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Forward Contract Indexed to Issuer's Equity, Basis Spread

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Forward Sale Agreement, Compensation Received by Counterparty

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Forward Sale Agreement Equity Offering Shares

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Forward Sale Agreement Gross Sales Price

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Long-Term Debt And Equity Financings [Line Items]

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Maximum Value Of Shares To Be Issued Under ATM Program

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Period End Net Cash Settlement Price

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Period End Net Share Settlement Price

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- Definition

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

The per share price of the Company's stock at which the contract holder of the freestanding contract has the right to purchase or sell the Company's stock at a future date.

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The number of issuer's shares to which the forward contract is indexed.

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Amount that would be paid upon settlement of forward contract indexed to equity.

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Number of shares as a settlement alternative for each freestanding forward contract.

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- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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The cash inflow from the additional capital contribution to the entity.

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The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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Number of shares issued during the period from a dividend reinvestment plan (DRIP). A dividend reinvestment plan allows the shareholders to reinvest dividends paid to them by the entity on new issues of stock by the entity.

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Number of shares of stock issued attributable to transactions classified as other.

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Value of shares of stock issued attributable to transactions classified as other.

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Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Millions	1 Months Ended		3 Months Ended			9 Months Ended
	Aug. 31, 2022 USD ($)	Apr. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) shares	Mar. 31, 2022 USD ($) shares	Sep. 30, 2021 shares	Sep. 30, 2022 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) shares	Aug. 29, 2022 USD ($)	May 31, 2021 USD ($)
Long-Term Debt And Equity Financings [Line Items]
Shares issued under the DRPlus and 401(k) plan \| shares			0.1		0.1	0.4	0.4
Issuances of common stock						$ 29,000,000	$ 297,000,000
Stock Issued During Period, Shares, Other \| shares			0.0	0.4	0.0	0.4	0.5
Stock Issued During Period, Value, Other				$ 31,000,000
Maximum Value Of Shares To Be Issued Under ATM Program									$ 750,000,000
Forward Contract Indexed to Issuer's Equity, Basis Spread			75			75
Minimum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						$ 86.35
Maximum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						94.80
Weighted Average
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						$ 90.31
Dividend reinvestment and 401 (k) plans
Long-Term Debt And Equity Financings [Line Items]
Issuances of common stock			$ 4,000,000			$ 29,000,000
Accrued Proceeds from Issuance of Common Stock						$ 8,000,000
Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) \| shares			6.6			6.6
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value \| shares			6.6			6.6
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value			$ 587,000,000			$ 587,000,000
Period End Net Cash Settlement Price			58,000,000			58,000,000
Period End Net Share Settlement Price			700,000			700,000
Forward Sale Agreement Equity Offering Shares			6,600,000			6,600,000
Forward Sale Agreement Gross Sales Price			600,000,000			600,000,000
Forward Sale Agreement, Compensation Received by Counterparty			$ 6,000,000			$ 6,000,000
Union Electric Company \| Secured Debt \| Senior Secured Notes 3.90% Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount		$ 525,000,000
Debt Instrument, Interest Rate, Stated Percentage		3.90%
Proceeds from Issuance of Secured Debt		$ 519,000,000
Ameren Illinois Company \| Unsecured Debt \| Senior Secured Notes 3.85% Due 2032
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage								3.85%
Proceeds from Issuance of Secured Debt	$ 496,000,000
Ameren Illinois Company \| Unsecured Debt \| Senior Secured Notes 2.70% Due 2022
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage								2.70%
Ameren Transmission Company of Illinois \| Unsecured Debt \| Senior Unsecured Notes, 2.96%, Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 95,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.96%			2.96%
Proceeds from Issuance of Debt	$ 95,000,000
Ameren Transmission Company of Illinois \| Unsecured Debt \| Senior Unsecured Notes, 3.43%, Due 2050
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.43%			3.43%
Long-Term Debt, Maturity, Year One			$ 50,000,000			$ 50,000,000