SIGNIFICANT ACCOUNTING MATTERS - Reconciliation of Cash (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|---|---|
| Significant Accounting Matters [Line Items] | ||||
| Cash and Cash Equivalents | $ 375 | $ 197 | ||
| Restricted Cash | 72 | 71 | ||
| Total Cash, Cash Equivalents and Restricted Cash | 447 | 268 | $ 279 | $ 246 |
| AEP Texas | ||||
| Significant Accounting Matters [Line Items] | ||||
| Cash and Cash Equivalents | 0 | 0 | ||
| Restricted Cash | 13 | 14 | ||
| Total Cash, Cash Equivalents and Restricted Cash | 13 | 14 | 14 | 24 |
| APCo | ||||
| Significant Accounting Matters [Line Items] | ||||
| Cash and Cash Equivalents | 4 | 5 | ||
| Restricted Cash | 25 | 18 | ||
| Total Cash, Cash Equivalents and Restricted Cash | 29 | 23 | 24 | 20 |
| SWEPCo | ||||
| Significant Accounting Matters [Line Items] | ||||
| Cash and Cash Equivalents | 2 | 2 | ||
| Restricted Cash | 14 | 15 | ||
| Total Cash, Cash Equivalents and Restricted Cash | $ 16 | $ 17 | $ 21 | $ 5 |