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Property and Equipment, Net - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Property Plant And Equipment [Line Items]      
Depreciation expense $ 35 $ 28 $ 19
Internally developed software      
Property Plant And Equipment [Line Items]      
Depreciation expense $ 24 $ 17 $ 10