SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Trading Securities, Amortized Cost, Maturing in one year or less	$ 0
Trading Securities, Amortized Cost, Maturing after one year through five years	0
Trading Securities, Amortized Cost, Maturing after five years through ten years	0
Trading Securities, Amortized Cost, Maturing after ten years through twenty years	27,203
Trading Securities, Amortized Cost, Maturing after twenty years	0
Trading Securities, Amortized Cost	27,203	$ 27,203
Trading Securities, Fair Value, Maturing in one year or less	0
Trading Securities, Fair Value, Maturing after one year through five years	0
Trading Securities, Fair Value, Maturing after five years through ten years	0
Trading Securities, Fair Value, Maturing after ten years through twenty years	21,040
Trading Securities, Fair Value, Maturing after twenty years	0
Trading Securities, Fair Value	21,040	25,636
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	2,500
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	66,644
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	352,386
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	265,561
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	857,422
Available-for-sale Securities, Amortized Cost	1,544,513	1,529,946
Available-for-sale Securities, Fair Value, Maturing in one year or less	2,496
Available-for-sale Securities, Fair Value, Maturing after one year through five years	68,453
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	370,139
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	277,549
Available-for-sale Securities, Fair Value, Maturing after twenty years	889,587
Available-for-sale Securities, Fair Value	1,608,224	1,551,557
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	807
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	59,949
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	44,006
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	124,627
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	208,555
Held-to-maturity Securities, Amortized Cost	437,944	236,094
Held-to-maturity Securities, Fair Value, Maturing in one year or less	808
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	61,827
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	46,085
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	126,785
Held-to-maturity Securities, Fair Value, Maturing after twenty years	213,732
Debt Securities, Held-to-maturity, Fair Value	$ 449,237	$ 237,805