ACCOUNTING STANDARDS - Additional information (Details) - USD ($) $ in Thousands	Jun. 30, 2021		Mar. 31, 2021	Jan. 01, 2021	Dec. 31, 2020		Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	$ 32,457	[1]	$ 32,663		$ 35,820	[1]	$ 28,064	$ 20,804	$ 13,908
Allowance for credit losses on OBSC exposures	718	[1]	$ 718		0
Minimum loan balance to individual evaluation for impairment					500
Accrued interest receivable on available-for-sale debt securities	6,100				5,700
ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans					$ 1,100
Allowance for credit losses on OBSC exposures	$ 718
Transition Adjustment | ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans				$ 397
Allowance for credit losses on OBSC exposures				$ 718

[1] – Beginning January 1, 2021, allowance for credit losses is based on current expected credit loss methodology. Prior to January 1, 2021, allowance for loan loss was based on incurred loss methodology