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Regulatory assets (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021
Regulatory Assets [Line Items] |  |
Current regulatory assets | $ 165,092 | $ 118,691
Regulatory assets | 329,659 | 357,851
Total regulatory assets | 494,751 | 476,542
Regulatory assets not earning a rate of return | 242,500 | 296,600
Natural gas costs recoverable through rate adjustments |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 141,306 | 86,371
Regulatory assets | $ 0 | 5,186
Natural gas costs recoverable through rate adjustments | Minimum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 1 year |
Natural gas costs recoverable through rate adjustments | Maximum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 2 years |
Conservation programs |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 1 year |
Current regulatory assets | $ 8,544 | 8,225
Cost recovery mechanisms |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 4,019 | 4,536
Regulatory assets | $ 67,171 | 44,870
Cost recovery mechanisms | Minimum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 1 year |
Cost recovery mechanisms | Maximum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 10 years |
Decoupling |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 1 year |
Current regulatory assets | $ 1,801 | 9,131
Other regulatory assets |  |
Regulatory Assets [Line Items] |  |
Current regulatory assets | 9,422 | 10,428
Regulatory assets | $ 11,010 | 9,742
Other regulatory assets | Minimum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 1 year |
Other regulatory assets | Maximum |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 16 years |
Pension and postretirement benefits |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | ** |
Regulatory assets | $ 143,349 | 142,681
Plant costs/asset retirement obligation costs |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Over plant lives |
Regulatory assets | $ 44,462 | 63,116
Manufactured gas plant sites remediation |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | - |
Regulatory assets | $ 26,624 | 26,053
Plants to be retired |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | - |
Regulatory assets | $ 21,525 | 50,070
Taxes recoverable from customers |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Over plant lives |
Regulatory assets | $ 12,330 | 12,339
Long-term debt refinancing costs |  |
Regulatory Assets [Line Items] |  |
Regulatory asset, recovery period | Up to 38 years |
Regulatory assets | $ 3,188 | $ 3,794

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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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