v3.26.1
Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Detail of regulatory liabilities    
Total regulatory liabilities $ 1,977,868 $ 1,947,030
Less: current regulatory liabilities 194,643 210,909
Total non-current regulatory liabilities 1,783,225 1,736,121
AROs and removal costs    
Detail of regulatory liabilities    
Total regulatory liabilities 298,964 286,907
Other postretirement benefits    
Detail of regulatory liabilities    
Total regulatory liabilities 226,529 233,952
Four Corners coal reclamation    
Detail of regulatory liabilities    
Total regulatory liabilities 97,048 97,988
Income taxes — deferred investment tax credit    
Detail of regulatory liabilities    
Total regulatory liabilities 80,553 81,949
Deferred fuel and purchased power    
Detail of regulatory liabilities    
Total regulatory liabilities 61,437 0
Income taxes — change in state rates    
Detail of regulatory liabilities    
Total regulatory liabilities 55,201 56,260
RES    
Detail of regulatory liabilities    
Total regulatory liabilities 56,847 54,551
Sundance maintenance    
Detail of regulatory liabilities    
Total regulatory liabilities 25,969 25,668
Spent nuclear fuel    
Detail of regulatory liabilities    
Total regulatory liabilities 16,928 20,492
DSM    
Detail of regulatory liabilities    
Total regulatory liabilities 12,498 26,228
TCA Balancing Account    
Detail of regulatory liabilities    
Total regulatory liabilities 10,654 4,860
TEAM    
Detail of regulatory liabilities    
Total regulatory liabilities 3,436 3,738
Deferred fuel and purchased power — mark-to-market (Note 10)    
Detail of regulatory liabilities    
Total regulatory liabilities 0 3,641
Other    
Detail of regulatory liabilities    
Total regulatory liabilities 1,977 3,063
ACC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities 832,335 847,572
FERC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities $ 197,492 $ 200,161