Fair value disclosures (Policie

Fair value disclosures (Policies)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair value measurements	The Company measures its investments in certain fixed-income and equity securities at fair value with changes in fair value recognized in income.
Investments	The Company did not elect the fair value option, which records gains and losses in income, for its available-for-sale securities, which include mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as investments on the Consolidated Balance Sheets.

Business segment data (Policies

Business segment data (Policies)	6 Months Ended
	Jun. 30, 2020
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.

Contingencies (Policies)

Contingencies (Policies)	6 Months Ended
	Jun. 30, 2020
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.

Accounts receivable and allowan

Accounts receivable and allowance for doubtful accounts Receivables and allowance for expected credit losses (Tables)	6 Months Ended
	Jun. 30, 2020
Credit Loss [Abstract]
Financing Receivable, Allowance for Credit Loss [Table Text Block]	Details of the Company's expected credit losses were as follows: Electric Natural gas Construction Construction 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

Inventories and natural gas i_3

Inventories and natural gas in storage (Tables)	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Inventories	Inventories on the Consolidated Balance Sheets were as follows: June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Aggregates held for resale $ 165,357 $ 147,030 $ 147,723 Asphalt oil 57,207 80,418 41,912 Materials and supplies 27,805 28,746 22,512 Merchandise for resale 22,974 27,167 22,232 Natural gas in storage (current) 11,776 15,841 22,058 Other 17,718 26,742 21,970 Total $ 302,837 $ 325,944 $ 278,407

Earnings per common share (Tabl

Earnings per common share (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 2019 2020 2019 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 200,522 198,270 200,481 197,341 Effect of dilutive performance share awards and restricted stock units 17 17 16 15 Weighted average common shares outstanding - diluted 200,539 198,287 200,497 197,356 Shares excluded from the calculation of diluted earnings per share 187 — 191 93 Dividends declared per common share $ .2075 $ .2025 $ .4150 $ .4050

Accumulated other comprehensi_2

Accumulated other comprehensive income (loss) (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Accumulated comprehensive loss	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 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) Net Unrealized Postretirement Net Unrealized Total (In thousands) At December 31, 2018 $ (2,161) $ (36,069) $ (112) $ (38,342) Other comprehensive income before reclassifications — — 39 39 Amounts reclassified from accumulated other comprehensive loss 397 310 28 735 Net current-period other comprehensive income 397 310 67 774 At March 31, 2019 $ (1,764) $ (35,759) $ (45) $ (37,568) Other comprehensive income before reclassifications — — 79 79 Amounts reclassified from accumulated other comprehensive loss 111 276 12 399 Net current-period other comprehensive income 111 276 91 478 At June 30, 2019 $ (1,653) $ (35,483) $ 46 $ (37,090)
Reclassification out of accumulated other comprehensive loss	The following amounts were reclassified between accumulated other comprehensive loss and 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 June 30, June 30, 2020 2019 2020 2019 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (148) $ (147) $ (295) $ (295) Interest expense 36 36 72 (213) Income taxes (112) (111) (223) (508) Amortization of postretirement liability losses included in net periodic benefit cost (635) (365) (1,246) (775) Other income 155 89 304 189 Income taxes (480) (276) (942) (586) Reclassification adjustment on available-for-sale investments included in net income (9) (15) (8) (50) Other income 2 3 2 10 Income taxes (7) (12) (6) (40) Total reclassifications $ (599) $ (399) $ (1,171) $ (1,134)

Revenue from contracts with c_3

Revenue from contracts with customers (Tables)	6 Months Ended
	Jun. 30, 2020
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 16. Three Months Ended June 30, 2020 Electric Natural gas Pipeline Construction Construction 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 Three Months Ended June 30, 2019 Electric Natural gas Pipeline Construction Construction Other Total (In thousands) Residential utility sales $ 26,437 $ 71,010 $ — $ — $ — $ — $ 97,447 Commercial utility sales 33,231 41,250 — — — — 74,481 Industrial utility sales 9,344 5,577 — — — — 14,921 Other utility sales 1,879 — — — — — 1,879 Natural gas transportation — 10,706 24,804 — — — 35,510 Natural gas gathering — — 2,396 — — — 2,396 Natural gas storage — — 2,623 — — — 2,623 Contracting services — — — 297,124 — — 297,124 Construction materials — — — 444,768 — — 444,768 Intrasegment eliminations — — — (145,925) — — (145,925) Inside specialty contracting — — — — 319,276 — 319,276 Outside specialty contracting — — — — 133,288 — 133,288 Other 8,417 2,923 6,293 — 9 2,903 20,545 Intersegment eliminations — — (7,513) (168) (721) (2,879) (11,281) Revenues from contracts with customers 79,308 131,466 28,603 595,799 451,852 24 1,287,052 Revenues out of scope 1,703 2,401 77 — 12,340 — 16,521 Total external operating revenues $ 81,011 $ 133,867 $ 28,680 $ 595,799 $ 464,192 $ 24 $ 1,303,573 Six Months Ended June 30, 2020 Electric Natural gas Pipeline Construction Construction 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 Six Months Ended June 30, 2019 Electric Natural gas Pipeline Construction Construction Other Total (In thousands) Residential utility sales $ 62,993 $ 271,619 $ — $ — $ — $ — $ 334,612 Commercial utility sales 68,902 163,043 — — — — 231,945 Industrial utility sales 18,228 14,188 — — — — 32,416 Other utility sales 3,678 — — — — — 3,678 Natural gas transportation — 22,276 49,862 — — — 72,138 Natural gas gathering — — 4,517 — — — 4,517 Natural gas storage — — 5,269 — — — 5,269 Contracting services — — — 380,164 — — 380,164 Construction materials — — — 624,077 — — 624,077 Intrasegment eliminations — — — (181,066) — — (181,066) Inside specialty contracting — — — — 618,805 — 618,805 Outside specialty contracting — — — — 240,686 — 240,686 Other 17,538 6,836 8,989 — 26 10,747 44,136 Intersegment eliminations — — (31,468) (264) (849) (10,704) (43,285) Revenues from contracts with customers 171,339 477,962 37,169 822,911 858,668 43 2,368,092 Revenues out of scope 2,239 (1,948) 124 — 26,257 — 26,672 Total external operating revenues $ 173,578 $ 476,014 $ 37,293 $ 822,911 $ 884,925 $ 43 $ 2,394,764
Contract balances	The changes in contract assets and liabilities were as follows: June 30, 2020 December 31, 2019 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 136,514 $ 109,078 $ 27,436 Receivables, net Contract liabilities - current (158,272) (142,768) (15,504) Accounts payable Contract liabilities - noncurrent (72) (19) (53) Noncurrent liabilities - other Net contract liabilities $ (21,830) $ (33,709) $ 11,879

