Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details) $ in Thousands, MMBTU in Millions		Mar. 31, 2023 USD ($) MMBTU	Dec. 31, 2022 USD ($) MMBTU
Derivative [Line Items]
Current, Assets		$ 125,377	$ 587,029
Long-term, Assets		64,498	94,621
Current, Liabilities		112,634	124,976
Long-term, Liabilities		14,476	18,366
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Current, Assets		125,377	587,029
Long-term, Assets		64,498	94,621
Assets	[1]	189,875	681,650
Current, Liabilities		112,634	124,976
Long-term, Liabilities		14,476	18,366
Derivative Liability	[2]	$ 127,110	$ 143,342
Not Designated as Hedging Instrument [Member] | Natural Gas Derivatives [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		285.0	322.0
Not Designated as Hedging Instrument [Member] | Electric Portfolio [Member]
Derivative [Line Items]
Assets		$ 135,643	$ 337,703
Derivative Liability		77,182	87,120
Not Designated as Hedging Instrument [Member] | Natural Gas Portfolio [Member]
Derivative [Line Items]
Assets		54,232	343,947
Derivative Liability		$ 49,928	$ 56,222
Not Designated as Hedging Instrument [Member] | Electric Generation Fuel [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		227.9	234.9
Not Designated as Hedging Instrument [Member] | Purchased Electricity [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		3.9	5.3

[1] _______________ 1 Balance sheet classification: Current and Long-term Unrealized gain on derivative instruments.

[2] 2 Balance sheet classification: Current and Long-term Unrealized loss on derivative instruments.