Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2024 MWh MMBTU lb gal	Sep. 30, 2024 MWh MMBTU lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	17	25
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	271	253
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	5	5
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	186	0
Union Electric Company \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	17	25
Union Electric Company \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	53	49
Union Electric Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	0	0
Union Electric Company \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	186	0
Ameren Illinois Company \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	0	0
Ameren Illinois Company \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	218	204
Ameren Illinois Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	5	5
Ameren Illinois Company \| 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

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:energyItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal mass used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountMass
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:volumeItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_TradingActivityByTypeAxis=aee_FuelOilsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TradingActivityByTypeAxis=srt_NaturalGasReservesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TradingActivityByTypeAxis=aee_PowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TradingActivityByTypeAxis=aee_UraniumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=aee_UnionElectricCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=aee_AmerenIllinoisCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: