Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3521-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3044-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=123431023&loc=SL98516268-108586

+ Details

Name:	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of long-term debt and lease obligation, classified as noncurrent.

+ References

+ Details

Name:	us-gaap_LongTermDebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_ShorttermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=aee_UnionElectricCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=aee_AmerenIllinoisCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Assets and Liabilities) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	$ 161	$ 155	$ 267	$ 301
Short-term debt	1,021	545
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8	17	145
Short-term debt	285	165
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133	$ 242	$ 147
Short-term debt	141	103
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments in industrial development revenue bonds	248	248
Short-term debt	1,021	545
Long-term debt (including current portion)	13,590	13,067
Debt Issuance Costs, Net	97	94
Carrying Amount \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments in industrial development revenue bonds	248	248
Short-term debt	285	165
Long-term debt (including current portion)	6,139	5,619
Debt Issuance Costs, Net	43	38
Carrying Amount \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term debt	141	103
Long-term debt (including current portion)	4,394	4,392
Debt Issuance Costs, Net	37	39
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,021	545
Long-term Debt, Fair Value	12,516	14,521
Fair Value \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	161	155
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,021	545
Long-term Debt, Fair Value	12,016	13,930
Fair Value \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	500	591
Fair Value \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	285	165
Long-term Debt, Fair Value	5,641	6,321
Fair Value \| Union Electric Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Union Electric Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	285	165
Long-term Debt, Fair Value	5,641	6,321
Fair Value \| Union Electric Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term Debt, Fair Value	141	103
Long-term Debt, Fair Value	4,037	4,971
Fair Value \| Ameren Illinois Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	146	133
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Ameren Illinois Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	141	103
Long-term Debt, Fair Value	4,037	4,971
Fair Value \| Ameren Illinois Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	$ 0	$ 0