Business Segment Information (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Revenues	$ 3,812,019			$ 3,389,100			$ 9,987,742	$ 9,137,348
Utilities Operating Expense, Fuel Used	822,798			647,982			1,803,594	1,787,148
Utilities Operating Expense, Purchased Power	269,740			213,072			991,591	641,919
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	771,166			722,887			2,168,296	2,111,692
Other Regulatory Charges Credits Net	(23,815)			(102,911)			(96,615)	132,043
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	698,424	$ 471,954	$ 362,422	645,754	$ 51,732	$ 76,536	1,532,800	774,022
Preferred dividend requirements of subsidiaries and net income (loss) attributable to noncontrolling interests	4,624			814			10,310	4,879
Net Income (Loss) Available to Common Stockholders, Basic	693,800			644,940			1,522,490	769,143
Other Nonoperating Income (Expense)	(50,409)			(66,932)			(79,405)	(460,226)
Utility [Member] | Pension Plan [Member] | Group annuity contract purchase
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment					8,000
Corporate Segment and Other Operating Segment [Member] | Pension Plan [Member] | Group annuity contract purchase
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment					$ 317,000
Operating Segments [Member] | Utility [Member]
Revenues	3,797,332			3,370,138			9,942,652	9,083,715
Utilities Operating Expense, Fuel Used	817,038			637,074			1,787,794	1,755,701
Utilities Operating Expense, Purchased Power	265,629			205,144			980,555	617,348
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	763,966			714,162			2,139,736	2,080,867
Other Regulatory Charges Credits Net	(23,815)			(102,911)			(96,615)	132,043
Segment Reporting, Other Segment Item, Amount	1,159,927			1,129,807			3,223,380	3,071,595
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	814,587			786,862			1,907,802	1,426,161
Operating Segments [Member] | Corporate Segment and Other Operating Segment [Member]
Revenues	14,709			18,985			45,157	53,687
Consolidation, Eliminations
Revenues	(22)			(23)			(67)	(54)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(73,181)			(77,582)			(222,970)	(236,028)
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment | Corporate Segment and Other Operating Segment [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(42,982)			(63,526)			(152,032)	(165,888)
Other Nonoperating Income (Expense)								(316,738)
Income Tax (Expense) Benefit on Reconciling Items	$ 0			$ 0			$ 0	$ 66,515