Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 2	$ 10	$ 8
Interest cost	13	22	40	64
Expected return on plan assets	(51)	(50)	(154)	(149)
Special termination benefit	0	0	0	1
Total	(35)	(26)	(104)	(76)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	1	1
Interest cost	1	0	1	1
Expected return on plan assets	0	0	0	0
Special termination benefit	0	0	0	0
Total	$ 1	$ 1	$ 2	$ 2