Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 3	$ 4	$ 6
Interest cost	28	36	56	71
Expected return on plan assets	(44)	(53)	(88)	(105)
Recognized actuarial (gain) loss	0	0	0	0
Amortization of prior service cost (credit), net	0	0	0	0
Special termination benefit	2	0	3	1
Total	(12)	(14)	(25)	(27)
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	0	1
Interest cost	0	0	1	1
Expected return on plan assets	0	0	0	0
Recognized actuarial (gain) loss	0	1	0	1
Amortization of prior service cost (credit), net	(1)	0	(2)	0
Special termination benefit	0	0	0	0
Total	$ (1)	$ 2	$ (1)	$ 3