CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Operating Revenues	$ 418,236	$ 439,527	$ 854,089	$ 776,253
Operating Expenses
Fuel	64,630	105,809	188,700	188,773
Purchased Power	47,136	53,487	83,576	84,031
Transmission and Other PPFAC Recoverable Costs	15,362	20,911	31,961	37,746
Increase (Decrease) to Reflect PPFAC Recovery Treatment	26,583	(2,365)	34,497	(14,246)
Total Fuel and Purchased Power	153,711	177,842	338,734	296,304
Operations and Maintenance	119,983	101,337	228,042	198,570
Depreciation	47,424	54,450	94,564	108,048
Amortization	9,803	9,939	19,494	19,857
Taxes Other Than Income Taxes	17,103	15,266	34,380	31,965
Total Operating Expenses	348,024	358,834	715,214	654,744
Operating Income	70,212	80,693	138,875	121,509
Other Income (Expense)
Interest Expense	(24,172)	(21,144)	(47,488)	(42,634)
Allowance For Borrowed Funds	1,161	803	2,169	1,413
Allowance For Equity Funds	3,249	2,370	6,142	4,041
Unrealized Gains (Losses) on Investments	433	(3,937)	1,793	(6,721)
Other, Net	3,666	3,436	5,757	6,422
Total Other Income (Expense)	(15,663)	(18,472)	(31,627)	(37,479)
Income Before Income Tax Expense	54,549	62,221	107,248	84,030
Income Tax Expense	6,823	7,247	12,629	9,636
Net Income	$ 47,726	$ 54,974	$ 94,619	$ 74,394