Postretirement Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 2
Interest cost	669	659
Expected return on plan assets	(769)	(829)
Amortization of prior service credits	(19)	(20)
Recognized net actuarial loss/(gain)	76	67
Net periodic benefit (income)/cost	(42)	(121)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	12
Interest cost	34	31
Expected return on plan assets	(3)	(2)
Amortization of prior service credits		(3)
Recognized net actuarial loss/(gain)	(36)	(44)
Net periodic benefit (income)/cost	8	(6)
Operating Income (Loss) | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	1	2
Operating Income (Loss) | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	13	11
Other Income | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	(43)	(123)
Other Income | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	(5)	(18)
Operating Income (Loss) Before Taxes | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	(42)	(121)
Operating Income (Loss) Before Taxes | Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit (income)/cost included in Earnings/(loss) from operations, Other income, net and Earnings/(loss) before income taxes	$ 8	$ (7)