Goodwill and Other Intangible Assets - Changes in the Carrying Amount of Goodwill by Reporting Segment (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018		Dec. 31, 2018
Goodwill [Line Items]
Acquired goodwill			$ 4,822
Goodwill impairment	$ (2,168)	[1]	(2,168)	[2]
Balance as of December 31, 2018	2,654		2,654
NCSA [Member]
Goodwill [Line Items]
Acquired goodwill			2,525
Goodwill impairment			(1,484)
Balance as of December 31, 2018	1,041		1,041
EARC [Member]
Goodwill [Line Items]
Acquired goodwill			461
Goodwill impairment			(40)
Balance as of December 31, 2018	421		421
MENA [Member]
Goodwill [Line Items]
Acquired goodwill			46
Balance as of December 31, 2018	46		46
APAC [Member]
Goodwill [Line Items]
Acquired goodwill			52
Goodwill impairment			(52)
Technology [Member]
Goodwill [Line Items]
Acquired goodwill			1,738
Goodwill impairment			(592)
Balance as of December 31, 2018	$ 1,146		$ 1,146

[1] Represents impairment of goodwill associated with our NCSA, EARC, APAC and Technology reporting units, resulting from our annual impairment assessment. See Note 9, Goodwill and Other Intangible Assets, for further discussion.

[2] Represents impairment of goodwill associated with our NCSA, EARC, APAC and Technology reporting units, resulting from our impairment assessment during the fourth quarter of 2018. See Note 9, Goodwill and Other Intangible Assets, for further discussion. The goodwill impairment values are included within the applicable operating group’s Operating loss.