Derivatives And Risk Management (Energy Commodity Derivatives) (Details) frequency in Thousands, Volt in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 Volt frequency	Dec. 31, 2019 Volt frequency
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	366	133
2021	0	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 | Volt	871	2,984
2021 | Volt	1,490	1,040
2022 | Volt	0	0
2023	0	0
2024	0	0
Thereafter | Volt	0	0
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	1,491	1,724
2021	246	246
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 | Volt	27,035	37,848
2021 | Volt	21,700	13,108
2022 | Volt	2,700	675
2023 | Volt	0	0
2024	0	0
Thereafter | Volt	0	0
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	3	2
2021	0	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 | Volt	10,232	9,813
2021 | Volt	305	153
2022 | Volt	450	225
2023 | Volt	0	0
2024 | Volt	0	0
Thereafter | Volt	0	0
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	395	442
2021	123	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 | Volt	61,330	78,803
2021 | Volt	32,120	25,523
2022 | Volt	7,820	4,725
2023 | Volt	0	0
2024 | Volt	0	0
Thereafter | Volt	0	0