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Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2022 MWh MMBTU lb gal | Dec. 31, 2021 MWh MMBTU lb gal
Fuel oils |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal | 21 | 30
Natural gas |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 196 | 179
Power |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 9 | 12
Uranium |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Mass | lb | 496 | 586
Union Electric Company | Fuel oils |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal | 21 | 30
Union Electric Company | Natural gas |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 44 | 35
Union Electric Company | Power |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 3 | 6
Union Electric Company | Uranium |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Mass | lb | 496 | 586
Ameren Illinois Company | Fuel oils |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Volume | gal | 0 | 0
Ameren Illinois Company | Natural gas |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU | 152 | 144
Ameren Illinois Company | Power |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | MWh | 6 | 6
Ameren Illinois Company | Uranium |  |
Derivative [Line Items] |  |
Derivative, Nonmonetary Notional Amount, Mass | lb | 0 | 0

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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 Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Nominal mass used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Definition Nominal volume used to calculate payments on a derivative instrument. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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