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, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Accrued pension liabilities	$ (6,162)	$ (5,472)
Qualified Defined  Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	3	2
Accrued pension liabilities	(6,162)	(5,472)
Net (unfunded) funded status of the plans	(6,159)	(5,470)
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	387	297
Accrued pension liabilities	0	0
Net (unfunded) funded status of the plans	$ 387	$ 297