Customer Requested Rate on Equity

No definition available.

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- Definition

Incentive adder to FERC allowed base return on common equity

+ References

No definition available.

+ Details

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- Definition

The amount of cash paid for the settlement of litigation or for other legal issues during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

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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.

+ References

No definition available.

+ Details

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- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current 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 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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Rate and Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Public Utilities, General Disclosures [Line Items]
Current regulatory liabilities		$ 149	$ 128
Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Current regulatory liabilities		$ 62	92
Midwest Independent Transmission System Operator, Inc [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage		12.38%
Payments for Legal Settlements			21
Midwest Independent Transmission System Operator, Inc [Member] \| Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Payments for Legal Settlements			$ 17
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 27
Midwest Independent Transmission System Operator, Inc [Member] \| Ameren Transmission Company of Illinois
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 23
Administrative Law Judge \| Midwest Independent Transmission System Operator, Inc [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage		9.70%
Incentive adder to FERC allowed base return on common equity		0.50%
Administrative Law Judge \| Midwest Independent Transmission System Operator, Inc [Member] \| Maximum
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage		10.20%
Pending Ferc Case \| Midwest Independent Transmission System Operator, Inc [Member]
Public Utilities, General Disclosures [Line Items]
Current regulatory liabilities		$ 44
Pending Ferc Case \| Midwest Independent Transmission System Operator, Inc [Member] \| Ameren Illinois Company
Public Utilities, General Disclosures [Line Items]
Current regulatory liabilities		$ 26
Final Rate Order \| Midwest Independent Transmission System Operator, Inc [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage		10.32%
Customer Requested Rate on Equity		9.15%
Incentive adder to FERC allowed base return on common equity		0.50%
Final Rate Order \| Midwest Independent Transmission System Operator, Inc [Member] \| Maximum
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage		10.82%