CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
OPERATING REVENUES (Note 2)	$ 1,768,801	$ 1,637,759	$ 4,029,507	$ 3,704,417
OPERATING EXPENSES
Fuel and purchased power	631,382	614,520	1,426,418	1,416,778
Operations and maintenance	308,061	250,019	837,905	777,337
Depreciation and amortization	229,450	203,438	664,761	590,445
Taxes other than income taxes	52,777	53,169	170,592	167,949
Other expense	145	350	2,306	1,648
Total	1,221,815	1,121,496	3,101,982	2,954,157
OPERATING INCOME	546,986	516,263	927,525	750,260
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	9,588	11,976	28,790	40,071
Pension and other postretirement non-service credits - net (Note 5)	12,188	10,174	36,633	30,513
Other income (Note 9)	6,774	15,941	43,234	28,424
Other expense (Note 9)	(4,013)	(6,972)	(14,580)	(15,916)
Total	24,537	31,119	94,077	83,092
INTEREST EXPENSE
Interest charges	109,925	96,909	318,590	278,860
Allowance for borrowed funds used during construction	(11,901)	(9,092)	(36,078)	(34,131)
Total	98,024	87,817	282,512	244,729
Income Before Income Taxes	473,499	459,565	739,090	588,623
Income Taxes	74,227	57,045	110,539	74,125
Net Income	399,272	402,520	628,551	514,498
Less: Net income attributable to noncontrolling interests (Note 6)	4,306	4,306	12,918	12,918
Net Income Attributable to Common Shareholders	$ 394,966	$ 398,214	$ 615,633	$ 501,580
Weighted-average common shares outstanding - basic (in shares)	113,729	113,464	113,682	113,411
Weighted-average common shares outstanding - diluted (in shares)	117,119	113,838	115,717	113,718
Earnings Per Weighted-Average Common Share Outstanding
Net income attributable to common shareholders - basic (in dollars per share)	$ 3.47	$ 3.51	$ 5.42	$ 4.42
Net income attributable to common shareholders - diluted (in dollars per share)	$ 3.37	$ 3.50	$ 5.32	$ 4.41