Restructuring and Other Charges,Net - Activity Related to Layoff Costs and Other Costs Included Within Restructuring Reserve (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	$ 47	$ 45
Restructuring and other charges, net	212	119
Cash payments	(93)	(102)
Other	(11)	(15)
Restructuring reserve ending balance	155	47
Layoff Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	5	11
Restructuring and other charges, net	52	2
Cash payments	(9)	(7)
Other	(6)	(1)
Restructuring reserve ending balance	42	5
Other Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve beginning balance	42	34
Restructuring and other charges, net	160	117
Cash payments	(84)	(95)
Other	(5)	(14)
Restructuring reserve ending balance	$ 113	$ 42