v3.25.1
Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Dec. 31, 2024
Detail of regulatory liabilities    
Total regulatory liabilities $ 2,136,096 $ 2,062,233
Less: current regulatory liabilities 225,332 206,955
Total non-current regulatory liabilities 1,910,764 1,855,278
Asset retirement obligations and removal costs    
Detail of regulatory liabilities    
Total regulatory liabilities 330,787 358,403
Other postretirement benefits    
Detail of regulatory liabilities    
Total regulatory liabilities 233,978 238,113
Four Corners coal reclamation    
Detail of regulatory liabilities    
Total regulatory liabilities 97,532 77,532
Deferred fuel and purchased power — mark-to-market (Note 9)    
Detail of regulatory liabilities    
Total regulatory liabilities 85,540 0
Renewable energy standard    
Detail of regulatory liabilities    
Total regulatory liabilities 70,217 68,523
Income taxes — deferred investment tax credit    
Detail of regulatory liabilities    
Total regulatory liabilities 66,336 66,327
Income taxes — change in rates    
Detail of regulatory liabilities    
Total regulatory liabilities 59,142 59,133
Demand side management    
Detail of regulatory liabilities    
Total regulatory liabilities 27,157 23,927
Spent nuclear fuel    
Detail of regulatory liabilities    
Total regulatory liabilities 25,355 26,818
Sundance maintenance    
Detail of regulatory liabilities    
Total regulatory liabilities 23,860 23,086
TCA Balancing Account    
Detail of regulatory liabilities    
Total regulatory liabilities 11,189 14,834
Property tax deferral    
Detail of regulatory liabilities    
Total regulatory liabilities 4,238 4,785
Tax expense adjustor mechanism    
Detail of regulatory liabilities    
Total regulatory liabilities 4,192 4,343
Other    
Detail of regulatory liabilities    
Total regulatory liabilities 115 113
ACC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities 889,034 888,896
FERC | Excess deferred income taxes - Tax Cuts and Jobs Act    
Detail of regulatory liabilities    
Total regulatory liabilities $ 207,424 $ 207,400