SECURITIES (Amortized Cost of HTM Securities by Security Type and Credit Rating) (Details) $ in Thousands	Sep. 30, 2020 USD ($)
HTM Securities, Amortized Cost	$ 546,661
Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	533,742
Moody's Not Rated - Agency [Member] | Standard Poors Not Rated - Agency [Member]
HTM Securities, Amortized Cost	8,309
Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	4,610
U.S. government and agency securities
HTM Securities, Amortized Cost	2,767
U.S. government and agency securities | Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	0
U.S. government and agency securities | Moody's Not Rated - Agency [Member] | Standard Poors Not Rated - Agency [Member]
HTM Securities, Amortized Cost	2,767
U.S. government and agency securities | Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	0
Obligations of states and political subdivisions
HTM Securities, Amortized Cost	538,352
Obligations of states and political subdivisions | Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	533,742
Obligations of states and political subdivisions | Moody's Not Rated - Agency [Member] | Standard Poors Not Rated - Agency [Member]
HTM Securities, Amortized Cost	0
Obligations of states and political subdivisions | Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	4,610
Total mortgage-back securities
HTM Securities, Amortized Cost	5,542
Total mortgage-back securities | Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	0
Total mortgage-back securities | Moody's Not Rated - Agency [Member] | Standard Poors Not Rated - Agency [Member]
HTM Securities, Amortized Cost	5,542
Total mortgage-back securities | Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	$ 0