v3.26.1
Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
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 941 953
Level 3 [Member] | Reported Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,834 1,674
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 34 36
Level 3 [Member] | Estimate of Fair Value Measurement [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 1,500 1,326
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 31 33
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