Schedule of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Gross goodwill			$ 3,091
Goodwill [Roll Forward]
Goodwill	$ 1,007	$ 973
Goodwill, Impaired, Accumulated Impairment Loss			(2,118)
Acquisition	5	25
Adjustments to the allocation of purchase price	61	9
Goodwill	1,073	1,007
Americas
Goodwill [Line Items]
Gross goodwill			2,124
Goodwill [Roll Forward]
Goodwill	552	537
Goodwill, Impaired, Accumulated Impairment Loss			1,587
Acquisition	0	2
Adjustments to the allocation of purchase price	0	13
Goodwill	552	552
International
Goodwill [Line Items]
Gross goodwill			967
Goodwill [Roll Forward]
Goodwill	455	436
Goodwill, Impaired, Accumulated Impairment Loss			$ 531
Acquisition	5	23
Adjustments to the allocation of purchase price	61	(4)
Goodwill	$ 521	$ 455