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 Goodwill Measurement 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, 2019 Goodwill Measurement Balance at June 30, 2019 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 209,421 14,473 — 223,894 Construction services 109,765 — — 109,765 Total $ 664,922 $ 14,473 $ — $ 679,395 Balance at January 1, 2019 Goodwill Measurement Balance at December 31, 2019 (In thousands) Natural gas distribution $ 345,736 $ — $ — $ 345,736 Construction materials and contracting 209,421 14,482 (6,669) 217,234 Construction services 109,765 8,623 — 118,388 Total $ 664,922 $ 23,105 $ (6,669) $ 681,358
Other amortizable intangible assets	Other amortizable intangible assets were as follows: June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Customer relationships $ 30,087 $ 14,601 $ 17,958 Less accumulated amortization 5,239 5,629 6,268 24,848 8,972 11,690 Noncompete agreements 4,229 3,179 3,439 Less accumulated amortization 2,084 1,798 1,957 2,145 1,381 1,482 Other 13,060 6,578 8,094 Less accumulated amortization 8,538 5,608 6,020 4,522 970 2,074 Total $ 31,515 $ 11,323 $ 15,246
Estimated amortization expense	Estimated amortization expense for identifiable intangible assets as of June 30, 2020, was: Remainder of 2021 2022 2023 2024 Thereafter (In thousands) Amortization expense $ 5,313 $ 5,199 $ 4,711 $ 4,490 $ 4,160 $ 7,642

Regulatory assets and liabili_2

Regulatory assets and liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated * June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 42,582 $ 65,448 $ 42,823 Cost recovery mechanisms Up to 1 year 7,781 7,484 6,288 Conservation programs Up to 1 year 7,256 6,529 6,963 Other Up to 1 year 2,938 1,200 7,539 60,557 80,661 63,613 Noncurrent: Pension and postretirement benefits ** 157,033 165,861 157,069 Asset retirement obligations Over plant lives 68,191 64,215 66,000 Plant to be retired - 49,185 16,933 32,931 Natural gas costs recoverable through rate adjustments Up to 3 years 27,184 29,095 46,381 Manufactured gas plant site remediation - 14,826 15,387 15,126 Cost recovery mechanisms Up to 10 years 13,140 11,004 13,108 Taxes recoverable from customers Over plant lives 10,890 11,755 11,486 Long-term debt refinancing costs Up to 17 years 3,980 4,592 4,286 Other Up to 19 years 6,596 8,322 7,397 351,025 327,164 353,784 Total regulatory assets $ 411,582 $ 407,825 $ 417,397 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments $ 29,557 $ 25,737 $ 23,825 Electric fuel and purchased power deferral 7,799 4,686 5,824 Taxes refundable to customers 4,012 7,104 3,472 Other 6,632 12,447 9,814 48,000 49,974 42,935 Noncurrent: Taxes refundable to customers 236,142 256,921 246,034 Plant removal and decommissioning costs 173,399 173,661 173,722 Pension and postretirement benefits 18,015 15,215 18,065 Other 11,096 10,067 9,549 438,652 455,864 447,370 Total regulatory liabilities $ 486,652 $ 505,838 $ 490,305 Net regulatory position $ (75,070) $ (98,013) $ (72,908) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. ** Recovered as expense is incurred or cash contributions are made.
Regulatory Liabilities	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated * June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Regulatory assets: Current: Natural gas costs recoverable through rate adjustments Up to 1 year $ 42,582 $ 65,448 $ 42,823 Cost recovery mechanisms Up to 1 year 7,781 7,484 6,288 Conservation programs Up to 1 year 7,256 6,529 6,963 Other Up to 1 year 2,938 1,200 7,539 60,557 80,661 63,613 Noncurrent: Pension and postretirement benefits ** 157,033 165,861 157,069 Asset retirement obligations Over plant lives 68,191 64,215 66,000 Plant to be retired - 49,185 16,933 32,931 Natural gas costs recoverable through rate adjustments Up to 3 years 27,184 29,095 46,381 Manufactured gas plant site remediation - 14,826 15,387 15,126 Cost recovery mechanisms Up to 10 years 13,140 11,004 13,108 Taxes recoverable from customers Over plant lives 10,890 11,755 11,486 Long-term debt refinancing costs Up to 17 years 3,980 4,592 4,286 Other Up to 19 years 6,596 8,322 7,397 351,025 327,164 353,784 Total regulatory assets $ 411,582 $ 407,825 $ 417,397 Regulatory liabilities: Current: Natural gas costs refundable through rate adjustments $ 29,557 $ 25,737 $ 23,825 Electric fuel and purchased power deferral 7,799 4,686 5,824 Taxes refundable to customers 4,012 7,104 3,472 Other 6,632 12,447 9,814 48,000 49,974 42,935 Noncurrent: Taxes refundable to customers 236,142 256,921 246,034 Plant removal and decommissioning costs 173,399 173,661 173,722 Pension and postretirement benefits 18,015 15,215 18,065 Other 11,096 10,067 9,549 438,652 455,864 447,370 Total regulatory liabilities $ 486,652 $ 505,838 $ 490,305 Net regulatory position $ (75,070) $ (98,013) $ (72,908) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. ** Recovered as expense is incurred or cash contributions are made.

Fair value measurements (Tables

Fair value measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Available-for-sale securities	Details of available-for-sale securities were as follows: June 30, 2020 Cost Gross Gross 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 June 30, 2019 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 10,771 $ 94 $ 35 $ 10,830 U.S. Treasury securities 180 — — 180 Total $ 10,951 $ 94 $ 35 $ 11,010 December 31, 2019 Cost Gross Gross Fair Value (In thousands) Mortgage-backed securities $ 9,804 $ 87 $ 10 $ 9,881 U.S. Treasury securities 1,228 1 — 1,229 Total $ 11,032 $ 88 $ 10 $ 11,110
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, 2020, Using Quoted Prices in Significant Significant 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 June 30, 2019, Using Quoted Prices in Significant Significant Balance at June 30, 2019 (In thousands) Assets: Money market funds $ — $ 10,816 $ — $ 10,816 Insurance contract* — 83,134 — 83,134 Available-for-sale securities: Mortgage-backed securities — 10,830 — 10,830 U.S. Treasury securities — 180 — 180 Total assets measured at fair value $ — $ 104,960 $ — $ 104,960 * The insurance contract invests approximately 51 percent in fixed-income investments, 22 percent in common stock of large-cap companies, 12 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 4 percent in target date investments and 1 percent in cash equivalents. Fair Value Measurements at December 31, 2019, Using Quoted Prices in Significant Significant Balance at December 31, 2019 (In thousands) Assets: Money market funds $ — $ 8,440 $ — $ 8,440 Insurance contract* — 87,009 — 87,009 Available-for-sale securities: Mortgage-backed securities — 9,881 — 9,881 U.S. Treasury securities — 1,229 — 1,229 Total assets measured at fair value $ — $ 106,559 $ — $ 106,559 * The insurance contract invests approximately 51 percent in fixed-income investments, 23 percent in common stock of large-cap companies, 12 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 3 percent in target date investments and 1 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, 2020 June 30, 2019 December 31, 2019 (In thousands) Carrying amount $ 2,281,876 $ 2,379,806 $ 2,243,107 Fair value $ 2,563,734 $ 2,521,325 $ 2,418,631

