Revenue Recognition - Summary of RPOs Expected Revenue Recognition (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 20,085	$ 10,913
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 2,521
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
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	$ 8,588
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	$ 8,976
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period