v3.26.1
Segment Information - Schedule of Segment Profit or Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Segment Reporting Information [Line Items]    
Operating Revenue $ 347,026 $ 337,353
Operating and Maintenance Expenses 50,255 48,881
Depreciation and Amortization 29,979 29,375
Property Taxes 4,462 4,228
Interest Expense 12,636 11,553
Selling, General, and Administrative Expenses 21,771 21,292
Income Tax Expense (Benefit) 4,876 10,085
Net Income 72,610 68,099
Electric    
Segment Reporting Information [Line Items]    
Operating Revenue 165,870 149,720
Manufacturing    
Segment Reporting Information [Line Items]    
Operating Revenue 89,559 81,685
Plastics    
Segment Reporting Information [Line Items]    
Operating Revenue 91,597 105,948
Operating Segments    
Segment Reporting Information [Line Items]    
Interest Expense 12,481 11,426
Income Tax Expense (Benefit) 7,684 11,557
Net Income 72,473 69,679
Operating Segments | Electric    
Segment Reporting Information [Line Items]    
Operating Revenue 165,870 149,720
Production Fuel and Purchased Power 47,786 45,191
Operating and Maintenance Expenses 50,255 48,881
Depreciation and Amortization 23,445 22,377
Property Taxes 4,462 4,228
Interest Expense 11,736 10,657
Income Tax Expense (Benefit) (5,182) (4,008)
Other Segment Items (1,882) (2,314)
Net Income 35,250 24,708
Operating Segments | Manufacturing    
Segment Reporting Information [Line Items]    
Operating Revenue 89,559 81,685
Depreciation and Amortization 4,787 5,424
Interest Expense 599 623
Cost of Goods Sold 71,201 68,516
Selling, General, and Administrative Expenses 12,229 10,743
Income Tax Expense (Benefit) 1,247 272
Other Segment Items 0 (1)
Net Income 4,283 1,532
Operating Segments | Plastics    
Segment Reporting Information [Line Items]    
Operating Revenue 91,597 105,948
Depreciation and Amortization 1,672 1,546
Interest Expense 146 146
Cost of Goods Sold 40,015 40,087
Selling, General, and Administrative Expenses 6,879 6,985
Income Tax Expense (Benefit) 11,619 15,293
Other Segment Items (2) (2)
Net Income $ 32,940 $ 43,439