Short-Term Debt and Liquidity (Short-Term Debt outstanding) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Short-term debt	$ 868	$ 536
Union Electric Company
Short-term Debt [Line Items]
Short-term debt	444	170
Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	424	366
Commercial Paper
Short-term Debt [Line Items]
Short-term debt	868	536
Commercial Paper \| Parent Company
Short-term Debt [Line Items]
Short-term debt	0	0
Commercial Paper \| Union Electric Company
Short-term Debt [Line Items]
Short-term debt	444	170
Commercial Paper \| Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	$ 424	$ 366

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
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Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant