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v3.23.3

Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 USD ($) shares | Mar. 31, 2023 USD ($) shares | Sep. 30, 2022 USD ($) shares | Sep. 30, 2023 USD ($) $ / shares shares | Sep. 30, 2022 USD ($) shares
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Shares issued under the DRPlus and 401(k) plan | shares | 0.2 |  | 0.1 | 0.4 | 0.4
Issuances of common stock |  |  |  | $ 28,000,000 | $ 29,000,000
Stock Issued During Period, Shares, Other | shares | 0.0 | 0.5 | 0.0 | 0.5 | 0.4
Stock Issued During Period, Value, Other |  | $ 37,000,000 |  |  |
Common Stock, Shares Authorized Under DRPlus Plan | shares | 3.0 |  |  | 3.0 |
Maximum Value Of Shares To Be Issued Under ATM Program | $ 910,000,000 |  |  | $ 910,000,000 |
Forward Contract Indexed to Issuer's Equity, Basis Spread | 75 |  |  | 75 |
Termination of a financing obligation |  |  |  | $ 240,000,000 | $ 0
Minimum |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares |  |  |  | $ 81.83 |
Maximum |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares |  |  |  | 94.63 |
Weighted Average |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share | $ / shares |  |  |  | $ 91.23 |
Dividend reinvestment and 401 (k) plans |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Issuances of common stock | $ 5,000,000 |  |  | $ 28,000,000 |
Accrued Proceeds from Issuance of Common Stock |  |  |  | $ 7,000,000 |
Forward Sale Agreements Outstanding |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value | shares | 4.3 |  |  | 4.3 |
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value | $ 390,000,000 |  |  | $ 390,000,000 |
Period End Net Cash Settlement Price | 72,000,000 |  |  | 72,000,000 |
Period End Net Share Settlement Price | 1,000,000 |  |  | 1,000,000 |
Forward Sale Agreement Equity Offering Shares | 4,300,000 |  |  | 4,300,000 |
Forward Sale Agreement Gross Sales Price | 392,000,000 |  |  | 392,000,000 |
Union Electric Company |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Termination of a financing obligation |  |  |  | 240,000,000 | 0
Union Electric Company | Secured Debt | Senior Secured Notes 5.45% Due 2053 |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Debt Instrument, Face Amount | $ 500,000,000 |  |  | $ 500,000,000 |
Debt Instrument, Interest Rate, Stated Percentage | 5.45% |  |  | 5.45% |
Ameren Illinois Company |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Capital contributions from parent |  |  |  | $ 50,000,000 | 0
Termination of a financing obligation |  |  |  | 0 | 0
Ameren Illinois Company | Other Paid-in Capital: |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Capital contributions from parent | $ 50,000,000 |  | $ 0 | 50,000,000 | $ 0
Ameren Illinois Company | Secured Debt | First Mortgage Bonds 0.375% Due 2023 |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Debt Instrument, Face Amount | $ 100,000,000 |  |  | $ 100,000,000 |
Debt Instrument, Interest Rate, Stated Percentage | 0.375% |  |  | 0.375% |
Ameren Illinois Company | Secured Debt | First Mortgage Bonds 4.95% Due 2033 |  |  |  |  |
Long-Term Debt And Equity Financings [Line Items] |  |  |  |  |
Debt Instrument, Face Amount | $ 500,000,000 |  |  | $ 500,000,000 |
Debt Instrument, Interest Rate, Stated Percentage | 4.95% |  |  | 4.95% |

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