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Property and Plant, Net (Schedule of Capitalized Software and Deferred Cloud Implementation Costs) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Capitalized software costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Capitalized Computer Software, Amortization | $ 222 | $ 224 | $ 212
Capitalized Computer Software, Gross | 1,174 | 1,996 |
Capitalized Computer Software, Accumulated Amortization | (572) | (1,348) |
Hosting Arrangement, Service Contract, Implementation Cost, Expense, Amortization | 19 | 20 | 17
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, before Accumulated Amortization | 142 | 157 |
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, Accumulated Amortization | (59) | (71) |
Ameren Missouri | Capitalized software costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Capitalized Computer Software, Amortization | 113 | 118 | 114
Capitalized Computer Software, Gross | 562 | 881 |
Capitalized Computer Software, Accumulated Amortization | (290) | (567) |
Hosting Arrangement, Service Contract, Implementation Cost, Expense, Amortization | 8 | 9 | 8
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, before Accumulated Amortization | 63 | 71 |
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, Accumulated Amortization | (28) | (32) |
Ameren Illinois | Capitalized software costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Capitalized Computer Software, Amortization | 101 | 100 | 92
Capitalized Computer Software, Gross | 570 | 867 |
Capitalized Computer Software, Accumulated Amortization | (261) | (552) |
Hosting Arrangement, Service Contract, Implementation Cost, Expense, Amortization | 10 | 10 | $ 9
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, before Accumulated Amortization | 76 | 82 |
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, Accumulated Amortization | $ (29) | $ (36) |
Minimum | Software and Software Development Costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Property, Plant and Equipment, Useful Life | 2 years |  |
Minimum | Capitalized software costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life | 5 years |  |
Maximum | Software and Software Development Costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Property, Plant and Equipment, Useful Life | 15 years |  |
Maximum | Capitalized software costs |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Finite-Lived Intangible Asset, Useful Life | 15 years |  |

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