Consolidated Statements of Patronage Capital and Membership Fees and Accumulated Other Comprehensive (Deficit) Margin - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Members' Capital
Balance			$ 859,440	$ 809,523
Components of comprehensive margin:
Net margin	$ 21,426	$ 23,277	42,880	43,875
Unrealized gain (loss) on available-for-sale securities	1	93	(38)	377
Balance	902,282	853,775	902,282	853,775
Patronage Capital and Membership Fees
Increase (Decrease) in Members' Capital
Balance			859,810	809,465
Components of comprehensive margin:
Net margin			42,880	43,875
Balance	902,690	853,340	902,690	853,340
Accumulated Other Comprehensive (Deficit) Margin
Increase (Decrease) in Members' Capital
Balance			(370)	58
Components of comprehensive margin:
Unrealized gain (loss) on available-for-sale securities			(38)	377
Balance	$ (408)	$ 435	$ (408)	$ 435