Accounting for Derivative Instruments and Hedging Activities Derivative Assets and Liabilities (Details) $ in Thousands, MMBTU in Millions		Sep. 30, 2022 USD ($) MMBTU	Dec. 31, 2021 USD ($) MMBTU
Derivative [Line Items]
Current, Assets		$ 212,583	$ 128,210
Long-term, Assets		65,515	26,197
Current, Liabilities		71,213	63,309
Long-term, Liabilities		49,798	40,965
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Current, Assets		212,583	128,210
Long-term, Assets		65,515	26,197
Assets	[1]	278,098	154,407
Current, Liabilities		71,213	63,309
Long-term, Liabilities		49,798	40,965
Derivative Liability	[2]	$ 121,011	$ 104,274
Not Designated as Hedging Instrument [Member] | Natural Gas Derivatives [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		314.0	347.0
Not Designated as Hedging Instrument [Member] | Electric Portfolio [Member]
Derivative [Line Items]
Assets		$ 146,637	$ 74,829
Derivative Liability		97,291	85,424
Not Designated as Hedging Instrument [Member] | Natural Gas Portfolio [Member]
Derivative [Line Items]
Assets		131,461	79,578
Derivative Liability		$ 23,720	$ 18,850
Not Designated as Hedging Instrument [Member] | Electric Generation Fuel [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		211.4	238.0
Not Designated as Hedging Instrument [Member] | Purchased Electricity [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU		6.9	8.1

[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.