Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4	$ 3
Interest cost	13	21
Expected return on plan assets	(51)	(50)
Total	(34)	(26)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	0	1
Expected return on plan assets	0	0
Total	$ 0	$ 1