Postretirement Benefit Plans - Qualified Defined Benefit Pension Plans and Retiree Medical and Life Insurance Plans by Asset Category (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 24,515	$ 24,884
Buy-In Contract
Defined Benefit Plan Disclosure [Line Items]
Plan with benefit obligations equal to plan assets	1,100	1,100
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,789	1,952
U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,802	3,162
International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,875	2,298
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	423	459
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,510	4,491
U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,376	2,219
U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,120	572
Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(1,284)	(1,165)
Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,949	1,980
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	826	730
Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,951	4,703
Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,267	3,383
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	847	689
Loan, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(497)	(497)
(Payables) Receivables, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(439)	(92)
Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	15,560	15,968
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	6,583	7,521
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,789	1,952
Level 1 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,715	3,060
Level 1 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,853	2,245
Level 1 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	163	183
Level 1 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 1 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 1 | U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 1 | Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		0
Level 1 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	63	81
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	7,700	6,877
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 2 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	8	6
Level 2 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	17
Level 2 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	260	276
Level 2 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,495	4,272
Level 2 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,376	2,219
Level 2 | U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,120	572
Level 2 | Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(1,284)	(1,165)
Level 2 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	725	680
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,277	1,570
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 3 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	79	96
Level 3 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	22	36
Level 3 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 3 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	15	219
Level 3 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 3 | U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	0
Level 3 | Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		0
Level 3 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,161	1,219
NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 9,891	$ 9,505