Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net margins including noncontrolling interest	$ 20,058	$ 8,400	$ 33,288
Adjustments to reconcile net margins to net cash provided by operating activities:
Depreciation, amortization and depletion	171,460	184,047	190,237
Amortization of NRECA Retirement Security Plan prepayment	5,372	5,372	5,372
Amortization of debt issuance costs	2,423	3,105	2,479
Impairment loss and other closure costs	261,600	29,098	0
Deferred impairment loss and other closure costs	(261,600)	(29,098)	0
Deposits associated with generator interconnection requests	9,880	6,716	17,130
Rate stabilization	(47,127)	(95,613)	(78,457)
Capital credit allocations from cooperatives and income from coal mines under (over) refund distributions	(9,911)	(14,115)	512
Changes in operating assets and liabilities:
Accounts receivable	18,019	(30,135)	(3,618)
Coal inventory	(20,256)	24,978	(3,453)
Materials and supplies	(13,380)	(6,281)	(4,714)
Accounts payable and accrued expenses	2,333	19,102	13,114
Accrued interest	(1,882)	(285)	(1,804)
Accrued property taxes	(4,492)	2,600	1,082
New Horizon Mine environmental obligation	(44,869)	44,869	0
Other	36,773	(164)	(1,261)
Net cash provided by operating activities	124,401	152,596	169,907
Investing activities
Purchases of plant	(179,398)	(121,527)	(118,422)
Changes in deferred charges	4,339	(4,617)	(13,054)
Proceeds from other investments	0	94	72
Net cash used in investing activities	(175,059)	(126,050)	(131,404)
Financing activities
Changes in Member advances	(2,969)	(282)	183
Payments of long-term debt	(394,447)	(232,946)	(94,288)
Proceeds from issuance of long-term debt	550,000	0	0
Debt issuance costs	(664)	(1,475)	0
Change in short-term borrowings, net	(89,297)	224,105	49,997
Retirement of patronage capital	(10,044)	(8,445)	(18,067)
Equity distribution to noncontrolling interest	(1,882)	(1,320)	(2,693)
Other	(703)	(637)	(573)
Net cash provided by (used in) financing activities	49,994	(21,000)	(65,441)
Net increase (decrease) in cash, cash equivalents and restricted cash and investments	(664)	5,546	(26,938)
Cash, cash equivalents and restricted cash and investments – beginning	110,682	105,136	132,074
Cash, cash equivalents and restricted cash and investments – ending	110,018	110,682	105,136
Supplemental cash flow information:
Cash paid for interest	173,147	145,350	143,394
Cash paid for income taxes	0	0	0
Supplemental disclosure of noncash investing and financing activities:
Change in plant expenditures included in accounts payable	$ 1,005	$ (1,076)	$ 1,383