v3.25.2
Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 1,087,482 $ 1,103,633
Total Regulatory Liabilities 667,520 661,592
Net Regulatory Assets 419,962 442,041
Accumulated retirement costs for other obligations    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 15,051 29,975
Deferral of effects on net margin | Hawk Road Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 15,096 15,404
Major maintenance reserve    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 84,016 99,987
Deferred debt service adder    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 194,365 186,757
Asset retirement obligations    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 168,864 102,858
Revenue deferral plan    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 153,527 197,373
Amortization period, regulatory liability 5 years  
Natural gas hedges    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 36,027 28,624
Other regulatory liabilities    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 574 614
Other regulatory liabilities | Maximum    
Regulatory Assets and Liabilities    
Amortization period, regulatory liability 2 years  
Premium and loss on reacquired debt    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 21,429 21,587
Premium and loss on reacquired debt | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 19 years  
Amortization of financing leases    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 22,127 24,699
Outage costs    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 48,867 45,749
Coal-fired maintenance outage costs | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 60 months  
Nuclear refueling outage costs | Minimum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 18 months  
Nuclear refueling outage costs | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 24 months  
Asset retirement obligations | Ashpond and other    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 257,523 268,074
Depreciation expense | Plant Vogtle    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 31,990 32,702
Operating license expected extension period for Plant Vogtle 20 years  
Operating license period 40 years  
Depreciation expense | Plant Wansley    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 326,644 337,181
Deferred charges related to Vogtle Units No. 3 and No. 4 training costs | Deferred charges related to Vogtle Units No. 3 and No. 4 training costs    
Regulatory Assets and Liabilities    
Total Regulatory Assets 54,082 54,545
Interest rate options cost    
Regulatory Assets and Liabilities    
Total Regulatory Assets 127,053 130,456
Deferral of effects on net margin | TA Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 121,868 124,840
Deferral of effects on net margin | BC Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 32,995 27,841
Inventory adjustments | TA Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 14,212 14,723
Other regulatory assets    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 28,692 $ 21,236
Other regulatory assets | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 29 years