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Regulatory assets and liabilities Regulatory Liabilities (Details 2) - USD ($) $ in Thousands | Jun. 30, 2020 | Dec. 31, 2019 | Jun. 30, 2019
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Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Current | $ 48,000 | $ 42,935 | $ 49,974
Regulatory Liability, Noncurrent | 438,652 | 447,370 | 455,864
Total regulatory liabilities | 486,652 | 490,305 | 505,838
Net regulatory position | (75,070) | (72,908) | (98,013)
Natural gas costs refundable through rate adjustments |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Current | 29,557 | 23,825 | 25,737
Electric fuel and purchased power deferral |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Current | 7,799 | 5,824 | 4,686
Taxes refundable to customers |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Current | 4,012 | 3,472 | 7,104
Regulatory Liability, Noncurrent | 236,142 | 246,034 | 256,921
Plant removal and decommissioning costs |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Noncurrent | 173,399 | 173,722 | 173,661
Pension and postretirement benefits |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Noncurrent | 18,015 | 18,065 | 15,215
Other Regulatory Liabilities |  |  |
Regulatory Liabilities [Line Items] |  |  |
Regulatory Liability, Current | 6,632 | 9,814 | 12,447
Regulatory Liability, Noncurrent | $ 11,096 | $ 9,549 | $ 10,067

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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 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 Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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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- Definition The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent 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 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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