Business Segment Information (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Revenues	$ 3,187,626	$ 2,846,874
Utilities Operating Expense, Fuel Used	611,824	344,522
Utilities Operating Expense, Purchased Power	363,043	345,746
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	673,565	672,667
Other Regulatory Charges Credits Net	119,299	(16,843)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	390,805	362,422
Preferred dividend requirements of subsidiaries and net income (loss) attributable to noncontrolling interests	5,889	1,662
Net Income (Loss) Available to Common Stockholders, Basic	384,916	360,760
Other Nonoperating Income (Expense)	22,963	14,726
Operating Segments [Member] | Utility [Member]
Revenues	3,170,273	2,829,597
Utilities Operating Expense, Fuel Used	605,295	338,983
Utilities Operating Expense, Purchased Power	358,505	342,084
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	662,442	662,474
Other Regulatory Charges Credits Net	119,299	(16,843)
Segment Reporting, Other Segment Item, Amount	879,347	1,011,857
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	545,385	491,042
Operating Segments [Member] | Corporate Segment and Other Operating Segment [Member]
Revenues	17,378	17,303
Consolidation, Eliminations
Revenues	(25)	(26)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(70,757)	(75,248)
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment | Corporate Segment and Other Operating Segment [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (83,823)	$ (53,372)