SECURITIES (Amortized Cost of HTM Securities by Security Type and Credit Rating) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
HTM Securities, Amortized Cost	$ 535,722	$ 544,851
Moody's AAA/AA/A
HTM Securities, Amortized Cost	528,157	532,157
Moody's Not Rated - Agency
HTM Securities, Amortized Cost	7,565	8,084
Moody's Not Rated - Non-Agency
HTM Securities, Amortized Cost		4,610
U.S. government and agency securities
HTM Securities, Amortized Cost	2,637	2,751
U.S. government and agency securities | Moody's AAA/AA/A
HTM Securities, Amortized Cost	0	0
U.S. government and agency securities | Moody's Not Rated - Agency
HTM Securities, Amortized Cost	2,637	2,751
U.S. government and agency securities | Moody's Not Rated - Non-Agency
HTM Securities, Amortized Cost	0	0
Obligations of states and political subdivisions
HTM Securities, Amortized Cost	528,157	536,767
Obligations of states and political subdivisions | Moody's AAA/AA/A
HTM Securities, Amortized Cost	528,157	532,157
Obligations of states and political subdivisions | Moody's Not Rated - Agency
HTM Securities, Amortized Cost	0	0
Obligations of states and political subdivisions | Moody's Not Rated - Non-Agency
HTM Securities, Amortized Cost	0	4,610
Mortgage-backed securities
HTM Securities, Amortized Cost	4,928	5,333
Mortgage-backed securities | Moody's AAA/AA/A
HTM Securities, Amortized Cost	0	0
Mortgage-backed securities | Moody's Not Rated - Agency
HTM Securities, Amortized Cost	4,928	5,333
Mortgage-backed securities | Moody's Not Rated - Non-Agency
HTM Securities, Amortized Cost	$ 0	$ 0