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Multi-year rate plan revenue requirement approved by the ICC.

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Rate And Regulatory Matters [Line Items]

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Value established for a utility on which the entity is allowed to earn a particular rate of return

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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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Percentage of public utility's requested equity to capital, including debt and equity.

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Amount of public utility's requested rate increase (decrease) with regulatory agency.

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Percentage of public utility's requested return on equity.

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Rate And Regulatory Matters (Narrative-Illinois) (Details) - Ameren Illinois Company - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Rate And Regulatory Matters [Line Items]
Annual investment in energy-efficiency programs		$ 126
IETL \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Multi-year rate plan approved revenue requirement						$ 1,206
Public Utilities, Approved Rate Increase (Decrease), Amount						$ 308
IETL \| Electric Distribution \| Forecast
Rate And Regulatory Matters [Line Items]
Multi-year rate plan approved revenue requirement			$ 1,421	$ 1,367	$ 1,287
Pending Rate Case \| Electric Distribution \| Subsequent Event
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 61
Public Utilities, Requested Equity Capital Structure, Percentage	50.00%
Pending Rate Case \| Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 140
Public Utilities, Requested Equity Capital Structure, Percentage		52.00%
Public Utilities, Requested Return on Equity, Percentage		10.70%
Rate Base		$ 3,300