Revenue Recognition - Summary of RPOs Expected Revenue Recognition (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 10,913	$ 3,901
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 7,113
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 2,887
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 913
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period