Consolidated Statement of Equity - USD ($) $ in Thousands	Patronage capital	Accumulated other comprehensive income (loss)	Noncontrolling interest	Total
Equity at beginning of year at Dec. 31, 2014	$ 908,669	$ (828)	$ 109,302
Change in Equity
Net margins attributable to the Association	53,413			$ 53,413
Retirement of patronage capital	(10,000)
Unrealized gain (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 comprehensive income (loss) attributable to noncontrolling interest			(489)	(489)
Equity distribution to noncontrolling interest			(56)
Equity at end of year 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 gain (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 comprehensive income (loss) attributable to noncontrolling interest			449	449
Equity distribution to noncontrolling interest			(59)
Equity at end of year at Dec. 31, 2016	961,364	(286)	109,147	1,070,225
Change in Equity
Net margins attributable to the Association	61,656			61,656
Retirement of patronage capital	(20,000)
Unrealized gain (loss) on securities available for sale		43
Unrecognized actuarial gain (loss) on postretirement benefit obligation		106
Reclassification adjustment for actuarial (gain) loss on postretirement benefit obligation included in net income		(73)
Net comprehensive income (loss) attributable to noncontrolling interest			2,148	2,148
Equity at end of year at Dec. 31, 2017	$ 1,003,020	$ (210)	$ 111,295	$ 1,114,105