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Derivative Instruments - Fair Values of Derivative Contracts Recorded in Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Derivatives, Fair Value [Line Items] |  |  |
Energy Marketing Contracts Assets, Current |  | $ 0.1 | $ 0.6
Energy Marketing Contract Liabilities, Current |  | 0.5 | 0.0
Energy Marketing Contract Liabilities, Total | [1] | 1.8 | 0.1
Energy Marketing Contracts Assets, Total | [2] | 0.1 | 0.7
Mark To Market Energy Assets [Member] | Propane Swap Agreement [Member] | Derivatives designated as hedging instrument [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Energy Marketing Contracts Assets, Current |  | 0.1 | 0.6
Mark To Market Energy Assets [Member] | Interest Rate Swap [Member] | Derivatives designated as hedging instrument [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Energy Marketing Contracts Assets, Current |  | 0.0 | 0.1
Mark-to-market energy liabilities [Member] | Propane Swap Agreement [Member] | Derivatives designated as hedging instrument [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Energy Marketing Contract Liabilities, Current |  | 0.3 | 0.0
Mark-to-market energy liabilities [Member] | Interest Rate Swap [Member] | Derivatives designated as hedging instrument [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Energy Marketing Contract Liabilities, Current |  | $ 1.5 | $ 0.1
[1] | (1) Derivative liabilities, at fair value, include $0.5 million in current liabilities in the condensed consolidated balance sheet at September 30, 2025 and no current derivative liabilities at December 31, 2024, with the remainder of the balances classified as long-term.
[2] | (1) Derivative assets, at fair value, include $0.1 million in current assets in the condensed consolidated balance sheet at September 30, 2025 and $0.6 million at December 31, 2024, with the remainder of the balances classified as long-term

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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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 182 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480401/815-10-55-182 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4B -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4B -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4B -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A + Details
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- Definition Current liabilities attributable to energy marketing activities (trading activities). Current energy marketing (trading activities) are when entities engage in both financial and physical trading to increase profits, manage their commodity price risk and enhance system reliability. They may trade electricity, coal, natural gas and oil. These entities typically use a variety of financial instruments, including forward contracts, options and swaps. + 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(20)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
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