INVESTMENTS IN OTHER ASSOCIATIONS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Investment in other associations
Investment in other associations	$ 162,562	$ 161,945
Impairment during the period	0	0
Basin Electric Power Cooperative
Investment in other associations
Investment in other associations	117,368	117,368
National Rural Utilities Cooperative Finance Corporation - patronage capital
Investment in other associations
Investment in other associations	11,761	11,761
National Rural Utilities Cooperative Finance Corporation - capital term certificates
Investment in other associations
Investment in other associations	15,885	15,953
CoBank, ACB
Investment in other associations
Investment in other associations	11,141	10,201
Western Fuels Association
Investment in other associations
Investment in other associations	2,193	2,409
Other
Investment in other associations
Investment in other associations	$ 4,214	$ 4,253

Amount of investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117539-209714

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
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