Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 3
Interest cost	28	35
Expected return on plan assets	(44)	(52)
Amortization of prior service cost (credit), net	0	0
Special termination benefit	1	1
Total	(13)	(13)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of prior service cost (credit), net	(1)	0
Special termination benefit	0	0
Total	$ 0	$ 1