Benefit Obligations (Schedule of Net Periodic Benefit Costs Recognized) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 7	$ 14	$ 14
Interest cost	42	45	85	91
Expected return on plan assets	(52)	(51)	(103)	(101)
Recognized actuarial (gain) loss	15	8	29	15
Prior service credit	1	0	1	0
Curtailment (gain) loss	0	0	0	(1)
Total	13	9	26	18
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1	1
Interest cost	3	2	6	6
Expected return on plan assets	0	0	0	0
Recognized actuarial (gain) loss	(1)	0	(1)	(1)
Prior service credit	0	0	0	0
Curtailment (gain) loss	0	0	0	0
Total	$ 3	$ 3	$ 6	$ 6