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Summary of Significant Accounting Policies - Regulatory Liabilities (Detail) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2017
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Regulatory Liability [Line Items] |  |  |
Total Regulatory Liabilities | $ 64.0 | $ 47.9 |
Less: Current Portion of Regulatory Liabilities | 17.2 | 13.5 |
Regulatory Liabilities-noncurrent | 46.8 | 34.4 |
Rate Adjustment Mechanisms |  |  |
Regulatory Liability [Line Items] |  |  |
Total Regulatory Liabilities | 13.6 | 9.3 |
Income Taxes |  |  |
Regulatory Liability [Line Items] |  |  |
Total Regulatory Liabilities | $ 50.4 | $ 38.6 | $ 48.9

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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 -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + 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 -Topic 980 -SubTopic 405 -Name Accounting Standards Codification -Section 25 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477571/980-405-25-1 + 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 -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
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