XML 61 R81.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value Measurements (Schedule of Valuation Process and Unobservable Inputs) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Discounted Cash Flow | Minimum | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Minimum | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.43%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.40)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Minimum | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.39%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 27aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[5] 25aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs (1,833)aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (1,594)aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis (6)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (3)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Minimum | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 35aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 34aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Minimum | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Minimum | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.57%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.10)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Minimum | Union Electric Company | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.39%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 27aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4] 25aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs (1,833)aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (1,594)aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis   (3)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Minimum | Union Electric Company | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 35aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 34aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Minimum | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.43%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.40)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Minimum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Nodal basis (6)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (4)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Average bid/ask consensus pricing 27aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 27aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Maximum | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   2.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Maximum | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 13.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis 0.10aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Maximum | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.50%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 50aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[5] 51aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs 2,743aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 945aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (1)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Maximum | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 40aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 41aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Maximum | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   2.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Maximum | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 13.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.10)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Maximum | Union Electric Company | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.50%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 50aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4] 51aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs 2,743aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 945aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis   (1)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Maximum | Union Electric Company | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 40aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 41aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Maximum | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 2.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis 0.10aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Maximum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Nodal basis 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Average bid/ask consensus pricing 38aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 36aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Weighted Average | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   1.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Weighted Average | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 3.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.20)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Weighted Average | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.42%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 32aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[5] 32aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs 171aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 305aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis (2)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (2)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Weighted Average | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 36aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 36aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Weighted Average | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Escalation rate 5.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1],[2]  
Counterparty credit risk   1.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Discounted Cash Flow | Weighted Average | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 5.00%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.10)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Weighted Average | Union Electric Company | Power    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.26%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 0.42%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Average bid/ask consensus peak and off-peak pricing 32aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4] 40aee_FairValueInputsOfferedQuotesTwo
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Estimated auction price for FTRs 171aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 305aee_FairValueAssumptionsEstimatedAuctionPricing
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Nodal basis   (2)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[4]
Discounted Cash Flow | Weighted Average | Union Electric Company | Uranium    
Fair Value Inputs [Abstract]    
Average bid/ask consensus pricing 36aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 36aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Discounted Cash Flow | Weighted Average | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Counterparty credit risk 0.83%us-gaap_FairValueInputsCounterpartyCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]  
Nodal basis (0.20)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]  
Discounted Cash Flow | Weighted Average | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Credit risk 0.43%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4] 2.00%us-gaap_FairValueInputsEntityCreditRisk
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[3],[4]
Nodal basis (2)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] (2)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Average bid/ask consensus pricing 32aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1] 30aee_FairValueInputsOfferedQuotesOne
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_DiscountedCashFlowMember
[1]
Option Model | Minimum | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 3.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 10.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Minimum | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 31.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.40)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Minimum | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 3.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 10.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Minimum | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 31.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.40)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Minimum | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 50.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.10)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Maximum | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 39.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 35.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Maximum | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 144.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Maximum | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 39.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 35.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Maximum | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 144.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Maximum | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 144.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis 0aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Weighted Average | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 32.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 16.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Weighted Average | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 63.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.20)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Weighted Average | Union Electric Company | Fuel Oils    
