Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2
Interest cost	27	28
Expected return on plan assets	(49)	(44)
Recognized actuarial (gain) loss	0	0
Amortization of prior service cost (credit), net	0	0
Special termination benefit	0	1
Total	(20)	(13)
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
Recognized actuarial (gain) loss	0	0
Amortization of prior service cost (credit), net	0	(1)
Special termination benefit	0	0
Total	$ 0	$ 0