Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Range [Domain] Statistical Measurement [Domain] Accounting Policies [Line Items] Accounting Policies [Line Items] [Line Items] for Accounting Policies [Table] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Title of 12(b) Security Title of 12(b) Security Carrying Amount(a) Reported Value Measurement [Member] Forward Contract Indexed to Issuer's Equity, Type [Axis] Forward Contract Indexed to Issuer's Equity, Type [Axis] Subsequent Event Subsequent Event [Member] Document Fiscal Year Focus Document Fiscal Year Focus Adjustment to Compensation, Amount Adjustment to Compensation Amount Eligible Item or Group for Fair Value Option [Axis] Financial Instrument [Axis] Partnership Funding Commitment Partnership Funding Commitment [Member] Partnership Funding Commitment [Member] Ameren Missouri Interconnection Agreement With Ameren Illinois Ameren Missouri Interconnection Agreement With Ameren Illinois [Member] Ameren Missouri Interconnection Agreement With Ameren Illinois Customer [Axis] Customer [Axis] Segment Reporting [Abstract] Segment Reporting [Abstract] Common Stock Common Stock, Value, Issued Employee payroll taxes related to stock-based compensation Payment, Tax Withholding, Share-Based Payment Arrangement Depreciation and amortization Depreciation, Amortization and Accretion, Net Interest Charges Interest charges Interest Expense, Operating and Nonoperating Property Damage European Mutual Association for Nuclear Insurance Property Damage European Mutual Association for Nuclear Insurance [Member] Property Damage European Mutual Association for Nuclear Insurance Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent RETIREMENT BENEFITS Retirement Benefits [Text Block] Restatement Determination Date Restatement Determination Date Defined Benefit Plan, Expected Return (Loss) on Plan Assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Derivative Instrument [Axis] Derivative Instrument [Axis] Schedule of Effective Income Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Miscellaneous expense Other Noninterest Expense First Mortgage Bonds 4.80% Due 2036 First Mortgage Bonds 4.80% Due 2036 [Member] First Mortgage Bonds 4.80% Due 2036 Generation Facilities Generation Facilities [Member] Generation Facilities Beginning of period End of period Accounts Receivable, Allowance for Credit Loss Pension and other postretirement benefits Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits U.S. Treasury and agency securities US Treasury and Government [Member] Regulatory liabilities Regulatory Liability, Noncurrent Fuel oils Fuel Oils [Member] Fuel Oils [Member] Sales and maturities of securities – nuclear decommissioning trust fund Proceeds from Decommissioning Trust Fund Assets Forward Sale Agreements Outstanding Forward Sale Agreements Outstanding [Member] Forward Sale Agreements Outstanding Amendment Flag Amendment Flag Current Liabilities: Liabilities, Current [Abstract] Consolidated Entities [Axis] Consolidated Entities [Axis] Bad debt expense Accounts Receivable, Credit Loss Expense (Reversal) Open Gross Derivative Volumes By Commodity Type Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Other revenues not from contracts with customers Revenue Not from Contract with Customer, Other Shares outstanding Entity Common Stock, Shares Outstanding Allowance for equity funds used during construction Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Shares issued for stock-based compensation Stock Issued During Period, Shares, Other (in shares) Stock Issued During Period, Shares, Other Effective Income Tax Rate Reconciliation, Percent [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Future Decommissioning Cost Future Decommissioning Cost Future Decommissioning Cost Loss Contingencies [Table] Loss Contingencies [Table] Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events Sub-limit of Amount of Weekly indemnity Coverage Thereafter Not Exceeding Policy Limit for Non-Nuclear Events Sub-limit of Amount of Weekly indemnity Coverage Thereafter Not Exceeding Policy Limit for Non-Nuclear Events Long-Term Debt And Equity Financings [Line Items] Long-Term Debt And Equity Financings [Line Items] Long-Term Debt And Equity Financings [Line Items] Number Of Weeks Of Coverage After The First Twelve Weeks Of An Outage Number of weeks of coverage after the first twelve weeks of an outage Number of weeks of coverage after the first twelve weeks of an outage Short-term Debt, Weighted Average Interest Rate, over Time Short-Term Debt, Weighted Average Interest Rate, over Time RELATED PARTY TRANSACTIONS Related Party Transactions Disclosure [Text Block] Consolidated Entities [Domain] Consolidated Entities [Domain] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Liabilities settled Asset Retirement Obligation, Liabilities Settled Missouri Credit Agreement Missouri Credit Agreement [Member] Missouri Credit Agreement [Member] Entity Address, State or Province Entity Address, State or Province Other Other [Member] Other [Member] RATE AND REGULATORY MATTERS Public Utilities Disclosure [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Senior Unsecured Notes 3.65% Due 2026 Senior Unsecured Notes 3.65% Due 2026 [Member] Senior Unsecured Notes 3.65% Due 2026 Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Fuel and purchased power Fuel and purchased power Utilities Operating Expense, Fuel Used and Purchased Power Utilities Operating Expense, Fuel Used and Purchased Power Segment Reporting, Long-Lived Asset, Expenditure for Addition Segment Reporting, Long-Lived Asset, Expenditure for Addition Commodity Forward Price Measurement Input, Commodity Forward Price [Member] Derivative, Notional Amount Derivative, Notional Amount Weighted-average Common Shares Outstanding – Basic Weighted-average Common Shares Outstanding – Basic Weighted Average Number of Shares Outstanding, Basic Purchased Power Purchased Power [Member] Purchased Power Total Related Party Other Operations and Maintenance Total Related Party Other Operations and Maintenance [Member] Total Related Party Other Operations and Maintenance Retirement Benefits [Abstract] Retirement Benefits [Abstract] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Asset Retirement Obligation Asset Retirement Obligation, Beginning Balance Asset Retirement Obligation, Ending Balance Asset Retirement Obligation Regulatory Asset Regulatory Asset, Noncurrent Loss Contingencies [Line Items] Loss Contingencies [Line Items] Number of reportable segments Number of Reportable Segments Total current liabilities Liabilities, Current Taxes other than income taxes Taxes other than income taxes Taxes, Miscellaneous Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Operating Revenues External revenues Revenue from Contract with Customer, Including Assessed Tax Entity Address, City or Town Entity Address, City or Town Schedule of Cash