XML 45 R31.htm IDEA: XBRL DOCUMENT v3.21.1
Components of Gas Inventory (Detail) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 0.4 $ 0.6 $ 0.4
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   0.2  
Propane      
Public Utilities, Inventory [Line Items]      
Weighted average cost inventory amount $ 0.3 $ 0.3 $ 0.3