Restructuring and Other Charges,Net - Activity Related to Layoff Costs and Other Costs Included Within Restructuring Reserve (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	$ 47	$ 45
Cash payments	(14)	(102)
Restructuring and other charges, net	30	119
Other	(2)	(15)
Restructuring reserve ending balance	61	47
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	5	11
Cash payments	(3)	(7)
Restructuring and other charges, net	2	2
Other		(1)
Restructuring reserve ending balance	4	5
Other Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	42	34
Cash payments	(11)	(95)
Restructuring and other charges, net	28	117
Other	(2)	(14)
Restructuring reserve ending balance	$ 57	$ 42