Derivative Financial Instruments (Derivative Instruments with Credit Risk-Related Contingent Features) (Details) $ in Millions	Sep. 30, 2023 USD ($)
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	$ 55
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	43
Union Electric Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	14
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	8
Ameren Illinois Company
Derivative [Line Items]
Aggregate Fair Value of Derivative Liabilities	41
Cash Collateral Posted	0
Potential Aggregate Amount of Additional Collateral Required	$ 35

The aggregate fair value of assets posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4H

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-5

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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4H

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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