v3.26.1
Segment Information (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Reportable_segment
Jun. 30, 2025
USD ($)
Segment Reporting [Line Items]        
Operating revenues $ 392,599 $ 342,713 $ 890,169 $ 809,343
Fuel, purchased supply and direct transmission expense (exclusive of depreciation and depletion shown separately below) 89,823 75,271 235,388 213,468
Operating, general, and administrative 79,095 62,336 153,635 119,045
Administrative and general 42,356 33,773 88,475 75,130
Property and other taxes 50,101 48,168 100,505 91,408
Depreciation and depletion 66,978 62,379 133,809 124,779
Interest expense, net (40,332) (36,254) (80,248) (72,765)
Other income, net 4,546 78 7,603 4,006
Income tax expense (3,466) (3,382) (17,262) (18,586)
Net Income 24,994 21,228 $ 88,450 98,168
Number of Reportable Segments | Reportable_segment     2  
Regulated Electric Segment | Operating Segments        
Segment Reporting [Line Items]        
Operating revenues 324,254 279,468 $ 686,308 614,951
Fuel, purchased supply and direct transmission expense (exclusive of depreciation and depletion shown separately below) 72,836 59,603 163,111 152,355
Operating, general, and administrative 91,739 73,615 181,340 146,094
Property and other taxes 39,056 37,318 78,267 70,604
Depreciation and depletion 55,562 52,387 111,031 104,875
Interest expense, net (30,589) (27,562) (60,774) (55,318)
Other income, net 2,941 121 4,486 2,611
Income tax expense (5,451) (4,230) (16,934) (14,102)
Net Income 31,962 24,874 79,337 74,214
Regulated Natural Gas | Operating Segments        
Segment Reporting [Line Items]        
Operating revenues 68,345 63,245 203,861 194,392
Fuel, purchased supply and direct transmission expense (exclusive of depreciation and depletion shown separately below) 16,987 15,668 72,277 61,113
Operating, general, and administrative 25,551 22,773 52,682 47,943
Property and other taxes 11,044 10,850 22,196 20,645
Depreciation and depletion 11,416 9,992 22,778 19,904
Interest expense, net (8,086) (7,297) (15,957) (14,331)
Other income, net 1,167 456 1,791 1,547
Income tax expense 304 201 (2,831) (4,226)
Net Income (3,268) (2,678) 16,931 27,777
Regulated Electric and Natural Gas Segments | Operating Segments        
Segment Reporting [Line Items]        
Operating revenues 392,599 342,713 890,169 809,343
Fuel, purchased supply and direct transmission expense (exclusive of depreciation and depletion shown separately below) 89,823 75,271 235,388 213,468
Operating, general, and administrative 117,290 96,388 234,022 194,037
Property and other taxes 50,100 48,168 100,463 91,249
Depreciation and depletion 66,978 62,379 133,809 124,779
Interest expense, net (38,675) (34,859) (76,731) (69,649)
Other income, net 4,108 577 6,277 4,158
Income tax expense (5,147) (4,029) (19,765) (18,328)
Net Income 28,694 22,196 96,268 101,991
Other Operating Segment | Operating Segments        
Segment Reporting [Line Items]        
Net Income $ (3,700) $ (968) $ (7,818) $ (3,823)