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Long-term debt outstanding	Long-term debt outstanding was as follows: Weighted June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Senior Notes due on dates ranging from October 22, 2022 to June 15, 2060 4.43 % $ 1,900,000 $ 1,656,000 $ 1,850,000 Commercial paper supported by revolving credit agreements 1.02 % 290,100 433,350 222,900 Term Loan Agreement due on September 3, 2032 2.00 % 9,100 209,800 9,100 Credit agreements due on June 7, 2024 3.25 % 11,200 11,075 89,050 Medium-Term Notes due on dates ranging from September 1, 2020 to March 16, 2029 6.68 % 50,000 50,000 50,000 Other notes due on dates ranging from July 15, 2021 to November 30, 2038 4.59 % 28,342 26,105 29,117 Less unamortized debt issuance costs 6,668 6,164 7,010 Less discount 198 360 50 Total long-term debt 2,281,876 2,379,806 2,243,107 Less current maturities 16,560 51,822 16,540 Net long-term debt $ 2,265,316 $ 2,327,984 $ 2,226,567
Schedule of debt maturities	Long-term debt maturities, which excludes unamortized debt issuance costs and discount, at June 30, 2020, were as follows: Remainder of 2021 2022 2023 2024 Thereafter (In thousands) Long-term debt maturities $ 15,762 $ 1,522 $ 148,021 $ 77,921 $ 362,722 $ 1,682,794

Cash flow information (Tables)

Cash flow information (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 2019 (In thousands) Interest, net* $ 47,769 $ 45,702 Income taxes paid, net** $ 735 $ 4,124 * AFUDC - borrowed was $1.3 million and $1.2 million for the six months ended June 30, 2020 and 2019, respectively. ** Income taxes paid, including discontinued operations, were $882,000 and $2.0 million for the six months ended June 30, 2020 and 2019, respectively. Noncash investing and financing transactions were as follows: June 30, 2020 June 30, 2019 December 31, 2019 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 24,181 $ 24,990 $ 54,880 Property, plant and equipment additions in accounts payable $ 36,493 $ 27,312 $ 46,119 Accrual for holdback payment related to a business combination $ 5,000 $ — $ — Debt assumed in connection with a business combination $ — $ 1,163 $ 1,163

Business segment data (Tables)

Business segment data (Tables)	6 Months Ended
	Jun. 30, 2020
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, 2020 2019 2020 2019 (In thousands) External operating revenues: Regulated operations: Electric $ 76,438 $ 81,011 $ 162,346 $ 173,578 Natural gas distribution 141,494 133,867 467,937 476,014 Pipeline 23,421 21,369 29,752 26,272 241,353 236,247 660,035 675,864 Nonregulated operations: Pipeline 4,237 7,311 8,561 11,021 Construction materials and contracting 621,045 595,799 883,190 822,911 Construction services 496,405 464,192 1,008,610 884,925 Other (112) 24 (94) 43 1,121,575 1,067,326 1,900,267 1,718,900 Total external operating revenues $ 1,362,928 $ 1,303,573 $ 2,560,302 $ 2,394,764 Intersegment operating revenues: Regulated operations: Electric $ 196 $ — $ 391 $ — Natural gas distribution 185 — 370 — Pipeline 7,857 7,426 33,040 31,349 8,238 7,426 33,801 31,349 Nonregulated operations: Pipeline 142 87 158 119 Construction materials and contracting 90 168 152 264 Construction services 779 721 3,249 849 Other 2,973 2,879 5,946 10,704 3,984 3,855 9,505 11,936 Intersegment eliminations (12,222) (11,281) (43,306) (43,285) Total intersegment operating revenues $ — $ — $ — $ — Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 (In thousands) Operating income (loss): Electric $ 12,810 $ 9,791 $ 27,669 $ 27,779 Natural gas distribution 678 (2,621) 50,677 47,696 Pipeline 12,225 10,698 23,644 20,602 Construction materials and contracting 74,741 46,178 31,472 4,597 Construction services 37,882 31,966 61,678 59,431 Other (82) 1,299 185 1,425 Total operating income $ 138,254 $ 97,311 $ 195,325 $ 161,530 Net income (loss): Regulated operations: Electric $ 12,153 $ 7,471 $ 23,527 $ 22,976 Natural gas distribution (959) (6,252) 31,410 30,248 Pipeline 8,684 6,378 16,070 13,382 19,878 7,597 71,007 66,606 Nonregulated operations: Pipeline 268 742 255 579 Construction materials and contracting 53,020 29,166 14,806 (5,283) Construction services 27,932 22,845 44,755 42,869 Other (1,256) 2,795 (5,442) (537) 79,964 55,548 54,374 37,628 Income from continuing operations 99,842 63,145 125,381 104,234 Loss from discontinued operations, net of tax (139) (1,320) (548) (1,483) Net income $ 99,703 $ 61,825 $ 124,833 $ 102,751

Employee benefit plans (Tables)

Employee benefit plans (Tables)	6 Months Ended
	Jun. 30, 2020
Retirement Benefits [Abstract]
Schedule of net benefit costs	Components of net periodic benefit cost (credit) for the Company's pension and other postretirement benefit plans were as follows: Pension Benefits Other Three Months Ended June 30, 2020 2019 2020 2019 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 414 $ 227 Interest cost 3,074 3,840 627 713 Expected return on assets (5,214) (3,998) (1,401) (1,182) Amortization of prior service credit — — (402) (228) Amortization of net actuarial (gain) loss 1,723 1,418 142 (42) Net periodic benefit cost (credit), including amount capitalized (417) 1,260 (620) (512) Less amount capitalized — — 35 27 Net periodic benefit cost (credit) $ (417) $ 1,260 $ (655) $ (539) Pension Benefits Other Six Months Ended June 30, 2020 2019 2020 2019 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 766 $ 571 Interest cost 6,047 7,613 1,218 1,493 Expected return on assets (9,975) (9,118) (2,649) (2,402) Amortization of prior service credit — — (699) (577) Amortization of net actuarial loss 3,586 2,773 144 55 Net periodic benefit cost (credit), including amount capitalized (342) 1,268 (1,220) (860) Less amount capitalized — — 67 58 Net periodic benefit cost (credit) $ (342) $ 1,268 $ (1,287) $ (918)

