Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total	Postretirement Medical Benefit Plans	Executive Benefit Restoration Plan	Patronage capital	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss) Postretirement Medical Benefit Plans	Accumulated other comprehensive income (loss) Executive Benefit Restoration Plan	Noncontrolling interest
Equity at beginning of period at Dec. 31, 2022				$ 984,865	$ (468)			$ 126,180
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net margins attributable to the Association	$ (17,457)			(17,457)
Unrealized gain on securities available for sale	61				61
Amortization of prior service credit into other income		$ (409)	$ 289			$ (409)	$ 289
Net comprehensive income attributable to noncontrolling interest	(2,394)							2,394
Equity distribution to noncontrolling interest								(949)
Equity at end of period at Mar. 31, 2023	1,094,506			967,408	(527)			127,625
Equity at beginning of period at Dec. 31, 2023	1,118,011			984,581	(839)			134,269
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net margins attributable to the Association	(15,028)			(15,028)
Unrealized gain on securities available for sale	10				10
Amortization of prior service credit into other income		$ (409)	$ 289			$ (409)	$ 289
Net comprehensive income attributable to noncontrolling interest	(2,704)							2,704
Equity distribution to noncontrolling interest								(10,028)
Equity at end of period at Mar. 31, 2024	$ 1,095,549			$ 969,553	$ (949)			$ 126,945