Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 2	$ 7	$ 7
Interest cost	28	26	86	78
Expected return on plan assets	(46)	(52)	(139)	(157)
Special termination benefit	0	0	0	1
Total	(15)	(24)	(46)	(71)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	1	1	2	2
Expected return on plan assets	0	0	0	0
Special termination benefit	0	0	0	0
Total	$ 1	$ 1	$ 2	$ 2