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Number of Months Between Callaway Maintenance Outages

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Provision For Depreciation Percent Of Average Depreciable Cost

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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

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

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Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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Amount of accumulated impairment loss for asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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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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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).

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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 unrecorded obligation to transfer funds in future for fixed or minimum amount or quantity of product and service at fixed or minimum price. Includes, but is not limited to, lease not yet commenced and take-or-pay and throughput contracts.

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Summary Of Significant Accounting Policies (Narrative) (Details) customer in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) mi² segment customer	Dec. 31, 2023 USD ($)	Dec. 31, 2022 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	74,000,000	73,000,000
Cash Surrender Value of Life Insurance	260,000,000	248,000,000
Loans, Gross, Insurance Policy	$ 110,000,000	104,000,000
Ameren Missouri
Accounting Policies [Line Items]
Public Utilities, Area Serviced \| mi²	24,000
Number of Months Between Callaway Maintenance Outages	18 months
Ameren Missouri \| 4.85% Securitized Utility Tariff Bonds Due 2039 \| Secured Debt
Accounting Policies [Line Items]
Debt instrument face amount	$ 476,000,000	0
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	118,000,000	111,000,000
Loans, Gross, Insurance Policy	$ 110,000,000	$ 104,000,000
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	1.3
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	2,000,000	$ 9,000,000	$ 7,000,000
Partnership Funding Commitment [Member]
Accounting Policies [Line Items]
Unrecorded Unconditional Purchase Obligation	$ 35,000,000