Fair Value Inputs [Abstract]    
Volatilities 32.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4] 16.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]
Option Model | Weighted Average | Union Electric Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 53.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.30)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Option Model | Weighted Average | Ameren Illinois Company | Natural Gas    
Fair Value Inputs [Abstract]    
Volatilities 94.00%us-gaap_FairValueAssumptionsExpectedVolatilityRate
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[4]  
Nodal basis (0.10)aee_FairValueInputsNodalBasis
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_OptionModelMember
[1]  
Fundamental Energy Production Model | Minimum | Power    
Fair Value Inputs [Abstract]    
Escalation rate 0.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[6] 3.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Fundamental Energy Production Model | Minimum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Escalation rate 0.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7] 3.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Fundamental Energy Production Model | Maximum | Power    
Fair Value Inputs [Abstract]    
Escalation rate 1.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[6] 4.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Fundamental Energy Production Model | Maximum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Escalation rate 1.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7] 4.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Fundamental Energy Production Model | Weighted Average | Power    
Fair Value Inputs [Abstract]    
Escalation rate 1.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7] 4.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Fundamental Energy Production Model | Weighted Average | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Escalation rate 1.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7] 4.00%aee_FairValueInputsEscalationRate
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1],[7]
Estimated future gas prices 4aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1] 5aee_FairValueAssumptionsEstimatedFuturePrices
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_FundamentalEnergyProductionModelMember
[1]
Contract Price Allocation | Minimum | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 5aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 5aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Contract Price Allocation | Minimum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 5aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 5aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Contract Price Allocation | Maximum | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 7aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 7aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Contract Price Allocation | Maximum | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 7aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 7aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Contract Price Allocation | Weighted Average | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 6aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 6aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Contract Price Allocation | Weighted Average | Ameren Illinois Company | Power    
Fair Value Inputs [Abstract]    
Estimated renewable energy credit costs 6aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1] 6aee_FairValueAssumptionsEstimatedRenewableEnergyCreditCosts
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
/ us-gaap_RangeAxis
= us-gaap_WeightedAverageMember
/ us-gaap_ValuationTechniqueAxis
= aee_ContractPriceAllocationMember
[1]
Derivative liabilities | Fuel Oils    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (8)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6] (3)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6]
Derivative liabilities | Natural Gas    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities 2us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6]  
Derivative liabilities | Power    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (144)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6],[8] (110)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6],[9]
Derivative liabilities | Uranium    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (2)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6] (6)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
[6]
Derivative liabilities | Union Electric Company | Fuel Oils    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (8)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6] (3)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6]
Derivative liabilities | Union Electric Company | Natural Gas    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (1)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6]  
Derivative liabilities | Union Electric Company | Power    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (2)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6],[8] (2)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6],[9]
Derivative liabilities | Union Electric Company | Uranium    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (2)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6] (6)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_UraniumMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6]
Derivative liabilities | Ameren Illinois Company | Natural Gas    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (1)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
[6]  
Derivative liabilities | Ameren Illinois Company | Power    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative liabilities (142)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
[6],[8] (108)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByLiabilityClassAxis
= aee_DerivativeLiabilitiesMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
[6],[9]
Derivative assets | Fuel Oils    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 2us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
[6] 8us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
[6]
Derivative assets | Natural Gas    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
[6]  
Derivative assets | Power    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 11us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
[6],[8] 21us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
[6],[9]
Derivative assets | Union Electric Company | Fuel Oils    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 2us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6] 8us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_FuelOilsMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6]
Derivative assets | Union Electric Company | Power    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 11us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6],[8] 21us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_PowerMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
/ dei_LegalEntityAxis
= aee_UnionElectricCompanyMember
[6],[9]
Derivative assets | Ameren Illinois Company | Natural Gas    
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]    
Derivative assets 1us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeByNatureAxis
= aee_NaturalGasMember
/ us-gaap_FairValueByAssetClassAxis
= aee_DerivativeAssetsMember
/ dei_LegalEntityAxis
= aee_AmerenIllinoisCompanyMember
[6]  
[1] Generally, significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.
[2] Escalation rate applies to fuel oil prices 2017 and beyond.
[3] Counterparty credit risk is applied only to counterparties with derivative asset balances. Ameren Missouri and Ameren Illinois credit risk is applied only to counterparties with derivative liability balances.
[4] Generally, significant increases (decreases) in this input in isolation would result in a significantly lower (higher) fair value measurement.
[5] The balance at Ameren is comprised of Ameren Missouri and Ameren Illinois power contracts, which respond differently to unobservable input changes due to their opposing positions. As such, refer to the power sensitivity analysis for each company above.
[6] The derivative asset and liability balances are presented net of counterparty credit considerations.
[7] Escalation rate applies to power prices 2026 and beyond.
[8] Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2018. Valuations beyond 2018 use fundamentally modeled pricing by month for peak and off-peak demand.
[9] Power valuations use visible third-party pricing evaluated by month for peak and off-peak demand through 2017. Valuations beyond 2017 use fundamentally modeled pricing by month for peak and off-peak demand.