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	$ 1,362,928		$ 1,303,573		$ 2,560,302	$ 2,394,764
Operating Expenses	1,224,674		1,206,262		2,364,977	2,233,234
Net income	99,703	$ 25,130	61,825	$ 40,926	124,833	102,751
Receivables, net	$ 920,824		$ 890,579		$ 920,824	$ 890,579	$ 836,605
Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		(7,700)
Operating Expenses		(1,200)
Net income		(6,700)
Accounts Payable		(1,200)
Receivables, net		$ (7,700)

Receivables and allowance for_3

Receivables and allowance for expected credit losses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Credit Loss [Abstract]
Receivables past due 90 days or more	$ 45,100		$ 46,700	$ 47,200
Accounts Receivable, Allowance for Credit Loss	$ 11,090	$ 11,125	$ 8,497	$ 8,200

Accounts receivable and allow_2

Accounts receivable and allowance for doubtful accounts Receivables and allowance for expected credit losses (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	$ 11,125	$ 8,497
Current expected credit loss provision	1,075	3,555
Less write-offs charged against the allowance	1,399	1,265
Credit loss recoveries collected	289	338
Balance	11,090	11,125
Electric
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	492	328
Current expected credit loss provision	303	555
Less write-offs charged against the allowance	224	500
Credit loss recoveries collected	88	109
Balance	659	492
Natural gas distribution
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	1,817	1,056
Current expected credit loss provision	190	1,156
Less write-offs charged against the allowance	677	624
Credit loss recoveries collected	201	229
Balance	1,531	1,817
Construction materials and contracting
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	5,983	5,357
Current expected credit loss provision	(314)	694
Less write-offs charged against the allowance	44	68
Credit loss recoveries collected	0	0
Balance	5,625	5,983
Construction services
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,833	1,756
Current expected credit loss provision	896	1,150
Less write-offs charged against the allowance	454	73
Credit loss recoveries collected	0	0
Balance	$ 3,275	$ 2,833

Inventories and natural gas i_4

Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Inventory Disclosure [Abstract]
Aggregates held for resale	$ 165,357	$ 147,723	$ 147,030
Asphalt oil	57,207	41,912	80,418
Materials and supplies	27,805	22,512	28,746
Merchandise for resale	22,974	22,232	27,167
Natural gas in storage (current)	11,776	22,058	15,841
Other	17,718	21,970	26,742
Total	302,837	278,407	325,944
Natural gas in storage noncurrent	$ 48,300	$ 48,400	$ 48,200

Earnings per common share (Deta

Earnings per common share (Details) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Weighted average common shares outstanding - basic	200,522	198,270	200,481	197,341
Effect of dilutive performance share awards and restricted stock units	17	17	16	15
Weighted average common shares outstanding - diluted	200,539	198,287	200,497	197,356
Shares excluded from the calculation of diluted earnings per share	187	0	191	93
Dividends declared per common share	$ 0.2075	$ 0.2025	$ 0.4150	$ 0.4050

Accumulated other comprehensi_3

Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	$ 2,836,592	$ 2,847,246	$ 2,605,692	$ 2,566,775	$ 2,847,246	$ 2,566,775
Other comprehensive income	586	707	478	774	1,293	1,252
Balance	2,897,687	2,836,592	2,660,301	2,605,692	2,897,687	2,660,301
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(1,319)	(1,430)	(1,764)	(2,161)	(1,430)	(2,161)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from (to) accumulated other comprehensive loss	112	111	111	397
Other comprehensive income	112	111	111	397
Balance	(1,207)	(1,319)	(1,653)	(1,764)	(1,207)	(1,653)
Postretirement liability adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(40,272)	(40,734)	(35,759)	(36,069)	(40,734)	(36,069)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from (to) accumulated other comprehensive loss	480	462	276	310
Other comprehensive income	480	462	276	310
Balance	(39,792)	(40,272)	(35,483)	(35,759)	(39,792)	(35,483)
Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	196	62	(45)	(112)	62	(112)
Other comprehensive income (loss) before reclassifications	(13)	135	79	39
Amounts reclassified from (to) accumulated other comprehensive loss	7	(1)	12	28
Other comprehensive income	(6)	134	91	67
Balance	190	196	46	(45)	190	46
Total accumulated other comprehensive loss
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(41,395)	(42,102)	(37,568)	(38,342)	(42,102)	(38,342)
Other comprehensive income (loss) before reclassifications	(13)	135	79	39
Amounts reclassified from (to) accumulated other comprehensive loss	599	572	399	735
Other comprehensive income	586	707	478	774
Balance	$ (40,809)	$ (41,395)	$ (37,090)	$ (37,568)	$ (40,809)	$ (37,090)

Reclassification out of accumul

Reclassification out of accumulated other comprehensive income (loss) (Details 2) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Interest expense	$ (24,818)		$ (25,429)		$ (49,371)	$ (48,836)
Income taxes	(23,657)		(10,352)		(29,631)	(17,668)
Other income	10,063		1,615		9,058	9,208
Net Income	99,703	$ 25,130	61,825	$ 40,926	124,833	102,751
Reclassification out of accumulated other comprehensive income
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Net Income	(599)		(399)		(1,171)	(1,134)
Reclassification adjustment for loss on derivative instruments included in net income | Reclassification out of accumulated other comprehensive income | Interest rate contract
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Interest expense	(148)		(147)		(295)	(295)
Income taxes	36		36		72	(213)
Net Income	(112)		(111)		(223)	(508)
Amortization of postretirement liability losses included in net periodic benefit cost | Reclassification out of accumulated other comprehensive income
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Income taxes	155		89		304	189
Other income	(635)		(365)		(1,246)	(775)
Net Income	(480)		(276)		(942)	(586)
Reclassification adjustment on available-for-sale investments included in net income | Reclassification out of accumulated other comprehensive income
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Income taxes	2		3		2	10
Other income	(9)		(15)		(8)	(50)
Net Income	$ (7)		$ (12)		$ (6)	$ (40)

