v3.26.1
Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
 6 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 1,037,131 $ 1,023,859
Total Regulatory Liabilities 931,187 869,860
Net Regulatory Assets 105,944 153,999
Deferral of effects on net margin | Hawk Road Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 14,480 14,788
Major maintenance reserve    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 132,304 109,028
Deferred debt service adder    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 197,794 201,836
Asset retirement obligations    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities 328,857 245,133
Revenue deferral plan    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 75,920 107,784
Amortization period, regulatory liability 5 years  
Other revenue deferral plan    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 1,595 0
Amortization period, regulatory liability 3 years  
Natural gas hedges    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 0 10,642
Deferral of direct pay nuclear production tax credits    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 180,082 180,082
Amortization period, regulatory liability 3 years  
Other regulatory liabilities    
Regulatory Assets and Liabilities    
Total Regulatory Liabilities $ 155 567
Other regulatory liabilities | Maximum    
Regulatory Assets and Liabilities    
Amortization period, regulatory liability 1 year  
Premium and loss on reacquired debt    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 26,416 20,173
Premium and loss on reacquired debt | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 30 years  
Amortization of financing leases    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 16,393 19,556
Outage costs    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 59,834 46,781
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 $ 219,511 228,400
Depreciation expense | Plant Vogtle    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 30,567 31,279
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 $ 305,570 316,106
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 53,157 53,619
Interest rate options cost    
Regulatory Assets and Liabilities    
Total Regulatory Assets 120,247 123,650
Deferral of effects on net margin | TA Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 115,923 118,896
Deferral of effects on net margin | BC Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 9,925 13,868
Inventory adjustments | TA Smith Energy Facility    
Regulatory Assets and Liabilities    
Total Regulatory Assets 13,191 13,701
Accumulated retirement costs for other obligations    
Regulatory Assets and Liabilities    
Total Regulatory Assets 19,305 5,479
Natural gas hedges    
Regulatory Assets and Liabilities    
Total Regulatory Assets 15,176 0
Other regulatory assets    
Regulatory Assets and Liabilities    
Total Regulatory Assets $ 31,916 $ 32,351
Other regulatory assets | Maximum    
Regulatory Assets and Liabilities    
Amortization period, other regulatory assets 28 years