Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 3	$ 3
Interest cost	2,080	1,988	2,455
Expected return on plan assets	(3,789)	(3,848)	(3,756)
Amortization of prior service credits	(81)	(80)	(80)
Recognized net actuarial loss/(gain)	913	1,219	1,032
Settlement/curtailment (gain)/loss	(4)	193	9
Net periodic benefit (income)/cost	(878)	(525)	(337)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	72	87	89
Interest cost	98	97	130
Expected return on plan assets	(10)	(7)	(9)
Amortization of prior service credits	(35)	(35)	(38)
Recognized net actuarial loss/(gain)	(111)	(56)	(63)
Settlement/curtailment (gain)/loss			(4)
Net periodic benefit (income)/cost	14	86	105
Operating Income (Loss) | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	3	3	3
Operating Income (Loss) | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	79	90	91
Other Income | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(881)	(528)	(340)
Other Income | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(58)	(1)	16
Operating Income (Loss) Before Taxes | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(878)	(525)	(337)
Operating Income (Loss) Before Taxes | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	$ 21	$ 89	$ 107