Benefit Plans (Postretirement Health Costs) (Details) (Post-Retirement [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Post-Retirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 18	$ 34	$ 29
Interest cost	115	139	135
Amortization of net loss	40	39	32
Amortization of Prior service cost	45	21	21
Termination and curtailment	(26)	(4)	0
Net periodic benefit costs	$ 102	$ 187	$ 175