Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues
Revenues	$ 938,383	$ 901,873	$ 2,732,901	$ 2,725,795
Expenses
Total expenses	1,064,931	826,762	4,502,005	2,464,187
Operating income (loss)
Total operating income (loss)	(126,548)	75,111	(1,769,104)	261,608
Retirement defined benefits credit—other than service costs	1,106	1,256	3,669	3,561
Interest expense, net—other than on deposit liabilities and other bank borrowings	(32,085)	(32,629)	(96,076)	(91,259)
Allowance for borrowed funds used during construction	1,331	1,372	4,061	3,798
Allowance for equity funds used during construction	3,300	4,000	10,276	11,073
Interest income	3,662	0	9,929	0
Income (loss) before income taxes	(149,234)	49,110	(1,837,245)	188,781
Income tax expense (benefit)	(45,303)	7,521	(480,898)	36,915
Net income (loss)	(103,931)	41,589	(1,356,347)	151,866
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income (loss) for common stock	$ (104,402)	$ 41,118	$ (1,357,764)	$ 150,449
Basic earnings (loss) per common share (in dollars per share)	$ (0.91)	$ 0.37	$ (12.16)	$ 1.37
Diluted earnings (loss) per common share (in dollars per share)	$ (0.91)	$ 0.37	$ (12.16)	$ 1.37
Weighted-average number of common shares outstanding:
Basic (in shares)	114,358	109,728	111,636	109,606
Diluted (in shares)	114,358	109,917	111,636	109,932
Electric utility
Revenues
Revenues	$ 829,617	$ 794,987	$ 2,410,526	$ 2,419,539
Expenses
Total expenses	934,181	723,629	4,096,175	2,198,681
Operating income (loss)
Total operating income (loss)	(104,564)	71,358	(1,685,649)	220,858
Income (loss) before income taxes	(117,526)	55,415	(1,725,279)	175,391
Income tax expense (benefit)	(35,439)	11,456	(454,017)	38,126
Net income (loss)	(82,087)	43,959	(1,271,262)	137,265
Preferred stock dividends of subsidiaries	498	498	1,496	1,496
Net income (loss) for common stock	(82,585)	43,461	(1,272,758)	135,769
Bank
Revenues
Revenues	105,144	100,974	312,231	291,716
Expenses
Total expenses	81,972	88,415	320,913	230,769
Operating income (loss)
Total operating income (loss)	23,172	12,559	(8,682)	60,947
Income (loss) before income taxes	23,429	12,749	(7,864)	61,511
Income tax expense (benefit)	4,651	1,384	(1,789)	11,380
Net income (loss)	18,778	11,365	(6,075)	50,131
Preferred stock dividends of subsidiaries	0	0	0	0
Net income (loss) for common stock	18,778	11,365	(6,075)	50,131
Other
Revenues
Revenues	3,622	5,912	10,144	14,540
Expenses
Total expenses	48,778	14,718	84,917	34,737
Operating income (loss)
Total operating income (loss)	(45,156)	(8,806)	(74,773)	(20,197)
Income (loss) before income taxes	(55,137)	(19,054)	(104,102)	(48,121)
Income tax expense (benefit)	(14,515)	(5,319)	(25,092)	(12,591)
Net income (loss)	(40,622)	(13,735)	(79,010)	(35,530)
Preferred stock dividends of subsidiaries	(27)	(27)	(79)	(79)
Net income (loss) for common stock	$ (40,595)	$ (13,708)	$ (78,931)	$ (35,451)