MDU Resources (MDU) 10-Q 3 May 19 2019 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Entity Information [Line Items]
Entity registrant name	MDU RESOURCES GROUP INC
Entity central index key	0000067716
Current fiscal year end date	--12-31
Entity filer category	Large Accelerated Filer
Document type	10-Q
Document period end date	Mar. 31, 2019
Document fiscal year focus	2019
Document fiscal period focus	Q1
Amendment flag	false
Entity emerging growth company	false
Entity small business	false
Entity common stock, shares outstanding		198,083,324

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating revenues:
Operating revenues:	$ 1,091,191	$ 976,293
Operating expenses:
Operation and maintenance:	702,914	600,856
Purchased natural gas sold	183,829	181,967
Depreciation, depletion and amortization	59,897	52,729
Taxes, other than income	54,029	48,854
Electric fuel and purchased power	26,304	22,511
Total operating expenses	1,026,973	906,917
Operating income	64,218	69,376
Other income	7,595	582
Interest expense	23,407	20,447
Income before income taxes	48,406	49,511
Income taxes	7,317	7,551
Income from continuing operations	41,089	41,960
Income (loss) from discontinued operations, net of tax (Note 10)	(163)	477
Net income	$ 40,926	$ 42,437
Earnings per share - basic:
Income from continuing operations	$ 0.21	$ 0.22
Discontinued operations, net of tax	0	0
Earnings per share - basic	0.21	0.22
Earnings per share - diluted:
Income from continuing operations	0.21	0.22
Discontinued operations, net of tax	0	0
Earnings per share - diluted	$ 0.21	$ 0.22
Weighted average common shares outstanding - basic	196,401	195,304
Weighted average common shares outstanding - diluted	196,414	195,982
Regulated operation
Operating revenues:
Operating revenues:	$ 439,617	$ 424,459
Operating expenses:
Operation and maintenance:	87,770	86,112
Income from continuing operations	59,009	51,166
Nonregulated operation
Operating revenues:
Operating revenues:	651,574	551,834
Operating expenses:
Operation and maintenance:	615,144	514,744
Income from continuing operations	$ (17,920)	$ (9,206)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 40,926	$ 42,437
Other comprehensive income:
Reclassification adjustment for loss on derivative instruments included in net income, net of tax of $(249) and $56 for the three months ended in 2019 and 2018, respectively	397	92
Postretirement liability adjustment:
Amortization of postretirement liability losses included in net periodic benefit cost (credit), net of tax of $100 and $155 for the three months ended in 2019 and 2018, respectively	310	418
Foreign currency translation adjustment:
Foreign currency translation adjustment recognized during the period, net of tax of $0 and $(1) for the three months ended in 2019 and 2018, respectively	0	(2)
Net unrealized gain (loss) on available-for-sale investments:
Net unrealized gain (loss) on available-for-sale investments arising during the period, net of tax of $10 and $(28) for the three months ended in 2019 and 2018, respectively	39	(105)
Reclassification adjustment for loss on available-for-sale investments included in net income, net of tax of $7 and $7 for the three months ended in 2019 and 2018, respectively	28	30
Net unrealized gain (loss) on available-for-sale investments	67	(75)
Other comprehensive income	774	433
Comprehensive income attributable to common stockholders	$ 41,700	$ 42,870

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification adjustment for loss on derivative instruments included in net income, tax	$ (249)	$ 56
Amortization of postretirement liability losses included in net periodic benefit cost (credit), tax	100	155
Foreign currency translation adjustments recognized during the period, tax	0	(1)
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	10	(28)
Reclassification adjustment for loss on available-for-sale investments included in net income, tax	$ 7	$ 7

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Current assets:
Cash and cash equivalents	$ 49,721	$ 53,948	$ 58,764
Receivables, net	722,152	722,945	664,319
Inventories	311,535	287,309	257,792
Prepayments and other current assets	151,391	119,500	59,481
Current assets held for sale	430	430	458
Total current assets	1,235,229	1,184,132	1,040,814
Investments	144,616	138,620	138,451
Property, plant and equipment	7,502,368	7,397,321	6,842,967
Less accumulated depreciation, depletion and amortization	2,858,986	2,818,644	2,725,484
Net property, plant and equipment	4,643,382	4,578,677	4,117,483
Deferred charges and other assets:
Goodwill	679,395	664,922	631,791
Other intangible assets, net	11,680	10,815	3,465
Operating lease right-of-use assets (Note 11)	107,486	0	0
Other	455,048	408,857	412,456
Noncurrent assets held for sale	2,087	2,087	4,392
Total deferred charges and other assets	1,255,696	1,086,681	1,052,104
Total assets	7,278,923	6,988,110	6,348,852
Current liabilities:
Short-term borrowings	70,000	0	0
Long-term debt due within one year	251,846	251,854	149,199
Accounts payable	352,180	358,505	267,994
Taxes payable	55,319	41,929	57,354
Dividends payable	39,875	39,695	38,573
Accrued compensation	45,383	69,007	35,087
Current operating lease liabilities (Note 11)	30,978	0	0
Other accrued liabilities	213,541	221,059	204,328
Current liabilities held for sale	3,657	4,001	11,726
Total current liabilities	1,062,779	986,050	764,261
Long-term debt	1,946,181	1,856,841	1,630,343
Deferred credits and other liabilities:
Deferred income taxes	444,965	430,085	346,218
Noncurrent operating lease liabilities (Note 11)	76,444	0	0
Other	1,142,862	1,148,359	1,181,919
Total deferred credits and other liabilities	1,664,271	1,578,444	1,528,137
Commitments and contingencies
Stockholders' equity:
Authorized - 500,000,000 shares, $1.00 par value Shares issued - 198,316,808 at March 31, 2019, 195,843,297 at March 31, 2018 and 196,564,907 at December 31, 2018	198,317	196,565	195,843
Other paid-in capital	1,284,060	1,248,576	1,227,285
Retained earnings	1,164,509	1,163,602	1,051,469
Accumulated other comprehensive loss	(37,568)	(38,342)	(44,860)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)	(3,626)
Total stockholders' equity	2,605,692	2,566,775	2,426,111
Total liabilities and stockholders' equity	$ 7,278,923	$ 6,988,110	$ 6,348,852

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Stockholders' equity:
Common stock, shares issued	198,316,808	196,564,907	195,843,297
Treasury shares	538,921	538,921	538,921
Common stock, shares authorized	500,000,000	500,000,000	500,000,000
Common stock, par value	$ 1	$ 1	$ 1

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
Cumulative effect of adoption of ASU 2014-09 | Accounting Standards Update 2014-09	$ (970)			$ (970)
Balance (in shares) at Dec. 31, 2017		195,843,297
Treasury stock (in shares) at Dec. 31, 2017						(538,921)
Balance at Dec. 31, 2017	2,429,043	$ 195,843	$ 1,233,412	1,040,748	$ (37,334)	$ (3,626)
Balance (Accounting Standards Update 2014-09) at Dec. 31, 2017	2,428,073			1,039,778
Net income	42,437			42,437
Other comprehensive income	433				433
Reclassification of certain prior period tax effects from accumulated other comprehensive loss | Adjustments for new accounting pronouncement	0			7,959	(7,959)
Dividends declared on common stock	(38,705)			(38,705)
Stock-based compensation	1,223		1,223
Repurchase of common stock						(182,424)
Repurchase of common stock	(5,020)					$ (5,020)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings			(7,350)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)						182,424
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings						$ 5,020
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	$ (2,330)
Balance (in shares) at Mar. 31, 2018	195,843,297	195,843,297
Treasury stock (in shares) at Mar. 31, 2018						(538,921)
Balance at Mar. 31, 2018	$ 2,426,111	$ 195,843	1,227,285	1,051,469	(44,860)	$ (3,626)
Balance (in shares) at Dec. 31, 2018	196,564,907	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 Issued Shares 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
Balance (in shares) at Mar. 31, 2019	198,316,808	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)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 40,926	$ 42,437
Operating activities:
Income (loss) from discontinued operations, net of tax	(163)	477
Income from continuing operations	41,089	41,960
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	59,897	52,729
Deferred income taxes	12,658	(2,068)
Changes in current assets and liabilities, net of acquisitions:
Receivables	(2,641)	62,711
Inventories	(21,407)	(29,997)
Other current assets	(31,586)	22,506
Accounts payable	356	(31,864)
Other current liabilities	(6,310)	(5,115)
Other noncurrent changes	(49,965)	(5,302)
Net cash provided by continuing operations	2,091	105,560
Net cash provided by (used in) discontinued operations	(507)	231
Net cash provided by operating activities	1,584	105,791
Investing activities:
Capital expenditures	(133,839)	(105,136)
Acquisitions, net of cash acquired	(30,868)	0
Net proceeds from sale or disposition of property and other	4,938	5,966
Investments	(340)	(1,074)
Net cash used in investing activities	(160,109)	(100,244)
Financing activities:
Issuance of short-term borrowings	70,000	0
Issuance of long-term debt	141,338	101,588
Repayment of long-term debt	(52,964)	(37,047)
Proceeds from issuance of common stock	38,634	0
Dividends paid	(39,695)	(38,573)
Repurchase of common stock	0	(5,020)
Tax withholding on stock-based compensation	(3,015)	(2,330)
Net cash provided by financing activities	154,298	18,618
Increase (decrease) in cash and cash equivalents	(4,227)	24,165
Cash and cash equivalents -- beginning of year	53,948	34,599
Cash and cash equivalents -- end of period	$ 49,721	$ 58,764

Basis of presentation

Basis of presentation	3 Months Ended
	Mar. 31, 2019
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 2018 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. On January 2, 2019, the Company announced the completion of the Holding Company Reorganization, which resulted in Montana-Dakota becoming a subsidiary of the Company. The purpose of the reorganization was to make the public utility divisions into a subsidiary of the holding company, just as the other operating companies are wholly owned subsidiaries. Effective January 1, 2019, the Company adopted the requirements of the ASU on leases, as further discussed in Notes 6 and 11 . As such, results for reporting periods beginning January 1, 2019, are presented under the new guidance, while prior period amounts are not adjusted and continue to be reported in accordance with the historic accounting for leases. The assets and liabilities for the Company's discontinued operations have been classified as held for sale and the results of operations are shown in income (loss) from discontinued operations, other than certain general and administrative costs and interest expense which do not meet the criteria for income (loss) from discontinued operations. At the time the assets were classified as held for sale, depreciation, depletion and amortization expense was no longer recorded. Unless otherwise indicated, the amounts presented in the accompanying notes to the consolidated financial statements relate to the Company's continuing operations. For more information on the Company's discontinued operations, see Note 10 . Management has also evaluated the impact of events occurring after March 31, 2019

Seasonality of operations

Seasonality of operations	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Seasonality of operations	Seasonality of operations

Accounts receivable and allowan

Accounts receivable and allowance for doubtful accounts	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts Accounts receivable consists primarily of trade receivables from the sale of goods and services which are recorded at the invoiced amount net of allowance for doubtful accounts, and costs and estimated earnings in excess of billings on uncompleted contracts. The total balance of receivables past due 90 days or more was $38.3 million , $36.3 million and $30.0 million at March 31, 2019 and 2018 , and December 31, 2018 , respectively. The allowance for doubtful accounts is determined through a review of past due balances and other specific account data. Account balances are written off when management determines the amounts to be uncollectible. The Company's allowance for doubtful accounts at March 31, 2019 and 2018 , and December 31, 2018 , was $9.6 million , $8.2 million and $8.9 million

Inventories and natural gas in

Inventories and natural gas in storage	3 Months Ended
	Mar. 31, 2019
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 carried at lower of cost or net realizable value, or cost using the last-in, first-out method. All other inventories are stated at the lower of cost or net realizable value. The portion of the cost of natural gas in storage expected to be used within one year was included in inventories. Inventories on the Consolidated Balance Sheets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Aggregates held for resale $ 142,747 $ 123,053 $ 139,681 Asphalt oil 83,459 61,647 54,741 Materials and supplies 26,441 19,493 23,611 Merchandise for resale 25,104 16,378 22,552 Natural gas in storage (current) 11,464 10,936 22,117 Other 22,320 26,285 24,607 Total $ 311,535 $ 257,792 $ 287,309 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 deferred charges and other assets - other and was $ 48.2 million , $ 47.8 million and $ 48.5 million at March 31, 2019 and 2018 , and December 31, 2018

Earnings per common share

Earnings per common share	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 196,401 195,304 Effect of dilutive performance share awards and restricted stock units 13 678 Weighted average common shares outstanding - diluted 196,414 195,982 Shares excluded from the calculation of diluted earnings per share 64 — Dividends declared per common share $ .2025 $ .1975

New accounting standards

New accounting standards	3 Months Ended
	Mar. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New accounting standards	New accounting standards Recently adopted accounting standards ASU 2016-02 - Leases In February 2016, the FASB issued guidance regarding leases. The guidance required lessees to recognize a lease liability and a right-of-use asset on the balance sheet for operating and financing leases. The guidance remained largely the same for lessors, although some changes were made to better align lessor accounting with the new lessee accounting and to align with the revenue recognition standard. The guidance also required additional disclosures, both quantitative and qualitative, related to operating and financing leases for the lessee and sales-type, direct financing and operating leases for the lessor. The Company adopted the standard on January 1, 2019. In July 2018, the FASB issued ASU 2018-11 - Leases: Targeted Improvements, an accounting standard update to ASU 2016-02. This ASU provided an entity the option to adopt the guidance using one of two modified retrospective approaches. An entity could adopt the guidance using the modified retrospective transition approach beginning in the earliest year presented in the financial statements. This method of adoption would have required the restatement of prior periods reported and the presentation of lease disclosures under the new guidance for all periods reported. The additional transition method of adoption, introduced by ASU 2018-11, allowed entities the option to apply the guidance on the date of adoption by recognizing a cumulative effect adjustment to retained earnings during the period of adoption and did not require prior comparative periods to be restated. The Company adopted the standard on January 1, 2019, utilizing the additional transition method of adoption applied on the date of adoption and the practical expedient that allowed the Company to not reassess whether an expired or existing contract contained a lease, the classification of leases or initial direct costs. The Company did not identify any cumulative effect adjustments. The Company also adopted a short-term leasing policy as the lessee where leases with a term of 12 months or less are not included on the Consolidated Balance Sheet. As a practical expedient, a lessee may choose not to separate nonlease components from lease components and instead account for lease and nonlease components as a single lease component. The election shall be made by asset class. The Company has elected to adopt the lease/nonlease component practical expedient for all asset classes as the lessee. The Company did not elect the practical expedient to use hindsight when assessing the lease term or impairment of right-of-use assets for the existing leases on the date of adoption. In January 2018, the FASB issued a practical expedient for land easements under the new lease guidance. The practical expedient permits an entity to elect the option to not evaluate land easements under the new guidance if they existed or expired before the adoption of the new lease guidance and were not previously accounted for as leases under the previous lease guidance. Once an entity adopts the new guidance, the entity should apply the new guidance on a prospective basis to all new or modified land easements. The Company has adopted this practical expedient. The Company formed a lease implementation team to review and assess existing contracts to identify and evaluate those containing leases. Additionally, the team implemented new and revised existing software to meet the reporting and disclosure requirements of the standard. The Company also assessed the impact the standard had on its processes and internal controls and identified new and updated existing internal controls and processes to ensure compliance with the new lease standard; such modifications were not deemed to be significant. During the assessment phase, the Company used various surveys, reconciliations and analytic methodologies to ensure the completeness of the lease inventory. The Company determined that most of the current operating leases were subject to the guidance and were recognized as operating lease liabilities and right-of-use assets on the Consolidated Balance Sheet upon adoption. On January 1, 2019, the Company recorded approximately $112 million to right-of-use assets and lease liabilities as a result of the initial adoption of the guidance. In addition, the Company evaluated the impact the new guidance had on lease contracts where the Company is the lessor and determined it did not have a significant impact. ASU 2018-15 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract In August 2018, the FASB issued guidance on the accounting for implementation costs of a hosting arrangement that is a service contract. The guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract similar to the costs incurred to develop or obtain internal-use software and such capitalized costs to be expensed over the term of the hosting arrangement. Costs incurred during the preliminary and postimplementation stages should continue to be expensed as activities are performed. The capitalized costs are required to be presented on the balance sheet in the same line the prepayment for the fees associated with the hosting arrangement would be presented. In addition, the expense related to the capitalized implementation costs should be presented in the same line on the income statement as the fees associated with the hosting element of the arrangements. The Company adopted the guidance effective January 1, 2019, on a prospective basis. The adoption of the guidance did not have a material impact on its results of operations, financial position, cash flows, and disclosures. Recently issued accounting standards not yet adopted ASU 2017-04 - Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued guidance on simplifying the test for goodwill impairment by eliminating Step 2, which required an entity to measure the amount of impairment loss by comparing the implied fair value of reporting unit goodwill with the carrying amount of such goodwill. This guidance requires entities to perform a quantitative impairment test, previously Step 1, to identify both the existence of impairment and the amount of impairment loss by comparing the fair value of a reporting unit to its carrying amount. Entities will continue to have the option of performing a qualitative assessment to determine if the quantitative impairment test is necessary. The guidance also requires additional disclosures if an entity has one or more reporting units with zero or negative carrying amounts of net assets. The guidance will be effective for the Company on January 1, 2020, and must be applied on a prospective basis with early adoption permitted. The Company is evaluating the guidance and does not expect it to have a material impact on its results of operations, financial position, cash flows and disclosures. 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 modifies, among other things, the disclosures required for Level 3 fair value measurements, including the range and weighted average of significant unobservable inputs. The guidance removes, among other things, the disclosure requirement to disclose transfers between Levels 1 and 2. The guidance will be effective for the Company on January 1, 2020, including interim periods, with early adoption permitted. Level 3 fair value measurement disclosures should be applied prospectively while all other amendments should be applied retrospectively. The Company is evaluating the effects the adoption of the new guidance will have on its disclosures. 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 2018-18 - Clarifying the Interaction between Topic 808 and Topic 606

Comprehensive income (loss)

Comprehensive income (loss)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Comprehensive income (loss)	Comprehensive income (loss) The after-tax changes in the components of accumulated other comprehensive loss were as follows: Three Months Ended March 31, 2019 Net Unrealized Gain (Loss) on Derivative Postretirement Net Unrealized Total (In thousands) Balance at beginning of period $ (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 Balance at end of period $ (1,764 ) $ (35,759 ) $ (45 ) $ (37,568 ) Three Months Ended March 31, 2018 Net Unrealized Gain (Loss) on Derivative Postretirement Foreign Net Unrealized Total (In thousands) Balance at beginning of period $ (1,934 ) $ (35,163 ) $ (155 ) $ (82 ) $ (37,334 ) Other comprehensive loss before reclassifications — — (2 ) (105 ) (107 ) Amounts reclassified from accumulated other comprehensive loss 92 418 — 30 540 Net current-period other comprehensive income (loss) 92 418 (2 ) (75 ) 433 Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss (389 ) (7,520 ) (33 ) (17 ) (7,959 ) Balance at end of period $ (2,231 ) $ (42,265 ) $ (190 ) $ (174 ) $ (44,860 ) The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows: Three Months Ended Location on Consolidated Statements of Income March 31, 2019 2018 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (148 ) $ (148 ) Interest expense (249 ) 56 Income taxes (397 ) (92 ) Amortization of postretirement liability losses included in net periodic benefit cost (credit) (410 ) (573 ) Other income 100 155 Income taxes (310 ) (418 ) Reclassification adjustment on available-for-sale investments included in net income (35 ) (37 ) Other income 7 7 Income taxes (28 ) (30 ) Total reclassifications $ (735 ) $ (540 )

Revenue from contracts with cus

Revenue from contracts with customers	3 Months Ended
	Mar. 31, 2019
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. As part of the adoption of ASC 606 - Revenue from Contracts with Customers , the Company elected the practical expedient to not disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied (or partially unsatisfied) as of the end of the reporting period, along with an explanation of when such revenue would be expected to be recognized. This practical expedient was used since the performance obligations are part of contracts with an original duration of one year or less. The Company also elected the practical expedient to recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that the Company otherwise would have recognized is one year or less. Disaggregation In the following table, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 17 . Three Months Ended March 31, 2019 Electric Natural gas distribution Pipeline and midstream Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 36,555 $ 200,609 $ — $ — $ — $ — $ 237,164 Commercial utility sales 35,671 121,793 — — — — 157,464 Industrial utility sales 8,884 8,611 — — — — 17,495 Other utility sales 1,799 — — — — — 1,799 Natural gas transportation — 11,570 25,058 — — — 36,628 Natural gas gathering — — 2,121 — — — 2,121 Natural gas storage — — 2,646 — — — 2,646 Contracting services — — — 83,039 — — 83,039 Construction materials — — — 179,309 — — 179,309 Intrasegment eliminations* — — — (35,140 ) — — (35,140 ) Inside specialty contracting — — — — 299,530 — 299,530 Outside specialty contracting — — — — 107,398 — 107,398 Other 9,121 3,913 2,696 — 17 7,843 23,590 Intersegment eliminations — — (23,955 ) (95 ) (129 ) (7,824 ) (32,003 ) Revenues from contracts with customers 92,030 346,496 8,566 227,113 406,816 19 1,081,040 Revenues out of scope 536 (4,349 ) 47 — 13,917 — 10,151 Total external operating revenues $ 92,566 $ 342,147 $ 8,613 $ 227,113 $ 420,733 $ 19 $ 1,091,191 * Intrasegment revenues are presented 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. Three Months Ended March 31, 2018 Electric Natural gas distribution Pipeline and midstream Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 35,183 $ 192,886 $ — $ — $ — $ — $ 228,069 Commercial utility sales 34,701 116,891 — — — — 151,592 Industrial utility sales 8,770 7,809 — — — — 16,579 Other utility sales 1,836 — — — — — 1,836 Natural gas transportation — 11,179 21,818 — — — 32,997 Natural gas gathering — — 2,270 — — — 2,270 Natural gas storage — — 3,134 — — — 3,134 Contracting services — — — 74,064 — — 74,064 Construction materials — — — 173,591 — — 173,591 Intrasegment eliminations* — — — (34,270 ) — — (34,270 ) Inside specialty contracting — — — — 233,821 — 233,821 Outside specialty contracting — — — — 87,181 — 87,181 Other 8,252 3,999 3,326 — (86 ) 2,696 18,187 Intersegment eliminations — — (21,759 ) (101 ) (11 ) (2,638 ) (24,509 ) Revenues from contracts with customers 88,742 332,764 8,789 213,284 320,905 58 964,542 Revenues out of scope (1,338 ) (100 ) 44 — 13,145 — 11,751 Total external operating revenues $ 87,404 $ 332,664 $ 8,833 $ 213,284 $ 334,050 $ 58 $ 976,293 * Intrasegment revenues are presented 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: March 31, 2019 December 31, 2018 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 117,036 $ 104,239 $ 12,797 Receivables, net Contract liabilities - current (86,031 ) (93,901 ) 7,870 Accounts payable Contract liabilities - noncurrent (30 ) (135 ) 105 Deferred credits and other liabilities - other Net contract assets $ 30,975 $ 10,203 $ 20,772 The Company recognized $56.4 million in revenue for the three months ended March 31, 2019 , which was previously included in contract liabilities at December 31, 2018 . The Company recognized $52.0 million in revenue for the three months ended March 31, 2018 , which was previously included in contract liabilities at December 31, 2017 . The Company recognized a net increase in revenues of $18.7 million and $3.1 million for the three months ended March 31, 2019 and 2018

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2019
Business Acquisition [Line Items]
Business Combinations	Business combinations In March 2019, the Company acquired Viesko Redi-Mix, Inc., a provider of ready-mixed concrete in Oregon. The gross aggregate consideration for this acquisition was $32.1 million , subject to certain adjustments, which includes $1.2 million of debt assumed. The acquisition is 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 Sheet for these adjustments are considered provisional until final settlement has occurred. The purchase price adjustments for all business combinations that occurred during 2018 have been settled and the purchase price allocations are considered final; except for Sweetman Construction Company, which was acquired in October 2018. No material adjustments were made to the provisional accounting for the business combinations. Business combinations were accounted for in accordance with ASC 805 - Business Combinations . The results of the acquired businesses have been included in the Company's construction materials and contracting segment and Consolidated Financial Statements beginning on the acquisition date. Pro forma financial amounts reflecting the effects of the business combinations are not presented, as these business combinations were not material to the Company's financial position or results of operations.

Discontinued operations

Discontinued operations	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Discontinued operations	Discontinued operations The assets and liabilities of the Company's discontinued operations have been classified as held for sale and the results of operations are shown in income (loss) from discontinued operations, other than certain general and administrative costs and interest expense which do not meet the criteria for income (loss) from discontinued operations. At the time the assets were classified as held for sale, depreciation, depletion and amortization expense was no longer recorded. Dakota Prairie Refining On June 24, 2016, WBI Energy entered into a membership interest purchase agreement with Tesoro to sell all the outstanding membership interests in Dakota Prairie Refining to Tesoro. WBI Energy and Calumet each previously owned 50 percent of the Dakota Prairie Refining membership interests and were equal members in building and operating Dakota Prairie Refinery. To effectuate the sale, WBI Energy acquired Calumet’s 50 percent membership interest in Dakota Prairie Refining on June 27, 2016. The sale of the membership interests to Tesoro closed on June 27, 2016. The sale of Dakota Prairie Refining reduced the Company’s risk by decreasing exposure to commodity prices. In connection with the sale of Dakota Prairie Refining, Centennial guaranteed certain debt obligations of Dakota Prairie Refining and Tesoro agreed to indemnify Centennial for any losses and litigation expenses arising from the guarantee. On October 17, 2018, Centennial was released of any further liabilities or obligations under this guarantee. Fidelity In the second quarter of 2015, the Company began the marketing and sale process of Fidelity with an anticipated sale to occur within one year. Between September 2015 and March 2016, the Company entered into purchase and sale agreements to sell substantially all of Fidelity's oil and natural gas assets. The completion of these sales occurred between October 2015 and April 2016. In July 2018, the Company completed the sale of a majority of the remaining property, plant and equipment. The sale of Fidelity was part of the Company's strategic plan to grow its capital investments in the remaining business segments and to focus on creating a greater long-term value. Dakota Prairie Refining and Fidelity The carrying amounts of the major classes of assets and liabilities classified as held for sale on the Consolidated Balance Sheets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Assets Current assets: Receivables, net $ 430 $ 458 $ 430 Income taxes receivable (a) — 1,858 — Total current assets held for sale 430 2,316 430 Noncurrent assets: Net property, plant and equipment — 1,631 — Deferred income taxes 1,926 2,637 1,926 Other 161 161 161 Total noncurrent assets held for sale 2,087 4,429 2,087 Total assets held for sale $ 2,517 $ 6,745 $ 2,517 Liabilities Current liabilities: Accounts payable $ — $ — $ 80 Taxes payable 1,295 10,774 1,451 Other accrued liabilities 2,362 2,810 2,470 Total current liabilities held for sale 3,657 13,584 4,001 Noncurrent liabilities: Deferred income taxes (b) — 37 — Total noncurrent liabilities held for sale — 37 — Total liabilities held for sale $ 3,657 $ 13,621 $ 4,001 (a) On the Company's Consolidated Balance Sheets, these amounts were reclassified to taxes payable and are reflected in current liabilities held for sale. (b) On the Company's Consolidated Balance Sheets, these amounts were reclassified to deferred charges and other assets - deferred income taxes and are reflected in noncurrent assets held for sale. The reconciliation of the major classes of income and expense constituting pretax loss from discontinued operations to the after-tax income (loss) from discontinued operations on the Consolidated Statements of Income was as follows: Three Months Ended March 31, 2019 2018 (In thousands) Operating revenues $ 30 $ 66 Operating expenses 245 174 Operating loss (215 ) (108 ) Other income — 12 Interest expense — 575 Loss from discontinued operations before income taxes (215 ) (671 ) Income taxes (52 ) (1,148 ) Income (loss) from discontinued operations $ (163 ) $ 477

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	Leases Most of the leases the Company enters into are for equipment, buildings, easements and vehicles as part of their ongoing operations. The Company also leases certain equipment to third parties through its utility and construction services segments. The Company determines if an arrangement contains a lease at inception of a contract and accounts for all leases in accordance with ASC 842 - Leases. For more information on the adoption of ASC 842, see Note 6 . The recognition of leases requires the Company to make estimates and assumptions that affect the lease classification and the assets and liabilities recorded. The accuracy of lease assets and liabilities reported on the Consolidated Financial Statements depends on, among other things, management's estimates of interest rates used to discount the lease assets and liabilities to its present value, as well as the lease terms based on the unique facts and circumstances of each lease. Lessee accounting The leases the Company has entered into as part of their ongoing operations are considered operating leases and are recognized on the balance sheet as right-of-use assets, current lease liabilities and, if applicable, noncurrent lease liabilities. Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue. Generally, the leases for vehicles and equipment have a term of five years or less and buildings and easements have a longer term of up to 35 years or more. To date, the Company does not have any residual value guarantee amounts probable of being owed to a lessor, financing leases or material agreements with related parties. The Company has elected to recognize leases with an original lease term of 12 months or less in income on a straight-line basis over the term of the lease and not recognize a corresponding right-of-use asset or lease liability. Lease costs are included in operation and maintenance expense on the Company's Consolidated Statements of Income. The discount rate used to calculate the present value of the lease liabilities is based upon the implied rate within each contract. If the rate is unknown or cannot be determined, the Company uses an incremental borrowing rate which is determined by the length of the contract, asset class and the Company's borrowing rates as of the commencement date of the contract. The following table provides information on the Company's operating leases for the three months ended: March 31, 2019 (Dollars in thousands) Weighted average remaining lease term 2.63 years Weighted average discount rate 4.51 % Cash paid for amounts included in the measurement of lease liabilities $ 11,467 Lease costs: Operating lease cost $ 11,521 Variable lease cost 399 Short-term lease cost 17,238 Total lease costs $ 29,158 As of March 31, 2019 , the Company had operating leases that had not yet commenced and will create approximately $7.5 million of additional right-of-use assets and lease liabilities in future periods. The reconciliation of the future undiscounted cash flows to the operating lease liabilities presented on the Company's Consolidated Balance Sheet is as follows: March 31, 2019 (In thousands) Remainder of 2019 $ 26,655 2020 25,743 2021 18,503 2022 11,886 2023 6,723 Thereafter 43,401 Total 132,911 Less discount 25,489 Total operating lease liabilities $ 107,422 As previously disclosed in the 2018 Annual Report, the undiscounted annual minimum lease payments due under the Company's leases following the previous lease accounting standard as of December 31, 2018, were as follows: 2019 2020 2021 2022 2023 Thereafter (In thousands) Operating leases $ 37,740 $ 26,255 $ 17,868 $ 11,647 $ 7,278 $ 49,098
Leases of Lessor Disclosure [Text Block]	Lessor accounting The Company leases certain equipment to third parties which are considered operating leases. The Company recognized revenue from operating leases of $14.0 million for the three months ended March 31, 2019 . The majority of the Company's operating leases are short-term leases of less than 12 months. At March 31, 2019 , the Company had $11.3 million

