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Employee Benefits - Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
AOCI Attributable To Parent, Tax [Roll Forward] |  |  |
Net Change in AOCL | $ (26) | $ 21 | $ (297)
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance at beginning of period | 417 | 10,374 |
Recognition of Net Periodic Benefits Expense | 57 | 411 |
Deferrals | 30 | (122) |
Net Change in AOCL | 87 | 289 | 1,059
Balance at end of period | 464 | 417 | 10,374
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] |  |  |
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance at beginning of period | (769) | (677) |
Recognition of Net Periodic Benefits Expense | 57 | 29 |
Deferrals | 29 | (121) |
Net Change in AOCL | 86 | (92) |
Balance at end of period | (683) | (769) | (677)
Combined Pension Plan | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] |  |  |
AOCI Attributable To Parent, Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 381 | 367 |
Recognition of Net Periodic Benefits Expense | (25) | (23) |
Deferrals | 14 | 37 |
Net Change in AOCL | (11) | 14 |
Balance at End of Period | 370 | 381 | 367
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance at beginning of period | (1,045) | (985) |
Recognition of Net Periodic Benefits Expense | 76 | 50 |
Deferrals | (34) | (110) |
Net Change in AOCL | 42 | (60) |
Balance at end of period | (1,003) | (1,045) | (985)
Combined Pension Plan | Net actuarial (loss) gain |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | (1,819) | (1,752) |
Recognition of Net Periodic Benefits Expense | 108 | 80 |
Deferrals | (48) | (147) |
Net Change in AOCL | 60 | (67) |
Balance at End of Period | (1,759) | (1,819) | (1,752)
Combined Pension Plan | Settlement charge |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 383 | 383 |
Recognition of Net Periodic Benefits Expense | 0 | 0 |
Deferrals | 0 | 0 |
Net Change in AOCL | 0 | 0 |
Balance at End of Period | 383 | 383 | 383
Combined Pension Plan | Prior service benefit (cost) |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 10 | 17 |
Recognition of Net Periodic Benefits Expense | (7) | (7) |
Deferrals | 0 | 0 |
Net Change in AOCL | (7) | (7) |
Balance at End of Period | 3 | 10 | 17
Post-Retirement Benefit Plans | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] |  |  |
AOCI Attributable To Parent, Tax [Roll Forward] |  |  |
Balance at Beginning of Period | (94) | (104) |
Recognition of Net Periodic Benefits Expense | 6 | 7 |
Deferrals | (21) | 3 |
Net Change in AOCL | (15) | 10 |
Balance at End of Period | (109) | (94) | (104)
AOCI Attributable to Parent, Net of Tax [Roll Forward] |  |  |
Balance at beginning of period | 276 | 308 |
Recognition of Net Periodic Benefits Expense | (19) | (21) |
Deferrals | 63 | (11) |
Net Change in AOCL | 44 | (32) |
Balance at end of period | 320 | 276 | 308
Post-Retirement Benefit Plans | Net actuarial (loss) gain |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 337 | 371 |
Recognition of Net Periodic Benefits Expense | (17) | (20) |
Deferrals | 84 | (14) |
Net Change in AOCL | 67 | (34) |
Balance at End of Period | 404 | 337 | 371
Post-Retirement Benefit Plans | Prior service benefit (cost) |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 29 | 37 |
Recognition of Net Periodic Benefits Expense | (8) | (8) |
Deferrals | 0 | 0 |
Net Change in AOCL | (8) | (8) |
Balance at End of Period | 21 | 29 | 37
Post-Retirement Benefit Plans | Curtailment loss |  |  |
AOCI Attributable To Parent, Before Tax [Roll Forward] |  |  |
Balance at Beginning of Period | 4 | 4 |
Recognition of Net Periodic Benefits Expense | 0 | 0 |
Deferrals | 0 | 0 |
Net Change in AOCL | 0 | 0 |
Balance at End of Period | $ 4 | $ 4 | $ 4

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