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Components of Gas Inventory (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Public Utilities, Inventory [Line Items]    
Weighted average cost inventory amount $ 1.2 $ 1.1
Natural Gas
   
Public Utilities, Inventory [Line Items]    
Weighted average cost inventory amount 0.8 0.6
Propane
   
Public Utilities, Inventory [Line Items]    
Weighted average cost inventory amount 0.3 0.4
Liquefied Natural Gas & Other
   
Public Utilities, Inventory [Line Items]    
Weighted average cost inventory amount $ 0.1 $ 0.1