SECURITIES - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
OTTI, Sales and Calls, Pledged, Trading and Restricted Securities
Non-accrual debt securities	$ 0		$ 0
Accrued interest related to debt securities	$ 0		$ 0
Number of securities in unrealized loss position | item	0		0
Debt securities available for sale, allowance of credit losses	$ 0		$ 0
Allowance for credit losses	0		$ 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	78,400	$ 0	$ 152,981	$ 46,478
Gross gains realized on sale of securities available for sale	3,500		4,300	200
Gross losses realized on sale of securities available for sale	7		800
Debt and Equity Securities, Gain (Loss)	3,540		3,525	201
Proceeds from calls of securities	1,300	$ 10,000	13,500	$ 20,300
Fair value of securities pledged to secure public deposits and FHLB and FRB overnight borrowings	451,800		451,800		$ 402,200
Amount owned in FHLB, ACBB and FRB stock	23,362		23,362		$ 32,879
Other Assets
OTTI, Sales and Calls, Pledged, Trading and Restricted Securities
Accrued interest receivable on securities	$ 1,800		$ 1,800