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Goodwill and Intangibles - Schedule of Estimated Future Amortization Expense for Intangible Assets (Detail) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]    
2018 $ 5  
2019 5  
2020 4  
2021 3  
2022 3  
Thereafter 21  
Intangible assets $ 41 $ 44