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INVESTMENTS IN OTHER ASSOCIATIONS (Details) - USD ($)	6 Months Ended
INVESTMENTS IN OTHER ASSOCIATIONS (Details) - USD ($)	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	$ 185,673,000		$ 187,684,000
Impairment during the period	0	$ 0
Basin Electric Power Cooperative
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	135,652,000		135,652,000
National Rural Utilities Cooperative Finance Corporation - patronage capital
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	12,451,000		12,451,000
National Rural Utilities Cooperative Finance Corporation - capital term certificates
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	15,054,000		15,054,000
CoBank, ACB
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	16,946,000		18,809,000
Other
Equity Securities without Readily Determinable Fair Value [Line Items]
Investments in other associations	$ 5,570,000		$ 5,718,000