Consolidated Statement of Equity - USD ($) $ in Thousands	Patronage capital	Accumulated other comprehensive income (loss)	Noncontrolling interest	Total
Equity at beginning of period at Dec. 31, 2013	$ 865,379	$ 3,335	$ 110,740
Change in Equity
Net margins attributable to the Association	64,236			$ 64,236
Retirement of patronage capital	(20,946)
Unrecognized actuarial gain (loss) on postretirement benefit obligation		(4,194)
Reclassification adjustment for actuarial (gain) loss on postretirement benefit obligation included in net income		31
Net income (loss) attributable to noncontrolling interest			(1,383)	(1,383)
Equity distribution to noncontrolling interest			(55)
Equity at end of period at Dec. 31, 2014	908,669	(828)	109,302	1,017,143
Change in Equity
Net margins attributable to the Association	53,413			53,413
Retirement of patronage capital	(10,000)
Unrealized loss on securities available for sale		(125)
Unrecognized actuarial gain (loss) on postretirement benefit obligation		1,528
Reclassification adjustment for actuarial (gain) loss on postretirement benefit obligation included in net income		14
Net income (loss) attributable to noncontrolling interest			(489)	(489)
Equity distribution to noncontrolling interest			(56)
Equity at end of period at Dec. 31, 2015	952,082	589	108,757	1,061,428
Change in Equity
Net margins attributable to the Association	31,748			31,748
Retirement of patronage capital	(22,466)
Unrealized loss on securities available for sale		(13)
Unrecognized actuarial gain (loss) on postretirement benefit obligation		(821)
Reclassification adjustment for actuarial (gain) loss on postretirement benefit obligation included in net income		(41)
Net income (loss) attributable to noncontrolling interest			449	449
Equity distribution to noncontrolling interest			(59)
Equity at end of period at Dec. 31, 2016	$ 961,364	$ (286)	$ 109,147	$ 1,070,225