Name:	aee_ImpairmentAndOtherChargesLineItems
Namespace Prefix:	aee_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Unrecognized Tax Benefit Recorded In Other Deferred Credits And Liabilities

+ References

No definition available.

+ Details

Name:	aee_UnrecognizedTaxBenefitRecordedInOtherDeferredCreditsAndLiabilities
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Working Capital and Contingent Liability Payment

+ References

No definition available.

+ Details

Name:	aee_WorkingCapitalandContingentLiabilityPayment
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2420-110228

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 958

-SubTopic 225

-Section 45

-Paragraph 11

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=28367520&loc=d3e92212-112881

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Impairment

-URI http://asc.fasb.org/extlink&oid=6515133

+ Details

Name:	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow attributable to repayments of borrowings not otherwise defined in the taxonomy (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_RepaymentsOfOtherLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=aee_SeniorUnsecuredNotes8875Due2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=aee_NewAmerenEnergyResourcesCompanyLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Schedule I - Condensed Financial Information Of Parent (Impairment and Other Charges) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			9 Months Ended	1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	May 31, 2014
Impairment and Other Charges [Line Items]
Unrecognized Tax Benefit Recorded In Other Deferred Credits And Liabilities	$ 52	$ 84
Repayments of Other Long-term Debt	697us-gaap_RepaymentsOfOtherLongTermDebt	399us-gaap_RepaymentsOfOtherLongTermDebt	760us-gaap_RepaymentsOfOtherLongTermDebt
Parent Company
Impairment and Other Charges [Line Items]
Unrecognized Tax Benefit Recorded In Other Deferred Credits And Liabilities	53	53
Repayments of Other Long-term Debt	425	0	0
Parent Company \| Merchant Generation
Impairment and Other Charges [Line Items]
Impairment charge on long-lived assets and related charges		201	1,880
New Ameren Energy Resources Company, LLC
Impairment and Other Charges [Line Items]
Working Capital and Contingent Liability Payment				13
Senior Unsecured Notes8875 Due2014 [Member] \| Parent Company
Impairment and Other Charges [Line Items]
Repayments of Other Long-term Debt					$ 425
Long-term debt interest rate	8.875%				8.875%