Business Segment Information (Reconciliation of Operating Profit (Loss) from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenues	$ 3,328,849		$ 2,953,620		$ 6,175,723	$ 5,748,248
Utilities Operating Expense, Fuel Used	636,274		522,550		980,796	1,139,166
Utilities Operating Expense, Purchased Power	376,105		200,705		721,851	428,847
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	724,463		701,775		1,397,130	1,388,806
Other Regulatory Charges Credits Net	(55,957)		125,607		(72,800)	234,954
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	471,954	$ 362,422	51,732	$ 76,536	834,376	128,268
Preferred dividend requirements of subsidiaries and net income (loss) attributable to noncontrolling interests	4,024		2,810		5,686	4,065
Net Income (Loss) Available to Common Stockholders, Basic	467,930		48,922		828,690	124,203
Other Nonoperating Income (Expense)	(43,722)		(342,549)		(28,996)	(393,294)
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	3,315,723		2,941,404		6,145,320	5,713,577
Utilities Operating Expense, Fuel Used	631,773		514,223		970,756	1,118,627
Utilities Operating Expense, Purchased Power	372,842		193,010		714,926	412,204
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses	713,296		685,990		1,375,770	1,366,705
Other Regulatory Charges Credits Net	(55,957)		125,607		(72,800)	234,954
Segment Reporting, Other Segment Item, Amount	1,051,596		979,255		2,063,453	1,941,788
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	602,173		443,319		1,093,215	639,299
Operating Segments [Member] | Corporate Segment and Other Operating Segment [Member]
Revenues	13,144		12,227		30,448	34,703
Consolidation, Eliminations
Revenues	(18)		(11)		(45)	(32)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(74,541)		(78,885)		(149,789)	(158,446)
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment | Corporate Segment and Other Operating Segment [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(55,678)		(62,479)		(109,050)	(102,362)
Other Nonoperating Income (Expense)			(316,738)			(316,738)
Income Tax (Expense) Benefit on Reconciling Items	$ 0		$ 66,515		$ 0	$ 66,515