Postretirement Plans - Schedule of Allocation of Plan Assets (Details) - Pension - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Estimate of Fair Value Measurement
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 30,850	$ 33,056
Defined benefit plan, plan assets, amount	45,574	48,891	$ 49,825
Defined benefit plan, plan assets measured at net asset value	14,510	15,435
Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	6,525	5,950
Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	24,112	26,880
Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	213	226	268
Cash equivalents and other short-term investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	650	326
Cash equivalents and other short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	646	326
Cash equivalents and other short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	4
Real estate and real assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets measured at net asset value	2,925	3,138
Private equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets measured at net asset value	3,919	4,102
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets measured at net asset value	2,608	2,751
Cash
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	265	86
Receivables
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	382	438
Payables
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(433)	(124)
Corporate | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	16,322	17,809
Corporate | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	16,288	17,750
Corporate | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	34	59	70
U.S. government and agencies | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5,182	6,822
U.S. government and agencies | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5,182	6,822
U.S. government and agencies | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount
Mortgage backed and asset backed | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	783	505
Mortgage backed and asset backed | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	611	344
Mortgage backed and asset backed | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	172	161	162
Municipal | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	613	816
Municipal | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	613	816
Municipal | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount			$ 32
Sovereign | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	924	720
Sovereign | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	923	720
Sovereign | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1
Other | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5	9
Defined benefit plan, plan assets measured at net asset value	1,364	1,364
Other | Fixed income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2	6
Other | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3
Other | Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount		3
Assets | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount		69
Assets | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount		69
Assets | Real estate and real assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1
Assets | Real estate and real assets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1
Liabilities | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(194)
Liabilities | Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(194)
U.S. common and preferred stock | Equity securities:
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,645	3,391
U.S. common and preferred stock | Equity securities: | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,645	3,391
Non-U.S. common and preferred stock | Equity securities:
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,530	2,204
Non-U.S. common and preferred stock | Equity securities: | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,530	2,204
Non-U.S. common and preferred stock | Equity securities: | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount
Real assets | Real estate and real assets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	389	385
Real assets | Real estate and real assets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	348	349
Real assets | Real estate and real assets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	39	33
Real assets | Real estate and real assets | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2	3
Common or collective or pooled funds | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets measured at net asset value	1,309	1,378
Common or collective or pooled funds | Equity securities:
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets measured at net asset value	$ 2,385	$ 2,702