Disaggregation of revenue (Deta

Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 1,362,928	$ 1,303,573	$ 2,560,302	$ 2,394,764
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(12,222)	(11,281)	(43,306)	(43,285)
Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(164,719)	(145,925)	(208,823)	(181,066)
Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	38,315	35,510	77,545	72,138
Natural gas gathering
Disaggregation of Revenue [Line Items]
Revenues	1,181	2,396	3,271	4,517
Natural gas storage
Disaggregation of Revenue [Line Items]
Revenues	3,104	2,623	6,150	5,269
Contracting services
Disaggregation of Revenue [Line Items]
Revenues	303,356	297,124	401,757	380,164
Construction materials
Disaggregation of Revenue [Line Items]
Revenues	482,498	444,768	690,408	624,077
Inside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	324,921	319,276	697,130	618,805
Outside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	160,696	133,288	290,846	240,686
Other
Disaggregation of Revenue [Line Items]
Revenues	17,064	20,545	34,595	44,136
Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	1,347,026	1,287,052	2,530,574	2,368,092
Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	15,902	16,521	29,728	26,672
Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	106,607	97,447	325,657	334,612
Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	70,904	74,481	219,487	231,945
Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	13,730	14,921	32,618	32,416
Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	1,591	1,879	3,239	3,678
Electric
Disaggregation of Revenue [Line Items]
Revenues	76,438	81,011	162,346	173,578
Electric | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(196)	0	(391)	0
Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	7,717	8,417	16,167	17,538
Electric | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	75,015	79,308	161,221	171,339
Electric | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	1,423	1,703	1,125	2,239
Electric | Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	27,954	26,437	60,303	62,993
Electric | Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	29,877	33,231	63,464	68,902
Electric | Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	8,072	9,344	18,439	18,228
Electric | Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	1,591	1,879	3,239	3,678
Natural gas distribution
Disaggregation of Revenue [Line Items]
Revenues	141,494	133,867	467,937	476,014
Natural gas distribution | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(185)	0	(370)	0
Natural gas distribution | Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	10,350	10,706	22,148	22,276
Natural gas distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	2,711	2,923	5,209	6,836
Natural gas distribution | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	138,214	131,466	462,543	477,962
Natural gas distribution | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	3,280	2,401	5,394	(1,948)
Natural gas distribution | Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	78,653	71,010	265,354	271,619
Natural gas distribution | Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	41,027	41,250	156,023	163,043
Natural gas distribution | Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	5,658	5,577	14,179	14,188
Natural gas distribution | Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Pipeline
Disaggregation of Revenue [Line Items]
Revenues	27,658	28,680	38,313	37,293
Pipeline | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(7,999)	(7,513)	(33,198)	(31,468)
Pipeline | Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	27,965	24,804	55,397	49,862
Pipeline | Natural gas gathering
Disaggregation of Revenue [Line Items]
Revenues	1,181	2,396	3,271	4,517
Pipeline | Natural gas storage
Disaggregation of Revenue [Line Items]
Revenues	3,104	2,623	6,150	5,269
Pipeline | Other
Disaggregation of Revenue [Line Items]
Revenues	3,363	6,293	6,604	8,989
Pipeline | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	27,614	28,603	38,224	37,169
Pipeline | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	44	77	89	124
Construction materials and contracting
Disaggregation of Revenue [Line Items]
Revenues	621,045	595,799	883,190	822,911
Construction materials and contracting | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(90)	(168)	(152)	(264)
Construction materials and contracting | Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(164,719)	(145,925)	(208,823)	(181,066)
Construction materials and contracting | Contracting services
Disaggregation of Revenue [Line Items]
Revenues	303,356	297,124	401,757	380,164
Construction materials and contracting | Construction materials
Disaggregation of Revenue [Line Items]
Revenues	482,498	444,768	690,408	624,077
Construction materials and contracting | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Construction materials and contracting | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	621,045	595,799	883,190	822,911
Construction materials and contracting | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Construction services
Disaggregation of Revenue [Line Items]
Revenues	496,405	464,192	1,008,610	884,925
Construction services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(779)	(721)	(3,249)	(849)
Construction services | Inside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	324,921	319,276	697,130	618,805
Construction services | Outside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	160,696	133,288	290,846	240,686
Construction services | Other
Disaggregation of Revenue [Line Items]
Revenues	412	9	763	26
Construction services | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	485,250	451,852	985,490	858,668
Construction services | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	11,155	12,340	23,120	26,257
Other
Disaggregation of Revenue [Line Items]
Revenues	(112)	24	(94)	43
Other | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(2,973)	(2,879)	(5,946)	(10,704)
Other | Other
Disaggregation of Revenue [Line Items]
Revenues	2,861	2,903	5,852	10,747
Other | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	(112)	24	(94)	43
Other | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0

Contract balances (Details 2)

Contract balances (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract assets	$ 136,514		$ 136,514		$ 109,078
Change in contract assets			27,436
Contract liabilities - current	(158,272)		(158,272)		(142,768)
Change in contract liabilities - current			(15,504)
Contract liabilities - noncurrent	(72)		(72)		(19)
Change in contract liabilities - noncurrent			(53)
Net contract liabilities	(21,830)		(21,830)		$ (33,709)
Change in net contract liabilities			11,879
Amounts included in contract liability at the beginning of the period	32,300	$ 22,600	121,700	$ 79,000
Amounts from performance obligations satisfied in prior periods	$ 31,900	$ 20,600	$ 42,900	$ 32,500

Revenue from contracts with c_4

Revenue from contracts with customers Remaining performance obligations (Details 3) $ in Millions	Jun. 30, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 2,300
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,800
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 296
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	24 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-07-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 239.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	25 months

Business Combinations (Details)

Business Combinations (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 708,664,000	$ 679,395,000	$ 681,358,000	$ 664,922,000
Measurement period adjustments	(3,613,000)	$ 0	$ (6,669,000)
2020 Acquisition
Business Acquisition [Line Items]
Gross Aggregate Consideration	77,400,000
Cash Assumed	1,700,000
Business Combination, Consideration Transferred	70,700,000
Business Combination indemnity holdback liability	5,000,000
Current Assets	46,100,000
Property, Plant, and Equipment	4,900,000
Goodwill	27,300,000
Other Intangibles	20,600,000
Current Liabilities	21,200,000
Deferred Credits and Other Liabilities	300,000
Measurement period adjustments	$ (3,600,000)

Business Combinations (Details

Business Combinations (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 681,358,000	$ 708,664,000	$ 679,395,000	$ 664,922,000
2019 Acquisition
Business Acquisition [Line Items]
Gross Aggregate Consideration	56,800,000
Debt Assumed	1,200,000
Current Assets	15,800,000
Property, Plant, and Equipment	16,700,000
Goodwill	23,100,000
Other Intangibles	6,700,000
Deferred Charges and Other Assets	500,000
Current Liabilities	5,900,000
Deferred Credits and Other Liabilities	$ 100,000

