RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended | |
|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
|
| U.S. plans | Pension plans | |||
| Defined Benefit Plan, Expected Future Employer Contributions [Abstract] | |||
| Company contributions (reimbursements) | $ 61 | $ 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) | 120 | 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 | ||