CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Income Statement [Abstract]
OPERATING REVENUES (Note 4)	$ 1,149,597	$ 1,032,280
OPERATING EXPENSES
Fuel and purchased power	436,729	380,071
Operations and maintenance	276,700	300,109
Depreciation and amortization	239,858	234,940
Taxes other than income taxes	61,972	59,354
Other expense	3,164	584
Total	1,018,423	975,058
OPERATING INCOME	131,174	57,222
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	14,782	13,249
Pension and other postretirement non-service credits, net (Note 8)	3,982	2,958
Other income (Note 12)	4,981	17,461
Other expense (Note 12)	(2,740)	(2,570)
Total	21,005	31,098
INTEREST EXPENSE
Interest charges	125,759	104,943
Allowance for borrowed funds used during construction	(9,863)	(10,102)
Total	115,896	94,841
Income (Loss) Before Income Taxes	36,283	(6,521)
Income taxes (benefit)	1,169	(6,183)
NET INCOME (LOSS)	35,114	(338)
Less: Net income attributable to noncontrolling interests (Note 9)	2,194	4,306
Net Income (Loss) Attributable to Common Shareholders	$ 32,920	$ (4,644)
Weighted average common shares outstanding — basic (in shares)	121,360	119,594
Weighted-average common shares outstanding — diluted (in shares)	123,778	119,594
Earnings Per Weighted-Average Common Share Outstanding
Net income (loss) attributable to common shareholders - basic (in dollars per share)	$ 0.27	$ (0.04)
Net income (loss) attributable to common shareholders - diluted (in dollars per share)	$ 0.27	$ (0.04)