Consolidated Statements of Equity - USD ($) $ in Thousands	Patronage capital	Accumulated other comprehensive income (loss)	Noncontrolling interest	Total
Equity at beginning of period at Dec. 31, 2018	$ 1,015,754	$ 375	$ 110,169
Change in Equity
Net margins attributable to the Association	60,749			$ 60,749
Amortization of prior service cost		13		13
Unrecognized prior service cost		(214)		(214)
Net comprehensive income attributable to noncontrolling interest			3,239	3,239
Equity distribution to noncontrolling interest			(2,806)
Equity at end of period at Sep. 30, 2019	1,076,503	174	110,602	1,187,279
Equity at beginning of period at Jun. 30, 2019	1,021,358	184	110,841
Change in Equity
Net margins attributable to the Association	55,145			55,145
Amortization of prior service cost		(10)		(10)
Net comprehensive income attributable to noncontrolling interest			1,113	1,113
Equity distribution to noncontrolling interest			(1,352)
Equity at end of period at Sep. 30, 2019	1,076,503	174	110,602	1,187,279
Equity at beginning of period at Dec. 31, 2019	1,031,063	(1,518)	111,717	1,141,262
Change in Equity
Net margins attributable to the Association	45,652			45,652
Retirement of patronage capital	(47,665)
Amortization of prior service cost		1,287		1,287
Unrecognized prior service cost		(7,373)		(7,373)
Net comprehensive income attributable to noncontrolling interest			4,164	4,164
Equity distribution to noncontrolling interest			(2,456)
Equity at end of period at Sep. 30, 2020	1,029,050	(7,604)	113,425	1,134,871
Equity at beginning of period at Jun. 30, 2020	984,221	(7,781)	113,189
Change in Equity
Net margins attributable to the Association	44,829			44,829
Amortization of prior service cost		177		177
Net comprehensive income attributable to noncontrolling interest			1,424	1,424
Equity distribution to noncontrolling interest			(1,188)
Equity at end of period at Sep. 30, 2020	$ 1,029,050	$ (7,604)	$ 113,425	$ 1,134,871