Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues
Revenues	$ 897,360	$ 895,685	$ 1,794,518	$ 1,823,922
Expenses
Total expenses	2,616,335	802,706	3,437,074	1,637,425
Operating income (loss)
Total operating income (loss)	(1,718,975)	92,979	(1,642,556)	186,497
Retirement defined benefits credit—other than service costs	1,281	1,153	2,563	2,305
Interest expense, net—other than on deposit liabilities and other bank borrowings	(32,400)	(29,832)	(63,991)	(58,630)
Allowance for borrowed funds used during construction	1,344	1,295	2,730	2,426
Allowance for equity funds used during construction	3,336	3,772	6,976	7,073
Interest income	3,134	0	6,267	0
Loss before income taxes	(1,742,280)	69,367	(1,688,011)	139,671
Income tax expense (benefit)	(447,269)	14,284	(435,595)	29,394
Net income (loss)	(1,295,011)	55,083	(1,252,416)	110,277
Preferred stock dividends of subsidiaries	473	473	946	946
Net income (loss) for common stock	$ (1,295,484)	$ 54,610	$ (1,253,362)	$ 109,331
Basic earnings (loss) per common share (in dollars per share)	$ (11.74)	$ 0.50	$ (11.37)	$ 1.00
Diluted earnings (loss) per common share (in dollars per share)	$ (11.74)	$ 0.50	$ (11.37)	$ 1.00
Weighted-average number of common shares outstanding:
Basic (in shares)	110,303	109,573	110,260	109,544
Diluted (in shares)	110,303	109,780	110,260	109,870
Electric utility
Revenues
Revenues	$ 792,331	$ 794,191	$ 1,580,909	$ 1,624,552
Expenses
Total expenses	2,436,771	720,566	3,161,994	1,475,052
Operating income (loss)
Total operating income (loss)	(1,644,440)	73,625	(1,581,085)	149,500
Loss before income taxes	(1,658,653)	58,868	(1,607,753)	119,976
Income tax expense (benefit)	(429,758)	13,070	(418,578)	26,670
Net income (loss)	(1,228,895)	45,798	(1,189,175)	93,306
Preferred stock dividends of subsidiaries	499	499	998	998
Net income (loss) for common stock	(1,229,394)	45,299	(1,190,173)	92,308
Bank
Revenues
Revenues	101,943	96,885	207,087	190,742
Expenses
Total expenses	159,329	72,017	238,941	142,354
Operating income (loss)
Total operating income (loss)	(57,386)	24,868	(31,854)	48,388
Loss before income taxes	(57,106)	25,055	(31,293)	48,762
Income tax expense (benefit)	(11,319)	4,851	(6,440)	9,996
Net income (loss)	(45,787)	20,204	(24,853)	38,766
Preferred stock dividends of subsidiaries	0	0	0	0
Net income (loss) for common stock	(45,787)	20,204	(24,853)	38,766
Other
Revenues
Revenues	3,086	4,609	6,522	8,628
Expenses
Total expenses	20,235	10,123	36,139	20,019
Operating income (loss)
Total operating income (loss)	(17,149)	(5,514)	(29,617)	(11,391)
Loss before income taxes	(26,521)	(14,556)	(48,965)	(29,067)
Income tax expense (benefit)	(6,192)	(3,637)	(10,577)	(7,272)
Net income (loss)	(20,329)	(10,919)	(38,388)	(21,795)
Preferred stock dividends of subsidiaries	(26)	(26)	(52)	(52)
Net income (loss) for common stock	$ (20,303)	$ (10,893)	$ (38,336)	$ (21,743)