Employee Benefits - Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
AOCI Attributable To Parent, Tax [Roll Forward]
Net Change in AOCL	$ (297)	$ (222)	$ (17)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	11,840	11,162
Recognition of Net Periodic Benefits Expense	622	500
Deferrals	437	155
Net Change in AOCL	1,059	655	(133)
Balance at end of period	10,437	11,840	11,162
Reclassification of net actuarial loss and prior service credit to gain on the sale of business
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(1,741)	(2,469)
Recognition of Net Periodic Benefits Expense	493	437
Deferrals	571	291
Net Change in AOCL	1,064	728
Balance at end of period	(677)	(1,741)	(2,469)
Combined Pension Plan | Reclassification of net actuarial loss and prior service credit to gain on the sale of business
AOCI Attributable To Parent, Tax [Roll Forward]
Balance at beginning of period	559	755
Recognition of Net Periodic Benefits Expense	(166)	(137)
Deferrals	(26)	(59)
Net Change in AOCL	(192)	(196)
Balance at end of period	367	559	755
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(1,577)	(2,197)
Recognition of Net Periodic Benefits Expense	494	423
Deferrals	98	197
Net Change in AOCL	592	620
Balance at end of period	(985)	(1,577)	(2,197)
Combined Pension Plan | Net actuarial (loss) gain
AOCI Attributable To Parent, Before Tax [Roll Forward]
Balance at beginning of period	(2,564)	(2,993)
Recognition of Net Periodic Benefits Expense	688	186
Deferrals	124	243
Net Change in AOCL	812	429
Balance at end of period	(1,752)	(2,564)	(2,993)
Combined Pension Plan | Settlement charge
AOCI Attributable To Parent, Before Tax [Roll Forward]
Balance at beginning of period	383	0
Recognition of Net Periodic Benefits Expense	0	383
Deferrals	0	0
Net Change in AOCL	0	383
Balance at end of period	383	383	0
Combined Pension Plan | Prior service benefit (cost)
AOCI Attributable To Parent, Before Tax [Roll Forward]
Balance at beginning of period	45	41
Recognition of Net Periodic Benefits Expense	(28)	(9)
Deferrals	0	13
Net Change in AOCL	(28)	4
Balance at end of period	17	45	41
Post-Retirement Benefit Plans | Reclassification of net actuarial loss and prior service credit to gain on the sale of business
AOCI Attributable To Parent, Tax [Roll Forward]
Balance at beginning of period	54	90
Recognition of Net Periodic Benefits Expense	1	(5)
Deferrals	(159)	(31)
Net Change in AOCL	(158)	(36)
Balance at end of period	(104)	54	90
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(164)	(272)
Recognition of Net Periodic Benefits Expense	(1)	14
Deferrals	473	94
Net Change in AOCL	472	108
Balance at end of period	308	(164)	(272)
Post-Retirement Benefit Plans | Net actuarial (loss) gain
AOCI Attributable To Parent, Before Tax [Roll Forward]
Balance at beginning of period	(217)	(346)
Recognition of Net Periodic Benefits Expense	(3)	4
Deferrals	591	125
Net Change in AOCL	588	129
Balance at end of period	371	(217)	(346)
Post-Retirement Benefit Plans | Prior service benefit (cost)
AOCI Attributable To Parent, Before Tax [Roll Forward]
Balance at beginning of period	(5)	(20)
Recognition of Net Periodic Benefits Expense	1	15
Deferrals	41	0
Net Change in AOCL	42	15
Balance at end of period	37	(5)	(20)
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)