Consolidated Statements of Patronage Capital and Membership Fees and Accumulated Other Comprehensive (Deficit) Margin - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Members' Capital
Balance	$ 911,087	$ 859,440
Components of comprehensive margin:
Net margin	27,400	21,454
Unrealized loss on available-for-sale securities		(39)
Balance	938,487	880,855
Patronage Capital and Membership Fees
Increase (Decrease) in Members' Capital
Balance	911,087	859,810
Components of comprehensive margin:
Net margin	27,400	21,454
Balance	$ 938,487	881,264
Accumulated Other Comprehensive (Deficit) Margin
Increase (Decrease) in Members' Capital
Balance		(370)
Components of comprehensive margin:
Unrealized loss on available-for-sale securities		(39)
Balance		$ (409)

Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities, attributable to parent entity. Excludes amounts related to other than temporary impairment (OTTI) loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569643-111683

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84161450&loc=SL4573702-111684

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683

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Balance Type:	credit
Period Type:	duration