Consolidated Statements of Patronage Capital and Membership Fees (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Members' Capital
Net margin	$ 26,162		$ 9,383		$ 49,366	$ 32,979
Patronage Capital and Membership Fees
Increase (Decrease) in Members' Capital
Beginning balance	1,039,951	$ 1,016,747	985,882	$ 962,286	1,016,747	962,286
Net margin	26,162	23,204	9,383	23,596
Ending balance	$ 1,066,113	$ 1,039,951	$ 995,265	$ 985,882	$ 1,066,113	$ 995,265

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration