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Rate and Regulatory Matters (Regulatory Framework-Missouri) (Details) - Ameren Missouri - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2025	Jul. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Public Utilities, General Disclosures [Line Items]
Number of months to complete a regulatory rate review			11 months
PISA deferral percentage			85.00%
Depreciation percentage not included in PISA deferral			15.00%
Sharing Level For Fac	95.00%		95.00%
Percentage of variance not covered by FAC	5.00%		5.00%
Base rate reset period			4 years
Rush Island Energy Center
Public Utilities, General Disclosures [Line Items]
Regulatory asset, amortization period				15 years
Costs to be securitized				$ 476
Maximum
Public Utilities, General Disclosures [Line Items]
Percentage of energy sourced from renewable resources			100.00%
Public utilities, approved rate increase (decrease), percentage	2.25%	2.50%
PISA
Public Utilities, General Disclosures [Line Items]
Regulatory asset, amortization period	20 years		20 years

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- Definition

Costs to be securitized

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- Definition

The percentage of depreciation not allowed to be deferred under the PISA election.

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- Definition

Frequency Rates Must be Reset to Use the FAC

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- Definition

The number of months it takes to complete a regulatory rate review.

+ References

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- Definition

Deferral percentage of the depreciation expense on certain property, plant, and equipment placed in-service and not included in base rates.

+ References

No definition available.

+ Details

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- Definition

The maximum percentage of energy allowed to be sourced from renewable resources under the Renewable Solutions Program.

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- Definition

The percentage of the net energy cost variance from the amounts set in base rates not allowed to be recovered or refunded through the FAC.

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- Definition

The portion of the variance in net energy costs from the amount set in base rates Ameren Missouri is permitted to recover or refund, through customer rates, without a traditional regulatory rate review.

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- Definition

Percentage of public utility's approved rate increase (decrease) by regulatory agency.

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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.

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Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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