Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 4	$ 6	$ 10
Interest cost	28	34	84	105
Expected return on plan assets	(44)	(53)	(132)	(158)
Recognized actuarial (gain) loss	0	0	0	0
Amortization of prior service cost (credit), net	0	0	0	0
Special termination benefit	0	1	3	2
Total	(14)	(14)	(39)	(41)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	1
Interest cost	1	1	2	2
Expected return on plan assets	0	0	0	0
Recognized actuarial (gain) loss	0	0	0	1
Amortization of prior service cost (credit), net	(1)	0	(3)	0
Special termination benefit		0	0	0
Total	$ 0	$ 1	$ (1)	$ 4