The amount of expected costs to fund a capital project.

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- Definition

Ameren Illinois' electric energy efficiency investments under the FEJA.

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- Definition

Rate And Regulatory Matters [Line Items]

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- Definition

The aggregate revenue, whether regulated or unregulated, derived from the generation, transmission and distribution of electricity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(b))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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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.

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No definition available.

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- Definition

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

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- Definition

Amount of public utility's requested rate increase (decrease) with regulatory agency.

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-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
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Rate And Regulatory Matters [Line Items]
Regulatory assets	$ 1,509		$ 1,509		$ 1,437
Current regulatory assets	75		75		149
Regulatory liabilities	2,045		2,045		1,985
Electric	1,594	$ 1,725	4,183	$ 4,101
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory assets	921		921		816
Current regulatory assets	51		51		108
Regulatory liabilities	766		766		$ 768
Electric	463	562	1,343	1,365
Ameren Transmission Company of Illinois
Rate And Regulatory Matters [Line Items]
Estimated Capital Project Costs			85
Property, Plant and Equipment, Additions			32
IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Electric	76	$ 11	1	$ 24
2016 IEIMA Revenue Requirement Reconciliation \| IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Regulatory assets	24		24
2015 IEIMA Revenue Requirement Reconciliation \| IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Current regulatory assets	16		16
2017 IEIMA Revenue Requirement Reconciliation \| IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Regulatory liabilities	$ 1		1
Pending Rate Case \| IEIMA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 17
FEJA \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Equity Capital Structure, Percentage			50.00%
FEJA 2018 through 2021 \| Ameren Illinois Company \| Electric Distribution
Rate And Regulatory Matters [Line Items]
FEJA Energy Efficiency Investments			$ 99