CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Statement [Abstract]
OPERATING REVENUES (Note 4)	$ 5,339,939	$ 5,124,915	$ 4,695,991
OPERATING EXPENSES
Fuel and purchased power	1,933,420	1,822,566	1,792,657
Operations and maintenance	1,185,065	1,165,156	1,058,725
Depreciation and amortization	915,343	895,346	794,043
Taxes other than income taxes	234,797	227,395	224,013
Other expense	3,684	2,389	1,913
Total	4,272,309	4,112,852	3,871,351
OPERATING INCOME	1,067,630	1,012,063	824,640
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction (Note 1)	61,146	38,620	53,118
Pension and other postretirement non-service credits, net (Note 9)	12,420	48,870	40,648
Other income (Note 15)	49,406	48,614	33,666
Other expense (Note 15)	(30,265)	(34,136)	(25,056)
Total	92,707	101,968	102,376
INTEREST EXPENSE
Interest charges	469,701	425,742	374,887
Allowance for borrowed funds used during construction (Note 1)	(47,733)	(48,270)	(43,564)
Total	421,968	377,472	331,323
Income Before Income Taxes	738,369	736,559	595,693
Income Taxes (Note 5)	106,726	110,529	76,912
NET INCOME	631,643	626,030	518,781
Less: Net income attributable to noncontrolling interests (Note 12)	15,112	17,224	17,224
Net Income (Loss) Attributable to Common Shareholders	$ 616,531	$ 608,806	$ 501,557
Weighted average common shares outstanding — basic (in shares)	119,687	113,846	113,442
Weighted-average common shares outstanding — diluted (in shares)	121,971	116,232	113,804
Earnings Per Weighted-Average Common Share Outstanding
Net income attributable to common shareholders — basic (in dollars per share)	$ 5.15	$ 5.35	$ 4.42
Net income attributable to common shareholders — diluted (in dollars per share)	$ 5.05	$ 5.24	$ 4.41