DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES - Offsetting of Financial Assets and Derivative Assets (Details) - Interest rate swaps - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Offsetting of Financial Assets and Derivative Assets
Gross amounts of recognized assets	$ 178,930	$ 77,068
Gross amounts offset in the Statements of Condition	(92)	(76)
Net amounts of assets presented in the Statements of Condition	178,838	76,992
Gross amounts not offset in the Statements of Condition, financial instruments	0	0
Gross amounts not offset in the Statements of Condition, cash collateral received	0	0
Net Amount	178,838	76,992
Institutional counterparties
Offsetting of Financial Assets and Derivative Assets
Gross amounts of recognized assets	1,199	640
Gross amounts offset in the Statements of Condition	(92)	(54)
Net amounts of assets presented in the Statements of Condition	1,107	586
Gross amounts not offset in the Statements of Condition, financial instruments	0	0
Gross amounts not offset in the Statements of Condition, cash collateral received	0	0
Net Amount	1,107	586
Commercial counterparties
Offsetting of Financial Assets and Derivative Assets
Gross amounts of recognized assets	177,731	76,428
Gross amounts offset in the Statements of Condition	0	(22)
Net amounts of assets presented in the Statements of Condition	177,731	76,406
Gross amounts not offset in the Statements of Condition, financial instruments	0	0
Gross amounts not offset in the Statements of Condition, cash collateral received	0	0
Net Amount	$ 177,731	$ 76,406