CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Operating Revenues	$ 407,244	$ 429,546	$ 772,980	$ 882,302
Operating Expenses
Fuel	69,683	63,648	146,291	165,102
Purchased Power	31,345	27,440	61,812	53,670
Transmission and Other PPFAC Recoverable Costs	15,557	15,389	24,499	33,467
Increase (Decrease) to Reflect PPFAC Recovery Treatment	662	38,467	(580)	71,235
Total Fuel and Purchased Power	117,247	144,944	232,022	323,474
Operations and Maintenance	111,009	105,517	211,186	224,266
Depreciation	58,323	56,367	115,838	111,971
Amortization	7,621	7,773	15,402	15,509
Taxes Other Than Income Taxes	18,356	17,493	37,057	36,245
Total Operating Expenses	312,556	332,094	611,505	711,465
Operating Income	94,688	97,452	161,475	170,837
Other Income (Expense)
Interest Expense	(31,731)	(24,248)	(61,361)	(48,253)
Allowance For Borrowed Funds	4,549	1,877	8,898	3,753
Allowance For Equity Funds	11,264	5,407	20,951	10,659
Unrealized Gains (Losses) on Investments	1,624	128	1,708	990
Interest Income	1,898	859	3,660	2,071
Other, Net	(659)	(438)	(1,624)	(355)
Total Other Income (Expense)	(13,055)	(16,415)	(27,768)	(31,135)
Income Before Income Tax Expense	81,633	81,037	133,707	139,702
Income Tax Expense	9,971	10,603	17,614	18,087
Net Income	$ 71,662	$ 70,434	$ 116,093	$ 121,615