RETIREMENT BENEFITS PLANS - Fair Value of Other Postretirement Benefits Plan Assets (Details) - Other postretirement benefits expense (income) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Fair Value of Other Postretirement Benefits Plan Assets [Line Items] | ||
| Cash equivalents | $ 3 | $ 3 |
| Common collective and other trusts measured at net asset value | 17 | 15 |
| Total other postretirement benefits plan assets | 20 | 18 |
| Quoted prices in active markets for identical assets (Level 1) | ||
| Fair Value of Other Postretirement Benefits Plan Assets [Line Items] | ||
| Cash equivalents | 3 | 3 |
| Total other postretirement benefits plan assets | 3 | 3 |
| Other observable inputs (Level 2) | ||
| Fair Value of Other Postretirement Benefits Plan Assets [Line Items] | ||
| Cash equivalents | 0 | 0 |
| Total other postretirement benefits plan assets | 0 | 0 |
| Unobservable inputs (Level 3) | ||
| Fair Value of Other Postretirement Benefits Plan Assets [Line Items] | ||
| Cash equivalents | 0 | 0 |
| Total other postretirement benefits plan assets | $ 0 | $ 0 |