SECURITIES - Summary of amortized cost of securities held to maturity and their estimated fair value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 23,325	$ 7,005
Gross Unrecognized Gains	8	0
Gross Unrecognized Losses	(186)	(26)
Estimated Fair Value	23,147	6,979
Collateralized loan obligation
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,000	7,005
Gross Unrecognized Gains	0	0
Gross Unrecognized Losses	0	(26)
Estimated Fair Value	3,000	$ 6,979
Asset-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,325
Gross Unrecognized Gains	0
Gross Unrecognized Losses	(186)
Estimated Fair Value	15,139
Corporate Bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,000
Gross Unrecognized Gains	8
Gross Unrecognized Losses	0
Estimated Fair Value	$ 5,008