[Line Items] for Accounting Policies [Table]

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- Definition

The increase to assets and liabilities as a result of adopting ASC 842 - Leases

+ References

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- Definition

Corporate owned life insurance, borrowings

+ References

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- Definition

The non-service costs and income components of the net periodic benefit cost.

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- Definition

Amount of liabilties for purchased receivables

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- Definition

Provision For Depreciation Percent Of Average Depreciable Cost

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- Definition

Public Utilities, Area Serviced

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No definition available.

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- Definition

Public Utilities, Number of Customers

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- Definition

Sharing Level For Fac

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- Definition

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (d)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer).

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
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-Section 50
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Net carrying amount of the assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), when the reporting entity is not the VIE's primary beneficiary.

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Summary Of Significant Accounting Policies (Narrative) (Details) customer in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) mi² customer	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Line Items]
Balance Sheet impact of ASC 842	$ 40
Payables for purchased receivables	33	$ 31
Deferred Compensation Liability, Classified, Noncurrent	80	86
Cash Surrender Value of Life Insurance	244	265
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	22	17
Goodwill	411	411
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	16
Defined Benefit Plan, Non-service Cost or Income Components	70	44	$ 56
Corporate owned life insurance, borrowings	113	120
Ameren Illinois Company
Accounting Policies [Line Items]
Cash Surrender Value of Life Insurance	$ 122	129
Public Utilities, Area Serviced \| mi²	40,000
Goodwill	$ 411	411
Defined Benefit Plan, Non-service Cost or Income Components	$ 34	10	24
Union Electric Company
Accounting Policies [Line Items]
Public Utilities, Area Serviced \| mi²	24,000
Defined Benefit Plan, Non-service Cost or Income Components	$ 17	$ 22	$ 18
Minimum
Accounting Policies [Line Items]
Percent of average depreciable cost	3.00%	3.00%	3.00%
Maximum
Accounting Policies [Line Items]
Percent of average depreciable cost	4.00%	4.00%	4.00%
Power \| Ameren Illinois Company
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	1.2
Power \| Union Electric Company
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	1.2
Natural gas \| Ameren Illinois Company
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	0.8
Natural gas \| Union Electric Company
Accounting Policies [Line Items]
Public Utilities, Number of Customers \| customer	0.1
FAC \| Union Electric Company
Accounting Policies [Line Items]
Sharing Level For Fac	95.00%
Ameren Illinois Electric Distribution [Member]
Accounting Policies [Line Items]
Goodwill	$ 238
Ameren Illinois Gas [Member]
Accounting Policies [Line Items]
Goodwill	80
Ameren Illinois Transmission [Member]
Accounting Policies [Line Items]
Goodwill	93
Ameren Transmission [Member]
Accounting Policies [Line Items]
Goodwill	$ 93