Segment Information - Reconciliation of Information Reported by Segment to Condensed Consolidated Statement of Comprehensive Income Amounts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Revenue	$ 2,048	$ 1,990	$ 4,360	$ 4,282
Income/(loss) from operations	176	63	535	322
Amortization	(123)	(140)	(250)	(281)
Interest expense	(56)	(52)	(110)	(103)
Other income, net	67	63	122	119
INCOME FROM OPERATIONS BEFORE INCOME TAXES	187	74	547	338
Operating Segments [Member]
Revenue:
Revenue	2,022	1,958	4,303	4,226
Income/(loss) from operations	357	304	919	851
Segment Reconciling Items [Member]
Revenue:
Revenue	26	32	57	56
Amortization	(123)	(140)	(250)	(281)
Transaction and integration expenses	0	(55)	(6)	(98)
Unallocated, net	(58)	(46)	(128)	(150)
Interest expense	(56)	(52)	(110)	(103)
Other income, net	$ 67	$ 63	$ 122	$ 119