Business Segments (Corporate Items) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues - divested business	$ 1,414	$ 1,096	$ 4,165	$ 3,197
Expenses:
Amortization expense of acquired intangible assets	26	25	76	76
Merger and strategic initiatives expense	1	10	12	25
Restructuring charges	11	30	36	30
Extinguishment of debt			36	11
Operating income	326	226	916	757
Corporate Items
Segment Reporting Information [Line Items]
Revenues - divested business	0	0	0	10
Expenses:
Amortization expense of acquired intangible assets	26	25	76	76
Merger and strategic initiatives expense	1	10	12	25
Restructuring charges	11	30	36	30
Provision for notes receivable	6	20	6	20
Extinguishment of debt	0	0	36	11
Charitable donations	0	0	17	0
Expenses - divested business	0	0	0	8
Other	(1)	4	7	10
Total expenses	43	89	190	180
Operating income	$ (43)	$ (89)	$ (190)	$ (170)