Postretirement Benefit Plans (Cost of Postretirement Benefit Plans and Changes in Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Defined Benefit Plan, Benefit Obligation [Line Items]
Pension And Postretirement Cost Of Benefit Plans	$ 5,977
Changes in other comprehensive income
Net actuarial loss (gain) - current year	(12,263)
Prior service cost (credit) - current year	11
Prior service cost amortization	(646)
Net actuarial (gain) loss amortization	(3,962)
Total changes in other comprehensive income	(16,860)
Cost of postretirement benefit plans and changes in other comprehensive income	(10,883)
Principal pension plans
Defined Benefit Plan, Benefit Obligation [Line Items]
Pension And Postretirement Cost Of Benefit Plans	4,405
Changes in other comprehensive income
Net actuarial loss (gain) - current year	(9,218)
Prior service cost (credit) - current year	0
Prior service cost amortization	(246)
Net actuarial (gain) loss amortization	(3,664)
Total changes in other comprehensive income	(13,128)
Cost of postretirement benefit plans and changes in other comprehensive income	(8,723)
Other Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Benefit Obligation [Line Items]
Pension And Postretirement Cost Of Benefit Plans	645
Changes in other comprehensive income
Net actuarial loss (gain) - current year	(1,151)
Prior service cost (credit) - current year	11
Prior service cost amortization	(7)
Net actuarial (gain) loss amortization	(343)
Total changes in other comprehensive income	(1,490)
Cost of postretirement benefit plans and changes in other comprehensive income	(845)
Principal Retiree Health and Life Insurance Plans [Member]
Defined Benefit Plan, Benefit Obligation [Line Items]
Pension And Postretirement Cost Of Benefit Plans	927
Changes in other comprehensive income
Net actuarial loss (gain) - current year	(1,894)
Prior service cost (credit) - current year	0
Prior service cost amortization	(393)
Net actuarial (gain) loss amortization	45
Total changes in other comprehensive income	(2,242)
Cost of postretirement benefit plans and changes in other comprehensive income	$ (1,315)