Achieved Percentage of Energy Efficiency Earnings For Incentive Award

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- Definition

Amount of megawatts

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- Definition

Ameren Missouri's average annual electric efficiency investments under the MEEIA

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- Definition

The percentage of depreciation not allowed to be deferred under the PISA election.

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- Definition

Estimated incremental capital investment to modernize the electric grid

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- Definition

Incentive Award if Energy Efficiency Goals Are Achieved

+ References

No definition available.

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- Definition

Ameren Missouri's electric energy efficiency investments under the MEEIA.

+ References

No definition available.

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- Definition

Deferral percentage of the depreciation expense on certain property, plant, and equipment placed in-service and not included in base rates.

+ References

No definition available.

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- Definition

Percentage of energy customers receive from renewable resources

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No definition available.

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- Definition

Rate And Regulatory Matters [Line Items]

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- Definition

Recovery period for plant in service accounting deferrals

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- Definition

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

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

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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.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Rate And Regulatory Matters (Narrative-Missouri) (Detail) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2018 USD ($) MWh	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) MWh	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 4,652		$ 4,652		$ 4,387
Total operating revenues		1,724	$ 1,723	4,872	$ 4,775
Union Electric Company
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 2,799		$ 2,799		$ 2,664
PISA Deferral Percentage				85.00%
Recovery period for plant in service accounting deferrals				20 years
Depreciation Percentage Not Included in PISA Deferral				15.00%
MEEIAEnergyEfficiencyInvestments				$ 226
AnnualMEEIAEnergyEfficiencyInvestments				65
Electricity \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				167
Estimated incremental capital Investment				1,000
Incentive Award if Energy Efficiency Goals Are Achieved				$ 30
Achieved Percentage of Energy Efficiency Earnings For Incentive Award		100.00%		100.00%
TCJA - Excess Amounts Collected in Rates
Rate And Regulatory Matters [Line Items]
Regulatory Liability, Noncurrent		$ 60		$ 60
TCJA - Excess Accumulated Deferred Income Tax Amortization \| Electricity \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 74
Wind Generation Facility \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh				400
Renewable Choice Program \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh				400
Renewable Choice Program \| Electricity \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Percentage of Energy Received From Renewable Resources				100.00%
Renewable Choice Program - Megawatts Owned \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh				200
MEEIA 2016 \| Final Rate Order \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Total operating revenues				$ 5
MEEIA 2016 \| Final Rate Order \| Electricity \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Incentive Award if Energy Efficiency Goals Are Achieved				$ 27
Achieved Percentage of Energy Efficiency Earnings For Incentive Award		100.00%		100.00%
MEEIA 2013 \| Electricity \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Total operating revenues				$ 9
Maximum
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Percentage				2.85%
Subsequent Event \| Wind Generation Facility \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh	157
Subsequent Event \| MEEIA 2016 \| Final Rate Order \| Union Electric Company
Rate And Regulatory Matters [Line Items]
Total operating revenues	$ 6