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Regulatory liabilities (Details 2) - USD ($) $ in Thousands | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020 | Sep. 30, 2020
Regulatory Liabilities [Line Items] |  |  |
Regulatory liabilities due within one year | $ 16,491 | $ 31,450 | $ 39,837
Regulatory liabilities | 426,141 | 428,075 | 434,936
Total regulatory liabilities | 442,632 | 459,525 | 474,773
Net regulatory position | 69,748 | (11,617) | (25,884)
Taxes refundable to customers |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory liabilities due within one year | 3,867 | 3,557 | 4,223
Regulatory liabilities | $ 218,566 | 227,850 | 232,186
Taxes refundable to customers | Minimum [Member] |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Up to 1 year |  |
Taxes refundable to customers | Maximum [Member] |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Over plant lives |  |
Electric fuel and purchased power deferral |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Up to 1 year |  |
Regulatory liabilities due within one year | $ 3,205 | 3,667 | 6,171
Natural gas costs refundable through rate adjustments |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | - |  |
Regulatory liabilities due within one year | $ 0 | 18,565 | 20,556
Other regulatory liabilities |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory liabilities due within one year | 9,419 | 5,661 | 8,887
Regulatory liabilities | $ 17,977 | 16,065 | 11,392
Other regulatory liabilities | Minimum [Member] |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Up to 1 year |  |
Other regulatory liabilities | Maximum [Member] |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Up to 21 years |  |
Plant removal and decommissioning costs |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | Over plant lives |  |
Regulatory liabilities | $ 172,683 | 167,171 | 173,367
Pension and postretirement benefits |  |  |
Regulatory Liabilities [Line Items] |  |  |
Estimated Recovery or Refund Period as of September 30, 2021 | ** |  |
Regulatory liabilities | $ 16,915 | $ 16,989 | $ 17,991

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- Definition The net amount of all regulatory assets less all regulatory liabilities as of the end of the period. + 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 http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition Describes the continual or periodic assessment of the probability of future recovery of regulatory assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 40 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499898&loc=d3e44174-110380 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121557228&loc=d3e43603-110378 + Details
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- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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- Definition The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
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