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Components of Gas Inventory (Detail) - USD ($)
$ in Millions
Sep. 30, 2022
Dec. 31, 2021
Sep. 30, 2021
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 1.7 $ 1.0 $ 0.9
Liquefied Natural Gas & Other      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount 0.2 0.1 0.1
Natural Gas      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount 1.1 0.5 0.4
Propane      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 0.4 $ 0.4 $ 0.4