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Callaway Energy Center (Tables) | 12 Months Ended
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Dec. 31, 2025
Nuclear Waste Matters [Abstract] |
Proceeds From Sale Of Investments In Nuclear Decommissioning Trust Fund And Gross Realized Gains And Losses | The following table presents proceeds from the sales and maturities of investments in Ameren Missouri’s nuclear decommissioning trust fund and the gross realized gains and losses resulting from those sales for the years ended December 31, 2025, 2024, and 2023:
| 2025 |  | 2024 |  | 2023
Proceeds from sales and maturities | $ | 416 |  |  | $ | 564 |  |  | $ | 240 |
Gross realized gains | 37 |  |  | 44 |  |  | 6 |
Gross realized losses | 7 |  |  | 28 |  |  | 11 |
Fair Value Of Securities In Nuclear Decommissioning Trust Fund | The following table presents the cost and fair value of investments in debt and equity securities in Ameren’s and Ameren Missouri’s nuclear decommissioning trust fund at December 31, 2025 and 2024:
Security Type | Cost |  | Gross Unrealized Gain |  | Gross Unrealized Loss |  | Fair Value
2025 |  |  |  |  |  |  |
Debt securities | $ | 488 |  |  | $ | 7 |  |  | $ | 9 |  |  | $ | 486 |
Equity securities | 179 |  |  | 858 |  |  | 9 |  |  | 1,028 |
Cash and cash equivalents | 8 |  |  | — |  |  | — |  |  | 8 |
Other(a) | 4 |  |  | — |  |  | — |  |  | 4 |
Total | $ | 679 |  |  | $ | 865 |  |  | $ | 18 |  |  | $ | 1,526 |
2024 |  |  |  |  |  |  |
Debt securities | $ | 437 |  |  | $ | 2 |  |  | $ | 17 |  |  | $ | 422 |
Equity securities | 179 |  |  | 740 |  |  | 8 |  |  | 911 |
Cash and cash equivalents | 10 |  |  | — |  |  | — |  |  | 10 |
Other(a) | (1) |  |  | — |  |  | — |  |  | (1) |
Total | $ | 625 |  |  | $ | 742 |  |  | $ | 25 |  |  | $ | 1,342 |
(a)Represents net receivables and payables relating to pending securities sales, interest, and securities purchases.
Fair Value Of Securities In Nuclear Decommissioning Trust Fund Classified by Contractual Maturity Date | The following table presents the costs and fair values of investments in debt securities in Ameren’s and Ameren Missouri’s nuclear decommissioning trust fund according to their contractual maturities at December 31, 2025:
| Cost |  | Fair Value
Less than 5 years | $ | 207 |  |  | $ | 208 |
5 years to 10 years | 139 |  |  | 141 |
Due after 10 years | 142 |  |  | 137 |
Total | $ | 488 |  |  | $ | 486 |
Schedule of Insurance Coverage | The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at January 1, 2026:
Type and Source of Coverage | Most Recent Renewal Date | Maximum Coverages |  | Maximum Assessments for Single Incidents |
Public liability and nuclear worker liability: |  |  |  |  |
American Nuclear Insurers | January 1, 2026 | $ | 500 |  |  | $ | — |  |
Pool participation | (a) | 15,763 |  | (a) | 166 |  | (b)
|  | $ | 16,263 |  | (c) | $ | 166 |  |
Property damage: |  |  |  |  |
NEIL and EMANI | April 1, 2025 | $ | 3,200 |  | (d) | $ | 22 |  | (e)
Accidental outage: |  |  |  |  |
NEIL | April 1, 2025 | $ | 490 |  | (f) | $ | 9 |  | (e)
(a)Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program. (b)Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $500 million in the event of an incident at any licensed United States commercial reactor, payable at $25 million per year. (c)Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors. (d)NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $0.7 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events. (e)All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL. (f)Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $291 million.

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