Supplemental Information (Schedule Of Excise Taxes) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Accounting Policies [Line Items] | ||||
| Excise tax expense | $ 109 | $ 99 | $ 273 | $ 254 |
| Union Electric Company | ||||
| Accounting Policies [Line Items] | ||||
| Excise tax expense | 75 | 69 | 162 | 150 |
| Ameren Illinois Company | ||||
| Accounting Policies [Line Items] | ||||
| Excise tax expense | $ 34 | $ 30 | $ 111 | $ 104 |