v3.26.3
Business Segment Information (Details)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
segment
Sep. 30, 2025
USD ($)
Segment Reporting [Line Items]                
Income Tax Expense (Benefit) $ 40,098     $ 20,368     $ 87,189 $ 62,943
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 62,672     56,014     125,997 90,325
Net Income (Loss) Attributable to Parent 94,167 $ 48,420 $ 110,121 63,729 $ 28,749 $ 101,143    
Segment Reporting, Long-Lived Asset, Expenditure for Addition 241,635     251,139     691,781 547,963
UTILITY OPERATING REVENUES 582,128     529,344     1,545,938 1,445,728
Fuel Costs 116,775     138,017     313,402 344,499
Cost of Goods and Services Sold 61,354     38,604     126,767 105,373
Utilities Operating Expense, Maintenance and Operations 148,181     135,041     439,418 419,957
Depreciation and amortization 95,494     93,239     284,271 271,313
Taxes other than income taxes 10,374     6,262     31,384 19,565
Allowance for equity funds used during construction (2,204)     (622)     (5,648) (2,023)
Interest Expense 48,820     42,211     143,147 132,794
Segment Reporting, Other Segment Item, Amount 564     210     11 982
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 102,770     76,382     $ 213,186 153,268
Number of Reportable Segments | segment             1  
Other Segments [Member]                
Segment Reporting [Line Items]                
Income Tax Expense (Benefit) (1,536)     (3,498)     $ (6,304) (7,709)
Net Income (Loss) Attributable to Parent (8,998)     (6,843)     (25,013) (23,726)
UTILITY OPERATING REVENUES 0     0        
Utilities Operating Expense, Maintenance and Operations 79     156     243 374
Interest Expense 10,494     10,447     31,479 31,342
Segment Reporting, Other Segment Item, Amount (38)     (262)     (405) (281)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest (10,534)     (10,341)     (31,317) (31,435)
Corporate Segment                
Segment Reporting [Line Items]                
Income Tax Expense (Benefit) 41,634     23,866     93,493 70,652
Net Income (Loss) Attributable to Parent 71,670     62,857     151,010 114,051
Segment Reporting, Long-Lived Asset, Expenditure for Addition 241,635     251,139     691,781 547,963
UTILITY OPERATING REVENUES 582,128     529,344     1,545,938 1,445,728
Fuel Costs 116,775     138,017     313,402 344,499
Cost of Goods and Services Sold 61,354     38,604     126,767 105,373
Utilities Operating Expense, Maintenance and Operations 148,102     134,885     439,175 419,583
Depreciation and amortization 95,494     93,239     284,271 271,313
Taxes other than income taxes 10,374     6,262     31,384 19,565
Allowance for equity funds used during construction (2,204)     (622)     (5,648) (2,023)
Interest Expense 38,326     31,764     111,668 101,452
Segment Reporting, Other Segment Item, Amount 603     472     416 1,263
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 113,304     86,723     244,503 184,703
Electricity [Member]                
Segment Reporting [Line Items]                
UTILITY OPERATING REVENUES $ 582,128     $ 529,344     $ 1,545,938 $ 1,445,728