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Revenue from contracts with customers - Schedule of Disaggregation of revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | $ 313,627 | $ 290,712 | $ 1,340,324 | $ 1,222,036
Other revenues | 1,409 | (1,018) | 731 | 404
Total external operating revenues | 315,036 | 289,694 | 1,341,055 | 1,222,440
Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total external operating revenues | 319,535 | 293,660 | 1,389,191 | 1,265,850
Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | (4,681) | (3,988) | (48,676) | (43,492)
Total external operating revenues | (4,681) | (3,988) | (48,676) | (43,492)
Natural gas transportation |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 63,531 | 57,215 | 192,428 | 172,173
Natural gas storage |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 5,680 | 6,053 | 16,882 | 16,766
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 31,722 | 29,477 | 108,236 | 73,688
Residential utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 99,955 | 99,004 | 557,485 | 539,456
Commercial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 98,073 | 84,335 | 448,008 | 393,874
Industrial utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 17,398 | 16,571 | 60,369 | 63,525
Other utility sales |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 1,949 | 2,045 | 5,592 | 6,046
Electric | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 118,676 | 111,641 | 335,284 | 321,300
Other revenues | (1,014) | (3,173) | (7,476) | (5,915)
Total external operating revenues | 117,662 | 108,468 | 327,808 | 315,385
Electric | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | (138) | (12) | (457) | (71)
Total external operating revenues | (138) | (12) | (457) | (71)
Electric | Natural gas transportation | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Electric | Natural gas storage | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Electric | Other | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 19,118 | 16,182 | 53,832 | 44,998
Electric | Residential utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 35,730 | 37,076 | 103,984 | 107,735
Electric | Commercial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 52,492 | 46,648 | 144,397 | 129,783
Electric | Industrial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 9,525 | 9,702 | 27,936 | 32,809
Electric | Other utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 1,949 | 2,045 | 5,592 | 6,046
Natural gas distribution | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 141,862 | 131,468 | 882,169 | 788,319
Other revenues | 2,353 | 2,122 | 8,088 | 6,200
Total external operating revenues | 144,215 | 133,590 | 890,257 | 794,519
Natural gas distribution | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | (92) | (31) | (278) | (108)
Total external operating revenues | (92) | (31) | (278) | (108)
Natural gas distribution | Natural gas transportation | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 16,292 | 15,279 | 49,816 | 43,194
Natural gas distribution | Natural gas storage | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Natural gas distribution | Other | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 7,983 | 9,736 | 43,086 | 18,705
Natural gas distribution | Residential utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 64,225 | 61,928 | 453,501 | 431,721
Natural gas distribution | Commercial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 45,581 | 37,687 | 303,611 | 264,091
Natural gas distribution | Industrial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 7,873 | 6,869 | 32,433 | 30,716
Natural gas distribution | Other utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Pipeline | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 53,089 | 47,602 | 122,871 | 112,399
Other revenues | 70 | 33 | 119 | 119
Total external operating revenues | 53,159 | 47,635 | 122,990 | 112,518
Pipeline | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | (4,269) | (3,924) | (47,401) | (43,249)
Total external operating revenues | (4,269) | (3,924) | (47,401) | (43,249)
Pipeline | Natural gas transportation | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 47,239 | 41,936 | 142,612 | 128,979
Pipeline | Natural gas storage | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 5,680 | 6,053 | 16,882 | 16,766
Pipeline | Other | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 4,439 | 3,537 | 10,778 | 9,903
Pipeline | Residential utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Pipeline | Commercial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Pipeline | Industrial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Pipeline | Other utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 1 | 0 | 18
Other revenues | 0 | 0 | 0 | 0
Total external operating revenues | 0 | 1 | 0 | 18
Other | Intersegment eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | (182) | (21) | (540) | (64)
Total external operating revenues | (182) | (21) | (540) | (64)
Other | Natural gas transportation | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Natural gas storage | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Other | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 182 | 22 | 540 | 82
Other | Residential utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Commercial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Industrial utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | 0 | 0 | 0 | 0
Other | Other utility sales | Operating Segments |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from contracts with customers | $ 0 | $ 0 | $ 0 | $ 0

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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. 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