Comprehensive Income Reclassifications out of Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax (expense) or benefit	$ 513		$ 478	$ 1,004		$ 892
Net of tax	884		802	1,682		1,503
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	5	[1]		10	[1]
Total before tax	5			10
Tax (expense) or benefit	(2)			(4)
Net of tax	$ 3			$ 6

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