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Risk Management Activities - Outstanding commodity derivative instruments designated as hedging instruments (Details) - Commodity risk management
Dec. 31, 2021
MWh
t
Dec. 31, 2020
MWh
t
Electricity | Cash flow hedges    
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]    
Notional amount sold 0 95,000
Notional amount purchased 0 0
Electricity | Non-Hedges    
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]    
Notional amount sold 46,139,000 12,944,000
Notional amount purchased 14,951,000 8,258,000
Emissions | Non-Hedges    
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]    
Notional amount sold 445,000 1,831,000
Notional amount purchased 2,030,000 2,112,000
Notional amount purchased | t 350,000 2,365,000
Notional amount sold | t 350,000 2,160,000
Coal | Non-Hedges    
Disclosure of information about terms and conditions of hedging instruments and how they affect future cash flows [line items]    
Notional amount purchased | t 9,352,000 9,078,000
Notional amount sold | t 0 0