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DERIVATIVE FINANCIAL INSTRUMENTS (Cash collateral on derivative financial instruments narrative) (Details) - USD ($)
Mar. 31, 2021
Dec. 31, 2020
Derivative [Line Items]    
Cash pledged as collateral $ 2,900,000 $ 3,800,000
Counterparties    
Derivative [Line Items]    
Cash pledged as collateral $ 0 $ 0