Amounts Recognized on Balance Sheets Related to Qualified Defined Benefit Pension Plans and Retiree Medical and Life Insurance Plans (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Accrued postretirement benefit liabilities	$ (15,278)		$ (13,502)
Qualified Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Prepaid pension asset	185		178
Accrued postretirement benefit liabilities	(15,278)		(13,502)
Accumulated other comprehensive loss (pre-tax) related to net actuarial losses	19,121		15,698
Accumulated other comprehensive loss (pre-tax) related to prior service cost (credit)	418		377
Total	19,539	[1]	16,075	[1]
Retiree Medical And Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Accrued postretirement benefit liabilities	(1,220)		(1,274)
Accumulated other comprehensive loss (pre-tax) related to net actuarial losses	777		648
Accumulated other comprehensive loss (pre-tax) related to prior service cost (credit)	(3)		(10)
Total	$ 774	[1]	$ 638	[1]

[1] Accumulated other comprehensive loss for postretirement benefit plan adjustments, after tax, of $13.5 billion and $11.2 billion at December 31, 2012 and 2011 (Note 1) includes $19.5 billion ($12.6 billion after tax) and $16.1 billion ($10.4 billion after tax) for qualified defined benefit pension plans, $774 million ($500 million after tax) and $638 million ($413 million after tax) for retiree medical and life insurance plans, and $626 million ($406 million after tax) and $596 million ($385 million after tax) for other plans.