v3.26.1
Business Segment Information (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Revenues $ 3,523,638   $ 3,328,849   $ 6,711,264 $ 6,175,723
Utilities Operating Expense, Fuel Used 759,343   636,274   1,371,167 980,796
Utilities Operating Expense, Purchased Power 307,243   376,105   670,286 721,851
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses 771,418   724,463   1,444,983 1,397,130
Other Regulatory Charges (Credits) - Net (15,360)   (55,957)   103,939 (72,800)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 487,820 $ 390,805 471,954 $ 362,422 878,625 834,376
Preferred dividend requirements of subsidiaries and net income (loss) attributable to noncontrolling interests 5,213   4,024   11,102 5,686
Net Income (Loss) Available to Common Stockholders, Basic 482,607   467,930   867,523 828,690
Other Nonoperating Income (Expense) (49,987)   (43,722)   (27,024) (28,996)
Operating Segments [Member] | Utility [Member]            
Revenues 3,513,488   3,315,723   6,683,761 6,145,320
Utilities Operating Expense, Fuel Used 756,802   631,773   1,362,097 970,756
Utilities Operating Expense, Purchased Power 305,250   372,842   663,755 714,926
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses 758,723   713,296   1,421,165 1,375,770
Other Regulatory Charges (Credits) - Net (15,360)   (55,957)   103,939 (72,800)
Segment Reporting, Other Segment Item, Amount 1,077,697   1,051,596   1,957,044 2,063,453
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 630,376   602,173   1,175,761 1,093,215
Operating Segments [Member] | Corporate Segment and Other Operating Segment [Member]            
Revenues 10,157   13,144   27,535 30,448
Consolidation, Eliminations            
Revenues (7)   (18)   (32) (45)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (70,019)   (74,541)   (140,776) (149,789)
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment | Corporate Segment and Other Operating Segment [Member]            
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest $ (72,537)   $ (55,678)   $ (156,360) $ (109,050)