Flow, Supplemental Disclosures Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Industrial Industrial [Member] Industrial [Member] Other Affiliated Entities And Intercompany Eliminations Other Affiliated Entities And Intercompany Eliminations [Member] Other Affiliated Entities And Intercompany Eliminations Ameren Illinois Transmission Ameren Illinois Transmission Segment [Member] Ameren Illinois Transmission Segment [Member] Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss) Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss) Defined Benefit Plan, Amortization Period of Actuarial Gain (Loss) Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Nuclear Waste Matters [Table] Nuclear Waste Matters [Table] Nuclear Waste Matters [Table] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Dividends on preferred stock Payments of Ordinary Dividends, Preferred Stock and Preference Stock New CCR Rules Estimate New CCR Rules Estimate [Member] New CCR Rules Estimate [Member] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Net income attributable to Ameren common shareholders Net income attributable to Ameren common shareholders Net Income (Loss) Available to Common Stockholders, Basic Shares issued under the DRPlus and 401(k) plan Stock Issued During Period, Value, Dividend Reinvestment Plan Level 2 Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Credit Agreements Credit Agreements [Member] Credit Agreements [Member] Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Current maturities of long-term debt Long-Term Debt, Current Maturities Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Amount Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Amount Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Amount Name of Property [Axis] Name of Property [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Change in derivative financial instruments Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Retainage payable Retainage Payable, Current Retainage Payable, Current Public Utilities, General Disclosures [Abstract] Public Utilities, General Disclosures [Abstract] Accrued capital expenditures, including nuclear fuel expenditures Capital Expenditures Incurred but Not yet Paid Litigation Case [Axis] Litigation Case [Axis] Schedule Of Segment Reporting Information By Segment Segment Reporting [Table Text Block] Noncontrolling Interests: Noncontrolling Interest [Member] Unrealized net loss on derivative hedging instruments, tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Deferred Credits and Other Liabilities: Liabilities, Other than Long-Term Debt, Noncurrent [Abstract] Related Party, Type [Axis] Related and Nonrelated Parties [Axis] Revenue from Contract with Customer Revenue from Contract with Customer [Policy Text Block] Pension and other postretirement benefit plan activity, tax Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax Shares issued under the DRPlus and 401(k) plan Stock Issued During Period, Shares, Dividend Reinvestment Plan Document Period End Date Document Period End Date Changes in assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Other Nonoperating Income (Expense) [Table] Other Nonoperating Income (Expense) [Table] Other Nonoperating Income (Expense) Debt Instrument, Face Amount Debt Instrument, Face Amount Operating Expenses: Costs and Expenses [Abstract] Security Exchange Name Security Exchange Name Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Estimated capital costs to comply with existing and known federal and state air emissions regulations Estimated capital costs to comply with existing and known federal and state air emission standards. Estimated capital costs to comply with existing and known federal and state air emission standards. Multi-year rate plan approved revenue requirement Multi-year rate plan approved revenue requirement Multi-year rate plan revenue requirement approved by the ICC. Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Ameren Missouri and Ameren Illinois Transmission Services from ATXI Ameren Missouri and Ameren Illinois Transmission Services from ATXI [Member] Ameren Missouri and Ameren Illinois Transmission Services from ATXI Interest accrued Interest Payable, Current Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Approved rate base Approved rate base Approved rate base Trading Symbol(s) Trading Symbol Consolidation, Variable Interest Entity, Policy Consolidation, Variable Interest Entity, Policy [Policy Text Block] Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 Capital expenditures Capital expenditures Payments to Acquire Property, Plant, and Equipment Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques [Table Text Block] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Purchased Power Purchased Power Utilities Operating Expense, Purchased Power Energy Storage Facility Energy Storage Facility [Member] Energy Storage Facility Public Utilities, Approved Rate Increase (Decrease), Amount Public Utilities, Approved Rate Increase (Decrease), Amount Company Selected Measure Name Company Selected Measure Name Sale of Stock [Domain] Sale of Stock [Domain] Dividends paid to noncontrolling interest holders Payments of Ordinary Dividends, Noncontrolling Interest Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Split Rail Solar Project Split Rail Solar Project [Member] Split Rail Solar Project Amortization of debt issuance costs and premium/discounts Amortization of Debt Issuance Costs and Discounts Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount Peak interest rate Peak Short Term Borrowings Interest Rate Peak Short Term Borrowings Interest Rate Income taxes payable to parent Income taxes payable to parent [Member] Income taxes payable to parent Life Insurance, Corporate Or Bank Owned Life Insurance, Corporate Or Bank Owned [Policy Text Block] Life Insurance, Corporate Or Bank Owned Rate And Regulatory Matters [Table] Rate and Regulatory Matters [Table] Rate and Regulatory Matters [Table] Debt securities: Debt Securities [Member] Fair Value by Asset Class [Domain] Asset Class [Domain] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Cash Flows From Operating Activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy Threshold amount for retrospective insurance assessment for covered loss under public liability and nuclear worker liability insurance policy Miscellaneous accounts receivable Other Receivables, Net, Current Interest income Investment Income, Interest and Dividend Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Weighted-average Common Shares Outstanding – Diluted Weighted-average Common Shares Outstanding – Diluted Weighted Average Number of Shares Outstanding, Diluted Public Utility [Axis] Public Utility [Axis] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Schedule of Cash and Cash Equivalents Including Restricted Cash [Table] Schedule of Cash and Cash Equivalents Including