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

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