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Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands
Sep. 30, 2023
Dec. 31, 2022
Level 2 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value $ 1,100,000 $ 1,113,500
Level 2 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 886,339 966,881
Level 3 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,450,000 1,200,000
Level 3 [Member] | Reported Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Finance Lease Obligation 43,304 45,730
Level 3 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,030,511 881,480
Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Finance Lease Obligation 38,200 41,700
Affiliated Entity [Member] | Level 3 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 51,547 51,547
Affiliated Entity [Member] | Level 3 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value $ 45,021 $ 42,836