Restricted Cash [Table] Tabular disclosure of the components of cash and cash equivalents, including restricted amounts. Dividends per common share Common Stock, Dividends, Per Share, Cash Paid Emerging growth company Entity Emerging Growth Company Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Derivatives, Policy Derivatives, Policy [Policy Text Block] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Derivative, Nonmonetary Notional Amount, Volume Derivative, Nonmonetary Notional Amount, Volume Underlying Security Market Price Change Underlying Security Market Price Change, Percent Deferred income taxes and tax credits, net Deferred Income Taxes and Tax Credits Commercial Paper Commercial Paper [Member] DERIVATIVE FINANCIAL INSTRUMENTS Derivative Instruments and Hedging Activities Disclosure [Text Block] Commercial Commercial [Member] Commercial [Member] Short-term debt Short-Term Debt Derivative Liability Derivative liabilities Derivative Liability, Subject to Master Netting Arrangement, before Offset Income Taxes [Line Items] Income Taxes [Line Items] [Line Items] for Income Taxes [Table] Net Liquidity Available Net Liquidity Available The net liquidity available is based on credit facility borrowings, commercial paper outstanding, and letters of credit issued under the Credit Agreements, along with cash and cash equivalents. Build-transfer Build-transfer [Member] Renewable generation facility acquired through a build-transfer agreement. Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Months to complete a rate proceeding Months to complete a rate proceeding Months to complete a rate proceeding Debt issuance costs Payment of Financing and Stock Issuance Costs Award Timing Predetermined Award Timing Predetermined [Flag] Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Number of Shares Indexed Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Number of Shares Indexed Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation activity APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Level 1 Fair Value, Inputs, Level 1 [Member] Schedule of Affiliate Receivables and Payables Schedule of Affiliate Receivables and Payables [Table Text Block] [Table Text Block] for Schedule of Affiliate Receivables and Payables Effective Income Tax Rate Reconciliation, Percent, Total Effective Income Tax Rate Reconciliation, Percent Schedule of Insurance Coverage at Callaway Energy Center Schedule Of Insurance Coverage [Table Text Block] Schedule Of Insurance Coverage [Table Text Block] Liabilities incurred Asset Retirement Obligation, Liabilities Incurred Assumed settlement of performance share units and restricted stock units Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements All Executive Categories All Executive Categories [Member] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Regulated Operations [Abstract] Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period Defined Benefit Plan, Difference Between Actual and Expected Return (Loss) on Plan Assets Amortization Period Asset Retirement Obligation Disclosure Schedule of Asset Retirement Obligations [Table Text Block] Money pool advances, net Payments for Advance to Affiliate Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Long-term Debt, Fair Value Long-Term Debt, Fair Value Components Of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Residential Residential [Member] Residential [Member] Scenario [Domain] Scenario [Domain] Effective Income Tax Rate Reconciliation, Tax Credit, Energy-Related, Amount Effective Income Tax Rate Reconciliation, Tax Credit, Energy-Related, Amount Settlements, assets Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Ameren Missouri Securitization Funding I, LLC Ameren Missouri Securitization Funding I, LLC [Member] Ameren Missouri Securitization Funding I, LLC Purchases of securities – nuclear decommissioning trust fund Payments to Acquire Investments to be Held in Decommissioning Trust Fund Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Stock Issued During Period, Value, Other Stock Issued During Period, Value, Other SEGMENT INFORMATION Segment Reporting [Text Block] Minimum Minimum [Member] Number of remediation sites Number of remediation sites Number Of Remediation Sites Dividends on common stock Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date Supplemental Cash Flow Information [Table] Supplemental Cash Flow Information [Table] Supplemental Cash Flow Information [Table] Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Amount Of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage Amount of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage Amount of weekly indemnity coverage commencing twelve weeks after power outage Payables for purchased receivables Payables for purchased receivables Amount of liabilties for purchased receivables Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Total equity Beginning of period End of period Equity, Including Portion Attributable to Noncontrolling Interest Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Nonrelated Party Nonrelated Party [Member] Unbilled revenue Unbilled Receivables, Current Estimate of possible loss Loss Contingency, Estimate of Possible Loss Public Utilities, Requested Rate Increase (Decrease), Amount Public Utilities, Requested Rate Increase (Decrease), Amount Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Derivative [Table] Derivative [Table] Issuances of common stock Proceeds from Issuance of Common Stock Radiation Event Radiation Event [Member] Radiation Event Common stock, shares authorized (in shares) Common Stock, Shares Authorized Earnings Per Share Reconciliation [Abstract] Earnings Per Share Reconciliation [Abstract] LONG-TERM DEBT AND EQUITY FINANCINGS Long Term Debt And Equity Financing [Text Block] This disclosure includes information about long-term debt outstanding, as well as indenture provisions and other covenants. Additionally, this disclosure provides information about equity financings." Common stock, no par value (in dollars per share) Common Stock, No Par Value Asset Retirement Obligation Disclosure [Abstract] Asset Retirement Obligation Disclosure [Abstract] Schedule of Financial Assets and Liabilities Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Exercise Price Award Exercise Price Cash Flows From Investing Activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Related Party Transaction [Axis] Related Party Transaction [Axis] Segment Reporting [Line Items] Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Segment [Domain] Segments [Domain] Frequency of Decommissioning Cost Study Frequency of Decommissioning Cost Study Frequency of Decommissioning Cost Study Interest Rate Swap Interest Rate Swap [Member] Measurement input Derivative Asset (Liability) Net, Measurement Input Scenario [Axis] Scenario [Axis] Maturities and extinguishment of long-term debt Repayments of Long-Term