Revenue requirement for the electric energy-efficiency investment

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- Definition

Estimated Capital Project Costs

+ References

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- Definition

Rate And Regulatory Matters [Line Items]

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

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- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

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- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ 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 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Rate And Regulatory Matters (Narrative-Illinois) (Detail) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
	Nov. 01, 2018	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 4,652	$ 4,652	$ 4,387
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 1,732	1,732	$ 1,629
Ameren Illinois Company \| Natural Gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount			17
Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount			50
Ameren Transmission Company of Illinois
Rate And Regulatory Matters [Line Items]
Estimated Capital Project Costs			81
Property, Plant and Equipment, Additions			$ 38
Final Rate Order \| Ameren Illinois Company \| Natural Gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Return on Equity, Percentage		9.87%
Public Utilities, Requested Equity Capital Structure, Percentage			50.00%
Rate Base			$ 1,600
TCJA - Reduction in Federal Statutory Income Tax Rate \| Ameren Illinois Company \| Natural Gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount			17
Subsequent Event \| Final Rate Order \| Ameren Illinois Company \| Natural Gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 32
Subsequent Event \| Final Rate Order \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Electric Energy-Efficiency Revenue Requirement	35
Subsequent Event \| Final Rate Order \| IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	72
Subsequent Event \| Final Rate Order \| FEJA energy-efficiency rider [Domain] \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 20
IEIMA \| 2018 IEIMA Revenue Requirement Reconciliation \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 25	$ 25