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Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Finance Lease Obligation $ 39 $ 42
Level 2 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,100 1,100
Level 2 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 938 969
Level 3 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,534 1,450
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 39 42
Level 3 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,163 1,167
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 35 40
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 52 52
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 $ 47 $ 46