CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
OPERATING REVENUES (Note 4)	$ 1,820,741	$ 1,768,801	$ 4,211,772	$ 4,029,507
OPERATING EXPENSES
Fuel and purchased power	655,969	631,382	1,513,048	1,426,418
Operations and maintenance	299,617	308,061	886,331	837,905
Depreciation and amortization	224,555	229,450	688,388	664,761
Taxes other than income taxes	58,416	52,777	175,421	170,592
Other expense	338	145	1,964	2,306
Total	1,238,895	1,221,815	3,265,152	3,101,982
OPERATING INCOME	581,846	546,986	946,620	927,525
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	17,671	9,588	45,687	28,790
Pension and other postretirement non-service credits, net (Note 7)	2,777	12,188	9,427	36,633
Other income (Note 11)	12,473	6,774	42,038	43,234
Other expense (Note 11)	(8,159)	(4,013)	(14,988)	(14,580)
Total	24,762	24,537	82,164	94,077
INTEREST EXPENSE
Interest charges	125,179	109,925	343,649	318,590
Allowance for borrowed funds used during construction	(13,979)	(11,901)	(35,640)	(36,078)
Total	111,200	98,024	308,009	282,512
Income Before Income Taxes	495,408	473,499	720,775	739,090
Income taxes	77,894	74,227	106,729	110,539
Net Income	417,514	399,272	614,046	628,551
Less: Net income attributable to noncontrolling interests (Note 8)	4,306	4,306	12,918	12,918
Net Income Attributable to Common Shareholders	$ 413,208	$ 394,966	$ 601,128	$ 615,633
Weighted-average common shares outstanding - basic (in shares)	119,623	113,729	119,578	113,682
Weighted-average common shares outstanding - diluted (in shares)	121,956	117,119	121,861	115,717
Earnings Per Weighted-Average Common Share Outstanding
Net income attributable to common shareholders — basic (in dollars per share)	$ 3.45	$ 3.47	$ 5.03	$ 5.42
Net income attributable to common shareholders — diluted (in dollars per share)	$ 3.39	$ 3.37	$ 4.93	$ 5.32