Summary Of Significant Accounting Policies (Schedule Of Inventories) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Line Items]
Fuel	$ 123	$ 154
Gas stored underground	71	82
Other materials and supplies	289	286
Total Inventories	483	522
Union Electric Company
Accounting Policies [Line Items]
Fuel	123	154
Gas stored underground	7	8
Other materials and supplies	228	226
Total Inventories	358	388
Ameren Illinois Company
Accounting Policies [Line Items]
Fuel	0	0
Gas stored underground	64	74
Other materials and supplies	61	60
Total Inventories	$ 125	$ 134

[Line Items] for Accounting Policies [Table]

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- Definition

Carrying amount as of the balance sheet date of coal, which is a combustible rock or minerals which are extracted from the ground and used as fuel.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, and deemed to be a current asset because it is expected to be used within twelve months or in the normal operating cycle.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 210
-SubTopic 10
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-Paragraph 1
-Subparagraph (b)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
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- Definition

The period end amount for a type of inventory held by the utility in a schedule of inventories.

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