Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ (3,914)	$ (17,228)	$ (15,848)
Other comprehensive income/(loss) before reclassifications	506	(658)	(646)
Amounts reclassified from AOCI	132	48	(109)
Net current period Other comprehensive income/(loss)	638	(610)	(755)
Ending balance	5,457	(3,914)	(17,228)
Other comprehensive income (loss), defined benefit plan, gain (loss) arising during period, after tax	25	(225)	(722)
Net actuarial (loss)/gain arising during the period, tax	(1)	(1)	13
Other comprehensive (income) loss, defined benefit plan, prior service cost (credit), reclassification adjustment from AOCI, after tax	(71)	(92)	(102)
Amortization of prior service credits included in net periodic pension cost, tax	(4)	0	(1)
Other comprehensive (income) loss, defined benefit plan, prior service cost (credit), after tax	6	140
Prior service credits arising during the period, tax	0	0	0
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(10,915)	(10,305)	(9,550)
Ending balance	(10,277)	(10,915)	(10,305)
Currency Translation Adjustments
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(178)	(134)	(167)
Other comprehensive income/(loss) before reclassifications	225	(44)	33
Amounts reclassified from AOCI	17
Net current period Other comprehensive income/(loss)	242	(44)	33
Ending balance	64	(178)	(134)
Unrealized Gains and Losses on Certain Investments
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	2	2
Other comprehensive income/(loss) before reclassifications			2
Amounts reclassified from AOCI
Net current period Other comprehensive income/(loss)			2
Ending balance	2	2	2
Unrealized Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(211)	12	(24)
Other comprehensive income/(loss) before reclassifications	262	(258)	41
Amounts reclassified from AOCI	37	35	(5)
Net current period Other comprehensive income/(loss)	299	(223)	36
Ending balance	88	(211)	12
Defined Benefit Pension Plans & Other Postretirement Benefits
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(10,528)	(10,185)	(9,359)
Other comprehensive income/(loss) before reclassifications	19	(356)	(722)
Amounts reclassified from AOCI	78	13	(104)
Net current period Other comprehensive income/(loss)	97	(343)	(826)
Ending balance	$ (10,431)	$ (10,528)	$ (10,185)