Derivative Instruments - Fair Values of Derivative Contracts Recorded in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Energy Marketing Contracts Assets, Current		$ 0.6	$ 1.0
Energy Marketing Contracts Assets, Total	[1]	0.7	1.0
Energy Marketing Contract Liabilities, Current		0.0	0.4
Energy Marketing Contract Liabilities, Total	[2]	0.1	1.3
Designated as Hedging Instrument [Member] | Mark-to-market energy liabilities | Propane Swap Agreement
Derivatives, Fair Value [Line Items]
Energy Marketing Contract Liabilities, Current		0.0	1.1
Designated as Hedging Instrument [Member] | Mark-to-market energy liabilities | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Energy Marketing Contract Liabilities, Current		0.1	0.2
Designated as Hedging Instrument [Member] | Mark To Market Energy Assets | Propane Swap Agreement
Derivatives, Fair Value [Line Items]
Energy Marketing Contracts Assets, Current		0.6	0.7
Designated as Hedging Instrument [Member] | Mark To Market Energy Assets | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Energy Marketing Contracts Assets, Current		$ 0.1	$ 0.3

[1]  (1) Derivative assets, at fair value included $0.6 million and $1.0 million in current assets in the consolidated balance sheets at December 31, 2024 and 2023, respectively, with the remainder of the balance classified as long-term

[2] (1) There were no current derivative liabilities at December 31, 2024. At December 31, 2023, current derivative liabilities amounted to $0.4 million with the remainder of the balance classified as long-term.