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Note 5 - Derivative Instruments (Details) - Gains and Losses on Derivative Instruments (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Nicor Gas [Member]
    
Note 5 - Derivative Instruments (Details) - Gains and Losses on Derivative Instruments [Line Items]    
Realized losses related to hedging natural gas costs $ 4 $ (35)
Elizabethtown Gas [Member]
    
Note 5 - Derivative Instruments (Details) - Gains and Losses on Derivative Instruments [Line Items]    
Realized losses related to hedging natural gas costs $ (6) $ (28)