Revenue Recognition - Summary of RPOs by Segment (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 11,512	$ 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	$ 6,519	$ 437
Remaining performance obligations, Percentage	57.00%	11.00%
EARC [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 1,502	$ 732
Remaining performance obligations, Percentage	13.00%	19.00%
MENA [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 2,164	$ 2,249
Remaining performance obligations, Percentage	19.00%	58.00%
APAC [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining performance obligations, Total	$ 713	$ 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	$ 614
Remaining performance obligations, Percentage	5.00%