Debt Debt Issuance Costs, Net Debt Issuance Costs, Net Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Component [Domain] Equity Component [Domain] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Measurement Input Type [Domain] Measurement Input Type [Domain] Secured Debt Secured Debt [Member] Ameren Illinois Company Ameren Illinois Company [Member] Ameren Illinois Company Adoption Date Trading Arrangement Adoption Date Other Income And Expenses Schedule of Other Nonoperating Income (Expense) [Table Text Block] Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Dividends on common stock Dividends, Common Stock, Cash Total shareholders’ equity Shareholders' equity, end of year Equity, Attributable to Parent Public Liability And Nuclear Worker Liability - Pool Participation Public Liability And Nuclear Worker Liability Pool Participation [Member] Public Liability and Nuclear worker liability - Pool participation Long-Term Debt And Equity Financings [Abstract] Long-Term Debt And Equity Financings [Abstract] Long-Term Debt and Equity Financings [Abstract] Taxes accrued Increase (Decrease) in Accrued Taxes Payable Pension and other postretirement benefits Assets for Plan Benefits, Defined Benefit Plan ASSETS Assets [Abstract] Ameren Illinois Interconnection Agreement With Ameren Missouri Ameren Illinois Interconnection Agreement With Ameren Missouri [Member] Ameren Illinois Interconnection Agreement With Ameren Missouri Regulatory Agency [Axis] Regulatory Agency [Axis] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Public Utilities, Requested Return on Equity, Percentage Public Utilities, Requested Return on Equity, Percentage Schedule of Cash and Cash Equivalents Including Restricted Cash Schedule of Cash and Cash Equivalents Including Restricted Cash [Table Text Block] [Table Text Block] for Tabular disclosure of the components of cash and cash equivalents, including restricted amounts. Forward Contract Indexed to Issuer's Equity, Type [Domain] Forward Contract Indexed to Issuer's Equity, Type [Domain] Insider Trading Policies and Procedures [Line Items] Regulatory Agency [Domain] Regulatory Agency [Domain] Accounts Receivable, Allowance for Credit Loss, Current Accounts Receivable, Allowance for Credit Loss, Current Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Current regulatory assets Regulatory Asset, Current Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Percent Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Percent Effective Income Tax Rate Reconciliation, Other Adjustments, Amortization Of Excess Deferred Income Taxes. Percent U.S. large capitalization US Large Capitalization [Member] U.S. large capitalization Insurance Aggregate Maximum Coverage Insurance aggregate maximum coverage Insurance aggregate maximum coverage Money pool interest (advances) Money Pool [Member] Money Pool Letter of Credit Letter of Credit [Member] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Excise tax expense Excise and Sales Taxes Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted Number of years the limit of liability and the maximum potential annual payments are adjusted Entity Central Index Key Entity Central Index Key Weighted Average Weighted Average [Member] Accidental Outage - Nuclear Electric Insurance Ltd Accidental Outage - Nuclear Electric Insurance Ltd [Member] Accidental Outage - Nuclear Electric Insurance Ltd Nuclear fuel expenditures Payments for Nuclear Fuel All Adjustments to Compensation All Adjustments to Compensation [Member] Name of Property [Domain] Name of Property [Domain] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Shareholders’ Equity: Equity, Attributable to Parent [Abstract] Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Net realized and unrealized gain – nuclear decommissioning trust fund Gain (Loss) on Investments Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Dividends on preferred stock Dividends, Preferred Stock, Cash Intersegment Eliminations Intersegment Eliminations [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Property Damage - Nuclear Electric Insurance Ltd Property Damage Nuclear Electric Insurance Ltd [Member] Property damage - Nuclear Electric Insurance Ltd Excluded receivables, payables, and accrued income, net Receivables Payables And Accrued Income Net Receivables, payables, and accrued income, net Eligible QIP investments Eligible QIP investments Eligible QIP investments City Area Code City Area Code Dividend reinvestment and 401 (k) plans Dividend reinvestment and 401 (k) plans [Member] Dividend reinvestment and 401 (k) plans Accumulated Other Comprehensive Income (Loss): AOCI Attributable to Parent [Member] Document Information [Table] Document Information [Table] All Individuals All Individuals [Member] Ameren (parent) Ameren (parent) [Member] Ameren (parent) Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Statement [Line Items] Statement [Line Items] TOTAL ASSETS Assets Derivative, Nonmonetary Notional Amount, Energy Measure Derivative, Nonmonetary Notional Amount, Energy Measure Entity [Domain] Entity [Domain] Accrual for environmental loss contingencies Accrual for Environmental Loss Contingencies Discounted cash flow Discounted Cash Flow [Member] Discounted Cash Flow [Member] Prior service cost (credit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Power Power [Member] Derivative instrument whose primary underlying risk is tied to power prices. Operating Segments Operating Segments [Member] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Assets, other Increase (Decrease) in Other Operating Assets Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] [Line Items] for Fair Value Inputs, Assets and Liabilities, Quantitative Information [Table] Nature of Operations Nature of Operations [Text Block] PEO PEO [Member] Cash Surrender Value of Life Insurance Cash Surrender Value of Life Insurance Amount of Megawatts Amount of Megawatts Amount of megawatts Union Electric Company Union Electric Company [Member] Union Electric Company Dilutive effect of forward sale agreements Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements Measurement Basis [Axis] Measurement Basis [Axis] Other deferred credits and liabilities Other Liabilities, Noncurrent Unconsolidated variable interest Noncontrolling Interest in Variable Interest Entity Goodwill Goodwill Retirement Plan Type [Axis] Retirement Plan Type [Axis] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Other Significant Noncash Transaction [Axis] Other Significant Noncash Transaction [Axis] Defined Benefit Plan, Non-service Cost or Income Components - Tracker Defined Benefit Plan, Non-service Cost Or Income Components - Tracker A regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred (expense) and the level of such costs included in customer rates (income). Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings: Retained Earnings [Member] Taxes accrued Taxes Payable, Current Total operating expenses Operating Expenses Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Common Stock, Shares, Outstanding Common stock shares outstanding at beginning of period Common stock shares outstanding at end of period Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Disaggregation of Revenue [Abstract] Disaggregation of Revenue [Abstract] Insurance Maximum Coverage per Incident Insurance maximum coverage per incident Insurance maximum coverage per incident First Mortgage Bonds 5.75% Due 2056 First Mortgage Bonds 5.75% Due 2056 [Member] First Mortgage Bonds 5.75% Due 2056 Corporate bonds Corporate Debt Securities [Member] Earnings per Common Share - Basic Earnings Per Share, Diluted Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] Basis Of Presentation And Significant Accounting Policies [Table] Basis Of Presentation And Significant Accounting Policies [Table] Basis Of Presentation And Significant Accounting Policies [Table] Entity Current Reporting Status Entity Current Reporting Status Net cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Litigation Case Type [Domain] Litigation Case [Domain] Ameren Missouri and Ameren Illinois Rent and Facility Services Ameren Missouri and Ameren Illinois Rent and Facility Services [Member] Ameren Missouri and Ameren Illinois Rent and Facility Services Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Net write-offs Accounts Receivable, Allowance for Credit Loss, Writeoff Natural gas Natural Gas [Member] Deferred Compensation Liability, Classified, Noncurrent Deferred Compensation Liability, Classified, Noncurrent Charged to other accounts Accounts Receivable, Credit Loss charged to other accounts Accounts Receivable, Credit Loss charged to other accounts Utilities Utilities [Member] Utilities [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Cash Flows From Financing Activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Property, Plant, and Equipment, Net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Other interest income Other Interest and Dividend Income Basis Of Presentation And Significant Accounting Policies [Line Items] Basis Of Presentation And Significant Accounting Policies [Line Items] Basis Of Presentation And Significant Accounting Policies [Line Items] Interest cost Defined Benefit Plan, Interest Cost Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract] Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract] Fair Value, Option, Eligible Item or Group [Domain] Financial Instruments [Domain] Nuclear Waste Matters [Line Items] Nuclear Waste Matters [Line Items] [Line Items] for Nuclear Waste Matters [Table] Public Liability And Nuclear Worker Liability - American Nuclear Insurers Public Liability And Nuclear Worker Liability American Nuclear Insurers [Member] Public Liability and Nuclear worker liability - American Nuclear Insurers Nodal Basis Measurement Input, Nodal Basis [Member] Measurement Input, Nodal Basis [Member] Ameren Illinois Natural Gas Ameren Illinois Gas Segment [Member] Ameren Illinois Gas Segment [Member] Miscellaneous income Other Income Accumulated deferred income taxes and tax credits, net Deferred Income Taxes and Other Tax Liabilities, Noncurrent Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Nuclear decommissioning trust fund Decommissioning Fund Investments Underlying Securities Award Underlying Securities Amount Less: Comprehensive Income Attributable to Noncontrolling Interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Fair Value Estimate of Fair Value Measurement [Member] Prepaid assets Prepaid Expense, Current Excise Taxes Excise Taxes [Policy Text Block] Policy regarding the collection and recording of excise taxes by the company. Nuclear decommissioning trust fund: Decommissioning Fund Investments, Fair Value Natural Gas Generation Facility Natural Gas Generation Facility [Member] Natural Gas Generation Facility First Mortgage Bonds 5.00% Due 2036 First Mortgage Bonds 5.00% Due 2036 [Member] First Mortgage Bonds 5.00% Due 2036 Preferred Stock Preferred Stock [Member] Issuance of common stock for stock-based compensation Issuance of common stock for stock-based compensation [Member] Issuance of common stock for stock-based compensation Donations Donations Donations for charitable, social or community welfare purposes. Other Payment for (Proceeds from) Other Investing Activity Inventories Increase (Decrease) in Inventories Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Segment Reporting [Table] Segment Reporting [Table] Stock Issued Stock Issued Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Table] Sale of Stock [Axis] Sale of Stock [Axis] Other current assets Other Assets, Current Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Other Nonoperating Income (Expense) [Abstract] Other Nonoperating Income (Expense) [Abstract] All Trading Arrangements All Trading Arrangements [Member] Long-Term Debt And Equity Financings [Table] Long-Term Debt And Equity Financings [Table] Long-Term Debt And Equity Financings [Table] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Operating Income Operating Income (Loss) Solar generation facility Solar generation facility [Member] Solar generation facility Current Fiscal Year End Date Current Fiscal Year End Date Non-Radiation Event Non-radiation event [Member] Non-radiation event Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Senior Secured Notes and First Mortgage Bonds Senior Secured Notes and First Mortgage Bonds [Member] Senior Secured Notes and First Mortgage Bonds Derivative [Line Items] Derivative [Line Items] Related Party Transaction [Domain] Related Party Transaction [Domain] Money pool advances, net Proceeds from Collection of Advance to Affiliate Revenues from alternative revenue programs Revenues From Alternative Revenue Programs Revenues From Alternative Revenue Programs Outstanding funding commitments Unrecorded Unconditional Purchase Obligation Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Table] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Table] Fair Value Inputs, Assets and Liabilities, Quantitative Information [Table] Entity File Number Entity File Number Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Service Cost Defined Benefit Plan, Service Cost Short-term debt, net Proceeds from (Repayments of) Short-Term Debt Income Taxes [Table] Income Taxes [Table] Income Taxes [Table] Equity securities: Equity Securities [Member] Dividends paid to noncontrolling interest holders Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Borrowings from money pool Borrowings From Money Pool Borrowings From Money Pool Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage Amount of additional weekly indemnity coverage commencing after initial indemnity coverage Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Amortization of nuclear fuel Amortization of Nuclear