Postretirement Benefit Plans - Amounts Recognized on Balance Sheets Related to Qualified Defined Benefit Pension Plans and Retiree Medical and Life Insurance Plans (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Accrued pension liabilities	$ (4,791)	$ (6,162)
Qualified Defined  Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	6	3
Accrued pension liabilities	(4,791)	(6,162)
Net (unfunded) funded status of the plans	(4,785)	(6,159)
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	564	387
Accrued pension liabilities	0	0
Net (unfunded) funded status of the plans	$ 564	$ 387