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