Fuel Common Stock, Shares, Issued Common Stock, Shares, Issued Measure: Measure [Axis] Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Percent Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Percent Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Percent Entity Information [Line Items] Entity Information [Line Items] Nuclear Waste Matters [Abstract] Nuclear Waste Matters [Abstract] Nuclear Waste Matters [Abstract] Asset retirement obligations Asset Retirement Obligations, Noncurrent Equity Components [Axis] Equity Components [Axis] Debt Instrument, Repurchase Amount Debt Instrument, Repurchase Amount Related Party Related Party [Member] Product and Service [Domain] Product and Service [Domain] Regulatory assets and liabilities Increase (Decrease) in Regulatory Assets and Liabilities Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Entity Interactive Data Current Entity Interactive Data Current Long-Term Debt Long-Term Debt [Member] Less: Net Income Attributable to Noncontrolling Interests Net income attributable to noncontrolling interest holders Net Income (Loss) Attributable to Noncontrolling Interest Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Non-service cost components of net periodic benefit income Total non-service cost components Defined Benefit Plan, Non-service Cost Or Income Components The non-service costs and income components of the net periodic benefit cost. Capital contributions from parent Proceeds from Contributions from Parent Accounts and wages payable Accounts Payable, Related Parties, Current Accounts Payable and Accrued Liabilities, Current Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor Entity Small Business Entity Small Business Comprehensive Income Attributable to Ameren Common Shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Termination Date Trading Arrangement Termination Date Illinois Credit Agreement Illinois Credit Agreement [Member] Illinois Credit Agreement [Member] Utility Plant [Domain] Utility Plant [Domain] Settlement, liabilities Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Pension and other postretirement benefit plan activity, net of income taxes (benefit) Change in deferred retirement benefit costs Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other current liabilities Other Liabilities, Current Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount Other assets Other Assets, Noncurrent Document Type Document Type Other Significant Noncash Transaction, Name [Domain] Other Significant Noncash Transaction, Name [Domain] Gain (Loss) on Extinguishment of Debt Gain (Loss) on Extinguishment of Debt Supplemental Information [Abstract] Supplemental Information [Abstract] Supplemental Information [Abstract] Fair Value as of Grant Date Award Grant Date Fair Value SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Other Nonoperating Income (Expense) [Line Items] Other Nonoperating Income (Expense) [Line Items] [Line Items] for Other Nonoperating Income (Expense) [Table] Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Arrangement Duration Trading Arrangement Duration Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Issuances of long-term debt Proceeds from Issuance of Long-Term Debt Local Phone Number Local Phone Number Manufactured Gas Plant Manufactured Gas Plant [Member] Manufactured Gas Plant [Member] Other Postretirement Benefit Plan, Defined Benefit Other Postretirement Benefits Plan [Member] Supplemental Information Additional Financial Information Disclosure [Text Block] Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Public Utilities, Approved Equity Capital Structure, Percentage Public Utilities, Approved Equity Capital Structure, Percentage Income Before Income Taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Commitments and Contingencies Commitments and Contingencies Revenues Revenues Average daily amount outstanding Short-Term Debt, Average Outstanding Amount Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Income (Loss) from Equity Method Investments Income (Loss) from Equity Method Investments Disclosure Fair Value Measurements Schedule Of Carrying Amounts And Estimated Fair Values Of Long Term Debt And Preferred Stock [Abstract] Disclosure Fair Value Measurements Schedule Of Carrying Amounts And Estimated Fair Values Of Long Term Debt And Preferred Stock [Abstract] Disclosure Fair Value Measurements Schedule Of Carrying Amounts And Estimated Fair Values Of Long Term Debt And Preferred Stock [Abstract] Accounts and wages payable Increase (Decrease) in Accounts Payable and Accrued Liabilities Rate And Regulatory Matters [Line Items] Rate And Regulatory Matters [Line Items] Rate And Regulatory Matters [Line Items] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Money pool borrowings, net Proceeds from (Repayments of) Money Pool Borrowings Proceeds from (Repayments of) Money Pool Borrowings LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Inventories Inventory, Net All Award Types Award Type [Domain] Income taxes receivable from parent Income taxes receivable from parent [Member] Income taxes receivable from parent Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Fair Value Disclosures Fair Value Disclosures [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Total investments and other assets Regulated Entity, Other Assets, Noncurrent Common Stock, Shares Authorized Under Dividend Reinvestment Plan Common Stock, Shares Authorized Under Dividend Reinvestment Plan Common Stock, Shares Authorized Under Dividend Reinvestment Plan Natural gas purchased for resale Natural gas purchased for resale Utilities Operating Expense, Gas and Petroleum Purchased Period End Net Cash Settlement Price Period End Net Cash Settlement Price Period End Net Cash Settlement Price PEO Name PEO Name Schedule of Short-term Debt [Table] Short-Term Debt [Table] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] IETL IETL [Member] Illinois Energy Transition Legislation Entity Tax Identification Number Entity Tax Identification Number Allowance for Doubtful Accounts Receivable [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Legal Entity [Axis] Legal Entity [Axis] Actual debt-to-capital ratio Ratio of Indebtedness to Net Capital Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Public Utilities, Requested Equity Capital Structure, Percentage Public Utilities, Requested Equity Capital Structure, Percentage Cash, cash equivalents, and restricted cash at beginning of year Cash, cash equivalents, and restricted cash at end of period Total cash, cash equivalents, and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Preferred Stock Dividends Noncontrolling interests - preferred stock dividends Preferred Stock Dividends, Income Statement Impact Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit Amount of weekly indemnity coverage thereafter not exceeding policy limit Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code