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Commitments and Contingencies (Details)
$ in Millions
12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]      
2016 $ 1    
2017 1    
2018 1    
2019 1    
2020 1    
Operating lease rent expense $ 1 $ 1 $ 1
Gas Market Manipulation Cases [Member]      
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]      
Loss Contingency, Pending Claims, Number 1