Goodwill and other intangible a

Goodwill and other intangible assets	3 Months Ended
	Mar. 31, 2019
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: Three Months Ended March 31, 2019 Balance at January 1, 2019 Goodwill Acquired the Year Balance at March 31, 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 Three Months Ended March 31, 2018 Balance at January 1, 2018 Goodwill Acquired the Year Balance at March 31, 2018 (In thousands) Natural gas distribution $ 345,736 $ — $ 345,736 Construction materials and contracting 176,290 — 176,290 Construction services 109,765 — 109,765 Total $ 631,791 $ — $ 631,791 Year Ended December 31, 2018 Balance at January 1, 2018 Goodwill Acquired the Year Balance at December 31, 2018 (In thousands) Natural gas distribution $ 345,736 $ — $ 345,736 Construction materials and contracting 176,290 33,131 209,421 Construction services 109,765 — 109,765 Total $ 631,791 $ 33,131 $ 664,922 During 2019 and 2018, the Company completed one and four business combinations, respectively, and the results of the acquired businesses have been included in the Company's construction materials and contracting segment. These business combinations increased the construction materials and contracting segment's goodwill balance at March 31, 2019 and December 31, 2018, as noted in the previous tables. As a result of the business combinations, other intangible assets increased $1.5 million at March 31, 2019, compared to December 31, 2018. For more information related to business combinations, see Note 9 . Other amortizable intangible assets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Customer relationships $ 14,471 $ 14,668 $ 22,720 Less accumulated amortization 5,156 13,007 13,535 9,315 1,661 9,185 Noncompete agreements 3,179 2,430 2,605 Less accumulated amortization 1,730 1,842 1,956 1,449 588 649 Other 6,458 6,458 6,458 Less accumulated amortization 5,542 5,242 5,477 916 1,216 981 Total $ 11,680 $ 3,465 $ 10,815 Amortization expense for amortizable intangible assets for the three months ended March 31, 2019 and 2018, was $600,000 and $400,000 , respectively. Estimated amortization expense for identifiable intangible assets as of March 31, 2019 , was: Remainder of 2019 2020 2021 2022 2023 Thereafter (In thousands) Amortization expense $ 1,403 $ 1,632 $ 1,242 $ 1,219 $ 1,237 $ 4,947

Regulatory assets and liabiliti

Regulatory assets and liabilities	3 Months Ended
	Mar. 31, 2019
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets and Liabilities	Regulatory assets and liabilities The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery Period * March 31, 2019 December 31, 2018 (In thousands) Regulatory assets: Pension and postretirement benefits (a) (e) $ 165,879 $ 165,898 Natural gas costs recoverable through rate adjustments (a) (b) Up to 3 years 91,465 42,652 Asset retirement obligations (a) Over plant lives 63,633 60,097 Cost recovery mechanisms (a) (b) Up to 4 years 17,835 17,948 Manufactured gas plant site remediation (a) - 17,111 17,068 Taxes recoverable from customers (a) Over plant lives 11,858 11,946 Plant to be retired (a) - 6,691 — Conservation programs (b) Up to 1 year 6,094 7,494 Long-term debt refinancing costs (a) Up to 19 years 4,746 4,898 Costs related to identifying generation development (a) Up to 8 years 2,394 2,508 Other (a) (b) Up to 20 years 5,827 9,608 Total regulatory assets 393,533 340,117 Regulatory liabilities: Taxes refundable to customers (c) (d) 267,777 277,833 Plant removal and decommissioning costs (c) (d) 173,911 173,143 Natural gas costs refundable through rate adjustments (d) 29,739 29,995 Pension and postretirement benefits (c) 12,991 15,264 Other (c) (d) 33,976 25,197 Total regulatory liabilities 518,394 521,432 Net regulatory position $ (124,861 ) $ (181,315 ) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. (a) Included in deferred charges and other assets - other on the Consolidated Balance Sheets. (b) Included in prepayments and other current assets on the Consolidated Balance Sheets. (c) Included in deferred credits and other liabilities - other on the Consolidated Balance Sheets. (d) Included in other accrued liabilities on the Consolidated Balance Sheets. (e) Recovered as expense is incurred or cash contributions are made. The regulatory assets are expected to be recovered in rates charged to customers. A portion of the Company's regulatory assets are not earning a return; however, these regulatory assets are expected to be recovered from customers in future rates. As of March 31, 2019 and December 31, 2018 , approximately $279.4 million and $313.5 million , respectively, of regulatory assets were not earning a rate of return. During the first quarter of 2019 and the fourth quarter of 2018, the Company experienced increased natural gas costs in certain jurisdictions where it supplies natural gas. The Company has recorded these natural gas costs as regulatory assets as they will be recovered from customers, as discussed in Note 19 . In February 2019, the Company announced that it intends to retire three aging coal-fired electric generation units within the next three years. 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 plant to be retired in future rates.

Fair value measurements

Fair value measurements	3 Months Ended
	Mar. 31, 2019
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 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 $80.2 million , $76.9 million and $73.8 million , at March 31, 2019 and 2018 , and December 31, 2018 , respectively, are classified as investments on the Consolidated Balance Sheets. The net unrealized gain on these investments was $6.4 million for the three months ended March 31, 2019 . The net unrealized loss on these investments was $500,000 for the three months ended March 31, 2018 . 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. The available-for-sale securities include mortgage-backed securities and U.S. Treasury securities. These available-for-sale securities are recorded at fair value and are classified as investments on the Consolidated Balance Sheets. Unrealized gains or losses are recorded in accumulated other comprehensive loss. Details of available-for-sale securities were as follows: March 31, 2019 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,679 $ 31 $ 88 $ 10,622 U.S. Treasury securities 179 — — 179 Total $ 10,858 $ 31 $ 88 $ 10,801 March 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,282 $ 4 $ 223 $ 10,063 U.S. Treasury securities 466 — 1 465 Total $ 10,748 $ 4 $ 224 $ 10,528 December 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,473 $ 21 $ 162 $ 10,332 U.S. Treasury securities 179 — — 179 Total $ 10,652 $ 21 $ 162 $ 10,511 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. For the three months ended March 31, 2019 and 2018 , there were no transfers between Levels 1 and 2. The Company's assets and liabilities measured at fair value on a recurring basis were as follows: Fair Value Measurements at March 31, 2019, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at March 31, 2019 (In thousands) Assets: Money market funds $ — $ 10,540 $ — $ 10,540 Insurance contract* — 80,243 — 80,243 Available-for-sale securities: Mortgage-backed securities — 10,622 — 10,622 U.S. Treasury securities — 179 — 179 Total assets measured at fair value $ — $ 101,584 $ — $ 101,584 * 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, 11 percent in common stock of small-cap companies, 3 percent in target date investments and 1 percent in cash equivalents. Fair Value Measurements at March 31, 2018, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at March 31, 2018 (In thousands) Assets: Money market funds $ — $ 9,085 $ — $ 9,085 Insurance contract* — 76,941 — 76,941 Available-for-sale securities: Mortgage-backed securities — 10,063 — 10,063 U.S. Treasury securities — 465 — 465 Total assets measured at fair value $ — $ 96,554 $ — $ 96,554 * The insurance contract invests approximately 49 percent in fixed-income investments, 22 percent in common stock of large-cap companies, 13 percent in common stock of mid-cap companies, 11 percent in common stock of small-cap companies, 3 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements at December 31, 2018, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2018 (In thousands) Assets: Money market funds $ — $ 10,799 $ — $ 10,799 Insurance contract* — 73,838 — 73,838 Available-for-sale securities: Mortgage-backed securities — 10,332 — 10,332 U.S. Treasury securities — 179 — 179 Total assets measured at fair value $ — $ 95,148 $ — $ 95,148 * The insurance contract invests approximately 53 percent in fixed-income investments, 21 percent in common stock of large-cap companies, 11 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 3 percent in target date investments and 2 percent in cash equivalents. 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 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: Carrying Amount Fair Value (In thousands) Long-term debt at March 31, 2019 $ 2,198,027 $ 2,263,305 Long-term debt at March 31, 2018 $ 1,779,542 $ 1,854,350 Long-term debt at December 31, 2018 $ 2,108,695 $ 2,183,819 The carrying amounts of the Company's remaining financial instruments included in current assets and current liabilities approximate their fair values

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt Certain debt instruments of the Company's subsidiaries contain restrictive covenants and cross-default provisions. In order to borrow under the respective credit 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 March 31, 2019 . 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 their credit agreements. The commercial paper borrowings may vary during the period, largely the result of fluctuations in working capital requirements due to the seasonality of the construction businesses. Short-term debt Cascade On January 18, 2019, Cascade entered into a $30.0 million term loan agreement with a variable interest rate and a due date of June 28, 2019; this agreement has been classified as short-term debt. On March 22, 2019, Cascade entered into a $40.0 million term loan agreement with a variable interest rate and a due date of December 31, 2019; this agreement has been classified as short-term debt. Long-term debt Long-term Debt Outstanding Long-term debt outstanding was as follows: Weighted Average Interest Rate at March 31, 2019 March 31, 2019 December 31, 2018 (In thousands) Senior Notes due on dates ranging from July 1, 2019 to January 15, 2055 4.57 % $ 1,381,000 $ 1,381,000 Commercial paper supported by revolving credit agreements 2.97 % 473,900 338,100 Term Loan Agreements due on dates ranging from October 17, 2019 to September 3, 2032 2.75 % 209,800 209,800 Credit agreements due on April 24, 2020 4.42 % 62,875 110,100 Medium-Term Notes due on dates ranging from September 1, 2020 to March 16, 2029 6.68 % 50,000 50,000 Other notes due on dates ranging from July 1, 2019 to November 30, 2038 5.00 % 26,251 25,229 Less unamortized debt issuance costs 5,410 5,207 Less discount 389 327 Total long-term debt 2,198,027 2,108,695 Less current maturities 251,846 251,854 Net long-term debt $ 1,946,181 $ 1,856,841 Schedule of Debt Maturities Long-term debt maturities, which excludes unamortized debt issuance costs and discount, as of March 31, 2019 , were as follows: Remainder of 2019 2020 2021 2022 2023 Thereafter (In thousands) Long-term debt maturities $ 251,846 $ 78,801 $ 431,930 $ 147,434 $ 120,239 $ 1,173,576

Cash flow information

Cash flow information	3 Months Ended
	Mar. 31, 2019
Supplemental Cash Flow Information [Abstract]
Cash flow information	Cash flow information Cash expenditures for interest and income taxes were as follows: Three Months Ended March 31, 2019 2018 (In thousands) Interest, net* $ 19,067 $ 17,910 Income taxes paid (refunded), net** $ 29 $ (1,056 ) * AFUDC - borrowed was $556,000 and $382,000 for the three months ended March 31, 2019 and 2018 , respectively. ** Income taxes paid, net of discontinued operations, were $132,000 and $1.7 million for the three months ended March 31, 2019 and 2018 , respectively. Noncash investing and financing transactions were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 2,731 $ — $ — Property, plant and equipment additions in accounts payable $ 27,655 $ 16,829 $ 42,355 Debt assumed in connection with a business combination $ 1,163 $ — $ — Issuance of common stock in connection with a business combination $ — $ — $ 18,186

Business segment data

Business segment data	3 Months Ended
	Mar. 31, 2019
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 and midstream 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 and Alaska and Hawaii. The construction services segment provides inside and outside specialty contracting 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. Its inside services include design, construction and maintenance of electrical and communication wiring and infrastructure, fire suppression systems, and mechanical piping and services. 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 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 the 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 that 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 Dakota Prairie Refining and Fidelity other than certain general and administrative costs and interest expense as described above. For more information on discontinued operations, see Note 10 . The information below follows the same accounting policies as described in Note 1 of the Company's Notes to Consolidated Financial Statements in the 2018 Annual Report. Information on the Company's segments was as follows: Three Months Ended March 31, 2019 2018 (In thousands) External operating revenues: Regulated operations: Electric $ 92,566 $ 87,404 Natural gas distribution 342,147 332,664 Pipeline and midstream 4,904 4,391 439,617 424,459 Nonregulated operations: Pipeline and midstream 3,709 4,442 Construction materials and contracting 227,113 213,284 Construction services 420,733 334,050 Other 19 58 651,574 551,834 Total external operating revenues $ 1,091,191 $ 976,293 Intersegment operating revenues: Regulated operations: Electric $ — $ — Natural gas distribution — — Pipeline and midstream 23,922 21,735 23,922 21,735 Nonregulated operations: Pipeline and midstream 33 24 Construction materials and contracting 95 101 Construction services 129 11 Other 7,824 2,638 8,081 2,774 Intersegment eliminations (32,003 ) (24,509 ) Total intersegment operating revenues $ — $ — Three Months Ended March 31, 2019 2018 (In thousands) Operating income (loss): Electric $ 17,987 $ 18,154 Natural gas distribution 50,317 48,540 Pipeline and midstream 9,904 8,168 Construction materials and contracting (41,580 ) (26,309 ) Construction services 27,465 20,634 Other 125 189 Total operating income $ 64,218 $ 69,376 Net income: Regulated operations: Electric $ 15,505 $ 13,084 Natural gas distribution 36,500 32,623 Pipeline and midstream 7,004 5,459 59,009 51,166 Nonregulated operations: Pipeline and midstream (163 ) (179 ) Construction materials and contracting (34,449 ) (23,521 ) Construction services 20,024 15,090 Other (3,332 ) (596 ) (17,920 ) (9,206 ) Income from continuing operations 41,089 41,960 Income (loss) from discontinued operations, net of tax (163 ) 477 Net income $ 40,926 $ 42,437

Employee benefit plans

Employee benefit plans	3 Months Ended
	Mar. 31, 2019
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 Postretirement Benefits Three Months Ended March 31, 2019 2018 2019 2018 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 344 $ 407 Interest cost 3,773 3,807 780 778 Expected return on assets (5,120 ) (4,998 ) (1,220 ) (1,167 ) Amortization of prior service credit — — (252 ) (349 ) Amortization of net actuarial loss 1,355 1,782 — 238 Net periodic benefit cost (credit), including amount capitalized 8 591 (348 ) (93 ) Less amount capitalized — — 31 40 Net periodic benefit cost (credit) $ 8 $ 591 $ (379 ) $ (133 ) 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 that generally provide for defined benefit payments at age 65 following the employee's retirement or, upon death, to their beneficiaries for a 15-year period. In February 2016, the Company froze the unfunded, nonqualified defined benefit plans to new participants and eliminated benefit increases. Vesting for participants not fully vested was retained. The Company's net periodic benefit cost for these plans was $1.1 million and $1.1 million for the three months ended March 31, 2019 and 2018

