Comprehensive Income Reclassifications out of Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax (expense) or benefit	$ 567		$ 571	$ 1,571		$ 1,463
Net of tax	989		937	2,671		2,440
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial losses	7	[1]		17	[1]
Prior service costs	(1)	[1]		(1)	[1]
Total before tax	6			16
Tax (expense) or benefit	(2)			(6)
Net of tax	$ 4			$ 10

[1] This accumulated other comprehensive loss component is included in the computation of net periodic pension cost (see Note 8 for additional details).