Lessor accounting (Details)

Lessor accounting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases [Abstract]
Operating Lease, Lease Income	$ 11.2	$ 12.5	$ 23.3	$ 26.5
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	$ 10.4		$ 10.4

Goodwill rollforward (Details)

Goodwill rollforward (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Goodwill [Roll Forward]
Balance at beginning of period	$ 681,358	$ 664,922	$ 664,922
Goodwill acquired during the year	30,919	14,473	23,105
Measurement period adjustments	(3,613)	0	(6,669)
Balance at end of period	708,664	679,395	681,358
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	217,234	209,421	209,421
Goodwill acquired during the year	6,483	14,473	14,482
Measurement period adjustments	0	0	(6,669)
Balance at end of period	223,717	223,894	217,234
Construction services
Goodwill [Roll Forward]
Balance at beginning of period	118,388	109,765	109,765
Goodwill acquired during the year	24,436	0	8,623
Measurement period adjustments	(3,613)	0	0
Balance at end of period	$ 139,211	$ 109,765	$ 118,388

Other intangible assets (Detail

Other intangible assets (Details 2) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 31,515,000	$ 11,323,000	$ 31,515,000	$ 11,323,000	$ 15,246,000
Amortization of intangible assets	2,700,000	500,000	4,700,000	1,100,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	30,087,000	14,601,000	30,087,000	14,601,000	17,958,000
Intangible assets, less accumulated amortization	5,239,000	5,629,000	5,239,000	5,629,000	6,268,000
Intangible assets, net (excluding goodwill)	24,848,000	8,972,000	24,848,000	8,972,000	11,690,000
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	4,229,000	3,179,000	4,229,000	3,179,000	3,439,000
Intangible assets, less accumulated amortization	2,084,000	1,798,000	2,084,000	1,798,000	1,957,000
Intangible assets, net (excluding goodwill)	2,145,000	1,381,000	2,145,000	1,381,000	1,482,000
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	13,060,000	6,578,000	13,060,000	6,578,000	8,094,000
Intangible assets, less accumulated amortization	8,538,000	5,608,000	8,538,000	5,608,000	6,020,000
Intangible assets, net (excluding goodwill)	$ 4,522,000	$ 970,000	4,522,000	$ 970,000	$ 2,074,000
Series of individually immaterial business combinations
Finite-Lived Intangible Assets [Line Items]
Other intangible assets acquired			$ 21,000,000

Future amortization expense (De

Future amortization expense (Details 3) $ in Thousands	Jun. 30, 2020USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Remainder of 2020	$ 5,313
2021	5,199
2022	4,711
2023	4,490
2024	4,160
Thereafter	$ 7,642

Regulatory assets and liabili_3

Regulatory assets and liabilities Regulatory Assets (Details 1) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Regulatory Assets [Line Items]
Regulatory Assets, Current	$ 60,557	$ 63,613	$ 80,661
Regulatory Assets, Noncurrent	351,025	353,784	327,164
Total regulatory assets	411,582	417,397	407,825
Regulatory assets not earning a rate of return	296,600	276,500	290,700
Natural gas costs recoverable through rate adjustments
Regulatory Assets [Line Items]
Regulatory Assets, Current	42,582	42,823	65,448
Regulatory Assets, Noncurrent	27,184	46,381	29,095
Cost recovery mechanisms
Regulatory Assets [Line Items]
Regulatory Assets, Current	7,781	6,288	7,484
Regulatory Assets, Noncurrent	$ 13,140	13,108	11,004
Conservation programs
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 1 year
Regulatory Assets, Current	$ 7,256	6,963	6,529
Pension and postretirement benefits
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	**
Regulatory Assets, Noncurrent	$ 157,033	157,069	165,861
Asset retirement obligations
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Over plant lives
Regulatory Assets, Noncurrent	$ 68,191	66,000	64,215
Plant to be retired
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	-
Regulatory Assets, Noncurrent	$ 49,185	32,931	16,933
Manufactured gas plant site remediation
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	-
Regulatory Assets, Noncurrent	$ 14,826	15,126	15,387
Taxes recoverable from customers
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Over plant lives
Regulatory Assets, Noncurrent	$ 10,890	11,486	11,755
Long-term debt refinancing costs
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 17 years
Regulatory Assets, Noncurrent	$ 3,980	4,286	4,592
Other Regulatory Assets
Regulatory Assets [Line Items]
Regulatory Assets, Current	2,938	7,539	1,200
Regulatory Assets, Noncurrent	$ 6,596	$ 7,397	$ 8,322
Minimum [Member] | Natural gas costs recoverable through rate adjustments
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 1 year
Minimum [Member] | Cost recovery mechanisms
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 1 year
Minimum [Member] | Other Regulatory Assets
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 1 year
Maximum [Member] | Natural gas costs recoverable through rate adjustments
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 3 years
Maximum [Member] | Cost recovery mechanisms
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 10 years
Maximum [Member] | Other Regulatory Assets
Regulatory Assets [Line Items]
Estimated Recovery Period as of June 30, 2020	Up to 19 years

Regulatory assets and liabili_4

Regulatory assets and liabilities Regulatory Liabilities (Details 2) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	$ 48,000	$ 42,935	$ 49,974
Regulatory Liability, Noncurrent	438,652	447,370	455,864
Total regulatory liabilities	486,652	490,305	505,838
Net regulatory position	(75,070)	(72,908)	(98,013)
Natural gas costs refundable through rate adjustments
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	29,557	23,825	25,737
Electric fuel and purchased power deferral
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	7,799	5,824	4,686
Taxes refundable to customers
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	4,012	3,472	7,104
Regulatory Liability, Noncurrent	236,142	246,034	256,921
Plant removal and decommissioning costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	173,399	173,722	173,661
Pension and postretirement benefits
Regulatory Liabilities [Line Items]
Regulatory Liability, Noncurrent	18,015	18,065	15,215
Other Regulatory Liabilities
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	6,632	9,814	12,447
Regulatory Liability, Noncurrent	$ 11,096	$ 9,549	$ 10,067

Fair value measurements Insuran

Fair value measurements Insurance contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 92.4	$ 83.1	$ 92.4	$ 83.1	$ 87
Net unrealized gain on investments used to satisfy obligations under nonqualified benefit plans	$ 9.1	$ 2.9	$ 5.4	$ 9.3

