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Components of Gas Inventory (Detail) - USD ($)
$ in Millions
Jun. 30, 2022
Dec. 31, 2021
Jun. 30, 2021
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 1.0 $ 1.0 $ 0.6
Liquefied Natural Gas & Other      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount 0.1 0.1 0.1
Natural Gas      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount   0.5  
Propane      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 0.4 $ 0.4 $ 0.3