First Mortgage Bonds 5.55% Due 2056 First Mortgage Bonds 5.55% Due 2056 [Member] First Mortgage Bonds 5.55% Due 2056 Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Restricted cash included in “Other current assets” Restricted Cash and Cash Equivalent, Current Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Asset Retirement Obligation [Table] Asset Retirement Obligation [Table] Asset Retirement Obligation [Table] Comprehensive Income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Stock-based compensation costs Share-Based Payment Arrangement, Noncash Expense Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Liability Public Liability [Member] Public Liability Customer [Domain] Customer [Domain] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Derivative Instruments Carrying Value Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Earnings per Common Share - Basic Earnings Per Share, Basic Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Amount Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Amount Effective Income Tax Rate Reconciliation, Other Adjustments, Depreciation Differences. Amount Measurement Input Type [Axis] Measurement Input Type [Axis] Customer deposits Contract with Customer, Liability, Current Total current assets Assets, Current Range [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Long-term debt, net Long-Term Debt, Excluding Current Maturities Ameren Missouri and Ameren Illinois miscellaneous support services and services provided to ATXI Ameren Missouri and Ameren Illinois miscellaneous support services and services provided to ATXI [Member] Ameren Missouri and Ameren Illinois miscellaneous support services and services provided to ATXI Award Type Award Type [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts receivable - trade (less allowance for doubtful accounts) Accounts Receivable, Related Parties, Current Accounts Receivable, after Allowance for Credit Loss, Current Retained earnings Retained Earnings (Accumulated Deficit) Corporate owned life insurance, borrowings Corporate Owned Life Insurance, Borrowings Corporate Owned Life Insurance, Borrowings Commodity Contract Commodity Contract [Member] Schedule of Short-term Debt Schedule of Short-Term Debt [Table Text Block] Deferred Compensation Deferred Compensation [Policy Text Block] Disclosure of accounting policy for deferred compensation; discloses methodologies for measurement, and the bases for recognizing related liabilities. Product and Service [Axis] Product and Service [Axis] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Disclosure Summary Of Significant Accounting Policies Schedule Of Excise Taxes [Abstract] Disclosure Summary Of Significant Accounting Policies Schedule Of Excise Taxes [Abstract] Disclosure Summary Of Significant Accounting Policies Schedule Of Excise Taxes [Abstract] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension Plan Pension Plan [Member] Short-term Debt [Line Items] Short-Term Debt [Line Items] Common Stock Common Stock [Member] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Ameren Services Support Services Agreement Ameren Services Support Services Agreement [Member] Ameren Services Support Services Agreement Weighted-average interest rate Short-Term Debt, Weighted Average Interest Rate, at Point in Time Advances to money pool Advances to Affiliate Derivative, Name [Domain] Derivative Contract [Domain] Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value Forward Contract Indexed to Equity, Settlement, Cash, Amount Depreciation and amortization Cost, Depreciation, Amortization and Depletion Equity Awards Adjustments Equity Awards Adjustments [Member] Ameren Illinois Electric Distribution Ameren Illinois Electric Distribution Segment [Member] Ameren Illinois Electric Distribution Segment [Member] TOTAL LIABILITIES AND EQUITY Liabilities and Equity Effective Income Tax Rate Reconciliation, Tax Credit, Energy-Related, Percent Effective Income Tax Rate Reconciliation, Tax Credit, Energy-Related, Percent Employee Stock Option Share-Based Payment Arrangement, Option [Member] Current asset retirement obligations Asset Retirement Obligation, Current Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Derivative Financial Instruments Derivative Financial Instruments [Member] Derivative Financial Instruments Noncontrolling Interests Equity, Attributable to Noncontrolling Interest Electric Electricity [Member] Segments [Axis] Segments [Axis] Liabilities, other Increase (Decrease) in Other Operating Liabilities Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Asset Class [Axis] Asset Class [Axis] Ameren Transmission Ameren Transmission Segment [Member] Ameren Transmission Segment [Member] Related Party, Type [Domain] Related and Nonrelated Parties [Domain] Schedule of Accounts, Notes, Loans and Financing Receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Tabular List, Table Tabular List [Table Text Block] Restricted cash included in “Other assets” Restricted Cash and Cash Equivalent, Noncurrent Other paid-in capital, principally premium on common stock Additional Paid in Capital Other Income, Net Total Other Income, Net Other Nonoperating Income (Expense) Accretion Asset Retirement Obligation, Accretion Expense Other Debt Securities Other Debt Obligations [Member] Total Shareholders’ Equity Parent [Member] Name Awards Close in Time to MNPI Disclosures, Individual Name Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Electric Distribution Electric Distribution [Member] Other operations and maintenance Other operations and maintenance expenses Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses Final Rate Order Final Rate Order [Member] Final Rate Order [Member] Summary Of Benefit Plan Costs Incurred Schedule of Defined Benefit Plans Disclosures [Table Text Block] Schedule of Other Assets and Other Liabilities Schedule of Other Assets and Other Liabilities [Table Text Block] Self-build Self-build [Member] Renewable generation facility that is self-built. Preferred stock Preferred Stock, Value, Issued Midwest Independent Transmission System Operator, Inc Midwest Independent Transmission System Operator, Inc [Member] Midwest Independent Transmission System Operator, Inc [Member] Adjustment to Compensation: Adjustment to Compensation [Axis] Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value Forward Contract Indexed to Equity, Settlement, Number of Shares Ameren Missouri and Ameren Illinois Miscellaneous Support Services Ameren Missouri and Ameren Illinois miscellaneous support services [Member] Ameren Missouri and Ameren Illinois miscellaneous support services Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation [Line Items] [Line Items] for Asset Retirement Obligation [Table] Hedging Designation [Domain] Hedging Designation [Domain] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Capital expenditures Payments to Acquire Productive Assets Total Related Party Operating Revenues Total Related Party Operating Revenues [Member] Total Related Party Operating Revenues [Member] Included in regulatory assets/liabilities Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Realized And Unrealized Gains Losses Included In Regulatory Assets Liabilities This element represents total gains or losses for the period (realized and unrealized), arising from assets and liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in regulatory assets or regulatory liabilities. Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Assets fair value Assets, Fair Value Disclosure Long-Term Debt, Carrying Amount Long-Term Debt and Lease Obligation Issuance of common stock under the DRPlus Issuance of common stock under the DRPlus [Member] Issuance of common stock under the DRPlus Short-term Debt, Maximum Amount Outstanding During Period Short-Term Debt, Maximum Amount Outstanding During Period Name Measure Name Requested rate base Requested rate base Requested rate base Income Taxes Income Tax Disclosure [Text Block] Pay vs Performance Disclosure [Line Items] Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items] Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items] [Line Items] for Tabular disclosure of the components of cash and cash equivalents, including restricted amounts. Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Other Other Noncash Income (Expense) Forward Sale Agreement Gross Sales Price Forward Sale Agreement Gross Sales Price Forward Sale Agreement Gross Sales Price Supplemental Cash Flow Information [Line Items] Supplemental Cash Flow Information [Line Items] [Line Items] for Supplemental Cash Flow Information [Table] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Number of Energy Center Scrubbers Number Of Energy Center Scrubbers Number of Energy Center Scrubbers to achieve compliance with regulations Deferred Retirement Benefit Costs Deferred Retirement Benefit Costs [Member] Deferred retirement benefit costs [Member] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Other Paid-in Capital: Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Elements [Abstract] Period End Net Share Settlement Price Period End Net Share Settlement Price Period End Net Share Settlement Price Intersegment revenues Revenues Revenue Not from Contract with Customer Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and Cash Equivalent CALLAWAY ENERGY CENTER Nuclear Plant Disclosure [Text Block] This disclosure describes the utility's legal obligations to perform retirement activities for long-lived nuclear assets and spent nuclear fuel. The disclosure includes the retirement obligation, regulatory authorities, recent activities, cost recoveries expected, trust funding and assets, and the regulatory assets and liabilities associated with decommissioning. Company Selected Measure Amount Company Selected Measure Amount Not Designated As Hedging Instrument Not Designated as Hedging Instrument [Member] Forward Contract Indexed to Issuer's Equity, Indexed Shares Forward Contract Indexed to Issuer's Equity, Indexed Shares SHORT-TERM DEBT AND LIQUIDITY Short-Term Debt [Text Block] Schedule of Generation and Storage Facilities Schedule of Generation Facilities [Table Text Block] Schedule of generation facility projects at Ameren Missouri. Accounting Policies [Table] Accounting Policies [Table] Accounting Policies [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Net Income Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Current Assets: Assets, Current [Abstract] Non-PEO NEO Non-PEO NEO [Member] Entity Address, Address Line One Entity Address, Address Line One Restricted cash included in “Nuclear decommissioning trust fund” Restricted Cash and Cash Equivalents, Nuclear Decommissioning Trust Fund Restricted cash and equivalents reserved for use associated with the Callaway Energy Center. Income Taxes Income Tax Expense (Benefit), Total Income taxes Income Tax Expense (Benefit) OTHER INCOME, NET Other Income and Other Expense Disclosure [Text Block] Accrued Proceeds from Issuance of Common Stock Accrued Proceeds from Issuance of Common Stock Accrued Proceeds from Issuance of Common Stock Investments and Other Assets: Regulated Entity, Other Assets, Noncurrent [Abstract] Award Timing Method Award Timing Method [Text Block] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Consolidation Consolidation, Policy [Policy Text Block] Net change in cash, cash equivalents, and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forecast Forecast [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Actuarial (gain) loss Defined Benefit Plan, Amortization of Gain (Loss) Pending Rate Case Pending Rate Case [Member] Pending Rate Case [Member] Maximum Value Of Shares To Be Issued Under ATM Program Maximum Value Of Shares To Be Issued Under ATM Program Maximum Value Of Shares To Be Issued Under ATM Program Net Income Available to Common Shareholder Net Income (Loss) Attributable to Parent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Balance Sheet Location [Axis] Location, Statement of Financial Position, Balance [Axis] Statement [Table] Statement [Table] Other Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Approved return on equity percentage Public Utilities, Approved Return on Equity, Percentage Restatement Determination Date: Restatement Determination Date [Axis] Current regulatory liabilities Regulatory Liability, Current Trading Activity [Axis] Trading Activity [Axis] Total deferred credits and other liabilities Liabilities, Other than Long-Term Debt, Noncurrent Receivables Increase (Decrease) in Receivables Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage Derivative Assets Derivative Asset, Subject to Master Netting Arrangement, before Offset Annual investment in energy-efficiency programs Annual investment in energy-efficiency programs Annual investment in energy-efficiency programs. Schedule of excise taxes Schedule of excise taxes [Table Text Block] Schedule of excise taxes [Table Text Block] Operating Revenues: Revenues [Abstract] Change in unrealized gains (losses) related to assets/liabilities held at period end Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Change In Realized Unrealized Gain Loss Still Held This element represents the change in unrealized gains (losses) related to assets and liabilities measured at fair value using significant unobservable inputs (Level 3) still held as of the reporting date. Beginning balance Ending balance Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Category of Item Purchased [Axis] Category of Item Purchased [Axis] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Forward Sale Agreement Equity Offering Shares Forward Sale Agreement Equity Offering Shares Forward Sale Agreement Equity Offering Shares Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]