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Regulatory Matters - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 27,342	$ 21,900
Regulatory assets, long-term	125,508	168,395
Regulatory liabilities, current	24,844	16,663
Regulatory liabilities, long -term	234,430	233,973
Deferred Income Taxes
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	0	0
Regulatory liabilities, long -term	129,437	134,719
Plant Removal Obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	8,306	0
Regulatory liabilities, long -term	101,595	98,707
Fuel Clause Adjustments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	1,554	10,947
Regulatory liabilities, long -term	$ 0	0
Regulatory Liabilities - Remaining Recovery/Refund Period	1 year
Alternative Revenue Program Riders
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	$ 5,772	3,581
Regulatory liabilities, long -term	3,336	470
Pension and Other Postretirement Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	2,603	1,959
Regulatory liabilities, long -term	$ 0	0
Regulatory Liabilities - Remaining Recovery/Refund Period	1 year
Derivative Instruments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	$ 6,214	0
Regulatory liabilities, long -term	$ 0	0
Regulatory Liabilities - Remaining Recovery/Refund Period	1 year
Other
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	$ 395	176
Regulatory liabilities, long -term	62	77
Pension and Other Postretirement Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	7,791	11,037
Regulatory assets, long-term	114,961	146,071
Alternative Revenue Program Riders
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	11,889	8,871
Regulatory assets, long-term	$ 5,564	9,373
Regulatory Assets - Remaining Recovery/Refund Period	2 years
Asset Retirement Obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 0	0
Regulatory assets, long-term	742	8,462
ISO Cost Recovery Trackers
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	0	1,079
Regulatory assets, long-term	$ 1,342	867
Regulatory Assets - Remaining Recovery/Refund Period	2 years
Unrecovered Project Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 2,136	361
Regulatory assets, long-term	$ 1,455	2,989
Regulatory Assets - Remaining Recovery/Refund Period	5 years
Deferred Rate Case Expenses
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 607	360
Regulatory assets, long-term	1,131	230
Debt Reacquisition Premiums
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	100	192
Regulatory assets, long-term	$ 240	341
Regulatory Assets - Remaining Recovery/Refund Period	30 years
Fuel Clause Adjustments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 4,819	0
Regulatory assets, long-term	$ 0	0
Regulatory Assets - Remaining Recovery/Refund Period	1 year
Other
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 0	0
Regulatory assets, long-term	$ 73	$ 62

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Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

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