Regulatory matters

Regulatory matters	3 Months Ended
	Mar. 31, 2019
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. The Company's most recent cases by jurisdiction are discussed in the following paragraphs. MNPUC On December 29, 2017, the MNPUC issued a notice of investigation related to tax changes with the enactment of the TCJA. On January 19, 2018, the MNPUC issued a notice of request for information, commission planning meeting and subsequent comment period. Pursuant to the notice, Great Plains provided preliminary impacts of the TCJA on January 30, 2018. On March 2, 2018, Great Plains submitted its initial filing addressing the impacts of the TCJA advocating existing rates are reasonable and a reduction in rates is not warranted. On August 9, 2018, the MNPUC ruled that Great Plains reduce rates to reflect TCJA impacts and to also provide a one-time refund that captures the TCJA impacts from January 1, 2018 through the implementation date of new rates. On December 5, 2018, the MNPUC issued an order requiring Great Plains reduce its rates by $400,000 on an annual basis and provide a one-time refund of approximately $400,000 , as previously mentioned. The required compliance filing was submitted to the MNPUC on January 4, 2019. On April 18, 2019, the MNPUC approved the decrease in rates effective May 1, 2019, as well as the TCJA refund, to be issued within 120 days of the implementation of new rates, for the period from January 1, 2018 through April 30, 2019. MTPSC On December 27, 2017, the MTPSC requested Montana-Dakota identify a plan for the impacts of the TCJA and to file a proposal for the impacts on the electric segment by March 31, 2018. On April 2, 2018, Montana-Dakota submitted its plan requesting the MTPSC recognize the identified need for additional rate relief and to consider the effects of the TCJA in a general electric rate case to be submitted by September 30, 2018. Montana-Dakota submitted the general electric rate case on September 28, 2018, as discussed below. On November 30, 2018, Montana-Dakota and interveners of the case submitted a stipulation and settlement agreement reflecting a one-time refund of approximately $1.5 million to account for all TCJA related impacts from January 1, 2018 through the date new rates are effective in the rate case noted below. A hearing was held on December 4, 2018, and the MTPSC issued an order accepting the stipulation and settlement agreement on December 21, 2018, requiring a one-time bill credit to occur in April 2019. The TCJA refund was credited to customers' bills on March 29, 2019. On September 28, 2018, Montana-Dakota filed an application with the MTPSC for an electric rate increase of approximately $11.9 million annually or approximately 18.9 percent above current rates. The requested increase is primarily to recover investments in facilities to enhance safety and reliability and the depreciation and taxes associated with the increase in investment. The increase was partially offset by tax savings related to the TCJA. On March 7, 2019, the MTPSC issued an interim order authorizing an interim increase of $7.9 million or approximately 12.8 percent, subject to refund, to be effective with service rendered on or after April 1, 2019. On April 24, 2019, Montana-Dakota submitted a settlement agreement reflecting a $9.0 million annual increase to be implemented in the first twelve months following the date of approval and an additional $300,000 annual increase to be implemented beginning twelve months after the date of approval. This matter is pending before the MTPSC. NDPSC On July 21, 2017, Montana-Dakota filed an application with the NDPSC for a natural gas rate increase of approximately $5.9 million annually or approximately 5.4 percent above current rates. The requested increase is primarily to recover the increased investment in distribution facilities to enhance system safety and reliability and the depreciation and taxes associated with the increase in investment. Montana-Dakota also introduced a SSIP and the proposed adjustment mechanism required to fund the SSIP. Montana-Dakota requested an interim increase of approximately $4.6 million or approximately 4.2 percent, subject to refund. On September 6, 2017, the NDPSC approved the request for interim rates effective with service rendered on or after September 19, 2017. On February 14, 2018, Montana-Dakota filed a revised interim increase request of approximately $2.7 million , subject to refund, incorporating the estimated impacts of the TCJA reduction in the federal corporate income tax rate. On March 1, 2018, the updated interim rates were implemented. The impact of the TCJA was submitted as part of a rebuttal testimony identifying a reduction of the adjusted revenue requirement to approximately $3.6 million . On July 19, 2018, a settlement was filed reflecting a revised annual revenue increase of approximately $2.5 million or approximately 2.3 percent. The proposed adjustment mechanism to fund the SSIP was not included in the settlement and was to be decided on separately by the NDPSC. On September 26, 2018, the NDPSC issued an order approving the settlement as filed but did not approve the SSIP recovery mechanism. On October 5, 2018, Montana-Dakota submitted a compliance filing, which included a plan for the one-time refund to be available March 1, 2019, for the interim amount to be refunded to customers. The NDPSC approved the compliance rates that were effective with service rendered on and after December 1, 2018. The interim refund of approximately $600,000 was credited to customers' bills on March 1, 2019. On January 10, 2018, the NDPSC issued a general order initiating the investigation into the effects of the TCJA. The order required regulatory deferral accounting on the impacts of the TCJA and for companies to file comments and the expected impacts. On February 15, 2018, Montana-Dakota filed a summary of the primary impacts of the TCJA on the electric and natural gas utilities. On March 9, 2018, Montana-Dakota submitted a request to decrease its electric rates by $7.2 million or 3.9 percent annually. On August 10, 2018, a settlement agreement was filed requesting a decrease in rates of approximately $8.4 million . On September 26, 2018, the NDPSC issued an order approving the settlement along with requiring an additional adjustment to the rates to return 100 percent of the tax-effective 2018 excess deferred income taxes. On October 10, 2018, Montana-Dakota submitted a compliance filing, which included a refund plan for the interim amount to be refunded to customers. On November 20, 2018, the NDPSC approved the compliance rates which were effective with service rendered on and after December 1, 2018. The NDPSC also approved a one-time refund of approximately $7.9 million to be credited to customers' bills by March 15, 2019, based on 4.7 percent of the revenues collected between January 1, 2018 through November 30, 2018. The TCJA refund was credited to customers' bills on March 15, 2019. On October 19, 2018, Great Plains and the NDPSC advocacy staff filed a settlement agreement to resolve all outstanding issues in the NDPSC's investigation into the TCJA and a revenue neutral tariff filing submitted by Great Plains. The settlement agreement provides for miscellaneous tariff changes and a reduction in annual revenues of $168,000 . On January 9, 2019, the NDPSC issued an order approving the settlement agreement and a refund requirement for the period from January 1, 2018 through the month preceding the effective date of the rate change. On January 23, 2019, the NDPSC approved the compliance rates which were effective February 1, 2019, along with the refund plan that provides for approximately $200,000 in refunds that were credited to customers' bills on April 12, 2019. OPUC On December 29, 2017, Cascade filed a request with the OPUC to use deferral accounting for the 2018 net benefits associated with the implementation of the TCJA. The deferral request was renewed on December 28, 2018. This matter is pending before the OPUC. On May 31, 2018, Cascade filed a general rate case with the OPUC requesting an overall increase to Cascade's natural gas rates of approximately $2.3 million or 3.5 percent on an annual basis, which incorporates the impact of the TCJA. On January 22, 2019, Cascade filed a stipulation with the OPUC for an annual increase in revenues of $1.7 million with a $500,000 reduction for excess deferred income taxes, for a net increase of $1.2 million . On March 14, 2019, the OPUC approved the settlement with rates effective April 1, 2019. SDPUC On December 29, 2017, the SDPUC issued an order initiating the investigation into the effects of the TCJA. The order required Montana-Dakota to provide comments by February 1, 2018, regarding the general effects of the TCJA on the cost of service in South Dakota and possible mechanisms for adjusting rates. The order also stated that all rates impacted by the federal income tax shall be adjusted effective January 1, 2018, subject to refund. On May 4, 2018 and June 2, 2018, Montana-Dakota submitted detailed plans to address the TCJA impacts on the natural gas and electric utilities, respectively, to the SDPUC staff. On September 28, 2018, a settlement agreement was submitted to the SDPUC reflecting a proposal to refund approximately $600,000 to electric customers and approximately $1.4 million to natural gas customers. These refunds reflect the impact of the TCJA on 2018. On October 23, 2018, an order was issued by the SDPUC approving the settlement agreement with the refunds being credited to customers' bills beginning on February 15, 2019. On December 3, 2018, Montana-Dakota submitted proposed rate changes to reflect 2018 pro forma results and the TCJA impacts. On December 28, 2018, the SDPUC approved an annual decrease in revenues of approximately $300,000 for the natural gas operations and approximately $100,000 for the electric operations. The decrease in revenues was effective January 1, 2019. The TCJA refund for both electric and natural gas was credited to customers' bills on February 15, 2019. WUTC On March 28, 2019, the WUTC approved an increase to Cascade's natural gas rates through an out-of-period purchased gas adjustment surcharge. The increase of approximately $48.0 million reflects unrecovered purchased gas costs from October 2018 through the end of January 2019 as a result of the rupture of the Enbridge pipeline in Canada on October 8, 2019, causing increased natural gas costs. The WUTC approved this amount, including interest, to be collected over three years beginning April 1, 2019. On March 29, 2019, Cascade filed a general rate case with the WUTC requesting an increase in annual revenue of $12.7 million or approximately 5.5 percent. This matter is pending before the WUTC. The WUTC has eleven months to process the request and issue an order. WYPSC On December 29, 2017, the WYPSC issued a general order requiring regulatory deferral accounting on the impacts of the TCJA. A technical conference was held on February 6, 2018, to discuss the implications of the TCJA. On March 23, 2018, the WYPSC issued an order requiring all public utilities to submit an initial assessment of the overall effects on the TCJA on their rates by March 30, 2018. On March 30, 2018, Montana-Dakota submitted its initial assessment indicating a rate reduction for its electric rates in the amount of approximately $1.1 million annually or approximately 4.2 percent. Revised electric rates reflecting this reduction were submitted to the WYPSC on June 13, 2018. Compliance rates were submitted to the WYPSC on April 4, 2019. On April 8, 2019, the WYPSC approved the Company's requested decrease in electric rates and required a refund to customers for the period from January 1, 2018 through the date prior to the implementation of the rates within 90 days of the effective date of the new rates. This matter is pending before the WYPSC. On March 30, 2018, Montana-Dakota reported its natural gas earnings do not support a decrease in rates and requested the WYPSC allow the impacts of the TCJA be addressed in a natural gas rate case to be submitted by June 1, 2019. This matter is pending before the WYPSC. FERC

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2019
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. The Company has accrued liabilities of $32.4 million , $37.4 million and $30.4 million , which have not been discounted, including liabilities held for sale, for contingencies, including litigation, production taxes, royalty claims and environmental matters at March 31, 2019 and 2018 , and December 31, 2018 , respectively. This includes amounts that have been accrued for matters discussed in Environmental matters within this note. The Company will continue to monitor each matter and adjust accruals as might be warranted based on new information and further developments. Management believes that the outcomes with respect to probable and reasonably possible losses in excess of the amounts accrued, net of insurance recoveries, while uncertain, either cannot be estimated or will not have a material effect upon the Company's financial position, results of operations or cash flows. Unless otherwise required by GAAP, legal costs are expensed as they are incurred. Environmental matters Portland Harbor Site In December 2000, Knife River - Northwest was named by the EPA as a PRP in connection with the cleanup of the Willamette River site adjacent to a commercial property site acquired by Knife River - Northwest from Georgia-Pacific West, Inc. The riverbed site is part of the Portland, Oregon, Harbor Superfund Site where the EPA wants responsible parties to share in the costs of cleanup. To date, costs of the overall remedial investigation and feasibility study of the harbor site are being recorded, and initially paid, through an administrative consent order by the LWG. Investigative costs are indicated to be in excess of $100 million . Remediation is expected to take up to 13 years with a present value cost estimate of approximately $1 billion . Corrective action will not be taken until remedial design/remedial action plans are approved by the EPA. Knife River - Northwest was also notified that the Portland Harbor Natural Resource Trustee Council intends to perform an injury assessment to natural resources resulting from the release of hazardous substances at the Harbor Superfund Site. It is not possible to estimate the costs of natural resource damages until an assessment is completed and allocations are undertaken. At this time, Knife River - Northwest does not believe it is a responsible party and has notified Georgia-Pacific West, Inc., that it intends to seek indemnity for liabilities incurred in relation to the above matters pursuant to the terms of their sale agreement. Knife River - Northwest has entered into an agreement tolling the statute of limitations in connection with the LWG's potential claim for contribution to the costs of the remedial investigation and feasibility study. LWG has stated its intent to file suit against Knife River - Northwest and others to recover LWG's investigation costs to the extent Knife River - Northwest cannot demonstrate its non-liability for the contamination or is unwilling to participate in an alternative dispute resolution process that has been established to address the matter. At this time, Knife River - Northwest has agreed to participate in the alternative dispute resolution process. The Company believes it is not probable that it will incur any material environmental remediation costs or damages in relation to the above referenced matter. Manufactured Gas Plant Sites There are three claims against Cascade for cleanup of environmental contamination at manufactured gas plant sites operated by Cascade's predecessors. The accruals related to these claims are reflected in regulatory assets. For more information, see Note 13 . The first claim is for contamination at a site in Eugene, Oregon, which was received in 1995. The Oregon DEQ released an ROD in January 2015 that selected a remediation alternative for the site as recommended in an earlier staff report. The total estimated cost for the selected remediation, including long-term maintenance, is approximately $3.5 million of which $400,000 has been incurred. Cascade and other PRPs will share in the cleanup costs with Cascade expecting to pay approximately 50 percent of the remediation and maintenance costs. Cascade has an accrual balance of $1.5 million for remediation of this site. In January 2013, the OPUC approved Cascade's application to defer environmental remediation costs at the Eugene site for a period of 12 months starting November 30, 2012. Cascade received orders reauthorizing the deferred accounting for the 12-month periods starting November 30, 2013, December 1, 2014, December 1, 2015, December 1, 2016, December 1, 2017 and December 1, 2018. The second claim is for contamination at the Bremerton Gasworks Superfund Site in Bremerton, Washington, which was received in 1997. A preliminary investigation has found soil and groundwater at the site contain contaminants requiring further investigation and cleanup. The EPA conducted a Targeted Brownfields Assessment of the site and released a report summarizing the results of that assessment in August 2009. The assessment confirms that contaminants have affected soil and groundwater at the site, as well as sediments in the adjacent Port Washington Narrows. Alternative remediation options have been identified with preliminary cost estimates ranging from $340,000 to $6.4 million . Data developed through the assessment and previous investigations indicates the contamination likely derived from multiple, different sources and multiple current and former owners of properties and businesses in the vicinity of the site may be responsible for the contamination. In April 2010, the Washington DOE issued notice it considered Cascade a PRP for hazardous substances at the site. In May 2012, the EPA added the site to the National Priorities List of Superfund sites. Cascade has entered into an administrative settlement agreement and consent order with the EPA regarding the scope and schedule for a remedial investigation and feasibility study for the site. Current estimates for the cost to complete the remedial investigation and feasibility study are approximately $7.6 million of which $3.3 million has been incurred. Cascade has accrued $4.3 million for the remedial investigation and feasibility study, as well as $6.4 million for remediation of this site; however, the accrual for remediation costs will be reviewed and adjusted, if necessary, after completion of the remedial investigation and feasibility study. In April 2010, Cascade filed a petition with the WUTC for authority to defer the costs incurred in relation to the environmental remediation of this site. The WUTC approved the petition in September 2010, subject to conditions set forth in the order. The third claim is for contamination at a site in Bellingham, Washington. Cascade received notice from a party in May 2008 that Cascade may be a PRP, along with other parties, for contamination from a manufactured gas plant owned by Cascade and its predecessor from about 1946 to 1962. Other PRPs reached an agreed order and work plan with the Washington DOE for completion of a remedial investigation and feasibility study for the site. A feasibility study prepared for one of the PRPs in March 2018 identifies five cleanup action alternatives for the site with estimated costs ranging from $8.0 million to $20.4 million with a selected preferred alternative having an estimated total cost of $9.3 million . The other PRPs will develop a cleanup action plan and, after public review of the cleanup action plan, develop design documents. Cascade believes its proportional share of any liability will be relatively small in comparison to other PRPs. The plant manufactured gas from coal between approximately 1890 and 1946. In 1946, shortly after Cascade's predecessor acquired the plant, it converted the plant to a propane-air gas facility. There are no documented wastes or by-products resulting from the mixing or distribution of propane-air gas. Cascade has recorded an accrual for this site for an amount that is not material. Cascade has received notices from and entered into agreement with certain of its insurance carriers that they will participate in defense of Cascade for certain of the contamination claims subject to full and complete reservations of rights and defenses to insurance coverage. To the extent these claims are not covered by insurance, Cascade intends to seek recovery through the OPUC and WUTC of remediation costs in its natural gas rates charged to customers. 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 who were the sellers in three purchase and sale agreements for periods ranging up to 10 years from the date of sale. 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 March 31, 2019 , the fixed maximum amounts guaranteed under these agreements aggregated $182.5 million . The amounts of scheduled expiration of the maximum amounts guaranteed under these agreements aggregate to $83.0 million in 2019 ; $92.5 million in 2020 ; $500,000 in 2021 ; $500,000 in 2022 ; $500,000 in 2023 ; $1.5 million thereafter; and $4.0 million , which has no scheduled maturity date. There were no amounts outstanding under the above guarantees at March 31, 2019 . 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 March 31, 2019 , the fixed maximum amounts guaranteed under these letters of credit aggregated $28.6 million . The amounts of scheduled expiration of the maximum amounts guaranteed under these letters of credit aggregate to $6.4 million in 2019 and $22.2 million in 2020 . There were no amounts outstanding under the above letters of credit at March 31, 2019 . 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 March 31, 2019 . 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 March 31, 2019 , approximately $903.9 million of surety bonds were outstanding, which were not reflected on the Consolidated Balance Sheet. Variable interest entities The Company evaluates its arrangements and contracts with other entities to determine if they are VIEs and if so, if the Company is the primary beneficiary. Fuel Contract Coyote Station entered into a coal supply agreement with Coyote Creek that provides for the purchase of coal necessary to supply the coal requirements of the Coyote Station for the period May 2016 through December 2040. Coal purchased under the coal supply agreement is reflected in inventories on the Company's 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 March 31, 2019 , 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 $37.9 million

Subsequent events

Subsequent events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent events	Subsequent Events On April 4, 2019, Centennial entered into a $150.0 million senior note purchase agreement with interest rates between 4.53 percent and 4.73 percent and maturities between April 4, 2029 and April 4, 2034. On April 12, 2019, Centennial entered into a $50.0 million

Basis of presentation (Policies

Basis of presentation (Policies)	3 Months Ended
	Mar. 31, 2019
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 2018

Accounts receivable and allow_2

Accounts receivable and allowance for doubtful accounts (Policies)	3 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Accounts receivable and allowance for doubtful accounts	Accounts receivable consists primarily of trade receivables from the sale of goods and services which are recorded at the invoiced amount net of allowance for doubtful accounts, and costs and estimated earnings in excess of billings on uncompleted contracts.The allowance for doubtful accounts is determined through a review of past due balances and other specific account data. 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)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventories and natural gas in storage	Natural gas in storage for the Company's regulated operations is generally carried at lower of cost or net realizable value, or cost using the last-in, first-out method. All other inventories are stated at the lower of cost or net realizable value.

Earnings per common share (Poli

Earnings per common share (Policies)	3 Months Ended
	Mar. 31, 2019
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.

New accounting standards (Polic

New accounting standards (Policies)	3 Months Ended
	Mar. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New accounting standards	Recently adopted accounting standards ASU 2016-02 - Leases In February 2016, the FASB issued guidance regarding leases. The guidance required lessees to recognize a lease liability and a right-of-use asset on the balance sheet for operating and financing leases. The guidance remained largely the same for lessors, although some changes were made to better align lessor accounting with the new lessee accounting and to align with the revenue recognition standard. The guidance also required additional disclosures, both quantitative and qualitative, related to operating and financing leases for the lessee and sales-type, direct financing and operating leases for the lessor. The Company adopted the standard on January 1, 2019. In July 2018, the FASB issued ASU 2018-11 - Leases: Targeted Improvements, an accounting standard update to ASU 2016-02. This ASU provided an entity the option to adopt the guidance using one of two modified retrospective approaches. An entity could adopt the guidance using the modified retrospective transition approach beginning in the earliest year presented in the financial statements. This method of adoption would have required the restatement of prior periods reported and the presentation of lease disclosures under the new guidance for all periods reported. The additional transition method of adoption, introduced by ASU 2018-11, allowed entities the option to apply the guidance on the date of adoption by recognizing a cumulative effect adjustment to retained earnings during the period of adoption and did not require prior comparative periods to be restated. The Company adopted the standard on January 1, 2019, utilizing the additional transition method of adoption applied on the date of adoption and the practical expedient that allowed the Company to not reassess whether an expired or existing contract contained a lease, the classification of leases or initial direct costs. The Company did not identify any cumulative effect adjustments. The Company also adopted a short-term leasing policy as the lessee where leases with a term of 12 months or less are not included on the Consolidated Balance Sheet. As a practical expedient, a lessee may choose not to separate nonlease components from lease components and instead account for lease and nonlease components as a single lease component. The election shall be made by asset class. The Company has elected to adopt the lease/nonlease component practical expedient for all asset classes as the lessee. The Company did not elect the practical expedient to use hindsight when assessing the lease term or impairment of right-of-use assets for the existing leases on the date of adoption. In January 2018, the FASB issued a practical expedient for land easements under the new lease guidance. The practical expedient permits an entity to elect the option to not evaluate land easements under the new guidance if they existed or expired before the adoption of the new lease guidance and were not previously accounted for as leases under the previous lease guidance. Once an entity adopts the new guidance, the entity should apply the new guidance on a prospective basis to all new or modified land easements. The Company has adopted this practical expedient. The Company formed a lease implementation team to review and assess existing contracts to identify and evaluate those containing leases. Additionally, the team implemented new and revised existing software to meet the reporting and disclosure requirements of the standard. The Company also assessed the impact the standard had on its processes and internal controls and identified new and updated existing internal controls and processes to ensure compliance with the new lease standard; such modifications were not deemed to be significant. During the assessment phase, the Company used various surveys, reconciliations and analytic methodologies to ensure the completeness of the lease inventory. The Company determined that most of the current operating leases were subject to the guidance and were recognized as operating lease liabilities and right-of-use assets on the Consolidated Balance Sheet upon adoption. On January 1, 2019, the Company recorded approximately $112 million to right-of-use assets and lease liabilities as a result of the initial adoption of the guidance. In addition, the Company evaluated the impact the new guidance had on lease contracts where the Company is the lessor and determined it did not have a significant impact. ASU 2018-15 - Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract In August 2018, the FASB issued guidance on the accounting for implementation costs of a hosting arrangement that is a service contract. The guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract similar to the costs incurred to develop or obtain internal-use software and such capitalized costs to be expensed over the term of the hosting arrangement. Costs incurred during the preliminary and postimplementation stages should continue to be expensed as activities are performed. The capitalized costs are required to be presented on the balance sheet in the same line the prepayment for the fees associated with the hosting arrangement would be presented. In addition, the expense related to the capitalized implementation costs should be presented in the same line on the income statement as the fees associated with the hosting element of the arrangements. The Company adopted the guidance effective January 1, 2019, on a prospective basis. The adoption of the guidance did not have a material impact on its results of operations, financial position, cash flows, and disclosures. Recently issued accounting standards not yet adopted ASU 2017-04 - Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued guidance on simplifying the test for goodwill impairment by eliminating Step 2, which required an entity to measure the amount of impairment loss by comparing the implied fair value of reporting unit goodwill with the carrying amount of such goodwill. This guidance requires entities to perform a quantitative impairment test, previously Step 1, to identify both the existence of impairment and the amount of impairment loss by comparing the fair value of a reporting unit to its carrying amount. Entities will continue to have the option of performing a qualitative assessment to determine if the quantitative impairment test is necessary. The guidance also requires additional disclosures if an entity has one or more reporting units with zero or negative carrying amounts of net assets. The guidance will be effective for the Company on January 1, 2020, and must be applied on a prospective basis with early adoption permitted. The Company is evaluating the guidance and does not expect it to have a material impact on its results of operations, financial position, cash flows and disclosures. 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 modifies, among other things, the disclosures required for Level 3 fair value measurements, including the range and weighted average of significant unobservable inputs. The guidance removes, among other things, the disclosure requirement to disclose transfers between Levels 1 and 2. The guidance will be effective for the Company on January 1, 2020, including interim periods, with early adoption permitted. Level 3 fair value measurement disclosures should be applied prospectively while all other amendments should be applied retrospectively. The Company is evaluating the effects the adoption of the new guidance will have on its disclosures. 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 2018-18 - Clarifying the Interaction between Topic 808 and Topic 606

Revenue from contracts with c_2

Revenue from contracts with customers (Policies)	3 Months Ended
	Mar. 31, 2019
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)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Business Combinations Policy [Policy Text Block]	Business combinations were accounted for in accordance with ASC 805 - Business Combinations . The results of the acquired businesses have been included in the Company's construction materials and contracting segment and Consolidated Financial Statements beginning on the acquisition date. Pro forma financial amounts reflecting the effects of the business combinations are not presented, as these business combinations were not material to the Company's financial position or results of operations.

Leases (Policies)

Leases (Policies)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lessee, Leases [Policy Text Block]	The leases the Company has entered into as part of their ongoing operations are considered operating leases and are recognized on the balance sheet as right-of-use assets, current lease liabilities and, if applicable, noncurrent lease liabilities. Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The Company determines the lease term based on the non-cancelable and cancelable periods in each contract. The non-cancelable period consists of the term of the contract that is legally enforceable and cannot be canceled by either party without incurring a significant penalty. The cancelable period is determined by various factors that are based on who has the right to cancel a contract. If only the lessor has the right to cancel the contract, the Company will assume the contract will continue. If the lessee is the only party that has the right to cancel the contract, the Company looks to asset, entity and market-based factors. If both the lessor and the lessee have the right to cancel the contract, the Company assumes the contract will not continue.

Fair value disclosures (Policie

Fair value disclosures (Policies)	3 Months Ended
	Mar. 31, 2019
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. The available-for-sale securities 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)	3 Months Ended
	Mar. 31, 2019
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)	3 Months Ended
	Mar. 31, 2019
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.

Inventories and natural gas i_3

Inventories and natural gas in storage (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventories	Inventories on the Consolidated Balance Sheets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Aggregates held for resale $ 142,747 $ 123,053 $ 139,681 Asphalt oil 83,459 61,647 54,741 Materials and supplies 26,441 19,493 23,611 Merchandise for resale 25,104 16,378 22,552 Natural gas in storage (current) 11,464 10,936 22,117 Other 22,320 26,285 24,607 Total $ 311,535 $ 257,792 $ 287,309

Earnings per common share (Tabl

Earnings per common share (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 (In thousands, except per share amounts) Weighted average common shares outstanding - basic 196,401 195,304 Effect of dilutive performance share awards and restricted stock units 13 678 Weighted average common shares outstanding - diluted 196,414 195,982 Shares excluded from the calculation of diluted earnings per share 64 — Dividends declared per common share $ .2025 $ .1975

Comprehensive income (loss) (Ta

Comprehensive income (loss) (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Accumulated comprehensive loss	The after-tax changes in the components of accumulated other comprehensive loss were as follows: Three Months Ended March 31, 2019 Net Unrealized Gain (Loss) on Derivative Postretirement Net Unrealized Total (In thousands) Balance at beginning of period $ (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 Balance at end of period $ (1,764 ) $ (35,759 ) $ (45 ) $ (37,568 ) Three Months Ended March 31, 2018 Net Unrealized Gain (Loss) on Derivative Postretirement Foreign Net Unrealized Total (In thousands) Balance at beginning of period $ (1,934 ) $ (35,163 ) $ (155 ) $ (82 ) $ (37,334 ) Other comprehensive loss before reclassifications — — (2 ) (105 ) (107 ) Amounts reclassified from accumulated other comprehensive loss 92 418 — 30 540 Net current-period other comprehensive income (loss) 92 418 (2 ) (75 ) 433 Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss (389 ) (7,520 ) (33 ) (17 ) (7,959 ) Balance at end of period $ (2,231 ) $ (42,265 ) $ (190 ) $ (174 ) $ (44,860 )
Reclassification out of accumulated other comprehensive loss	The following amounts were reclassified out of accumulated other comprehensive loss into net income. The amounts presented in parenthesis indicate a decrease to net income on the Consolidated Statements of Income. The reclassifications were as follows: Three Months Ended Location on Consolidated Statements of Income March 31, 2019 2018 (In thousands) Reclassification adjustment for loss on derivative instruments included in net income $ (148 ) $ (148 ) Interest expense (249 ) 56 Income taxes (397 ) (92 ) Amortization of postretirement liability losses included in net periodic benefit cost (credit) (410 ) (573 ) Other income 100 155 Income taxes (310 ) (418 ) Reclassification adjustment on available-for-sale investments included in net income (35 ) (37 ) Other income 7 7 Income taxes (28 ) (30 ) Total reclassifications $ (735 ) $ (540 )

Revenue from contracts with c_3

Revenue from contracts with customers (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of revenue	In the following table, revenue is disaggregated by the type of customer or service provided. The Company believes this level of disaggregation best depicts how the nature, amount, timing and uncertainty of revenue and cash flows are affected by economic factors. The table also includes a reconciliation of the disaggregated revenue by reportable segments. For more information on the Company's business segments, see Note 17 . Three Months Ended March 31, 2019 Electric Natural gas distribution Pipeline and midstream Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 36,555 $ 200,609 $ — $ — $ — $ — $ 237,164 Commercial utility sales 35,671 121,793 — — — — 157,464 Industrial utility sales 8,884 8,611 — — — — 17,495 Other utility sales 1,799 — — — — — 1,799 Natural gas transportation — 11,570 25,058 — — — 36,628 Natural gas gathering — — 2,121 — — — 2,121 Natural gas storage — — 2,646 — — — 2,646 Contracting services — — — 83,039 — — 83,039 Construction materials — — — 179,309 — — 179,309 Intrasegment eliminations* — — — (35,140 ) — — (35,140 ) Inside specialty contracting — — — — 299,530 — 299,530 Outside specialty contracting — — — — 107,398 — 107,398 Other 9,121 3,913 2,696 — 17 7,843 23,590 Intersegment eliminations — — (23,955 ) (95 ) (129 ) (7,824 ) (32,003 ) Revenues from contracts with customers 92,030 346,496 8,566 227,113 406,816 19 1,081,040 Revenues out of scope 536 (4,349 ) 47 — 13,917 — 10,151 Total external operating revenues $ 92,566 $ 342,147 $ 8,613 $ 227,113 $ 420,733 $ 19 $ 1,091,191 * Intrasegment revenues are presented 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. Three Months Ended March 31, 2018 Electric Natural gas distribution Pipeline and midstream Construction materials and contracting Construction services Other Total (In thousands) Residential utility sales $ 35,183 $ 192,886 $ — $ — $ — $ — $ 228,069 Commercial utility sales 34,701 116,891 — — — — 151,592 Industrial utility sales 8,770 7,809 — — — — 16,579 Other utility sales 1,836 — — — — — 1,836 Natural gas transportation — 11,179 21,818 — — — 32,997 Natural gas gathering — — 2,270 — — — 2,270 Natural gas storage — — 3,134 — — — 3,134 Contracting services — — — 74,064 — — 74,064 Construction materials — — — 173,591 — — 173,591 Intrasegment eliminations* — — — (34,270 ) — — (34,270 ) Inside specialty contracting — — — — 233,821 — 233,821 Outside specialty contracting — — — — 87,181 — 87,181 Other 8,252 3,999 3,326 — (86 ) 2,696 18,187 Intersegment eliminations — — (21,759 ) (101 ) (11 ) (2,638 ) (24,509 ) Revenues from contracts with customers 88,742 332,764 8,789 213,284 320,905 58 964,542 Revenues out of scope (1,338 ) (100 ) 44 — 13,145 — 11,751 Total external operating revenues $ 87,404 $ 332,664 $ 8,833 $ 213,284 $ 334,050 $ 58 $ 976,293 * Intrasegment revenues are presented 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 changes in contract assets and liabilities were as follows: March 31, 2019 December 31, 2018 Change Location on Consolidated Balance Sheets (In thousands) Contract assets $ 117,036 $ 104,239 $ 12,797 Receivables, net Contract liabilities - current (86,031 ) (93,901 ) 7,870 Accounts payable Contract liabilities - noncurrent (30 ) (135 ) 105 Deferred credits and other liabilities - other Net contract assets $ 30,975 $ 10,203 $ 20,772

Discontinued operations (Tables

Discontinued operations (Tables)	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Disposal groups, including discontinued operations	The carrying amounts of the major classes of assets and liabilities classified as held for sale on the Consolidated Balance Sheets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Assets Current assets: Receivables, net $ 430 $ 458 $ 430 Income taxes receivable (a) — 1,858 — Total current assets held for sale 430 2,316 430 Noncurrent assets: Net property, plant and equipment — 1,631 — Deferred income taxes 1,926 2,637 1,926 Other 161 161 161 Total noncurrent assets held for sale 2,087 4,429 2,087 Total assets held for sale $ 2,517 $ 6,745 $ 2,517 Liabilities Current liabilities: Accounts payable $ — $ — $ 80 Taxes payable 1,295 10,774 1,451 Other accrued liabilities 2,362 2,810 2,470 Total current liabilities held for sale 3,657 13,584 4,001 Noncurrent liabilities: Deferred income taxes (b) — 37 — Total noncurrent liabilities held for sale — 37 — Total liabilities held for sale $ 3,657 $ 13,621 $ 4,001 (a) On the Company's Consolidated Balance Sheets, these amounts were reclassified to taxes payable and are reflected in current liabilities held for sale. (b) On the Company's Consolidated Balance Sheets, these amounts were reclassified to deferred charges and other assets - deferred income taxes and are reflected in noncurrent assets held for sale.
Reconciliation of major classes of income and expense	The reconciliation of the major classes of income and expense constituting pretax loss from discontinued operations to the after-tax income (loss) from discontinued operations on the Consolidated Statements of Income was as follows: Three Months Ended March 31, 2019 2018 (In thousands) Operating revenues $ 30 $ 66 Operating expenses 245 174 Operating loss (215 ) (108 ) Other income — 12 Interest expense — 575 Loss from discontinued operations before income taxes (215 ) (671 ) Income taxes (52 ) (1,148 ) Income (loss) from discontinued operations $ (163 ) $ 477

