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Costs incurred related to the COVID-19 pandemic.

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Costs associated with the retirement of the Meramec Energy Center.

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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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Value established for a utility on which the entity is allowed to earn a particular rate of return

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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.

+ References

No definition available.

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Percentage of public utility's approved equity to capital, including debt and equity.

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Amount 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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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Amount of operating expense for depreciation and amortization of regulated operation.

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The amount of operating expenses for the period that are associated with the utility's normal revenue producing operation; including selling, general, and administrative expenses, costs incurred for routine plant repairs and maintenance, and operations.

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Rate and Regulatory Matters (Narrative-Missouri) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 28, 2021
Public Utilities, General Disclosures [Line Items]
Depreciation and amortization	$ 1,146	$ 1,075	$ 995
Other operations and maintenance	1,774	1,661	1,745
Regulatory assets	1,289	1,100
Revenues	6,394	5,794	5,910
Union Electric Company
Public Utilities, General Disclosures [Line Items]
Depreciation and amortization	632	604	556
Other operations and maintenance	$ 948	886	960
Sharing Level For Fac	95.00%
Percentage of variance not covered by FAC	5.00%
Regulatory assets	$ 523	347
Final Rate Order \| Union Electric Company
Public Utilities, General Disclosures [Line Items]
COVID-19 pandemic costs	9
Regulatory assets	5
Revenues	4
Final Rate Order \| Union Electric Company \| Electric
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	220
Rate Base	$ 10,200
Public Utilities, Approved Equity Capital Structure, Percentage	51.97%
Depreciation and amortization	$ 140
Other operations and maintenance	40
Meramec Energy Center costs	61
Final Rate Order \| Union Electric Company \| Natural gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	5
Rate Base	313
Final Rate Order \| Union Electric Company \| MEEIA 2019 [Domain] \| Electric
Public Utilities, General Disclosures [Line Items]
Revenues	9	$ 6
Incentive award if energy efficiency goals are achieved	13
MEEIA Energy Efficiency Investments For The 2023 Program Year	$ 75
Final Rate Order \| Union Electric Company \| MEEIA 2013 & 2016 \| Electric
Public Utilities, General Disclosures [Line Items]
Revenues			$ 37
Under Recovered PGA \| Union Electric Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets				$ 53
Minimum \| Under Recovered PGA \| Union Electric Company
Public Utilities, General Disclosures [Line Items]
Amortization Period	12 months
Maximum \| Under Recovered PGA \| Union Electric Company
Public Utilities, General Disclosures [Line Items]
Amortization Period	36 months