Available-for-sale securities (

Available-for-sale securities (Details 2) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Available-for-sale securities [Abstract]
Cost	$ 10,982	$ 11,032	$ 10,951
Gross Unrealized Gains	246	88	94
Gross Unrealized Losses	6	10	35
Fair Value	11,222	11,110	11,010
Mortgage-backed securities
Available-for-sale securities [Abstract]
Cost	9,812	9,804	10,771
Gross Unrealized Gains	239	87	94
Gross Unrealized Losses	6	10	35
Fair Value	10,045	9,881	10,830
U.S. Treasury securities
Available-for-sale securities [Abstract]
Cost	1,170	1,228	180
Gross Unrealized Gains	7	1	0
Gross Unrealized Losses	0	0	0
Fair Value	$ 1,177	$ 1,229	$ 180

Fair value measurements (Detail

Fair value measurements (Details 3) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	38.00%	51.00%	51.00%
Percentage investment in common stock of large-cap companies	23.00%	23.00%	22.00%
Percentage investment in common stock of mid-cap companies	9.00%	12.00%	12.00%
Percentage investment in common stock of small-cap companies	9.00%	10.00%	10.00%
Percentage investment in target date investments	4.00%	3.00%	4.00%
Percentage investment in cash and cash equivalents	17.00%	1.00%	1.00%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 112,113	$ 106,559	$ 104,960
Fair value, measurements, recurring | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	8,478	8,440	10,816
Fair value, measurements, recurring | Insurance contract*
Fair value measurements [Line Items]
Assets, fair value disclosure	92,413	87,009	83,134
Fair value, measurements, recurring | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	10,045	9,881	10,830
Fair value, measurements, recurring | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	1,177	1,229	180
Fair value, measurements, recurring | Fair value, inputs, level 2
Fair value measurements [Line Items]
Assets, fair value disclosure	112,113	106,559	104,960
Fair value, measurements, recurring | Fair value, inputs, level 2 | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	8,478	8,440	10,816
Fair value, measurements, recurring | Fair value, inputs, level 2 | Insurance contract*
Fair value measurements [Line Items]
Assets, fair value disclosure	92,413	87,009	83,134
Fair value, measurements, recurring | Fair value, inputs, level 2 | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	10,045	9,881	10,830
Fair value, measurements, recurring | Fair value, inputs, level 2 | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 1,177	$ 1,229	$ 180

Fair value measurements (Deta_2

Fair value measurements (Details 4)	3 Months Ended
	Jun. 30, 2019USD ($)
Fair Value Disclosures [Abstract]
Investments, Fair Value Disclosure	$ 0
Asset Impairment Charges	$ 2,000,000

Fair value measurements (Deta_3

Fair value measurements (Details 5) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,281,876	$ 2,243,107	$ 2,379,806
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,281,876	2,243,107	2,379,806
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 2,563,734	$ 2,418,631	$ 2,521,325

Long-term debt outstanding (Det

Long-term debt outstanding (Details 1) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,281,876	$ 2,243,107	$ 2,379,806
Long-term debt due within one year	16,560	16,540	51,822
Long-term debt	$ 2,265,316	2,226,567	2,327,984
Senior Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	4.43%
Long-term debt	$ 1,900,000	1,850,000	1,656,000
Commercial Paper
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	1.02%
Long-term debt	$ 290,100	222,900	433,350
Term Loan Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	2.00%
Long-term debt	$ 9,100	9,100	209,800
Credit Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	3.25%
Long-term debt	$ 11,200	89,050	11,075
Medium-term Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	6.68%
Long-term debt	$ 50,000	50,000	50,000
Other Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	4.59%
Long-term debt	$ 28,342	29,117	26,105
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs	6,668	7,010	6,164
Discount	$ 198	$ 50	$ 360

Schedule of debt maturities (De

Schedule of debt maturities (Details 2) $ in Thousands	Jun. 30, 2020USD ($)
Long-term debt maturities [Line Items]
Remainder of 2020	$ 15,762
2021	1,522
2022	148,021
2023	77,921
2024	362,722
Thereafter	$ 1,682,794

Cash flow information (Details)

Cash flow information (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Interest, net*	$ 47,769,000	$ 45,702,000
Income taxes paid, net**	735,000	4,124,000
AFUDC borrowed	1,300,000	1,200,000
Right-of-use assets obtained in exchange for new operating lease liabilities	24,181,000	24,990,000	$ 54,880,000
Property, plant and equipment additions in accounts payable	36,493,000	27,312,000	46,119,000
Accrual for holdback payment related to a business combination	5,000,000	0	0
Debt assumed in connection with a business combination	0	1,163,000	$ 1,163,000
Continuing and discontinued operations
Income taxes paid, net**	$ 882,000	$ 2,000,000

Business segment data (Details)

Business segment data (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 1,362,928		$ 1,303,573		$ 2,560,302	$ 2,394,764
Operating income (loss)	138,254		97,311		195,325	161,530
Income from continuing operations	99,842		63,145		125,381	104,234
Loss from discontinued operations, net of tax	(139)		(1,320)		(548)	(1,483)
Net income	99,703	$ 25,130	61,825	$ 40,926	124,833	102,751
Electric
Segment Reporting Information [Line Items]
Revenues	76,438		81,011		162,346	173,578
Operating income (loss)	12,810		9,791		27,669	27,779
Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	141,494		133,867		467,937	476,014
Operating income (loss)	678		(2,621)		50,677	47,696
Pipeline
Segment Reporting Information [Line Items]
Revenues	27,658		28,680		38,313	37,293
Operating income (loss)	12,225		10,698		23,644	20,602
Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	621,045		595,799		883,190	822,911
Operating income (loss)	74,741		46,178		31,472	4,597
Construction services
Segment Reporting Information [Line Items]
Revenues	496,405		464,192		1,008,610	884,925
Operating income (loss)	37,882		31,966		61,678	59,431
Other
Segment Reporting Information [Line Items]
Revenues	(112)		24		(94)	43
Operating income (loss)	(82)		1,299		185	1,425
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	(12,222)		(11,281)		(43,306)	(43,285)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	(196)		0		(391)	0
Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	(185)		0		(370)	0
Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	(7,999)		(7,513)		(33,198)	(31,468)
Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	(90)		(168)		(152)	(264)
Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	(779)		(721)		(3,249)	(849)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	(2,973)		(2,879)		(5,946)	(10,704)
Total intersegment operating revenues
Segment Reporting Information [Line Items]
Revenues	0		0		0	0
Regulated operation
Segment Reporting Information [Line Items]
Revenues	241,353		236,247		660,035	675,864
Income from continuing operations	19,878		7,597		71,007	66,606
Regulated operation | Electric
Segment Reporting Information [Line Items]
Revenues	76,438		81,011		162,346	173,578
Income from continuing operations	12,153		7,471		23,527	22,976
Regulated operation | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	141,494		133,867		467,937	476,014
Income from continuing operations	(959)		(6,252)		31,410	30,248
Regulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	23,421		21,369		29,752	26,272
Income from continuing operations	8,684		6,378		16,070	13,382
Regulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	8,238		7,426		33,801	31,349
Regulated operation | Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	196		0		391	0
Regulated operation | Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	185		0		370	0
Regulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	7,857		7,426		33,040	31,349
Nonregulated operation
Segment Reporting Information [Line Items]
Revenues	1,121,575		1,067,326		1,900,267	1,718,900
Income from continuing operations	79,964		55,548		54,374	37,628
Nonregulated operation | Pipeline
Segment Reporting Information [Line Items]
Revenues	4,237		7,311		8,561	11,021
Income from continuing operations	268		742		255	579
Nonregulated operation | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	621,045		595,799		883,190	822,911
Income from continuing operations	53,020		29,166		14,806	(5,283)
Nonregulated operation | Construction services
Segment Reporting Information [Line Items]
Revenues	496,405		464,192		1,008,610	884,925
Income from continuing operations	27,932		22,845		44,755	42,869
Nonregulated operation | Other
Segment Reporting Information [Line Items]
Revenues	(112)		24		(94)	43
Income from continuing operations	(1,256)		2,795		(5,442)	(537)
Nonregulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	3,984		3,855		9,505	11,936
Nonregulated operation | Intersegment eliminations | Pipeline
Segment Reporting Information [Line Items]
Revenues	142		87		158	119
Nonregulated operation | Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	90		168		152	264
Nonregulated operation | Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	779		721		3,249	849
Nonregulated operation | Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	$ 2,973		$ 2,879		$ 5,946	$ 10,704

