Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3	$ 7	$ 6
Interest cost	14	21	27	42
Expected return on plan assets	(52)	(49)	(103)	(99)
Special termination benefit	0	1	0	1
Total	(35)	(24)	(69)	(50)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	0	1	0
Interest cost	0	0	0	1
Expected return on plan assets	0	0	0	0
Special termination benefit	0	0	0	0
Total	$ 1	$ 0	$ 1	$ 1