Derivative Instruments (Details)	12 Months Ended
	Dec. 31, 2019
Electricity (In MWH) [Member] | First quarter 2020 [Member]
Derivative [Line Items]
Volume	186,005
Electricity (In MWH) [Member] | Second quarter 2020 [Member]
Derivative [Line Items]
Volume	95,000
Electricity (In MWH) [Member] | Third quarter 2020 [Member]
Derivative [Line Items]
Volume	85,000
Electricity (In MWH) [Member] | Fourth quarter 2020 [Member]
Derivative [Line Items]
Volume	44,680
Electricity (In MWH) [Member] | First quarter 2021 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Second quarter 2021 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Third quarter 2021 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Fourth quarter 2021 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | First quarter 2022 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Second quarter 2022 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Third quarter 2022 [Member]
Derivative [Line Items]
Volume
Electricity (In MWH) [Member] | Fourth quarter 2022 [Member]
Derivative [Line Items]
Volume
Natural gas (in Dth) [Member] | First quarter 2020 [Member]
Derivative [Line Items]
Volume	359,710
Natural gas (in Dth) [Member] | Second quarter 2020 [Member]
Derivative [Line Items]
Volume	138,920
Natural gas (in Dth) [Member] | Third quarter 2020 [Member]
Derivative [Line Items]
Volume	105,702
Natural gas (in Dth) [Member] | Fourth quarter 2020 [Member]
Derivative [Line Items]
Volume	83,051
Natural gas (in Dth) [Member] | First quarter 2021 [Member]
Derivative [Line Items]
Volume	79,500
Natural gas (in Dth) [Member] | Second quarter 2021 [Member]
Derivative [Line Items]
Volume	60,400
Natural gas (in Dth) [Member] | Third quarter 2021 [Member]
Derivative [Line Items]
Volume	45,700
Natural gas (in Dth) [Member] | Fourth quarter 2021 [Member]
Derivative [Line Items]
Volume	38,450
Natural gas (in Dth) [Member] | First quarter 2022 [Member]
Derivative [Line Items]
Volume	28,600
Natural gas (in Dth) [Member] | Second quarter 2022 [Member]
Derivative [Line Items]
Volume	16,450
Natural gas (in Dth) [Member] | Third quarter 2022 [Member]
Derivative [Line Items]
Volume	2,850
Natural gas (in Dth) [Member] | Fourth quarter 2022 [Member]
Derivative [Line Items]
Volume	1,450