Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Details) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	12 Months Ended
Dec. 31, 2024 MMBTU MWh lb gal	Dec. 31, 2023 MMBTU MWh lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	23	17
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	258	271
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	4	5
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	186
Ameren Missouri \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	23	17
Ameren Missouri \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	45	53
Ameren Missouri \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	0	0
Ameren Missouri \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	186
Ameren Illinois \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	0	0
Ameren Illinois \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	213	218
Ameren Illinois \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	4	5
Ameren Illinois \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

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- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

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- Definition

Nominal mass used to calculate payments on a derivative instrument.

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

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