Revenue Recognition - Summary of RPOs by Segment (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 10,186	$ 3,901
Remaining performance obligations, Percentage	100.00%	100.00%
NCSA [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 5,181	$ 437
Remaining performance obligations, Percentage	51.00%	11.00%
EARC [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 1,250	$ 732
Remaining performance obligations, Percentage	12.00%	19.00%
MENA [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 2,630	$ 2,249
Remaining performance obligations, Percentage	26.00%	58.00%
APAC [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 638	$ 483
Remaining performance obligations, Percentage	6.00%	12.00%
Technology [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 487
Remaining performance obligations, Percentage	5.00%