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Property and Plant, Net (Schedule of Capitalized Software, Future Amortization Expense) (Details) - Capitalized software costs
$ in Millions
Dec. 31, 2024
USD ($)
Finite-Lived Intangible Assets [Line Items]  
2025 $ 190
2026 147
2027 110
2028 69
2029 38
Ameren Missouri  
Finite-Lived Intangible Assets [Line Items]  
2025 98
2026 73
2027 54
2028 33
2029 17
Ameren Illinois  
Finite-Lived Intangible Assets [Line Items]  
2025 85
2026 70
2027 53
2028 34
2029 $ 20