Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1
Interest cost	705	520
Expected return on plan assets	(861)	(947)
Amortization of prior service credits	(20)	(20)
Recognized net actuarial loss/(gain)	42	227
Net periodic benefit (income)/cost	(133)	(219)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	18
Interest cost	37	24
Expected return on plan assets	(2)	(2)
Amortization of prior service credits	(6)	(9)
Recognized net actuarial loss/(gain)	(44)	(28)
Net periodic benefit (income)/cost	(3)	3
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	1	1
Operating Income (Loss) | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	15	19
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	(134)	(220)
Other Income | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	(15)	(15)
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	(133)	(219)
Operating Income (Loss) Before Taxes | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in (loss)/earning from operations, other income, and loss before income taxes	$ 0	$ 4