INVESTMENT SECURITIES - Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 21,699
Due from one year to five years	43,270
Due from five to ten years	58,019
Due after ten years	42,563
Mortgage-backed securities	581,021
Amortized Cost	746,572	$ 940,580
Estimated Fair Value
Due in one year or less	21,889
Due from one year to five years	44,969
Due from five to ten years	60,100
Due after ten years	44,098
Mortgage-backed securities	607,111
Estimated Fair Value	778,167	982,879
Amortized Cost
Due in one year or less	0
Due from one year to five years	0
Due from five to ten years	0
Due after ten years	0
Mortgage-backed securities	29,055
Amortized Cost	29,055	0
Estimated Fair Value
Due in one year or less	0
Due from one year to five years	0
Due from five to ten years	0
Due after ten years	0
Mortgage-backed securities	29,008
Estimated Fair Value	$ 29,008	$ 0