Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 7	$ 21	$ 21
Interest cost	42	45	127	136
Expected return on plan assets	(51)	(50)	(154)	(151)
Recognized actuarial (gain) loss	14	7	43	22
Prior service credit	0	1	1	1
Curtailment (gain) loss	0	0	0	(1)
Total	12	10	38	28
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1	1
Interest cost	3	3	9	9
Expected return on plan assets	0	0	0	0
Recognized actuarial (gain) loss	0	(1)	(1)	(2)
Prior service credit	0	0	0	0
Curtailment (gain) loss	0	0	0	0
Total	$ 3	$ 2	$ 9	$ 8