SECURITIES - Narrative (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
OTTI, Sales and Calls, Pledged, Trading and Restricted Securities
Number of securities in unrealized loss position \| security	0
Debt securities available for sale, allowance of credit losses	$ 0
Allowance for credit losses	$ 0
Guaranteed portion of student loan backed bonds	student loan backed bonds, which are guaranteed by the U.S. Department of Education for 97% to 100% of principal
Credit support for student loan backed bonds description	the bonds have credit support of 3% to 5%
Proceeds from sales of securities available for sale	$ 152,980	$ 46,478	$ 230,372
Gross gains realized on sale of securities available for sale	4,300	200
Gross losses realized on sale of securities available for sale	800		(7,900)
Debt and Equity Securities, Gain (Loss)	3,525	201	(7,921)
Proceeds from calls of securities	14,900	20,300	$ 3,300
Fair value of securities pledged to secure public deposits and FHLB and FRB overnight borrowings	402,800	402,200
Trading securities	$ 0	$ 0
Threshold for disclosure percentage	10.00%	10.00%
Amount owned in FHLB, ACBB and FRB stock	$ 23,362	$ 32,879
Other Assets
OTTI, Sales and Calls, Pledged, Trading and Restricted Securities
Accrued interest receivable on securities	$ 1,400

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