DEPOSITS - Summary of deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
DEPOSITS
Weighted Average Rate, Savings accounts	0.03%	0.12%
Weighted Average Rate, Certificates of deposit	0.58%	0.84%
Weighted Average Rate, Money market accounts	0.07%	0.24%
Weighted Average Rate, Interest-bearing checking accounts	0.18%	0.10%
Weighted Average Rate, Total	0.09	0.36
Liability, Savings accounts	$ 1,158,040	$ 414,809
Liability, Certificates of deposit ("CDs")	853,242	1,322,638
Liability, Money market accounts	3,621,552	1,716,624
Liability, Interest-bearing checking accounts	905,717	290,300
Liability, Non-interest bearing checking accounts	3,920,423	780,751
Liability, Total	$ 10,458,974	$ 4,525,122