Amount of megawatts

No definition available.

Name:	aee_AmountofMegawatts
Namespace Prefix:	aee_
Data Type:	num:energyItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of depreciation not allowed to be deferred under the PISA election.

+ References

No definition available.

+ Details

Name:	aee_DepreciationPercentageNotIncludedinPISADeferral
Namespace Prefix:	aee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated Capital Project Costs

+ References

No definition available.

+ Details

Name:	aee_EstimatedCapitalProjectCosts
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Infrastructure System Replacement Surcharge Return on Equity Percentage

+ References

No definition available.

+ Details

Name:	aee_ISRSReturnonEquityPercentage
Namespace Prefix:	aee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Months Between Callaway Maintenance Outages

+ References

No definition available.

+ Details

Name:	aee_NumberofMonthsBetweenCallawayMaintenanceOutages
Namespace Prefix:	aee_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Utilities, Approved Rate Increase (Decrease) on Interim Rates, Amount

+ References

No definition available.

+ Details

Name:	aee_PublicUtilitiesApprovedRateIncreaseDecreaseonInterimRatesAmount
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's requested return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=aee_PendingRateCaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_ElectricityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=aee_WindGenerationFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=aee_FinalRateOrderMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RegulatoryAssetAxis=aee_MEEIA20132016Domain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=aee_MEEIA2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Rate and Regulatory Matters (Narrative-Missouri) (Details) - Union Electric Company $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2018 MWh	Jun. 30, 2018 MWh	Dec. 31, 2019 USD ($) MWh	Dec. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Depreciation Percentage Not Included in PISA Deferral				15.00%
ISRS Return on Equity Percentage				9.725%
Pending Rate Case \| Electricity
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 1
Wind Generation Facility
Public Utilities, General Disclosures [Line Items]
Amount of Megawatts \| MWh		157	400	300
Estimated Capital Project Costs				$ 1,200
Final Rate Order \| Natural gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 1
Public Utilities, Requested Equity Capital Structure, Percentage				52.00%
ISRS Return on Equity Percentage				9.725%
Public Utilities, Approved Rate Increase (Decrease) on Interim Rates, Amount				$ 1
Final Rate Order \| MEEIA 2013 & 2016 \| Electricity
Public Utilities, General Disclosures [Line Items]
Revenues				$ 37
Final Rate Order \| MEEIA 2016 \| Electricity
Public Utilities, General Disclosures [Line Items]
Revenues					$ 11
Minimum \| Final Rate Order \| Natural gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage				9.40%
Maximum \| Final Rate Order \| Natural gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage				9.95%
Subsequent Event
Public Utilities, General Disclosures [Line Items]
Number of Months Between Callaway Maintenance Outages	18 months
Subsequent Event \| Pending Rate Case \| Electricity
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 32
Subsequent Event \| Final Rate Order \| Electricity
Public Utilities, General Disclosures [Line Items]
Number of Months Between Callaway Maintenance Outages	18 months
Subsequent Event \| Minimum \| Pending Rate Case \| Electricity
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage	9.40%
Subsequent Event \| Maximum \| Pending Rate Case \| Electricity
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage	9.80%