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease, Cost [Table Text Block]	The following table provides information on the Company's operating leases for the three months ended: March 31, 2019 (Dollars in thousands) Weighted average remaining lease term 2.63 years Weighted average discount rate 4.51 % Cash paid for amounts included in the measurement of lease liabilities $ 11,467 Lease costs: Operating lease cost $ 11,521 Variable lease cost 399 Short-term lease cost 17,238 Total lease costs $ 29,158
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The reconciliation of the future undiscounted cash flows to the operating lease liabilities presented on the Company's Consolidated Balance Sheet is as follows: March 31, 2019 (In thousands) Remainder of 2019 $ 26,655 2020 25,743 2021 18,503 2022 11,886 2023 6,723 Thereafter 43,401 Total 132,911 Less discount 25,489 Total operating lease liabilities $ 107,422 As previously disclosed in the 2018 Annual Report, the undiscounted annual minimum lease payments due under the Company's leases following the previous lease accounting standard as of December 31, 2018, were as follows: 2019 2020 2021 2022 2023 Thereafter (In thousands) Operating leases $ 37,740 $ 26,255 $ 17,868 $ 11,647 $ 7,278 $ 49,098

Goodwill and other intangible_2

Goodwill and other intangible assets (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	The changes in the carrying amount of goodwill were as follows: Three Months Ended March 31, 2019 Balance at January 1, 2019 Goodwill Acquired the Year Balance at March 31, 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 Three Months Ended March 31, 2018 Balance at January 1, 2018 Goodwill Acquired the Year Balance at March 31, 2018 (In thousands) Natural gas distribution $ 345,736 $ — $ 345,736 Construction materials and contracting 176,290 — 176,290 Construction services 109,765 — 109,765 Total $ 631,791 $ — $ 631,791 Year Ended December 31, 2018 Balance at January 1, 2018 Goodwill Acquired the Year Balance at December 31, 2018 (In thousands) Natural gas distribution $ 345,736 $ — $ 345,736 Construction materials and contracting 176,290 33,131 209,421 Construction services 109,765 — 109,765 Total $ 631,791 $ 33,131 $ 664,922
Other amortizable intangible assets	Other amortizable intangible assets were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Customer relationships $ 14,471 $ 14,668 $ 22,720 Less accumulated amortization 5,156 13,007 13,535 9,315 1,661 9,185 Noncompete agreements 3,179 2,430 2,605 Less accumulated amortization 1,730 1,842 1,956 1,449 588 649 Other 6,458 6,458 6,458 Less accumulated amortization 5,542 5,242 5,477 916 1,216 981 Total $ 11,680 $ 3,465 $ 10,815
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	Estimated amortization expense for identifiable intangible assets as of March 31, 2019 , was: Remainder of 2019 2020 2021 2022 2023 Thereafter (In thousands) Amortization expense $ 1,403 $ 1,632 $ 1,242 $ 1,219 $ 1,237 $ 4,947

Regulatory assets and liabili_2

Regulatory assets and liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Assets	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery Period * March 31, 2019 December 31, 2018 (In thousands) Regulatory assets: Pension and postretirement benefits (a) (e) $ 165,879 $ 165,898 Natural gas costs recoverable through rate adjustments (a) (b) Up to 3 years 91,465 42,652 Asset retirement obligations (a) Over plant lives 63,633 60,097 Cost recovery mechanisms (a) (b) Up to 4 years 17,835 17,948 Manufactured gas plant site remediation (a) - 17,111 17,068 Taxes recoverable from customers (a) Over plant lives 11,858 11,946 Plant to be retired (a) - 6,691 — Conservation programs (b) Up to 1 year 6,094 7,494 Long-term debt refinancing costs (a) Up to 19 years 4,746 4,898 Costs related to identifying generation development (a) Up to 8 years 2,394 2,508 Other (a) (b) Up to 20 years 5,827 9,608 Total regulatory assets 393,533 340,117 Regulatory liabilities: Taxes refundable to customers (c) (d) 267,777 277,833 Plant removal and decommissioning costs (c) (d) 173,911 173,143 Natural gas costs refundable through rate adjustments (d) 29,739 29,995 Pension and postretirement benefits (c) 12,991 15,264 Other (c) (d) 33,976 25,197 Total regulatory liabilities 518,394 521,432 Net regulatory position $ (124,861 ) $ (181,315 ) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. (a) Included in deferred charges and other assets - other on the Consolidated Balance Sheets. (b) Included in prepayments and other current assets on the Consolidated Balance Sheets. (c) Included in deferred credits and other liabilities - other on the Consolidated Balance Sheets. (d) Included in other accrued liabilities on the Consolidated Balance Sheets. (e) Recovered as expense is incurred or cash contributions are made.
Regulatory Liabilities	The following table summarizes the individual components of unamortized regulatory assets and liabilities: Estimated Recovery Period * March 31, 2019 December 31, 2018 (In thousands) Regulatory assets: Pension and postretirement benefits (a) (e) $ 165,879 $ 165,898 Natural gas costs recoverable through rate adjustments (a) (b) Up to 3 years 91,465 42,652 Asset retirement obligations (a) Over plant lives 63,633 60,097 Cost recovery mechanisms (a) (b) Up to 4 years 17,835 17,948 Manufactured gas plant site remediation (a) - 17,111 17,068 Taxes recoverable from customers (a) Over plant lives 11,858 11,946 Plant to be retired (a) - 6,691 — Conservation programs (b) Up to 1 year 6,094 7,494 Long-term debt refinancing costs (a) Up to 19 years 4,746 4,898 Costs related to identifying generation development (a) Up to 8 years 2,394 2,508 Other (a) (b) Up to 20 years 5,827 9,608 Total regulatory assets 393,533 340,117 Regulatory liabilities: Taxes refundable to customers (c) (d) 267,777 277,833 Plant removal and decommissioning costs (c) (d) 173,911 173,143 Natural gas costs refundable through rate adjustments (d) 29,739 29,995 Pension and postretirement benefits (c) 12,991 15,264 Other (c) (d) 33,976 25,197 Total regulatory liabilities 518,394 521,432 Net regulatory position $ (124,861 ) $ (181,315 ) * Estimated recovery period for regulatory assets currently being recovered in rates charged to customers. (a) Included in deferred charges and other assets - other on the Consolidated Balance Sheets. (b) Included in prepayments and other current assets on the Consolidated Balance Sheets. (c) Included in deferred credits and other liabilities - other on the Consolidated Balance Sheets. (d) Included in other accrued liabilities on the Consolidated Balance Sheets. (e) Recovered as expense is incurred or cash contributions are made.

Fair value measurements (Tables

Fair value measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Available-for-sale securities	Details of available-for-sale securities were as follows: March 31, 2019 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,679 $ 31 $ 88 $ 10,622 U.S. Treasury securities 179 — — 179 Total $ 10,858 $ 31 $ 88 $ 10,801 March 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,282 $ 4 $ 223 $ 10,063 U.S. Treasury securities 466 — 1 465 Total $ 10,748 $ 4 $ 224 $ 10,528 December 31, 2018 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (In thousands) Mortgage-backed securities $ 10,473 $ 21 $ 162 $ 10,332 U.S. Treasury securities 179 — — 179 Total $ 10,652 $ 21 $ 162 $ 10,511
Assets and liabilities measured at fair value on a recurring basis	The Company's assets and liabilities measured at fair value on a recurring basis were as follows: Fair Value Measurements at March 31, 2019, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at March 31, 2019 (In thousands) Assets: Money market funds $ — $ 10,540 $ — $ 10,540 Insurance contract* — 80,243 — 80,243 Available-for-sale securities: Mortgage-backed securities — 10,622 — 10,622 U.S. Treasury securities — 179 — 179 Total assets measured at fair value $ — $ 101,584 $ — $ 101,584 * 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, 11 percent in common stock of small-cap companies, 3 percent in target date investments and 1 percent in cash equivalents. Fair Value Measurements at March 31, 2018, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at March 31, 2018 (In thousands) Assets: Money market funds $ — $ 9,085 $ — $ 9,085 Insurance contract* — 76,941 — 76,941 Available-for-sale securities: Mortgage-backed securities — 10,063 — 10,063 U.S. Treasury securities — 465 — 465 Total assets measured at fair value $ — $ 96,554 $ — $ 96,554 * The insurance contract invests approximately 49 percent in fixed-income investments, 22 percent in common stock of large-cap companies, 13 percent in common stock of mid-cap companies, 11 percent in common stock of small-cap companies, 3 percent in target date investments and 2 percent in cash equivalents. Fair Value Measurements at December 31, 2018, Using Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance at December 31, 2018 (In thousands) Assets: Money market funds $ — $ 10,799 $ — $ 10,799 Insurance contract* — 73,838 — 73,838 Available-for-sale securities: Mortgage-backed securities — 10,332 — 10,332 U.S. Treasury securities — 179 — 179 Total assets measured at fair value $ — $ 95,148 $ — $ 95,148 * The insurance contract invests approximately 53 percent in fixed-income investments, 21 percent in common stock of large-cap companies, 11 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 3 percent in target date investments and 2 percent in cash equivalents.
Fair value of long term debt outstanding	The estimated fair value of the Company's Level 2 long-term debt was as follows: Carrying Amount Fair Value (In thousands) Long-term debt at March 31, 2019 $ 2,198,027 $ 2,263,305 Long-term debt at March 31, 2018 $ 1,779,542 $ 1,854,350 Long-term debt at December 31, 2018 $ 2,108,695 $ 2,183,819

Debt Debt (Tables)

Debt Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Long-term debt outstanding	Long-term debt outstanding was as follows: Weighted Average Interest Rate at March 31, 2019 March 31, 2019 December 31, 2018 (In thousands) Senior Notes due on dates ranging from July 1, 2019 to January 15, 2055 4.57 % $ 1,381,000 $ 1,381,000 Commercial paper supported by revolving credit agreements 2.97 % 473,900 338,100 Term Loan Agreements due on dates ranging from October 17, 2019 to September 3, 2032 2.75 % 209,800 209,800 Credit agreements due on April 24, 2020 4.42 % 62,875 110,100 Medium-Term Notes due on dates ranging from September 1, 2020 to March 16, 2029 6.68 % 50,000 50,000 Other notes due on dates ranging from July 1, 2019 to November 30, 2038 5.00 % 26,251 25,229 Less unamortized debt issuance costs 5,410 5,207 Less discount 389 327 Total long-term debt 2,198,027 2,108,695 Less current maturities 251,846 251,854 Net long-term debt $ 1,946,181 $ 1,856,841
Schedule of debt maturities	Long-term debt maturities, which excludes unamortized debt issuance costs and discount, as of March 31, 2019 , were as follows: Remainder of 2019 2020 2021 2022 2023 Thereafter (In thousands) Long-term debt maturities $ 251,846 $ 78,801 $ 431,930 $ 147,434 $ 120,239 $ 1,173,576

Cash flow information (Tables)

Cash flow information (Tables)	3 Months Ended
	Mar. 31, 2019
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: Three Months Ended March 31, 2019 2018 (In thousands) Interest, net* $ 19,067 $ 17,910 Income taxes paid (refunded), net** $ 29 $ (1,056 ) * AFUDC - borrowed was $556,000 and $382,000 for the three months ended March 31, 2019 and 2018 , respectively. ** Income taxes paid, net of discontinued operations, were $132,000 and $1.7 million for the three months ended March 31, 2019 and 2018 , respectively. Noncash investing and financing transactions were as follows: March 31, 2019 March 31, 2018 December 31, 2018 (In thousands) Right-of-use assets obtained in exchange for new operating lease liabilities $ 2,731 $ — $ — Property, plant and equipment additions in accounts payable $ 27,655 $ 16,829 $ 42,355 Debt assumed in connection with a business combination $ 1,163 $ — $ — Issuance of common stock in connection with a business combination $ — $ — $ 18,186

Business segment data (Tables)

Business segment data (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Information on the Company's businesses	Information on the Company's segments was as follows: Three Months Ended March 31, 2019 2018 (In thousands) External operating revenues: Regulated operations: Electric $ 92,566 $ 87,404 Natural gas distribution 342,147 332,664 Pipeline and midstream 4,904 4,391 439,617 424,459 Nonregulated operations: Pipeline and midstream 3,709 4,442 Construction materials and contracting 227,113 213,284 Construction services 420,733 334,050 Other 19 58 651,574 551,834 Total external operating revenues $ 1,091,191 $ 976,293 Intersegment operating revenues: Regulated operations: Electric $ — $ — Natural gas distribution — — Pipeline and midstream 23,922 21,735 23,922 21,735 Nonregulated operations: Pipeline and midstream 33 24 Construction materials and contracting 95 101 Construction services 129 11 Other 7,824 2,638 8,081 2,774 Intersegment eliminations (32,003 ) (24,509 ) Total intersegment operating revenues $ — $ — Three Months Ended March 31, 2019 2018 (In thousands) Operating income (loss): Electric $ 17,987 $ 18,154 Natural gas distribution 50,317 48,540 Pipeline and midstream 9,904 8,168 Construction materials and contracting (41,580 ) (26,309 ) Construction services 27,465 20,634 Other 125 189 Total operating income $ 64,218 $ 69,376 Net income: Regulated operations: Electric $ 15,505 $ 13,084 Natural gas distribution 36,500 32,623 Pipeline and midstream 7,004 5,459 59,009 51,166 Nonregulated operations: Pipeline and midstream (163 ) (179 ) Construction materials and contracting (34,449 ) (23,521 ) Construction services 20,024 15,090 Other (3,332 ) (596 ) (17,920 ) (9,206 ) Income from continuing operations 41,089 41,960 Income (loss) from discontinued operations, net of tax (163 ) 477 Net income $ 40,926 $ 42,437

Employee benefit plans (Tables)

Employee benefit plans (Tables)	3 Months Ended
	Mar. 31, 2019
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 Postretirement Benefits Three Months Ended March 31, 2019 2018 2019 2018 (In thousands) Components of net periodic benefit cost (credit): Service cost $ — $ — $ 344 $ 407 Interest cost 3,773 3,807 780 778 Expected return on assets (5,120 ) (4,998 ) (1,220 ) (1,167 ) Amortization of prior service credit — — (252 ) (349 ) Amortization of net actuarial loss 1,355 1,782 — 238 Net periodic benefit cost (credit), including amount capitalized 8 591 (348 ) (93 ) Less amount capitalized — — 31 40 Net periodic benefit cost (credit) $ 8 $ 591 $ (379 ) $ (133 )

Accounts receivable and allow_3

Accounts receivable and allowance for doubtful accounts (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Receivables [Abstract]
Receivables past due 90 days or more	$ 38.3	$ 30	$ 36.3
Allowance for doubtful accounts receivable	$ 9.6	$ 8.9	$ 8.2

Inventories and natural gas i_4

Inventories and natural gas in storage (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Inventory Disclosure [Abstract]
Aggregates held for resale	$ 142,747	$ 139,681	$ 123,053
Asphalt oil	83,459	54,741	61,647
Materials and supplies	26,441	23,611	19,493
Merchandise for resale	25,104	22,552	16,378
Natural gas in storage (current)	11,464	22,117	10,936
Other	22,320	24,607	26,285
Total	311,535	287,309	257,792
Natural gas in storage noncurrent	$ 48,200	$ 48,500	$ 47,800

Earnings per common share (Deta

Earnings per common share (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Weighted average common shares outstanding - basic	196,401	195,304
Effect of dilutive performance share awards and restricted stock units	13	678
Weighted average common shares outstanding - diluted	196,414	195,982
Shares excluded from the calculation of diluted earnings per share	64	0
Dividends declared per common share	$ 0.2025	$ 0.1975