Employee benefit plans (Details

Employee benefit plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Qualified plan | Underfunded plan | Pension benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	3,074,000	3,840,000	6,047,000	7,613,000
Expected return on assets	(5,214,000)	(3,998,000)	(9,975,000)	(9,118,000)
Amortization of prior service credit	0	0	0	0
Amortization of net actuarial (gain) loss	1,723,000	1,418,000	3,586,000	2,773,000
Net periodic benefit cost (credit), including amount capitalized	(417,000)	1,260,000	(342,000)	1,268,000
Less amount capitalized	0	0	0	0
Net periodic benefit cost (credit)	(417,000)	1,260,000	(342,000)	1,268,000
Qualified plan | Overfunded Plan | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	414,000	227,000	766,000	571,000
Interest cost	627,000	713,000	1,218,000	1,493,000
Expected return on assets	(1,401,000)	(1,182,000)	(2,649,000)	(2,402,000)
Amortization of prior service credit	(402,000)	(228,000)	(699,000)	(577,000)
Amortization of net actuarial (gain) loss	142,000	(42,000)	144,000	55,000
Net periodic benefit cost (credit), including amount capitalized	(620,000)	(512,000)	(1,220,000)	(860,000)
Less amount capitalized	35,000	27,000	67,000	58,000
Net periodic benefit cost (credit)	(655,000)	(539,000)	(1,287,000)	(918,000)
Nonqualified plan | Unfunded plan | Supplemental employee retirement plans
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Net periodic benefit cost (credit)	$ 900,000	$ 1,100,000	$ 1,900,000	$ 2,200,000

MNPUC (Details)

MNPUC (Details) - MNPUC [Member] - Gas Distribution [Member] - Great Plains Natural Gas Co. [Member] - Pending Rate Case [Member] - USD ($) $ in Millions	Jan. 01, 2020	Sep. 27, 2019
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 2.9
Public Utilities, Requested Rate Increase (Decrease), Percentage		12.00%
Public Utilities, Interim Rate Increase (Decrease), Amount	$ 2.6
Public Utilities, Interim Rate Increase (Decrease), Percentage	11.00%

MTPSC (Details 2)

MTPSC (Details 2) - Pending Rate Case [Member] - Gas Distribution [Member] - MTPSC [Member] - Montana-Dakota Utilities Co. [Member] - USD ($) $ in Millions	Feb. 01, 2021	Jun. 22, 2020
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 8.6
Public Utilities, Requested Rate Increase (Decrease), Percentage		13.40%
Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Interim Rate Increase (Decrease), Amount	$ 4.9
Public Utilities, Interim Rate Increase (Decrease), Percentage	8.20%

NDPSC (Details 3)

NDPSC (Details 3) - Pending Rate Case [Member] - Electric - NDPSC [Member] - Montana-Dakota Utilities Co. [Member] - Subsequent Event [Member] $ in Millions	Jul. 17, 2020USD ($)
Public Utilities, General Disclosures [Line Items]
Total Transmission Cost Adjustment Rider	$ 15.5
Public Utilities, Requested Rate Increase (Decrease), Amount	6.3
Transmission Capital Projects Increase (Decrease)	$ 3.3

OPUC (Details 4)

OPUC (Details 4) - OPUC - Pending Rate Case [Member] - Gas Distribution [Member] - Cascade Natural Gas [Member]	Mar. 31, 2020USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 4,900,000
Public Utilities, Requested Rate Increase (Decrease), Percentage	7.20%
Environmental Remediation Deferred Costs Increase (Decrease) Amount	$ 364,000

WUTC (Details 5)

WUTC (Details 5) - Pending Rate Case [Member] - WUTC [Member] - Cascade Natural Gas [Member] - USD ($) $ in Millions	Jun. 19, 2020	May 29, 2020
Pipeline Cost Recovery Mechanism [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 1
Public Utilities, Requested Rate Increase (Decrease), Percentage		0.40%
Gas Distribution [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 13.8
Public Utilities, Requested Rate Increase (Decrease), Percentage	5.30%

Litigation (Details)

Litigation (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 34.5	$ 29.1	$ 32.1

Guarantees (Details 2)

Guarantees (Details 2)	Jun. 30, 2020USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 272,700,000
Fixed maximum amounts guaranteed by year 2020	91,800,000
Fixed maximum amounts guaranteed by year 2021	169,400,000
Fixed maximum amounts guaranteed by year 2022	400,000
Fixed maximum amounts guaranteed by year 2023	500,000
Fixed maximum amounts guaranteed by year 2024	500,000
Fixed maximum amounts guaranteed, thereafter	1,100,000
No scheduled maturity date	9,000,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	23,900,000
Letters of credit set to expire - 2020	20,400,000
Letters of credit set to expire - 2021	3,500,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 1,000,000,000

Variable interest entities (Det

Variable interest entities (Details 3) $ in Millions	Jun. 30, 2020USD ($)
Fuel contract
Variable Interest Entities [Line Items]
Variable interest entity, reporting entity involvement, maximum loss exposure, amount	$ 34.8