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Goodwill and Acquired Intangible Assets - Aggregate Amortization Expense for Acquired Intangible Assets (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]      
Amortization expense $ 2 $ 5 $ 10
Amortization expense - Remainder of 2017 7    
Amortization expense - 2018 3    
Amortization expense - 2019 $ 1