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Property and Plant, Net (Schedule of Capitalized Software, Future Amortization Expense) (Details) - Capitalized software costs $ in Millions	Dec. 31, 2025 USD ($)
Finite-Lived Intangible Assets [Line Items]
2026	$ 198
2027	152
2028	98
2029	63
2030	32
Ameren Missouri
Finite-Lived Intangible Assets [Line Items]
2026	96
2027	73
2028	46
2029	28
2030	14
Ameren Illinois
Finite-Lived Intangible Assets [Line Items]
2026	96
2027	73
2028	49
2029	32
2030	$ 17

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