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Derivatives - Narrative (Details) - 9 months ended Sep. 30, 2023 € in Millions, kr in Millions | EUR (€) MMBTU MWh Boe t | DKK (kr)
--- | --- | ---
LME forward financial sales contracts |  |
Derivative [Line Items] |  |
Open position to offset fixed prices (in tonnes) | t | 74,993 |
Fixed For Floating Swaps |  |
Derivative [Line Items] |  |
Open position to offset fixed prices (in tonnes) | t | 949 |
FX Swaps |  |
Derivative [Line Items] |  |
Derivative asset | € | € 8.2 |
Nordpool Power Price Swap | Grundartangi |  |
Derivative [Line Items] |  |
Derivative liability (in MwH) | MWh | 249,612 |
Indiana Hub Power Price Swaps |  |
Derivative [Line Items] |  |
Derivative liability (in MwH) | MWh | 44,160 |
USD ISK Forward Swap | Not designated as hedging instrument | Short |  |
Derivative [Line Items] |  |
Derivative, forward contracts | kr |  | kr 1,700.0
USD Euro Forward Swap | Not designated as hedging instrument | Short |  |
Derivative [Line Items] |  |
Derivative, forward contracts | € | € 5.3 |
Henry Hub Natural Gas Price Swaps |  |
Derivative [Line Items] |  |
Derivative liability (in MwH) | MMBTU | 900,000 |
HFO Price Swaps |  |
Derivative [Line Items] |  |
Derivative liability (in MwH) | Boe | 100,000 |

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