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Business segment data - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Jun. 30, 2024 | Mar. 31, 2024 | Sep. 30, 2023 | Jun. 30, 2023 | Mar. 31, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | $ 1,050,516 |  |  | $ 1,000,795 |  |  | $ 3,311,886 | $ 3,522,020
Operating income | 90,804 |  |  | 84,604 |  |  | 316,497 | 285,157
Income from continuing operations | 62,159 |  |  | 78,218 |  |  | 223,631 | 309,726
Discontinued operations, net of tax | 2,456 |  |  | (3,289) |  |  | 2,319 | (65,752)
Net income | 64,615 | $ 60,436 | $ 100,898 | 74,929 | $ 130,692 | $ 38,353 | 225,950 | 243,974
Operating Segments |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 1,054,646 |  |  | 1,004,592 |  |  | 3,355,897 | 3,560,199
Operating Segments | Electric |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 108,384 |  |  | 108,089 |  |  | 315,268 | 294,775
Operating income | 32,079 |  |  | 28,718 |  |  | 73,498 | 71,372
Operating Segments | Natural gas distribution |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 133,517 |  |  | 134,896 |  |  | 794,418 | 919,487
Operating income | (14,695) |  |  | (15,258) |  |  | 44,747 | 45,674
Operating Segments | Pipeline |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 47,628 |  |  | 40,404 |  |  | 112,471 | 89,086
Operating income | 22,179 |  |  | 17,767 |  |  | 68,101 | 44,693
Operating Segments | Construction services |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 760,986 |  |  | 717,406 |  |  | 2,089,711 | 2,218,672
Operating income | 53,709 |  |  | 50,091 |  |  | 143,902 | 139,619
Operating Segments | Other |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 1 |  |  | 0 |  |  | 18 | 0
Operating income | (2,468) |  |  | 3,286 |  |  | (13,751) | (16,201)
Intersegment eliminations |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (5,563) |  |  | (5,486) |  |  | (48,294) | (44,591)
Regulated operation |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 286,053 |  |  | 279,534 |  |  | 1,212,615 | 1,293,959
Income from continuing operations | 21,621 |  |  | 14,628 |  |  | 122,324 | 100,923
Regulated operation | Operating Segments |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 286,053 |  |  | 279,534 |  |  | 1,212,615 | 1,293,959
Regulated operation | Operating Segments | Electric |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 108,384 |  |  | 108,089 |  |  | 315,268 | 294,775
Income from continuing operations | 24,292 |  |  | 20,942 |  |  | 57,689 | 53,887
Regulated operation | Operating Segments | Natural gas distribution |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 133,517 |  |  | 134,896 |  |  | 794,418 | 919,487
Income from continuing operations | (17,481) |  |  | (17,764) |  |  | 17,581 | 18,007
Regulated operation | Operating Segments | Pipeline |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 44,152 |  |  | 36,549 |  |  | 102,929 | 79,697
Income from continuing operations | 14,810 |  |  | 11,450 |  |  | 47,054 | 29,029
Regulated operation | Intersegment eliminations |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (4,104) |  |  | (3,762) |  |  | (43,430) | (37,914)
Regulated operation | Intersegment eliminations | Electric |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (96) |  |  | (27) |  |  | (188) | (82)
Regulated operation | Intersegment eliminations | Natural gas distribution |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (104) |  |  | (69) |  |  | (209) | (208)
Regulated operation | Intersegment eliminations | Pipeline |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (3,904) |  |  | (3,666) |  |  | (43,033) | (37,624)
Nonregulated operation |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 764,463 |  |  | 721,261 |  |  | 2,099,271 | 2,228,061
Income from continuing operations | 40,538 |  |  | 63,590 |  |  | 101,307 | 208,803
Nonregulated operation | Operating Segments |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 764,463 |  |  | 721,261 |  |  | 2,099,271 | 2,228,061
Nonregulated operation | Operating Segments | Pipeline |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 3,476 |  |  | 3,855 |  |  | 9,542 | 9,389
Income from continuing operations | 374 |  |  | 508 |  |  | 447 | 337
Nonregulated operation | Operating Segments | Construction services |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 760,986 |  |  | 717,406 |  |  | 2,089,711 | 2,218,672
Income from continuing operations | 41,767 |  |  | 35,975 |  |  | 108,953 | 105,951
Nonregulated operation | Operating Segments | Other |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 1 |  |  | 0 |  |  | 18 | 0
Income from continuing operations | (1,603) |  |  | 27,107 |  |  | (8,093) | 102,515
Nonregulated operation | Intersegment eliminations |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (1,459) |  |  | (1,724) |  |  | (4,864) | (6,677)
Nonregulated operation | Intersegment eliminations | Pipeline |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | (27) |  |  | (35) |  |  | (263) | (265)
Nonregulated operation | Intersegment eliminations | Construction services |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | 0 |  |  | 0 |  |  | (336) | 0
Nonregulated operation | Intersegment eliminations | Other |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Revenues | $ (1,432) |  |  | $ (1,689) |  |  | $ (4,265) | $ (6,412)

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