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, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Accrued pension liabilities	$ (8,319)	$ (12,874)
Qualified Defined  Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	64	3
Accrued pension liabilities	(8,319)	(12,874)
Other noncurrent liabilities	0	0
Net (unfunded) funded status of the plans	(8,255)	(12,871)
Retiree Medical and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Other noncurrent assets	330	0
Accrued pension liabilities	0	0
Other noncurrent liabilities	0	(186)
Net (unfunded) funded status of the plans	$ 330	$ (186)