Benefit Plans (Changes in Accumulated Postretirement Benefit Obligation) (Details) (Postretirement Benefit Plan [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	$ 2,663	$ 2,505
Service cost	18	18	34
Interest cost	99	115	139
Benefits paid	(138)	(135)
Actuarial losses/(gains)	(327)	160
Other	2	0
Accrued postretirement health care costs at end of year	$ 2,317	$ 2,663	$ 2,505