Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 9	$ 7
Interest cost	39	43
Expected return on plan assets	(56)	(51)
Recognized actuarial (gain) loss	0	0	[1]
Prior service credit	0	1	[1]
Curtailment (gain) loss	0	0
Total	(8)	0	[1]
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	0
Interest cost	2	3
Expected return on plan assets	0	0
Recognized actuarial (gain) loss	0	0
Prior service credit	0	0
Curtailment (gain) loss	0	0
Total	$ 3	$ 3

[1] As Adjusted (Note 1)