Benefit Plans (Postretirement Health Care Costs) (Details) (Postretirement [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 8	$ 16	$ 25
Interest cost	27	35	87	104
Net loss	10	11	34	30
Prior service credit	(9)	(5)	(32)	(16)
Curtailment gain	0	0	(26)	0
Net postretirement health care costs	$ 33	$ 49	$ 79	$ 143