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Derivatives Instruments (Notional Volumes of Commodity Swaps and Forward Contracts Designated for Regulatory Deferral) (Details) - Regulatory deferral - Commodity swaps and forwards - Purchases bbl in Millions, T in Millions, MWh in Millions, MMBTU in Millions | 12 Months Ended
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Dec. 31, 2019 MMBTU MWh T bbl
Coal | 2020 |
Derivative [Line Items] |
Coal (metric tonnes) | T | 0
Coal | 2021-2022 |
Derivative [Line Items] |
Coal (metric tonnes) | T | 1
Natural gas | 2020 |
Derivative [Line Items] |
Natural Gas (Mmbtu) / Power (MWh) | MMBTU | 12
Natural gas | 2021-2022 |
Derivative [Line Items] |
Natural Gas (Mmbtu) / Power (MWh) | MMBTU | 21
Heavy fuel oil | 2020 |
Derivative [Line Items] |
Heavy fuel oil (bbls) | bbl | 0
Heavy fuel oil | 2021-2022 |
Derivative [Line Items] |
Heavy fuel oil (bbls) | bbl | 1
Power | 2020 |
Derivative [Line Items] |
Natural Gas (Mmbtu) / Power (MWh) | MWh | 1
Power | 2021-2022 |
Derivative [Line Items] |
Natural Gas (Mmbtu) / Power (MWh) | MWh | 3

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