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Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 16,566	$ 24,999
Regulatory assets, long-term	97,179	94,655
Regulatory liabilities, current	20,526	17,300
Regulatory liabilities, long -term	245,071	244,497
Deferred Income Taxes
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	0	0
Regulatory liabilities, long -term	130,429	131,480
Plant Removal Obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	8,492	8,509
Regulatory liabilities, long -term	106,181	105,733
Fuel Clause Adjustments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	3,654	365
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	$ 2,326	2,504
Regulatory liabilities, long -term	$ 0	0
Regulatory Liabilities - Remaining Recovery/Refund Period	1 year
North Dakota PTC Refunds
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	$ 0	0
Regulatory liabilities, long -term	8,254	7,136
Pension and Other Postretirement Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities, current	5,589	5,589
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	$ 465	333
Regulatory liabilities, long -term	207	148
Pension and Other Postretirement Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	0	0
Regulatory assets, long-term	89,474	88,354
Alternative Revenue Program Riders
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	3,705	5,679
Regulatory assets, long-term	$ 3,272	2,508
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	1,670	1,467
Deferred Income Taxes
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	0	0
Regulatory assets, long-term	729	0
ISO Cost Recovery Trackers
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	432	575
Regulatory assets, long-term	$ 201	314
Regulatory Assets - Remaining Recovery/Refund Period	2 years
Unrecovered Project Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 319	320
Regulatory assets, long-term	$ 916	990
Regulatory Assets - Remaining Recovery/Refund Period	5 years
Deferred Rate Case Expenses
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 377	377
Regulatory assets, long-term	$ 660	754
Regulatory Assets - Remaining Recovery/Refund Period	3 years
Fuel Clause Adjustments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 11,361	10,893
Regulatory assets, long-term	$ 0	0
Regulatory Assets - Remaining Recovery/Refund Period	1 year
Derivative Instruments
Schedule of Regulatory Assets and Liabilities [Line Items]
Regulatory assets - current	$ 347	7,130
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	$ 25	25
Regulatory assets, long-term	$ 257	$ 268

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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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