Components of Gas Inventory (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	$ 1.0	$ 1.8
Liquefied Natural Gas & Other
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	0.4	0.4
Natural Gas
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	0.3	1.0
Propane
Public Utilities, Inventory [Line Items]
Weighted average cost inventory amount	$ 0.3	$ 0.4