REGULATORY ASSETS AND LIABILITIES - REGULATORY LIABILITIES (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Regulatory liabilities | ||
| Other current liabilities | $ 18.4 | $ 11.4 |
| Regulatory liabilities | 651.4 | 643.4 |
| Total regulatory liabilities | 669.8 | 654.8 |
| Income tax related items | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | 298.7 | 305.9 |
| Removal costs | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | 226.7 | 219.4 |
| Pension and OPEB benefits | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | 85.9 | 85.7 |
| Energy costs refundable through rate adjustments | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | 18.4 | 11.4 |
| Derivatives | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | 16.8 | 8.3 |
| Other, net | ||
| Regulatory liabilities | ||
| Total regulatory liabilities | $ 23.3 | $ 24.1 |