Average daily commercial paper borrowings outstanding

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- Definition

Maximum ratio of indebtedness to net capital

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- Definition

Peak Short Term Borrowings

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- Definition

Peak Short Term Borrowings Interest Rate

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- Definition

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

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-Subparagraph (SX 210.9-03.13(2))

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-Publisher SEC

-Name Regulation S-X (SX)

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-Article 9

-Section 03

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-Name Regulation S-X (SX)

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-Name Regulation S-X (SX)

-Number 210

-Article 5

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-Publisher FASB

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-Paragraph 1

-Subparagraph (SX 210.5-02.19(a)(3))

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ 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 835

-SubTopic 30

-Section 45

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-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

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ Details

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- Definition

Identification of whether the entity has been in compliance with any credit facility debt covenants during the period.

+ References

+ Details

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- Definition

Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Subparagraph (SX 210.5-02.19(b),22(b))

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- 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.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

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- Definition

Total Aggregate Indebtedness divided by Net Capital.

+ References

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

-Publisher SEC

-Name Rule 15c3

-Number 240

-Article 15c3

-Section 1

-Subsection a

-Paragraph 1

-Subparagraph i

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Credit Facility Borrowings And Liquidity (Narrative) (Details) (USD $)	9 Months Ended					9 Months Ended
	Sep. 30, 2011 Commercial Paper [Member]	Sep. 30, 2011 2010 Credit Agreements [Member]	Sep. 30, 2011 2010 Credit Agreements [Member] 2010 Ameren Credit Agreement [Member]	Sep. 30, 2011 Ameren Revolving Credit Facility [Member]	Jun. 02, 2010 Ameren Revolving Credit Facility [Member]	Sep. 30, 2011 2010 Ameren Credit Agreement [Member]
Line of Credit Facility [Line Items]
Letters of credit, outstanding amount		$ 15,000,000
Available amounts under the facilities			1,800,000,000
Line of credit facility, maximum borrowing capacity	500,000,000				20,000,000
Commercial paper outstanding	330,000,000
Average daily commercial paper borrowings outstanding	335,000,000
Debt instrument, interest rate, effective percentage	0.85%				2.25%
Peak short-term borrowings	$ 435,000,000
Peak short-term borrowings interest rate	1.46%
Maximum consolidated indebtedness as a percent of total capitalization			65.00%	65.00%
Actual debt-to-capital ratio			48	48
Minimum ratio of consolidated funds from operations plus interest expense to consolidated interest expense as of balance sheet date						2.0
Current ratio of consolidated funds from operations plus interest expense to consolidated interest expense as of balance sheet date						4.9