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Summary of Significant Accounting Policies - Estimated Retirement Costs Collected from Customers (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
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Regulated Asset Liability [Line Items] |  |
Regulatory liability for utility plant retirement costs | $ 861,515 | $ 784,820
Utility Plant Retirement Costs [Member] |  |
Regulated Asset Liability [Line Items] |  |
Regulatory liability for utility plant retirement costs | $ 350,190 | $ 325,832

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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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