Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 7
Interest cost	43	46
Expected return on plan assets	(51)	(50)
Recognized actuarial (gain) loss	14	7
Prior service credit	0	0
Curtailment (gain) loss	0	(1)
Total	13	9
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	3	4
Expected return on plan assets	0	0
Recognized actuarial (gain) loss	0	(1)
Prior service credit	0	0
Curtailment (gain) loss	0	0
Total	$ 3	$ 3