| **Derivative Accounting - Gains and Losses from Derivative Instruments (Details) - USD ($) $ in Thousands** | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------|-----------------|
||
| Commodity Contracts | Fuel and purchased power | Not Designated as Hedging Instruments                      |            |   |   |
| **Derivative Instruments Not Designated as Cash Flows Hedges**                                              |            |   |   |
| Net Gain (Loss) Recognized in Income                                                                        | $ (370,145)     | $ 307,287 | $ 216,847 |

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| - References
No definition available.
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| - Definition
Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.
+ References
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