Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets period End	$ 9,150		$ 8,714
United States Pension Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation Period Start	19,293	[1]	17,506
Defined Benefit Plan, Service Cost	0		0		0
Defined Benefit Plan, Interest Cost	930		969		982
Defined Benefit Plan, Actuarial Net (Gains) Losses	2,334		1,860
Defined Benefit Plan, Benefits Paid	(1,057)		(1,042)
Defined Benefit Plan, Contributions by Plan Participants	0		0
Defined Benefit Plan, Plan Amendments	0		0
Defined Benefit Plan, Special Termination Benefits	0		0
Defined Benefit Plan, Settlements, Benefit Obligation	(11)		0
Defined Benefit Plan, Benefit Obligation Period End	21,489	[1]	19,293	[1]	17,506
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets Period Start	7,789		8,249
Defined Benefit Plan, Actual Return on Plan Assets	778		(16)
Defined Benefit Plan, Contributions by Employer	697		598
Defined Benefit Plan, Contributions by Plan Participants	0		0
Defined Benefit Plan, Benefits Paid	(1,057)		(1,042)
Defined Benefit Plan, Settlements, Plan Assets	(11)		0
Defined Benefit Plan, Fair Value of Plan Assets period End	8,196		7,789		8,249
Defined Benefit Plan, Funded Status of Plan [Abstract]
Defined Benefit Plan, Funded Status of Plan	(13,293)		(11,504)
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation Period Start	3,570	[1]	3,298
Defined Benefit Plan, Service Cost	56		52		58
Defined Benefit Plan, Interest Cost	164		180		196
Defined Benefit Plan, Actuarial Net (Gains) Losses	147		311
Defined Benefit Plan, Benefits Paid	(310)		(328)
Defined Benefit Plan, Contributions by Plan Participants	58		54
Defined Benefit Plan, Plan Amendments	(219)		0
Defined Benefit Plan, Special Termination Benefits	116		3
Defined Benefit Plan, Settlements, Benefit Obligation	0		0
Defined Benefit Plan, Benefit Obligation Period End	3,582	[1]	3,570	[1]	3,298
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets Period Start	972		1,120
Defined Benefit Plan, Actual Return on Plan Assets	134		(37)
Defined Benefit Plan, Contributions by Employer	222		235
Defined Benefit Plan, Contributions by Plan Participants	58		54
Defined Benefit Plan, Benefits Paid	(310)		(328)
Defined Benefit Plan, Fair Value of Plan Assets, Period Increase (Decrease)	(382)		(400)
Defined Benefit Plan, Settlements, Plan Assets	0		0
Defined Benefit Plan, Fair Value of Plan Assets period End	1,004		972		1,120
Defined Benefit Plan, Funded Status of Plan [Abstract]
Defined Benefit Plan, Funded Status of Plan	$ (2,578)		$ (2,598)

[1] (1) At each period-end presented, our accumulated benefit obligations for our pension plans are equal to the benefit obligations shown above.