Revenue Recognition - Summary of RPOs Expected Revenue Recognition (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 15,376	$ 10,913
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total RPOs	$ 6,189
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	9 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	$ 5,119
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	$ 4,068
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period