Postretirement Benefit Plans - Qualified Defined Benefit Pension Plans and Retiree Medical and Life Insurance Plans by Asset Category (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 24,884	$ 37,361
Buy-In Contract
Defined Benefit Plan Disclosure [Line Items]
Plan with benefit obligations equal to plan assets	1,100	1,500
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,952	991
U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,162	6,479
International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,298	4,882
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	459	869
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,491	6,397
U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,219	2,864
U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	572	228
Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(1,165)	636
Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,980	4,100
Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	730	701
Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0	130
Private equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,703	5,386
Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,383	3,059
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	689	556
Loan, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(497)	0
(Payables) Receivables, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(92)	83
Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	15,968	27,446
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	7,521	12,400
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,952	991
Level 1 | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3,060	6,444
Level 1 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,245	4,880
Level 1 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	183	36
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	0
Level 1 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	81	49
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	6,877	13,296
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	6	5
Level 2 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	17	0
Level 2 | Commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	276	833
Level 2 | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	4,272	6,295
Level 2 | U.S. Government securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2,219	2,864
Level 2 | U.S. Government-sponsored enterprise securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	572	228
Level 2 | Interest rate swaps, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	(1,165)	636
Level 2 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	680	2,435
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,570	1,750
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	96	30
Level 3 | International equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	36	2
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	219	102
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	0
Level 3 | Other fixed income investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1,219	1,616
NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 9,505	$ 9,832