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Disaggregation of revenue (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | $ 5,680,733 | $ 5,532,750 | $ 5,336,776
Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (77,606) | (76,969) | (77,149)
Intrasegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (501,044) | (550,815) | (525,749)
Natural gas transportation |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 162,409 | 157,232 | 147,114
Natural gas gathering |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues |  | 4,865 | 9,164
Natural gas storage |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 14,680 | 14,918 | 11,708
Contracting services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,017,471 | 1,069,665 | 1,088,633
Construction materials |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,712,503 | 1,659,152 | 1,627,833
Electrical & mechanical specialty contracting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,324,419 | 1,397,124 | 1,266,196
Transmission & distribution specialty contracting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 677,074 | 649,486 | 531,882
Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 81,407 | 68,865 | 82,669
Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 5,628,488 | 5,471,545 | 5,281,621
Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 52,245 | 61,205 | 55,155
Residential utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 671,562 | 599,051 | 608,821
Commercial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 465,841 | 409,350 | 438,431
Industrial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 72,721 | 62,987 | 64,660
Other utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 7,051 | 6,634 | 7,408
Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 349,039 | 331,538 | 351,725
Electric | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (543) | (491) | 0
Electric | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 42,902 | 32,452 | 35,574
Electric | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 355,564 | 329,479 | 347,712
Electric | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (6,525) | 2,059 | 4,013
Electric | Residential utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 126,841 | 122,663 | 125,369
Electric | Commercial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 137,556 | 131,477 | 141,596
Electric | Industrial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 41,757 | 36,744 | 37,765
Electric | Other utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 7,051 | 6,634 | 7,408
Natural gas distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 971,364 | 847,651 | 865,222
Natural gas distribution | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (576) | (534) | 0
Natural gas distribution | Natural gas transportation |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 48,408 | 45,546 | 45,449
Natural gas distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 10,567 | 10,753 | 12,726
Natural gas distribution | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 962,369 | 836,269 | 865,357
Natural gas distribution | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 8,995 | 11,382 | (135)
Natural gas distribution | Residential utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 544,721 | 476,388 | 483,452
Natural gas distribution | Commercial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 328,285 | 277,873 | 296,835
Natural gas distribution | Industrial utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 30,964 | 26,243 | 26,895
Natural gas distribution | Other utility sales |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 0 | 0 | 0
Pipeline |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 82,858 | 85,346 | 84,192
Pipeline | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (59,678) | (58,531) | (56,252)
Pipeline | Natural gas transportation |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 114,001 | 111,686 | 101,665
Pipeline | Natural gas gathering |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues |  | 4,865 | 9,164
Pipeline | Natural gas storage |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 14,680 | 14,918 | 11,708
Pipeline | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 13,667 | 12,216 | 17,687
Pipeline | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 82,670 | 85,154 | 83,972
Pipeline | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 188 | 192 | 220
Construction materials and contracting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 2,228,306 | 2,177,585 | 2,189,651
Construction materials and contracting | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (624) | (417) | (1,066)
Construction materials and contracting | Intrasegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (501,044) | (550,815) | (525,749)
Construction materials and contracting | Contracting services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,017,471 | 1,069,665 | 1,088,633
Construction materials and contracting | Construction materials |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,712,503 | 1,659,152 | 1,627,833
Construction materials and contracting | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 0 | 0 | 0
Construction materials and contracting | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 2,228,306 | 2,177,585 | 2,189,651
Construction materials and contracting | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 0 | 0 | 0
Construction services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 2,049,082 | 2,090,685 | 1,845,896
Construction services | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (2,555) | (5,038) | (3,370)
Construction services | Electrical & mechanical specialty contracting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,324,419 | 1,397,124 | 1,266,196
Construction services | Transmission & distribution specialty contracting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 677,074 | 649,486 | 531,882
Construction services | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 557 | 1,541 | 131
Construction services | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 1,999,495 | 2,043,113 | 1,794,839
Construction services | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 49,587 | 47,572 | 51,057
Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 84 | (55) | 90
Other | Intersegment eliminations |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | (13,630) | (11,958) | (16,461)
Other | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 13,714 | 11,903 | 16,551
Other | Revenues from contracts with customers |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | 84 | (55) | 90
Other | Revenues out of scope |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Operating revenues | $ 0 | $ 0 | $ 0

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