Restructuring, and Other Corporate Matters (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 542	$ 418	$ 309
Restructuring-related costs	0	0	52
Planned dispositions	5
Write down property and equipment	15
Merger-related costs	56	294	0
Settlement of commercial dispute		40
Legal proceedings		17
Other corporate matters	20	57	128
Exit costs and other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 70	$ 23	$ 75