Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 28	$ 28	$ 30
Interest cost	170	182	188
Expected return on plan assets	(206)	(202)	(197)
Amortization of prior service cost	1	1	1
Recognized actuarial (gain) loss	57	29	8
Curtailment (gain) loss	0	(2)	(4)
Settlement (gain) loss	0	0	0
Special termination benefits	0	0	0
Total	50	36	26
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	11	13	15
Expected return on plan assets	0	0	0
Amortization of prior service cost	1	0	0
Recognized actuarial (gain) loss	(1)	(2)	(4)
Curtailment (gain) loss	0	0	0
Settlement (gain) loss	0	0	0
Special termination benefits	0	0	0
Total	$ 12	$ 12	$ 12