New accounting standards ASU 20

New accounting standards ASU 2016-02 (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 112

Comprehensive income (loss) (De

Comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	$ 2,566,775	$ 2,429,043
Other comprehensive income	774	433
Balance	2,605,692	2,426,111
Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(2,161)	(1,934)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	397	92
Other comprehensive income	397	92
Balance	(1,764)	(2,231)
Postretirement liability adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(36,069)	(35,163)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	310	418
Other comprehensive income	310	418
Balance	(35,759)	(42,265)
Foreign currency translation adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Balance		(155)
Other comprehensive income before reclassifications		(2)
Amounts reclassified from accumulated other comprehensive loss		0
Other comprehensive income		(2)
Balance		(190)
Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(112)	(82)
Other comprehensive income before reclassifications	39	(105)
Amounts reclassified from accumulated other comprehensive loss	28	30
Other comprehensive income	67	(75)
Balance	(45)	(174)
Total accumulated other comprehensive loss
Accumulated other comprehensive income (loss) [Roll Forward]
Balance	(38,342)	(37,334)
Other comprehensive income before reclassifications	39	(107)
Amounts reclassified from accumulated other comprehensive loss	735	540
Other comprehensive income	774	433
Balance	$ (37,568)	(44,860)
Tax Cuts and Jobs Act [Member] | Adjustments for New Accounting Principle, Early Adoption [Member] | Net unrealized gain (loss) on derivative instruments qualifying as hedges
Accumulated other comprehensive income (loss) [Roll Forward]
Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss		(389)
Tax Cuts and Jobs Act [Member] | Adjustments for New Accounting Principle, Early Adoption [Member] | Postretirement liability adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss		(7,520)
Tax Cuts and Jobs Act [Member] | Adjustments for New Accounting Principle, Early Adoption [Member] | Foreign currency translation adjustment
Accumulated other comprehensive income (loss) [Roll Forward]
Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss		(33)
Tax Cuts and Jobs Act [Member] | Adjustments for New Accounting Principle, Early Adoption [Member] | Net unrealized gain (loss) on available-for-sale investments
Accumulated other comprehensive income (loss) [Roll Forward]
Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss		(17)
Tax Cuts and Jobs Act [Member] | Adjustments for New Accounting Principle, Early Adoption [Member] | Total accumulated other comprehensive loss
Accumulated other comprehensive income (loss) [Roll Forward]
Reclassification adjustment of prior period tax effects related to TCJA included in accumulated other comprehensive loss		$ (7,959)

Reclassification out of accumul

Reclassification out of accumulated other comprehensive income (loss) (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Interest expense	$ (23,407)	$ (20,447)
Other income	7,595	582
Income taxes	(7,317)	(7,551)
Net Income	40,926	42,437
Reclassification out of accumulated other comprehensive income
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Net Income	(735)	(540)
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)	(148)
Income taxes	(249)	56
Net Income	(397)	(92)
Amortization of postretirement liability losses included in net periodic benefit cost (credit) | Reclassification out of accumulated other comprehensive income
Reclassification adjustment out of accumulated other comprehensive income [Line Items]
Other income	(410)	(573)
Income taxes	100	155
Net Income	(310)	(418)
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]
Other income	(35)	(37)
Income taxes	7	7
Net Income	$ (28)	$ (30)

Disaggregation of revenue (Deta

Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,091,191	$ 976,293
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(32,003)	(24,509)
Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(35,140)	(34,270)
Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	36,628	32,997
Natural gas gathering
Disaggregation of Revenue [Line Items]
Revenues	2,121	2,270
Natural gas storage
Disaggregation of Revenue [Line Items]
Revenues	2,646	3,134
Contracting services
Disaggregation of Revenue [Line Items]
Revenues	83,039	74,064
Construction materials
Disaggregation of Revenue [Line Items]
Revenues	179,309	173,591
Inside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	299,530	233,821
Outside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	107,398	87,181
Other
Disaggregation of Revenue [Line Items]
Revenues	23,590	18,187
Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	1,081,040	964,542
Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	10,151	11,751
Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	237,164	228,069
Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	157,464	151,592
Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	17,495	16,579
Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	1,799	1,836
Electric
Disaggregation of Revenue [Line Items]
Revenues	92,566	87,404
Electric | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	0	0
Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	9,121	8,252
Electric | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	92,030	88,742
Electric | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	536	(1,338)
Electric | Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	36,555	35,183
Electric | Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	35,671	34,701
Electric | Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	8,884	8,770
Electric | Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	1,799	1,836
Natural gas distribution
Disaggregation of Revenue [Line Items]
Revenues	342,147	332,664
Natural gas distribution | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	0	0
Natural gas distribution | Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	11,570	11,179
Natural gas distribution | Other
Disaggregation of Revenue [Line Items]
Revenues	3,913	3,999
Natural gas distribution | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	346,496	332,764
Natural gas distribution | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	(4,349)	(100)
Natural gas distribution | Residential utility sales
Disaggregation of Revenue [Line Items]
Revenues	200,609	192,886
Natural gas distribution | Commercial utility sales
Disaggregation of Revenue [Line Items]
Revenues	121,793	116,891
Natural gas distribution | Industrial utility sales
Disaggregation of Revenue [Line Items]
Revenues	8,611	7,809
Natural gas distribution | Other utility sales
Disaggregation of Revenue [Line Items]
Revenues	0	0
Pipeline and midstream
Disaggregation of Revenue [Line Items]
Revenues	8,613	8,833
Pipeline and midstream | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(23,955)	(21,759)
Pipeline and midstream | Natural gas transportation
Disaggregation of Revenue [Line Items]
Revenues	25,058	21,818
Pipeline and midstream | Natural gas gathering
Disaggregation of Revenue [Line Items]
Revenues	2,121	2,270
Pipeline and midstream | Natural gas storage
Disaggregation of Revenue [Line Items]
Revenues	2,646	3,134
Pipeline and midstream | Other
Disaggregation of Revenue [Line Items]
Revenues	2,696	3,326
Pipeline and midstream | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	8,566	8,789
Pipeline and midstream | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	47	44
Construction materials and contracting
Disaggregation of Revenue [Line Items]
Revenues	227,113	213,284
Construction materials and contracting | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(95)	(101)
Construction materials and contracting | Intrasegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(35,140)	(34,270)
Construction materials and contracting | Contracting services
Disaggregation of Revenue [Line Items]
Revenues	83,039	74,064
Construction materials and contracting | Construction materials
Disaggregation of Revenue [Line Items]
Revenues	179,309	173,591
Construction materials and contracting | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0
Construction materials and contracting | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	227,113	213,284
Construction materials and contracting | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	0	0
Construction services
Disaggregation of Revenue [Line Items]
Revenues	420,733	334,050
Construction services | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(129)	(11)
Construction services | Inside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	299,530	233,821
Construction services | Outside specialty contracting
Disaggregation of Revenue [Line Items]
Revenues	107,398	87,181
Construction services | Other
Disaggregation of Revenue [Line Items]
Revenues	17	(86)
Construction services | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	406,816	320,905
Construction services | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	13,917	13,145
Other
Disaggregation of Revenue [Line Items]
Revenues	19	58
Other | Intersegment eliminations
Disaggregation of Revenue [Line Items]
Revenues	(7,824)	(2,638)
Other | Other
Disaggregation of Revenue [Line Items]
Revenues	7,843	2,696
Other | Revenues from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	19	58
Other | Revenues out of scope
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0

Contract balances (Details 2)

Contract balances (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract assets	$ 117,036		$ 104,239
Change in contract assets	12,797
Contract liabilities - current	(86,031)		(93,901)
Change in contract liabilities - current	7,870
Contract liabilities - noncurrent	(30)		(135)
Change in contract liabilities - noncurrent	105
Net contract assets	30,975		$ 10,203
Change in net contract assets	20,772
Amounts included in contract liability at the beginning of the period	56,400	$ 52,000
Amounts from performance obligations satisfied in prior periods	$ 18,700	$ 3,100

Business Combinations (Details)

Business Combinations (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Business Combinations [Abstract]
Payments to Acquire Businesses, Gross	$ 32.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 1.2

Discontinued operations Noncont

Discontinued operations Noncontrolling interest (Details)	Jun. 27, 2016	Jun. 24, 2016
WBI Energy | Dakota Prairie Refining, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Previous percentage of ownership	50.00%	50.00%

Major classes of assets and lia

Major classes of assets and liabilities held for sale (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Current assets:
Total current assets held for sale	$ 430	$ 430	$ 458
Noncurrent assets:
Total noncurrent assets held for sale	2,087	2,087	4,392
Current liabilities:
Total current liabilities held for sale	3,657	4,001	11,726
Discontinued operations, held-for-sale or disposed of by sale
Current assets:
Receivables, net	430	430	458
Income taxes receivable (a)	0	0	1,858
Total current assets held for sale	430	430	2,316
Noncurrent assets:
Net property, plant and equipment	0	0	1,631
Deferred income taxes	1,926	1,926	2,637
Other	161	161	161
Total noncurrent assets held for sale	2,087	2,087	4,429
Total assets held for sale	2,517	2,517	6,745
Current liabilities:
Accounts payable	0	80	0
Taxes payable	1,295	1,451	10,774
Other accrued liabilities	2,362	2,470	2,810
Total current liabilities held for sale	3,657	4,001	13,584
Noncurrent liabilities:
Deferred income taxes (b)	0	0	37
Total noncurrent liabilities held for sale	0	0	37
Total liabilities held for sale	$ 3,657	$ 4,001	$ 13,621

Reconciliation of income and ex

Reconciliation of income and expenses (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations	$ (163)	$ 477
Discontinued operations, held-for-sale or disposed of by sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	30	66
Operating expenses	245	174
Operating loss	(215)	(108)
Other income	0	12
Interest expense	0	575
Loss from discontinued operations before income taxes	(215)	(671)
Income taxes	(52)	(1,148)
Income (loss) from discontinued operations	$ (163)	$ 477

Lease costs (Details)

Lease costs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Weighted average remaining lease term	2 years 7 months 17 days
Weighted average discount rate	4.51%
Cash paid for amounts included in the measurement of lease liabilities	$ 11,467
Operating lease cost	11,521
Variable lease cost	399
Short-term lease cost	17,238
Total lease costs	29,158
Lessee, Operating Lease Not Yet Commenced, Value	$ 7,500

Operating lease liabilities und

Operating lease liabilities undiscounted cash flows maturity schedule (Details 2) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Remainder of 2019	$ 26,655
2020	25,743
2021	18,503
2022	11,886
2023	6,723
Thereafter	43,401
Total	132,911
Less discount	25,489
Total operating lease liabilities	$ 107,422

Leases Operating lease future m

Leases Operating lease future minimum lease payments (Details 3) $ in Thousands	Dec. 31, 2018USD ($)
Operating leases future minimum lease payments due [Abstract]
2019	$ 37,740
2020	26,255
2021	17,868
2022	11,647
2023	7,278
Thereafter	$ 49,098

Lessor accounting (Details 4)

Lessor accounting (Details 4) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating Lease, Lease Income	$ 14
Lessor, Operating Lease, Payments to be Received, Next Twelve Months	$ 11.3

Goodwill rollforward (Details)

Goodwill rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Goodwill [Roll Forward]
Balance at beginning of period	$ 664,922	$ 631,791	$ 631,791
Goodwill acquired during the year	14,473	0	33,131
Balance at end of period	679,395	631,791	664,922
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
Balance at end of period	345,736	345,736	345,736
Construction materials and contracting
Goodwill [Roll Forward]
Balance at beginning of period	209,421	176,290	176,290
Goodwill acquired during the year	14,473	0	33,131
Balance at end of period	223,894	176,290	209,421
Construction services
Goodwill [Roll Forward]
Balance at beginning of period	109,765	109,765	109,765
Goodwill acquired during the year	0	0	0
Balance at end of period	$ 109,765	$ 109,765	$ 109,765

Other intangible assets (Detail

Other intangible assets (Details 2) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 11,680,000	$ 3,465,000	$ 10,815,000
Amortization of intangible assets	600,000	400,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	14,471,000	14,668,000	22,720,000
Intangible assets, less accumulated amortization	5,156,000	13,007,000	13,535,000
Intangible assets, net (excluding goodwill)	9,315,000	1,661,000	9,185,000
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	3,179,000	2,430,000	2,605,000
Intangible assets, less accumulated amortization	1,730,000	1,842,000	1,956,000
Intangible assets, net (excluding goodwill)	1,449,000	588,000	649,000
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	6,458,000	6,458,000	6,458,000
Intangible assets, less accumulated amortization	5,542,000	5,242,000	5,477,000
Intangible assets, net (excluding goodwill)	916,000	$ 1,216,000	$ 981,000
Construction materials and contracting [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 1,500,000

Goodwill and other intangible_3

Goodwill and other intangible assets Future amortization expense (Details 3) $ in Thousands	Mar. 31, 2019USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2019	$ 1,403
2020	1,632
2021	1,242
2022	1,219
2023	1,237
Thereafter	$ 4,947

Regulatory assets and liabili_3

Regulatory assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Regulatory Assets and Liabilities
Regulatory Assets	$ 393,533	$ 340,117
Regulatory Liabilities	518,394	521,432
Net Regulatory Position	(124,861)	(181,315)
Regulatory assets not earning a rate of return	279,400	313,500
Taxes recoverable from/refundable to customers
Regulatory Assets and Liabilities
Regulatory Liabilities	267,777	277,833
Plant removal
Regulatory Assets and Liabilities
Regulatory Liabilities	173,911	173,143
Natural gas costs refundable through rate adjustments
Regulatory Assets and Liabilities
Regulatory Liabilities	29,739	29,995
Pension and postretirement benefits
Regulatory Assets and Liabilities
Regulatory Liabilities	12,991	15,264
Other Regulatory Assets/Liabilities
Regulatory Assets and Liabilities
Regulatory Liabilities	$ 33,976	25,197
Pension and postretirement benefits
Regulatory Assets and Liabilities
Estimated Recovery Period	(e)
Regulatory Assets	$ 165,879	165,898
Natural gas costs recoverable through rate adjustments
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 3 years
Regulatory Assets	$ 91,465	42,652
Asset Retirement Obligation Costs
Regulatory Assets and Liabilities
Estimated Recovery Period	Over plant lives
Regulatory Assets	$ 63,633	60,097
Cost recovery mechanisms
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 4 years
Regulatory Assets	$ 17,835	17,948
Manufactured gas plant site remediation
Regulatory Assets and Liabilities
Estimated Recovery Period	-
Regulatory Assets	$ 17,111	17,068
Taxes recoverable from/refundable to customers
Regulatory Assets and Liabilities
Estimated Recovery Period	Over plant lives
Regulatory Assets	$ 11,858	11,946
Plant removal
Regulatory Assets and Liabilities
Estimated Recovery Period	-
Regulatory Assets	$ 6,691	0
Conservation programs
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 1 year
Regulatory Assets	$ 6,094	7,494
Long-term debt refinancing costs
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 19 years
Regulatory Assets	$ 4,746	4,898
Costs related to identifying generation development
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 8 years
Regulatory Assets	$ 2,394	2,508
Other Regulatory Assets/Liabilities
Regulatory Assets and Liabilities
Estimated Recovery Period	Up to 20 years
Regulatory Assets	$ 5,827	$ 9,608

Fair value measurements Insuran

Fair value measurements Insurance contracts (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Investments used to satisfy nonqualified benefit plans obligations	$ 80,200,000	$ 76,900,000	$ 73,800,000
Net unrealized gain (loss) on investments used to satisfy obligations under nonqualified benefit plans	$ 6,400,000	$ (500,000)

Available-for-sale securities (

Available-for-sale securities (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Available-for-sale securities [Abstract]
Cost	$ 10,858	$ 10,652	$ 10,748
Gross Unrealized Gains	31	21	4
Gross Unrealized Losses	88	162	224
Fair Value	10,801	10,511	10,528
Mortgage-backed securities
Available-for-sale securities [Abstract]
Cost	10,679	10,473	10,282
Gross Unrealized Gains	31	21	4
Gross Unrealized Losses	88	162	223
Fair Value	10,622	10,332	10,063
U.S. Treasury securities
Available-for-sale securities [Abstract]
Cost	179	179	466
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	1
Fair Value	$ 179	$ 179	$ 465

