v3.25.1
Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
Detail of regulatory assets    
Total regulatory assets $ 1,694,830 $ 1,810,458
Less: current regulatory assets 322,070 420,969
Total non-current regulatory assets 1,372,760 1,389,489
Pension    
Detail of regulatory assets    
Total regulatory assets 739,549 750,976
Deferred fuel and purchased power    
Detail of regulatory assets    
Total regulatory assets 228,036 287,597
Income taxes — allowance for funds used during construction equity    
Detail of regulatory assets    
Total regulatory assets 192,894 192,936
Ocotillo deferral    
Detail of regulatory assets    
Total regulatory assets 111,064 114,775
Lease incentives    
Detail of regulatory assets    
Total regulatory assets 84,483 70,541
SCR deferral    
Detail of regulatory assets    
Total regulatory assets 81,639 83,123
Retired power plant costs    
Detail of regulatory assets    
Total regulatory assets 64,591 68,380
FERC Transmission true up    
Detail of regulatory assets    
Total regulatory assets 44,253 35,159
Income taxes — investment tax credit basis adjustment    
Detail of regulatory assets    
Total regulatory assets 34,839 34,834
Deferred compensation    
Detail of regulatory assets    
Total regulatory assets 34,423 33,108
Deferred property taxes    
Detail of regulatory assets    
Total regulatory assets 21,776 23,918
Palo Verde VIEs (Note 8)    
Detail of regulatory assets    
Total regulatory assets 20,571 20,611
Mead-Phoenix transmission line contributions in aid of construction (“CIAC”)    
Detail of regulatory assets    
Total regulatory assets 8,301 8,384
Active Union Medical Trust    
Detail of regulatory assets    
Total regulatory assets 6,664 9,673
Loss on reacquired debt    
Detail of regulatory assets    
Total regulatory assets 6,425 6,682
Navajo coal reclamation    
Detail of regulatory assets    
Total regulatory assets 5,747 7,905
Tax expense adjustor mechanism    
Detail of regulatory assets    
Total regulatory assets 4,370 4,534
PSA - interest    
Detail of regulatory assets    
Total regulatory assets 1,712 11,525
Deferred fuel and purchased power — mark-to-market (Note 9)    
Detail of regulatory assets    
Total regulatory assets 0 42,275
Other    
Detail of regulatory assets    
Total regulatory assets $ 3,493 $ 3,522