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Disaggregation of revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | $ 1,303,573 | $ 1,064,597 | $ 2,394,764 | $ 2,040,890
Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (11,281) | (9,981) | (43,285) | (34,490)
Intrasegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (145,925) | (125,567) | (181,066) | (159,837)
Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 35,510 | 31,371 | 72,138 | 64,368
Natural gas gathering |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,396 | 2,310 | 4,517 | 4,580
Natural gas storage |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,623 | 2,634 | 5,269 | 5,768
Contracting services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 297,124 | 247,558 | 380,164 | 321,622
Construction materials |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 444,768 | 387,632 | 624,077 | 561,223
Inside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 319,276 | 216,371 | 618,805 | 450,192
Outside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 133,288 | 95,261 | 240,686 | 182,442
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 20,545 | 19,225 | 44,136 | 37,412
Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 1,287,052 | 1,051,077 | 2,368,092 | 2,015,619
Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 16,521 | 13,520 | 26,672 | 25,271
Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 97,447 | 95,440 | 334,612 | 323,509
Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 74,481 | 73,496 | 231,945 | 225,088
Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 14,921 | 13,453 | 32,416 | 30,032
Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 1,879 | 1,874 | 3,678 | 3,710
Electric |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 81,011 | 78,499 | 173,578 | 165,904
Electric | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Electric | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 8,417 | 8,425 | 17,538 | 16,678
Electric | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 79,308 | 77,953 | 171,339 | 166,696
Electric | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 1,703 | 546 | 2,239 | (792)
Electric | Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 26,437 | 26,752 | 62,993 | 61,935
Electric | Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 33,231 | 32,676 | 68,902 | 67,377
Electric | Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 9,344 | 8,226 | 18,228 | 16,996
Electric | Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 1,879 | 1,874 | 3,678 | 3,710
Natural gas distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 133,867 | 129,540 | 476,014 | 462,204
Natural gas distribution | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Natural gas distribution | Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 10,706 | 10,084 | 22,276 | 21,263
Natural gas distribution | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,923 | 3,614 | 6,836 | 7,613
Natural gas distribution | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 131,466 | 128,433 | 477,962 | 461,197
Natural gas distribution | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,401 | 1,107 | (1,948) | 1,007
Natural gas distribution | Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 71,010 | 68,688 | 271,619 | 261,574
Natural gas distribution | Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 41,250 | 40,820 | 163,043 | 157,711
Natural gas distribution | Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 5,577 | 5,227 | 14,188 | 13,036
Natural gas distribution | Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Pipeline and midstream |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 28,680 | 24,060 | 37,293 | 32,893
Pipeline and midstream | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (7,513) | (6,539) | (31,468) | (28,298)
Pipeline and midstream | Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 24,804 | 21,287 | 49,862 | 43,105
Pipeline and midstream | Natural gas gathering |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,396 | 2,310 | 4,517 | 4,580
Pipeline and midstream | Natural gas storage |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,623 | 2,634 | 5,269 | 5,768
Pipeline and midstream | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 6,293 | 4,326 | 8,989 | 7,652
Pipeline and midstream | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 28,603 | 24,018 | 37,169 | 32,807
Pipeline and midstream | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 77 | 42 | 124 | 86
Construction materials and contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 595,799 | 509,388 | 822,911 | 722,672
Construction materials and contracting | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (168) | (235) | (264) | (336)
Construction materials and contracting | Intrasegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (145,925) | (125,567) | (181,066) | (159,837)
Construction materials and contracting | Contracting services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 297,124 | 247,558 | 380,164 | 321,622
Construction materials and contracting | Construction materials |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 444,768 | 387,632 | 624,077 | 561,223
Construction materials and contracting | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Construction materials and contracting | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 595,799 | 509,388 | 822,911 | 722,672
Construction materials and contracting | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Construction services |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 464,192 | 323,020 | 884,925 | 657,071
Construction services | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (721) | (540) | (849) | (550)
Construction services | Inside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 319,276 | 216,371 | 618,805 | 450,192
Construction services | Outside specialty contracting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 133,288 | 95,261 | 240,686 | 182,442
Construction services | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 9 | 103 | 26 | 17
Construction services | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 451,852 | 311,195 | 858,668 | 632,101
Construction services | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 12,340 | 11,825 | 26,257 | 24,970
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 24 | 90 | 43 | 146
Other | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (2,879) | (2,667) | (10,704) | (5,306)
Other | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 2,903 | 2,757 | 10,747 | 5,452
Other | Revenues from contracts with customers |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 24 | 90 | 43 | 146
Other | Revenues out of scope |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | $ 0 | $ 0 | $ 0 | $ 0

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