Bonds Interest Rate Assumption

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- Definition

Common Stock Equity To Total Capitalization

+ References

No definition available.

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- Details

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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- 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))

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

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- Definition

The cash inflow from parent as a source of financing that is recorded as additional paid in capital.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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- Definition

The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

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-Glossary Financing Activities

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Long-Term Debt And Equity Financings (Narrative) (Detail) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Apr. 30, 2015
Long-Term Debt And Equity Financings [Line Items]
Redemptions of Long-term Debt	$ 0us-gaap_RepaymentsOfLongTermDebt	$ 163,000,000us-gaap_RepaymentsOfLongTermDebt
Union Electric Company
Long-Term Debt And Equity Financings [Line Items]
Capital contribution from parent	224,000,000
Ameren Missouri And Ameren Illinois [Member]
Long-Term Debt And Equity Financings [Line Items]
Assumed interest rate	5.00%
Dividend rate	6.00%
Ameren Illinois Company
Long-Term Debt And Equity Financings [Line Items]
Redemptions of Long-term Debt	0	163,000,000
Ameren Illinois Company \| Federal Energy Regulatory Commission Restriction [Member]
Long-Term Debt And Equity Financings [Line Items]
Common stock equity to total capitalization	54.00%
Ameren Illinois Company \| Minimum \| Federal Energy Regulatory Commission Restriction [Member]
Long-Term Debt And Equity Financings [Line Items]
Common stock equity to total capitalization	30.00%
Subsequent Event [Member] \| Secured Debt [Member] \| Senior Secured Notes, 3.65%, Due 2045 [Member] \| Union Electric Company
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount			250,000,000
Debt Instrument, Interest Rate, Stated Percentage			3.65%
Proceeds from Issuance of Secured Debt			247,000,000
Subsequent Event [Member] \| Secured Debt [Member] \| Senior Secured Notes475 Due2015 [Member] \| Union Electric Company
Long-Term Debt And Equity Financings [Line Items]
Redemptions of Long-term Debt			$ 114,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.75%