Benefit Plans (Postretirement Health Care Costs) (Details) (Postretirement [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 5	$ 13	$ 16
Interest cost	23	27	74	87
Net loss	10	10	38	34
Prior service credit	(11)	(9)	(33)	(32)
Curtailment gain	0	0	0	(26)
Net postretirement health care costs	$ 25	$ 33	$ 92	$ 79