SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Trading Securities, Amortized Cost, Maturing in one year or less	$ 100
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	27,303	$ 27,246
Trading Securities, Fair Value, Maturing in one year or less	100
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	25,540
Trading Securities, Fair Value, Maturing after twenty years	0
Trading Securities, Fair Value	25,640	22,318
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	6,059
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	60,892
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	280,920
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	193,883
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	888,171
Available-for-sale Securities, Amortized Cost	1,429,925	926,112
Available-for-sale Securities, Fair Value, Maturing in one year or less	6,045
Available-for-sale Securities, Fair Value, Maturing after one year through five years	59,950
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	273,773
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	191,218
Available-for-sale Securities, Fair Value, Maturing after twenty years	869,326
Available-for-sale Securities, Fair Value	1,400,312	919,485
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	2,292
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	40,544
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	94,377
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	85,138
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	40,825
Held-to-maturity Securities, Amortized Cost	263,176	260,271
Held-to-maturity Securities, Fair Value, Maturing in one year or less	2,291
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	40,024
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	93,574
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	85,732
Held-to-maturity Securities, Fair Value, Maturing after twenty years	38,697
Held-to-maturity Securities, Fair Value	$ 260,318	$ 262,188