SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 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	23,276
Trading Securities, Fair Value, Maturing after twenty years	0
Trading Securities, Fair Value	23,276	25,636
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	0
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	60,411
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	478,140
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	446,834
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	704,684
Available-for-sale Securities, Amortized Cost	1,690,069	1,529,946
Available-for-sale Securities, Fair Value, Maturing in one year or less	0
Available-for-sale Securities, Fair Value, Maturing after one year through five years	62,725
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	500,140
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	463,236
Available-for-sale Securities, Fair Value, Maturing after twenty years	732,283
Available-for-sale Securities, Fair Value	1,758,384	1,551,557
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	0
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	57,360
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	40,458
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	118,611
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	212,706
Held-to-maturity Securities, Amortized Cost	429,135
Held-to-maturity Securities, Fair Value, Maturing in one year or less	0
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	59,541
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	42,822
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	123,188
Held-to-maturity Securities, Fair Value, Maturing after twenty years	225,255
Debt Securities, Held-to-maturity, Fair Value	$ 450,806	$ 237,805