Segment Information - Reconciliation of Information Reported by Segment to Consolidated Amounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Revenue	$ 1,859	$ 1,852	$ 6,141	$ 6,124
Income from operations	17	(26)	339	436
Amortization	(127)	(141)	(408)	(441)
Restructuring costs	0	(31)	0	(85)
Interest expense	(51)	(47)	(154)	(139)
Other income, net	70	38	189	115
INCOME/(LOSS) FROM OPERATIONS BEFORE INCOME TAXES	36	(35)	374	412
Operating Segments [Member]
Revenue:
Revenue	1,844	1,835	6,070	6,050
Income from operations	256	259	1,107	1,323
Segment Reconciling Items [Member]
Revenue:
Revenue	15	17	71	74
Amortization	(127)	(141)	(408)	(441)
Restructuring costs	0	(31)	0	(85)
Transaction and integration expenses	(50)	(74)	(148)	(177)
Unallocated, net (i)	(62)	(39)	(212)	(184)
Interest expense	(51)	(47)	(154)	(139)
Other income, net	$ 70	$ 38	$ 189	$ 115