Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating revenues
Other	$ 66,615	$ 61,420	$ 56,341
Operating revenues	1,467,416	1,533,571	1,400,801
Operating expenses
Purchased power	404,876	409,513	381,477
Fuel	258,894	329,046	236,089
Production	191,095	177,413	185,016
Transmission	187,874	175,889	182,327
General and administrative	88,621	79,640	57,243
Depreciation, amortization and depletion	171,460	184,047	190,237
Coal mining	44,548	9,899	5,323
Other	(31,341)	53,509	7,191
Operating expenses	1,316,027	1,418,956	1,244,903
Operating margins	151,389	114,615	155,898
Other income
Interest	8,614	4,447	3,609
Capital credits from cooperatives	19,369	26,185	9,466
Other	11,447	10,027	4,152
Other income	39,430	40,659	17,227
Interest expense
Interest	175,557	148,609	143,328
Interest charged during construction	(4,800)	(1,486)	(3,786)
Interest expense, net of amounts capitalized	170,757	147,123	139,542
Income tax expense (benefit)	4	(249)	295
Net margins including noncontrolling interest	20,058	8,400	33,288
Net margin attributable to noncontrolling interest	(9,971)	(8,400)	(6,942)
Net margins attributable to the Association	10,087	0	26,346
Member electric sales
Operating revenues
Operating revenues	1,208,352	1,213,234	1,161,291
Non-member electric sales
Operating revenues
Operating revenues	145,228	163,355	114,908
Rate stabilization
Operating revenues
Operating revenues	47,127	95,613	78,457
Provision for rate refunds
Operating revenues
Operating revenues	$ 94	$ (51)	$ (10,196)