Postretirement Benefit Plans (Benefit Obligations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension Benefit Plan [Member] | Principal pension plans
Projected Benefit Obligation
Participant contributions	$ (156)	$ (157)
Actuarial loss (gain)	(11,555)	(24,437)
Benefits paid	3,134	3,052
Acquisitions (dispositions)-net	0	0
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	0	0
Pension Benefit Plan [Member] | Other Pension Plan, Defined Benefit [Member]
Projected Benefit Obligation
Participant contributions	(14)	(16)
Actuarial loss (gain)	(2,459)	(3,962)
Benefits paid	477	425
Acquisitions (dispositions)-net	(31)	0
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	(34)	273
Pension Benefit Plan [Member] | Supplemental Employee Retirement Plan, Defined Benefit [Member]
Projected Benefit Obligation
Benefit obligation, Balance at December 31,	5,162	5,494
Pension Benefit Plan [Member] | Funded Plans With Assets Less Than ABO [Member]
Projected Benefit Obligation
Benefit obligation, Balance at December 31,	63,532	69,234
Pension Benefit Plan [Member] | Unfunded Plans [Member]
Projected Benefit Obligation
Benefit obligation, Balance at December 31,	6,512	6,828
Pension Benefit Plan [Member] | Projected Benefit Obligation [Member] | Principal pension plans
Projected Benefit Obligation
Benefit obligation, Balance at January 1,	63,502	60,510
Service cost for benefits earned	1,535	1,387
Interest cost on benefit obligation	2,460	2,479
Participant contributions	156	157
Plan amendments	0	0
Actuarial loss (gain)	(6,406)	2,021
Benefits paid	(3,134)	(3,052)
Acquisitions (dispositions)-net	0	0
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	0	0
Benefit obligation, Balance at December 31,	58,113	63,502
Pension Benefit Plan [Member] | Projected Benefit Obligation [Member] | Other Pension Plan, Defined Benefit [Member]
Projected Benefit Obligation
Benefit obligation, Balance at January 1,	13,584	11,637
Service cost for benefits earned	435	392
Interest cost on benefit obligation	523	514
Participant contributions	14	16
Plan amendments	11	(6)
Actuarial loss (gain)	(575)	890
Benefits paid	(477)	(425)
Acquisitions (dispositions)-net	46	230
Defined Benefit Plan, Foreign Currency Exchange Rate Gain (Loss)	(26)	336
Benefit obligation, Balance at December 31,	13,535	13,584
Retiree Benefit Plan [Member]
Projected Benefit Obligation
Actuarial loss (gain)	1,667	(182)
Retiree Benefit Plan [Member] | Projected Benefit Obligation [Member]
Projected Benefit Obligation
Benefit obligation, Balance at January 1,	11,804	13,056
Service cost for benefits earned	229	219
Interest cost on benefit obligation	410	491
Participant contributions	52	54
Plan amendments	0	(832)
Actuarial loss (gain)	(1,836)	(60)
Benefits paid	(746)	(758)
Net curtailment / other gain	0	366
Benefit obligation, Balance at December 31,	$ 9,913	$ 11,804