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Disaggregation of revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | $ 1,586,013 | $ 1,587,289 | $ 4,237,608 | $ 4,147,591
Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (7,983) | (7,543) | (51,356) | (50,849)
Intrasegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (201,630) | (234,693) | (394,126) | (443,516)
Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 39,870 | 38,742 | 120,875 | 116,287
Natural gas gathering |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: |  | 973 |  | 4,244
Natural gas storage |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 3,483 | 3,885 | 10,606 | 10,035
Contracting services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 415,106 | 448,569 | 791,964 | 850,326
Construction materials |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 617,823 | 608,673 | 1,332,997 | 1,299,081
Inside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 317,238 | 352,845 | 1,020,130 | 1,049,975
Outside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 185,842 | 187,202 | 502,328 | 478,047
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 21,487 | 16,972 | 60,820 | 51,568
Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 1,575,186 | 1,576,190 | 4,200,691 | 4,106,764
Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 10,827 | 11,099 | 36,917 | 40,827
Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 91,696 | 81,485 | 441,007 | 407,142
Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 74,371 | 64,419 | 308,797 | 283,906
Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 15,890 | 12,882 | 51,265 | 45,500
Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 1,993 | 1,779 | 5,384 | 5,018
Electric |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 98,930 | 87,447 | 267,254 | 249,793
Electric | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (136) | (195) | (407) | (586)
Electric | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 12,589 | 7,663 | 31,827 | 23,830
Electric | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 100,386 | 86,449 | 272,583 | 247,670
Electric | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (1,456) | 998 | (5,329) | 2,123
Electric | Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 36,412 | 33,086 | 99,106 | 93,389
Electric | Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 39,033 | 35,688 | 105,795 | 99,152
Electric | Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 10,495 | 8,428 | 30,878 | 26,867
Electric | Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 1,993 | 1,779 | 5,384 | 5,018
Natural gas distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 110,378 | 94,703 | 614,373 | 562,641
Natural gas distribution | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (142) | (185) | (425) | (555)
Natural gas distribution | Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 11,812 | 11,159 | 35,715 | 33,307
Natural gas distribution | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 2,110 | 2,590 | 7,913 | 7,800
Natural gas distribution | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 109,797 | 95,148 | 608,493 | 557,692
Natural gas distribution | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 581 | (445) | 5,880 | 4,949
Natural gas distribution | Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 55,284 | 48,399 | 341,901 | 313,753
Natural gas distribution | Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 35,338 | 28,731 | 203,002 | 184,754
Natural gas distribution | Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 5,395 | 4,454 | 20,387 | 18,633
Natural gas distribution | Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 0 | 0 | 0 | 0
Pipeline |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 30,968 | 32,068 | 68,653 | 70,381
Pipeline | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (3,908) | (3,622) | (38,000) | (36,820)
Pipeline | Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 28,058 | 27,583 | 85,160 | 82,980
Pipeline | Natural gas gathering |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: |  | 973 |  | 4,244
Pipeline | Natural gas storage |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 3,483 | 3,885 | 10,606 | 10,035
Pipeline | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 3,290 | 3,203 | 10,760 | 9,807
Pipeline | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 30,923 | 32,022 | 68,526 | 70,246
Pipeline | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 45 | 46 | 127 | 135
Construction materials and contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 831,189 | 822,439 | 1,730,521 | 1,705,629
Construction materials and contracting | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (110) | (110) | (314) | (262)
Construction materials and contracting | Intrasegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (201,630) | (234,693) | (394,126) | (443,516)
Construction materials and contracting | Contracting services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 415,106 | 448,569 | 791,964 | 850,326
Construction materials and contracting | Construction materials |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 617,823 | 608,673 | 1,332,997 | 1,299,081
Construction materials and contracting | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 0 | 0 | 0 | 0
Construction materials and contracting | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 831,189 | 822,439 | 1,730,521 | 1,705,629
Construction materials and contracting | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 0 | 0 | 0 | 0
Construction services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 514,523 | 550,608 | 1,556,737 | 1,559,217
Construction services | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (289) | (425) | (2,128) | (3,674)
Construction services | Inside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 317,238 | 352,845 | 1,020,130 | 1,049,975
Construction services | Outside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 185,842 | 187,202 | 502,328 | 478,047
Construction services | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 75 | 486 | 168 | 1,249
Construction services | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 502,866 | 540,108 | 1,520,498 | 1,525,597
Construction services | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 11,657 | 10,500 | 36,239 | 33,620
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 25 | 24 | 70 | (70)
Other | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | (3,398) | (3,006) | (10,082) | (8,952)
Other | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 3,423 | 3,030 | 10,152 | 8,882
Other | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | 25 | 24 | 70 | (70)
Other | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating revenues: | $ 0 | $ 0 | $ 0 | $ 0

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