INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Estimated Fair Value
Less than 12 months, estimated fair value	$ 3,034	$ 34,279
12 months or more, estimated fair value	4,271	3,950
Total estimated fair value	7,305	38,229
Unrealized Losses
Less than 12 months, unrealized losses	(5)	(347)
12 months or more, unrealized losses	(187)	(96)
Total unrealized losses	(192)	(443)
Corporate debt securities
Estimated Fair Value
Less than 12 months, estimated fair value	0	10,159
12 months or more, estimated fair value	1,380	0
Total estimated fair value	1,380	10,159
Unrealized Losses
Less than 12 months, unrealized losses	0	(233)
12 months or more, unrealized losses	(121)	0
Total unrealized losses	(121)	(233)
SBA pool securities
Estimated Fair Value
Less than 12 months, estimated fair value	0	0
12 months or more, estimated fair value	2,754	3,948
Total estimated fair value	2,754	3,948
Unrealized Losses
Less than 12 months, unrealized losses	0	0
12 months or more, unrealized losses	(66)	(96)
Total unrealized losses	(66)	(96)
Mortgage-backed securities
Estimated Fair Value
Less than 12 months, estimated fair value	3,034	24,120
12 months or more, estimated fair value	137	2
Total estimated fair value	3,171	24,122
Unrealized Losses
Less than 12 months, unrealized losses	(5)	(114)
12 months or more, unrealized losses	0	0
Total unrealized losses	$ (5)	$ (114)