Postretirement Benefit Plans - Amounts Recognized in Other Comprehensive Income (Loss) Related to Postretirement Benefit Plans, Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and (losses) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	$ 2,022	$ 3,405	$ (1,066)
Net prior service credit and (cost) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(149)	(1)	(1)
Incurred but Not Yet Recognized in FAS Expense	1,873	3,404	(1,067)
Actuarial gains and (losses) - Recognition of Previously Deferred Amounts	(1,493)	(2,043)	(689)
Amortization of actuarial losses and prior service credits, net of tax of $18 million in 2022, $130 million in 2021 and $119 million in 2020	268	256	249
Recognition of Previously Deferred Amounts	(1,225)	(1,787)	(440)
Qualified defined benefit pension plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and (losses) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	1,952	2,987	(1,005)
Net prior service credit and (cost) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(146)	(1)	(7)
Actuarial gains and (losses) - Recognition of Previously Deferred Amounts	(1,490)	(2,019)	(668)
Amortization of actuarial losses and prior service credits, net of tax of $18 million in 2022, $130 million in 2021 and $119 million in 2020	283	274	269
Retiree medical and life insurance plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and (losses) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(95)	342	43
Net prior service credit and (cost) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(1)	0	6
Actuarial gains and (losses) - Recognition of Previously Deferred Amounts	36	0	3
Amortization of actuarial losses and prior service credits, net of tax of $18 million in 2022, $130 million in 2021 and $119 million in 2020	(22)	(29)	(30)
Other plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial gains and (losses) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	165	76	(104)
Net prior service credit and (cost) - Incurred but Not Yet Recognized in Net Periodic Benefit Cost	(2)	0	0
Actuarial gains and (losses) - Recognition of Previously Deferred Amounts	(39)	(24)	(24)
Amortization of actuarial losses and prior service credits, net of tax of $18 million in 2022, $130 million in 2021 and $119 million in 2020	$ 7	$ 11	$ 10