Long-Term Debt and Equity Financings Environmental Bonds (Details) - Union Electric Company - Environmental Improvement And Pollution Control Revenue Bonds [Member]	6 Months Ended
Jun. 30, 2019 USD ($)
Series 1992 Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 47,000,000
Debt Instrument, Interest Rate, Stated Percentage	1.60%
Debt Instrument, Interest Rate During Period	2.36%
Series 1998 Due 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 60,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.90%
Debt Instrument, Interest Rate During Period	3.35%
Series B 1998 Due 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.90%
Debt Instrument, Interest Rate During Period	3.34%
Series C 1998 Due 2033 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 50,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Debt Instrument, Interest Rate During Period	3.83%

Face (par) amount of debt instrument at time of issuance.

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The average effective interest rate during the reporting period.

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Contractual interest rate for funds borrowed, under the debt agreement.

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