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Commitments and Contingencies (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]      
2018 $ 1    
2019 1    
2020 1    
2021 1    
2022 1    
Operating lease rent expense $ 1 $ 1 $ 1