RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2026 |
Dec. 31, 2025 |
Mar. 31, 2025 |
Dec. 31, 2025 |
|
| U.S. plans | Pension plans | ||||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | ||||
| Company contributions (reimbursements) | $ 55 | $ 55 | ||
| U.S. plans | Postretirement benefit plans | ||||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | ||||
| Company contributions (reimbursements) | 5 | 19 | ||
| Non-U.S. plans | Pension plans | ||||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | ||||
| Company contributions (reimbursements) | 118 | 363 | ||
| Discretionary contribution | $ 40 | |||
| Non-U.S. plans | Postretirement benefit plans | ||||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | ||||
| Company contributions (reimbursements) | $ 12 | $ 208 | ||
| Discretionary contribution | $ 210 | |||
| Korea | Pension plans | ||||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | ||||
| Discretionary contribution | $ 190 | |||