OFF-BALANCE-SHEET ARRANGEMENTS, COMMITMENTS AND CONTINGENCIES - Allowance for off-balance-sheet credit exposures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 1,455	$ 1,890	$ 1,971
Provision for (reversal of) off-balance-sheet credit exposures	91	(435)	(81)
Balance at end of period	6,386	1,455	1,890
Impact of CECL adoption
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	0	0
Balance at end of period	$ 4,840	$ 0	$ 0