Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets		$ 327,663	$ 245,981
Total Financial Liabilities		4,291	6,406
Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1]	89,227	76,037
Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1],[2]	187,431	166,300
Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[3]	212	166
Derivatives - Gas And Power [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[4]	50,793	3,478
Total Financial Liabilities	[4]	4,291	6,406
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets		121,305	77,619
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1]	89,227	76,037
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1],[2]	0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[3]	0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Derivatives - Gas And Power [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[4]	32,078	1,582
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets		3,917	646
Total Financial Liabilities		4,291	6,406
Significant Other Observable Inputs (Level 2) [Member] | Nuclear Decommissioning Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1]	0	0
Significant Other Observable Inputs (Level 2) [Member] | Nuclear Decommissioning Trust - Net Asset Value [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[1],[2]	0	0
Significant Other Observable Inputs (Level 2) [Member] | Unrestricted Investment And Other [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[3]	212	166
Significant Other Observable Inputs (Level 2) [Member] | Derivatives - Gas And Power [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[4]	3,705	480
Total Financial Liabilities	[4]	4,291	6,406
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets		15,010	1,416
Significant Unobservable Inputs (Level 3) | Derivatives - Gas And Power [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Financial Assets	[4]	$ 15,010	$ 1,416

[1] For additional information about our nuclear decommissioning trust, see Note 8—Investments.

[2] Nuclear decommissioning trust includes investments measured at net asset value per share (or its equivalent) as a practical expedient and these investments have not been categorized in the fair value hierarchy.  The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the Consolidated Balance Sheet.

[3] Unrestricted investments and other includes investments that are related to equity securities.

[4] Derivatives - gas and power represent natural gas futures contracts (Level 1 and Level 2) and financial transmission rights (Level 3).  Level 1 are indexed against NYMEX.  Level 2 are valued by ACES using observable market inputs for similar transactions.  Level 3 are valued by ACES using unobservable market inputs, including situations where there is little market activity.  Sensitivity in the market price of financial transmission rights could impact the fair value.  For additional information about our derivative financial instruments, see Note 1—Summary of Significant Accounting Policies.