Fair value measurements (Detail

Fair value measurements (Details 3) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Concentration risks, percentage [Abstract]
Percentage in fixed-income and other investments	51.00%	53.00%	49.00%
Percentage investment in common stock of large-cap companies	22.00%	21.00%	22.00%
Percentage investment in common stock of mid-cap companies	12.00%	11.00%	13.00%
Percentage investment in common stock of small-cap companies	11.00%	10.00%	11.00%
Percentage investment in target date investments	3.00%	3.00%	3.00%
Percentage investment in cash and cash equivalents	1.00%	2.00%	2.00%
Fair value, measurements, recurring
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 101,584	$ 95,148	$ 96,554
Fair value, measurements, recurring | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	10,540	10,799	9,085
Fair value, measurements, recurring | Insurance contract
Fair value measurements [Line Items]
Assets, fair value disclosure	80,243	73,838	76,941
Fair value, measurements, recurring | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	10,622	10,332	10,063
Fair value, measurements, recurring | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	179	179	465
Fair value, measurements, recurring | Fair value, inputs, level 2
Fair value measurements [Line Items]
Assets, fair value disclosure	101,584	95,148	96,554
Fair value, measurements, recurring | Fair value, inputs, level 2 | Money market funds
Fair value measurements [Line Items]
Assets, fair value disclosure	10,540	10,799	9,085
Fair value, measurements, recurring | Fair value, inputs, level 2 | Insurance contract
Fair value measurements [Line Items]
Assets, fair value disclosure	80,243	73,838	76,941
Fair value, measurements, recurring | Fair value, inputs, level 2 | Mortgage-backed securities
Fair value measurements [Line Items]
Assets, fair value disclosure	10,622	10,332	10,063
Fair value, measurements, recurring | Fair value, inputs, level 2 | U.S. Treasury securities
Fair value measurements [Line Items]
Assets, fair value disclosure	$ 179	$ 179	$ 465

Fair value measurements (Deta_2

Fair value measurements (Details 4) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,198,027	$ 2,108,695
Carrying Amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,198,027	2,108,695	$ 1,779,542
Fair Value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 2,263,305	$ 2,183,819	$ 1,854,350

Short-term debt (Details)

Short-term debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 22, 2019	Jan. 18, 2019	Dec. 31, 2018	Mar. 31, 2018
Short-term Debt [Line Items]
Short-term borrowings	$ 70,000			$ 0	$ 0
Term Loan Agreements
Short-term Debt [Line Items]
Short-term borrowings		$ 40,000	$ 30,000

Long-term debt outstanding (Det

Long-term debt outstanding (Details 2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Long-term debt outstanding [Line Items]
Long-term debt	$ 2,198,027	$ 2,108,695
Long-term debt due within one year	251,846	251,854	$ 149,199
Long-term debt	$ 1,946,181	1,856,841	$ 1,630,343
Senior Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	4.57%
Long-term debt	$ 1,381,000	1,381,000
Commercial Paper
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	2.97%
Long-term debt	$ 473,900	338,100
Term Loan Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	2.75%
Long-term debt	$ 209,800	209,800
Credit Agreements
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	4.42%
Long-term debt	$ 62,875	110,100
Medium-term Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	6.68%
Long-term debt	$ 50,000	50,000
Other Notes
Long-term debt outstanding [Line Items]
Weighted Average Interest Rate	5.00%
Long-term debt	$ 26,251	25,229
Long-term Debt
Long-term debt outstanding [Line Items]
Unamortized Debt Issuance Costs	5,410	5,207
Discount	$ 389	$ 327

Schedule of debt maturities (De

Schedule of debt maturities (Details 3) $ in Thousands	Mar. 31, 2019USD ($)
Long-term debt maturities [Line Items]
Remainder of 2019	$ 251,846
2020	78,801
2021	431,930
2022	147,434
2023	120,239
Thereafter	$ 1,173,576

Cash flow information (Details)

Cash flow information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Interest, net	$ 19,067,000	$ 17,910,000
Income taxes paid (refunded), net	29,000	(1,056,000)
AFUDC borrowed	556,000	382,000
Right-of-use assets obtained in exchange for new operating lease liabilities	2,731,000	0	$ 0
Property, plant and equipment additions in accounts payable	27,655,000	16,829,000	42,355,000
Debt assumed in connection with a business combination	1,163,000	0	0
Issuance of common stock in connection with a business combination	0	0	$ 18,186,000
Continuing and discontinued operations
Income taxes paid (refunded), net	$ 132,000	$ 1,700,000

Business segment data (Details)

Business segment data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 1,091,191	$ 976,293
Operating Income (Loss)	64,218	69,376
Income from continuing operations	41,089	41,960
Income (loss) from discontinued operations, net of tax	(163)	477
Net income	40,926	42,437
Electric
Segment Reporting Information [Line Items]
Revenues	92,566	87,404
Operating Income (Loss)	17,987	18,154
Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	342,147	332,664
Operating Income (Loss)	50,317	48,540
Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	8,613	8,833
Operating Income (Loss)	9,904	8,168
Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	227,113	213,284
Operating Income (Loss)	(41,580)	(26,309)
Construction services
Segment Reporting Information [Line Items]
Revenues	420,733	334,050
Operating Income (Loss)	27,465	20,634
Other
Segment Reporting Information [Line Items]
Revenues	19	58
Operating Income (Loss)	125	189
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	(32,003)	(24,509)
Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment eliminations | Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	(23,955)	(21,759)
Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	(95)	(101)
Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	(129)	(11)
Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	(7,824)	(2,638)
Total intersegment operating revenues
Segment Reporting Information [Line Items]
Revenues	0	0
Regulated operation
Segment Reporting Information [Line Items]
Revenues	439,617	424,459
Income from continuing operations	59,009	51,166
Regulated operation | Electric
Segment Reporting Information [Line Items]
Revenues	92,566	87,404
Income from continuing operations	15,505	13,084
Regulated operation | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	342,147	332,664
Income from continuing operations	36,500	32,623
Regulated operation | Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	4,904	4,391
Income from continuing operations	7,004	5,459
Regulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	23,922	21,735
Regulated operation | Intersegment eliminations | Electric
Segment Reporting Information [Line Items]
Revenues	0	0
Regulated operation | Intersegment eliminations | Natural gas distribution
Segment Reporting Information [Line Items]
Revenues	0	0
Regulated operation | Intersegment eliminations | Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	23,922	21,735
Nonregulated operation
Segment Reporting Information [Line Items]
Revenues	651,574	551,834
Income from continuing operations	(17,920)	(9,206)
Nonregulated operation | Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	3,709	4,442
Income from continuing operations	(163)	(179)
Nonregulated operation | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	227,113	213,284
Income from continuing operations	(34,449)	(23,521)
Nonregulated operation | Construction services
Segment Reporting Information [Line Items]
Revenues	420,733	334,050
Income from continuing operations	20,024	15,090
Nonregulated operation | Other
Segment Reporting Information [Line Items]
Revenues	19	58
Income from continuing operations	(3,332)	(596)
Nonregulated operation | Intersegment eliminations
Segment Reporting Information [Line Items]
Revenues	8,081	2,774
Nonregulated operation | Intersegment eliminations | Pipeline and midstream
Segment Reporting Information [Line Items]
Revenues	33	24
Nonregulated operation | Intersegment eliminations | Construction materials and contracting
Segment Reporting Information [Line Items]
Revenues	95	101
Nonregulated operation | Intersegment eliminations | Construction services
Segment Reporting Information [Line Items]
Revenues	129	11
Nonregulated operation | Intersegment eliminations | Other
Segment Reporting Information [Line Items]
Revenues	$ 7,824	$ 2,638

Employee benefit plans (Details

Employee benefit plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Qualified plan | Underfunded plan | Pension benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	$ 0	$ 0
Interest cost	3,773	3,807
Expected return on assets	(5,120)	(4,998)
Amortization of prior service credit	0	0
Amortization of net actuarial loss	1,355	1,782
Net periodic benefit cost (credit), including amount capitalized	8	591
Less amount capitalized	0	0
Net periodic benefit cost (credit)	8	591
Qualified plan | Overfunded Plan [Member] | Other postretirement benefits
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Service cost	344	407
Interest cost	780	778
Expected return on assets	(1,220)	(1,167)
Amortization of prior service credit	(252)	(349)
Amortization of net actuarial loss	0	238
Net periodic benefit cost (credit), including amount capitalized	(348)	(93)
Less amount capitalized	31	40
Net periodic benefit cost (credit)	(379)	(133)
Nonqualified plan | Unfunded plan | Supplemental employee retirement plans
Defined benefit plan disclosure, net periodic benefit cost [Line Items]
Net periodic benefit cost (credit)	$ 1,100	$ 1,100

MNPUC (Details)

MNPUC (Details) - Tax Cuts and Jobs Act [Member] - Subsequent Event [Member] - Natural gas rate proceeding [Member] - MNPUC [Member]	Apr. 18, 2019USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (400,000)
Public Utilities, Approved One-Time Increase (Decrease) to Customers, Amount	$ (400,000)

MTPSC (Details 2)

MTPSC (Details 2) - MTPSC - USD ($)	Apr. 24, 2019	Mar. 07, 2019	Dec. 21, 2018	Sep. 28, 2018
Electric rate proceeding
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount				$ 11,900,000
Public utilities, requested rate increase (decrease), percentage				18.90%
Public utilities, interim rate increase (decrease), amount		$ 7,900,000
Public utilities, interim rate increase (decrease), percentage		12.80%
Subsequent Event [Member] | Electric rate proceeding
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 9,000,000
Subsequent Event [Member] | Future Electric Rate Proceeding [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 300,000
Tax Cuts and Jobs Act [Member] | Electric rate proceeding
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved One-Time Increase (Decrease) to Customers, Amount			$ (1,500,000)

NDPSC (Details 3)

NDPSC (Details 3) - NDPSC - USD ($)	Jan. 23, 2019	Jan. 09, 2019	Nov. 20, 2018	Oct. 05, 2018	Sep. 26, 2018	Mar. 09, 2018	Mar. 01, 2018	Feb. 14, 2018	Sep. 06, 2017	Jul. 21, 2017
Natural gas rate proceeding [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount										$ 5,900,000
Public utilities, requested rate increase (decrease), percentage										5.40%
Public utilities, interim rate increase (decrease), amount									$ 4,600,000
Public utilities, interim rate increase (decrease), percentage									4.20%
Tax Cuts and Jobs Act [Member] | Natural gas rate proceeding [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities interm rate increase (decrese) revised								$ 2,700,000
Public utilities, requested rate increase (decrease), amended, amount							$ 3,600,000
Public Utilities, Approved Rate Increase (Decrease), Amount		$ (168,000)			$ 2,500,000
Public utilities, approved rate increase (decrease), percentage					2.30%
Public Utilities, Approved One-Time Increase (Decrease) to Customers, Amount	$ (200,000)			$ (600,000)
Tax Cuts and Jobs Act [Member] | Electric rate proceeding
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount						$ (7,200,000)
Public utilities, requested rate increase (decrease), percentage						(3.90%)
Public Utilities, Approved Rate Increase (Decrease), Amount					$ (8,400,000)
Public Utilities, Approved One-Time Increase (Decrease) to Customers, Amount			$ (7,900,000)
Public Utilities, Approved One-Time Increase (Decrease) to Customers, Percentage			(4.70%)

OPUC (Details 4)

OPUC (Details 4) - Tax Cuts and Jobs Act [Member] - Natural gas rate proceeding [Member] - OPUC - USD ($)	Mar. 14, 2019	May 31, 2018
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount		$ 2,300,000
Public utilities, requested rate increase (decrease), percentage		3.50%
Public Utilities, Approved Rate Increase (Decrease) in Revenues Only, Amount	$ 1,700,000
Public Utilities, Approved Rate Increase (Decrease) in Taxes Only, Amount	(500,000)
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 1,200,000

SDPUC (Details 5)

SDPUC (Details 5) - Tax Cuts and Jobs Act [Member] - SDPUC - USD ($)	Dec. 28, 2018	Oct. 23, 2018
Electric rate proceeding
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (100,000)	$ (600,000)
Natural gas rate proceeding [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (300,000)	$ (1,400,000)

WUTC (Details 6)

WUTC (Details 6) - Natural gas rate proceeding [Member] - WUTC - USD ($) $ in Millions	Mar. 29, 2019	Mar. 28, 2019
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 48
Public utilities, requested rate increase (decrease), amount	$ 12.7
Public utilities, requested rate increase (decrease), percentage	5.50%

WYPSC (Details 7)

WYPSC (Details 7) - Tax Cuts and Jobs Act [Member] - Subsequent Event [Member] - Electric rate proceeding - WYPSC $ in Millions	Apr. 08, 2019USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ (1.1)
Public utilities, approved rate increase (decrease), percentage	(4.20%)

Litigation (Details)

Litigation (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Loss Contingencies [Line Items]
Potential liabilities related to litigation and environmental matters	$ 32.4	$ 30.4	$ 37.4

Environmental matters (Details

Environmental matters (Details 2) - USD ($)	3 Months Ended
	Mar. 31, 2019	Jan. 06, 2017
Portland Harbor Site
Site Contingency [Line Items]
Environmental matters investigative costs	$ 100,000,000
Environmental matters, estimated costs		$ 1,000,000,000
Eugene, OR manufactured gas plant site
Site Contingency [Line Items]
Total estimated costs for site remediation	3,500,000
Incurred costs for site remediation	$ 400,000
Estimated proportional share of cleanup liability	50.00%
Environmental matters accrual for site remediation	$ 1,500,000
Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Environmental matters accrual for site remediation	6,400,000
Total estimated costs for site remedial investigation and feasibility study	7,600,000
Incurred costs for site remedial investigation and feasibility study	3,300,000
Environmental matters accrual of investigative costs	4,300,000
Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, preferred alternative estimate	9,300,000
Minimum | Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	340,000
Minimum | Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	8,000,000
Maximum | Bremerton, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	6,400,000
Maximum | Bellingham, WA manufactured gas plant site
Site Contingency [Line Items]
Site contingency, loss exposure not accrued, best estimate	$ 20,400,000

Guarantees (Details 3)

Guarantees (Details 3)	Mar. 31, 2019USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 182,500,000
Fixed maximum amounts guaranteed by year 2019	83,000,000
Fixed maximum amounts guaranteed by year 2020	92,500,000
Fixed maximum amounts guaranteed by year 2021	500,000
Fixed maximum amounts guaranteed by year 2022	500,000
Fixed maximum amounts guaranteed by year 2023	500,000
Fixed maximum amounts guaranteed, thereafter	1,500,000
No scheduled maturity date	4,000,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	28,600,000
Letters of credit set to expire - 2019	6,400,000
Letters of credit set to expire - 2020	22,200,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 903,900,000

Variable interest entities (Det

Variable interest entities (Details 4) $ in Millions	Mar. 31, 2019USD ($)
Fuel contract
Variable Interest Entities [Line Items]
Variable interest entity, reporting entity involvement, maximum loss exposure, amount	$ 37.9

Subsequent events (Details)

Subsequent events (Details) - USD ($) $ in Thousands	Apr. 12, 2019	Apr. 04, 2019	Mar. 31, 2019	Mar. 22, 2019	Jan. 18, 2019	Dec. 31, 2018	Mar. 31, 2018
Subsequent Event [Line Items]
Long-term debt			$ 2,198,027			$ 2,108,695
Short-term Debt			70,000			0	$ 0
Term Loan Agreements
Subsequent Event [Line Items]
Short-term Debt				$ 40,000	$ 30,000
Term Loan Agreements | Subsequent Event [Member]
Subsequent Event [Line Items]
Short-term Debt	$ 50,000
Senior Notes Member]
Subsequent Event [Line Items]
Long-term debt			$ 1,381,000			$ 1,381,000
Senior Notes Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Long-term debt		$ 150,000