CONSOLIDATED STATEMENTS OF PATRONAGE CAPITAL AND MEMBERSHIP FEES AND ACCUMULATED OTHER COMPREHENSIVE (DEFICIT) MARGIN - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Members' Capital
Net margin	$ (1,942)	$ 23,204	$ 3,196	$ 23,596	$ 55,895	$ 54,461	$ 51,199
Patronage Capital And Membership Fees
Increase (Decrease) in Members' Capital
Beginning balance		$ 1,016,747		$ 962,286	1,016,747	962,286	911,087
Net margin					55,895	54,461	51,199
Ending balance	$ 1,072,642		$ 1,016,747		$ 1,072,642	$ 1,016,747	$ 962,286

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e1377-109256

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration