SECURITIES (Amortized Cost of HTM Securities by Security Type and Credit Rating) (Details) $ in Thousands	Mar. 31, 2020 USD ($)
HTM Securities, Amortized Cost	$ 552,176
Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	536,747
Moody's Not Rated - Agency [Member] | Standard Poors Not Rated - Agency [Member]
HTM Securities, Amortized Cost	8,659
Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	6,770
U.S. government and agency securities
HTM Securities, Amortized Cost	2,797
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	2,797
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	543,517
Obligations of states and political subdivisions | Moody's AAA/AA/A | Standard & Poor's AAA/AA/A
HTM Securities, Amortized Cost	536,747
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	6,770
Total mortgage-back securities
HTM Securities, Amortized Cost	5,862
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	5,862
Total mortgage-back securities | Moody's Not Rated - Non-Agency [Member] | Standard Poors Not Rated - Non-Agency [Member]
HTM Securities, Amortized Cost	$ 0