[Line Items] for Accounting Policies [Table]

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- Definition

The resettlement of MISO-related purchase and sale transactions.

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- Definition

Number of Months Between Callaway Maintenance Outages

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Provision For Depreciation Percent Of Average Depreciable Cost

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- Definition

Public Utilities, Area Serviced

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Public Utilities, Number of Customers

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- Definition

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Portion of equity (net assets) in a variable interest entity (VIE) not attributable, directly or indirectly, to the parent entity. That is, this is the portion of equity in a VIE that is attributable to the noncontrolling interest (previously referred to as minority interest).

+ References

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount of increase (decrease) of physical assets used in the normal conduct of business and not intended for resale, from reclassification, impairment, donation, or changes classified as other. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

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Summary Of Significant Accounting Policies (Narrative) (Details) customer in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) mi² segment customer	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Accounting Policies [Line Items]
Goodwill	$ 411,000,000	$ 411,000,000
Number of reportable segments \| segment	4
Goodwill, Impairment Loss	$ 0
Noncontrolling Interest in Variable Interest Entity	73,000,000	68,000,000
Cash Surrender Value of Life Insurance	248,000,000	246,000,000
Loans, Gross, Insurance Policy	104,000,000	110,000,000
MISO Resettlements	$ 0
Ameren Missouri
Accounting Policies [Line Items]
Public Utilities, Area Serviced \| mi²	24,000
Number of Months Between Callaway Maintenance Outages	18 months
Ameren Illinois
Accounting Policies [Line Items]
Public Utilities, Area Serviced \| mi²	43,700
Goodwill	$ 411,000,000	411,000,000
Number of reportable segments \| segment	3
Goodwill, Impairment Loss	$ 0
Cash Surrender Value of Life Insurance	111,000,000	118,000,000
Loans, Gross, Insurance Policy	$ 104,000,000	$ 110,000,000
Minimum
Accounting Policies [Line Items]
Percent of average depreciable cost	3.00%	3.00%	3.00%
Maximum
Accounting Policies [Line Items]
Percent of average depreciable cost	4.00%	4.00%	4.00%
Electric \| Ameren Missouri
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	1.2
Power \| Ameren Illinois
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	1.2
Natural gas \| Ameren Missouri
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	0.1
Natural gas \| Ameren Illinois
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	0.8
Ameren Illinois Electric Distribution
Accounting Policies [Line Items]
Goodwill	$ 238,000,000
Ameren Illinois Gas
Accounting Policies [Line Items]
Goodwill	80,000,000
Ameren Illinois Transmission
Accounting Policies [Line Items]
Goodwill	93,000,000
Ameren Transmission
Accounting Policies [Line Items]
Goodwill	93,000,000
AROs \| Ameren Missouri
Accounting Policies [Line Items]
Noncash Depreciation related to ARO	9,000,000	$ 7,000,000	$ 14,000,000
Partnership Funding Commitment [Member]
Accounting Policies [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 14,000,000