1001 - Document - Cover link:presentationLink link:definitionLink link:calculationLink 1002 - Statement - Statements of Net Assets Available for Benefits link:presentationLink link:definitionLink link:calculationLink 1003 - Statement - Statements of Changes in Net Assets Available for Benefits link:presentationLink link:definitionLink link:calculationLink 1004 - Disclosure - Description of the Plan link:presentationLink link:definitionLink link:calculationLink 1005 - Disclosure - Summary of Significant Accounting Policies link:presentationLink link:definitionLink link:calculationLink 1006 - Disclosure - Fair Value Measurements link:presentationLink link:definitionLink link:calculationLink 1007 - Disclosure - Fully Benefit-Responsive Investment Contracts link:presentationLink link:definitionLink link:calculationLink 1008 - Disclosure - Transactions with Parties-in-Interest link:presentationLink link:definitionLink link:calculationLink 1009 - Disclosure - Reconciliation of Financial Statements to Form 5500 link:presentationLink link:definitionLink link:calculationLink 1010 - Disclosure - Federal Income Tax Status link:presentationLink link:definitionLink link:calculationLink 1011 - Disclosure - Subsequent Events link:presentationLink link:definitionLink link:calculationLink 1012 - Disclosure - Schedule H, Line 4i – Schedule of Assets (Held at End of Year) link:presentationLink link:definitionLink link:calculationLink 1013 - Disclosure - Summary of Significant Accounting Policies (Policies) link:presentationLink link:definitionLink link:calculationLink 1014 - Disclosure - Fair Value Measurements (Tables) link:presentationLink link:definitionLink link:calculationLink 1015 - Disclosure - Reconciliation of Financial Statements to Form 5500 (Tables) link:presentationLink link:definitionLink link:calculationLink 1016 - Disclosure - Description of the Plan - Additional Information (Details) link:presentationLink link:definitionLink link:calculationLink 1017 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details) link:presentationLink link:definitionLink link:calculationLink 1018 - Schedule - Fair Value Measurements - Summary of Plan assets measured at fair value on a recurring basis (Detail) link:presentationLink link:definitionLink link:calculationLink 1019 - Disclosure - Fair Value Measurements - Additional Information (Detail) link:presentationLink link:definitionLink link:calculationLink 1020 - Disclosure - Fully Benefit-Responsive Investment Contracts - Additional Information (Detail) link:presentationLink link:definitionLink link:calculationLink 1021 - Disclosure - Transactions with Parties-in-Interest - Additional Information (Detail) link:presentationLink link:definitionLink link:calculationLink 1022 - Schedule - Reconciliation of Financial Statements to Form 5500 - Summary of Reconciliation of Net Assets Available for Benefits Per the Financial Statements to From 5500 (Detail) link:presentationLink link:definitionLink link:calculationLink 1023 - Schedule - Reconciliation of Financial Statements to Form 5500 - Summary of Net Increase in Net Assets Available for Benefits Per the Financial Statements to Net Income Per the Form 5500 (Detail) link:presentationLink link:definitionLink link:calculationLink 1024 - Disclosure - Federal Income Tax Status - Additional Information (Detail) link:presentationLink link:definitionLink link:calculationLink 1025 - Disclosure - Schedule H, Line 4i – Schedule of Assets (Held at End of Year) (Detail) link:presentationLink link:definitionLink link:calculationLink 1026 - Disclosure - Description of the Plan - Additional Information (Details) Alternate link:presentationLink link:definitionLink link:calculationLink 1027 - Disclosure - Schedule H, Line 4i – Schedule of Assets (Held at End of Year) (Detail) Alternate link:presentationLink link:definitionLink link:calculationLink Cover [Abstract] Document Information [Table] Legal Entity [Axis] Entity [Domain] EBP 003 [Member] Document Information [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Registrant Name Entity Central Index Key EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Asset [Abstract] Assets EBP, Investment, Fair Value Investments, at fair value EBP, Investment, Fair value EBP, Investment, Contract Value Investments, at contract value EBP, Receivable [Abstract] Receivables EBP, Note Receivable from Participant Notes receivable from participants EBP, Participant Contribution, Receivable Participant contributions EBP, Employer Contribution, Receivable Employer contributions EBP, Investment Sale, Receivable Due from brokers for securities sold EBP, Investment Income, Receivable Dividends and interest EBP, Receivable Total receivables EBP, Asset Total assets EBP, Investment, Fair and Contract Value Total investments EBP, Liability [Abstract] Liabilities EBP, Accrued Expense Accrued expenses EBP, Liability for Investment Purchase Due to brokers for securities purchased EBP, Liability Total liabilities EBP, Net Asset Available for Benefit Net assets available for benefits Beginning of year End of year Net assets available for benefits per the financial statements EBP, Statement of Change in Net Asset Available for Benefit [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Change in Net Asset Available for Benefit, Increase [Abstract] Additions: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment Income EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Total income EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Interest on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution Participant contributions EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash Employer contributions EBP, Change in Net Asset Available for Benefit, Increase Total additions EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Deductions: EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease Total deductions EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Net increase Net increase in net assets available for benefits per the financial statements EBP, Description of Plan and Accounting Change [Abstract] EBP, Description of Plan [Table] EBP, Description of Plan [Line Items] EBP, Description of Plan [Text Block] Description of the Plan EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Line Items] EBP, Summary of Accounting Policy [Text Block] Summary of Significant Accounting Policies EBP, Investment, Fair Value and NAV [Abstract] EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Text Block] Fair Value Measurements EBP, Fully Benefit-Responsive Investment Contract [Abstract] EBP, Fully Benefit-Responsive Investment Contract [Table] EBP, Fully Benefit-Responsive Investment Contract [Line Items] EBP, Fully Benefit-Responsive Investment Contract [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Reconciliation of Financial Statement to Form 5500 [Abstract] EBP, Reconciliation of Financial Statement to Form 5500 [Table] EBP, Reconciliation of Financial Statement to Form 5500 [Line Items] EBP, Reconciliation of Financial Statement to Form 5500 [Text Block] Reconciliation of Financial Statements to Form 5500 EBP, Tax Status [Abstract] EBP, Tax Status [Table] EBP, Tax Status [Line Items] EBP, Tax Status [Text Block] Federal Income Tax Status EBP, Subsequent Event [Abstract] EBP, Subsequent Event [Table] EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Text Block] Subsequent Events EBP, Schedule of Asset Held for Investment [Abstract] EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Text Block] Schedule H, Line 4i - Schedule of Assets (Held at End of Year) EBP, Basis of Accounting [Policy Text Block] Basis of Accounting EBP, Use of Estimate [Policy Text Block] Use of Estimates EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition EBP, Note Receivable from Participant [Policy Text Block] Notes Receivable from Participants EBP, Expense [Policy Text Block] Administrative Expenses EBP, Risk and Uncertainty [Policy Text Block] Risks and Uncertainties Employee Benefit Plan Concentrations [Policy Text Block] Concentrations Employee Benefit Plan Concentrations Policy Text Block. EBP, Investment, Fair Value and NAV [Table Text Block] Summary of Plan assets measured at fair value on a recurring basis EBP, Reconciliation of Financial Statement to Form 5500 [Table Text Block] Summary of Reconciliation of Net Assets Available for Benefits Per the Financial Statements to From 5500 Employee Benefit Plan Reconciliation Of Net Increase In Net Assets As Per Form 5500 [Table Text Block] Summary of Net Increase in Net Assets Available for Benefits Per the Financial Statements to Net Income Per the Form 5500 Employee benefit plan reconciliation of net increase in net assets as per form 5500. EBP, Plan Name Plan Name EBP Annual Hours Of Service Required For Paticipation Eligibility Annual hours of service required for participation eligibility EBP annual hours of service required for paticipation eligibility. EBP, Description of Plan Amendment [Text Block] EBP, Description of plan amendment EBP, Participant Contribution, Automatic, Deferral Rate EBP, Participant contribution, Automatic, Deferral rate EBP, Participant Contribution, Plan Opting Decision Making, Number Of days, Maximum EBP, Participant contribution, Plan opting decision making, Number of days, Maximum EBP, Participant Contribution, Plan Opting Decision Making, Number Of days, Maximum. EBP Participant Age Increase In Deferral Rate Threshold EBP, Participant age increase in deferral rate threshold EBP, Participant Age, Increase In Deferral Rate, Threshold. EBP, Annual Increase In Deferral Rate Under AutoEscalation EBP, Annual increase in deferral rate under auto escalation EBP, Annual Increase In Deferral Rate Under Auto-Escalation. EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Participant contribution, Pretax, Maximum annual compensation to total compensation, Percentage EBP Participant Age CatchUp Contribution Threshold EBP, Participant age catch-up contribution threshold EBP, Participant Age, Catch-Up Contribution, Threshold. Employee Benefit Plan, CatchUp Contribution, Maximum, Amount Employee Benefit Plan, Catch-up contribution, Maximum, Amount Employee benefit plan, Catch-Up contribution, maximum, amount. EBP Additional Company Contributions Vesting Percentage EBP, Additional company contributions vesting percentage EBP, Additional Company Contributions, Vesting Percentage. EBP, Investment, Number of Shares EBP, Investment, Number of shares EBP, Investment, Number of shares EBP Participant Contribution Investment In Ameren Stock Fund Percentage Maximum EBP, Participant contribution investment in ameren stock fund percentage maximum EBP, Participant Contribution, Investment In Ameren Stock Fund, Percentage, Maximum. EBP Participant Contribution Rebalance Or Reallocate To Ameren Stock Fund Percentage Maximum EBP, Participant contribution, Rebalance or reallocate to ameren stock fund percentage maximum EBP, Participant Contribution, Rebalance Or Reallocate To Ameren Stock Fund, Percentage, Maximum. Employee Benefit Plan, Maximum Loan Allowed Employee Benefit Plan, Maximum loan allowed Employee Benefit Plan, Maximum Loan Allowed. EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount EBP, Note receivable from participant, Account, Minimum borrowing, Amount Employee Benefit Plan Note Receivable From Participant Account Maximum Borrowing Amount Threshold Employee Benefit Plan, Note receivable from participant account maximum borrowing amount threshold Employee Benefit Plan Note Receivable From Participant Account Maximum Borrowing Amount Threshold. EBP, Asset Held for Investment, Participant Loan, Interest Rate EBP, Asset held for investment, Participant loan, Interest rate Participation Eligibility Criteria [Axis] Participation Eligibility Criteria [Domain] One Year [Member] Consecutive Three Years [Member] Consecutive Two Years [Member] Employment Type [Axis] Employment Type [Domain] Temporary Employees [Member] Amendment Effect [Axis] Amendment Effect [Member] Participant Eligibilty [Member] CatchUp Contribution Limit [Member] Investment Type [Axis] Investments [Domain] EBP, Employer, Common Stock [Member] Common stocks-Plan sponsor stock EBP, Nonemployer, Common Stock [Member] Common stocks-other than Plan sponsor stock Investment, Identifier [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Maximum [Member] Minimum [Member] EBP, Risk and Uncertainty, Concentration of Investment, Benchmark Threshold Percentage EBP, Risk and uncertainty, Concentration of ivestment, Benchmark threshold percentage Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1 [Member] Quoted Prices In Active Markets for Identified Assets (Level 1) Fair Value Measured at Net Asset Value Per Share [Member] Measured at Net Asset Value as a Practical Expedient (a) American depositary receipts ADRs [Member] American depositary receipts (ADRs) Common Collective Trust [Member] Collective trust funds Collective Investment Trusts Mutual Fund [Member] Mutual funds EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Total assets reported at fair value EBP, Investment, Excluding plan interest in master trust, Fair value EBP, Investment, Excluding plan interest in master trust, Fair value Fair Value, Inputs, Level 3 [Member] SSGA Short Term Investment Fund [Member] SSGA Short Term Investment Fund EBP, Net Asset Value per Share or Unit EBP, net asset value per share or unit Fully Benefit Responsive Investment [Member] Fully Benefit Responsive Investment EBP, Investment, Excluding Plan Interest in Master Trust, Contract Value EBP, investment, Excluding plan interest in master trust, contract value EBP, Fully Benefit-Responsive Investment Contract, Limitation on Transacting at Contract Value, Not Probable [true false] EBP, Fully benefit-responsive investment contract, limitation on transacting at contract value, Not probable [true false] EBP, Fully Benefit-Responsive Investment Contract, Termination, Description EBP, Fully benefit-responsive investment contract, Termination, Description EBP, Related Party and Party-in-Interest [Axis] EBP, Related Party and Party-in-Interest [Domain] EBP, Trustee [Member] EBP, Investment, Excluding Plan Interest in Master Trust, Cost EBP, Investment, Excluding plan interest in master trust, cost EBP, Investment, Purchased, Number of Shares EBP, Investment, Purchased, Number of shares EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Cost EBP, Investment acquired, Excluding plan interest in master Trust, Cost EBP, Investment, Sold, Number of Shares EBP, Investment Sold, Excluding Plan Interest in Master Trust, Selling Price EBP, Investment Sold, Excluding plan interest in master Trust, Selling price EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment EBP, Change in net asset available for benefit, Increase from dividend income on investment EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Realized Gain (Loss) on Investment EBP, Change in net asset available for benefit, Increase (Decrease) from realized gain (Loss) on investment EBP Fees Paid For Services EBP, Fees paid for services EBP, Fees Paid For Services. EBP, Reconciliation to Form 5500, Net Asset Available for Benefit, Deemed Distribution Amounts allocated to deemed distributions of notes receivable from Participants EBP, Reconciliation to Form 5500, Net Asset Available for Benefit, Contract Value to Current Value Adjustment Adjustment from contract value to fair value for fully benefit-responsive investment contracts EBP, Form 5500 Caption, Net Assets Net assets available for benefits per the Form 5500 EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Increase For Adjustment From Contract Value To Fair value Current Period Adjustment from contract value to fair value for fully benefit-responsive investment contracts as of the current year-end EBP reconciliation to form 5500 change in net asset available for benefit increase for adjustment from contract value to fair value current period. EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Increase For Adjustment From Contract Value To Fair value Prior Period Adjustment from contract value to fair value for fully benefit-responsive investment contracts as of the prior year-end EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Increase For Adjustment From. Contract Value To Fair Value Prior Period. EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Net decrease in defaulted notes receivable from Participants Net decrease in defaulted notes receivable from Participants EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Net decrease in defaulted notes receivable from Participants. EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Interest income of defaulted notes receivable from Participants Interest income of defaulted notes receivable from Participants EBP Reconciliation To Form 5500 Change In Net Asset Available For Benefit Interest income of defaulted notes receivable from Participants. EBP, Form 5500 Caption, Net Income (Loss) Total net income per the Form 5500 EBP, Tax Determination Letter, Date EBP, Tax Determination Letter, Date Entity Tax Identification Number EBP, Plan Number EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Investment, Current Value, Type [Extensible Enumeration] EBP, Asset Held for Investment, Plan Interest in Master Trust, Current Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value EBP, Asset Held for Investment EBP, Asset Held for Investment, Party-in-Interest [true false]