Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 3	$ 8	$ 7
Interest cost	22	28	64	86
Expected return on plan assets	(50)	(46)	(149)	(139)
Special termination benefit	0	0	1	0
Total	(26)	(15)	(76)	(46)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	0	1	0
Interest cost	0	1	1	2
Expected return on plan assets	0	0	0	0
Special termination benefit	0	0	0	0
Total	$ 1	$ 1	$ 2	$ 2