SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Sep. 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	27,240
Trading Securities, Amortized Cost, Maturing after twenty years	0
Trading Securities, Amortized Cost	27,340	$ 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	25,664
Trading Securities, Fair Value, Maturing after twenty years	0
Trading Securities, Fair Value	25,764	22,318
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	5,004
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	64,250
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	268,844
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	222,061
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	891,738
Available-for-sale Securities, Amortized Cost	1,451,897	926,112
Available-for-sale Securities, Fair Value, Maturing in one year or less	4,990
Available-for-sale Securities, Fair Value, Maturing after one year through five years	63,572
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	259,593
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	218,114
Available-for-sale Securities, Fair Value, Maturing after twenty years	866,004
Available-for-sale Securities, Fair Value	1,412,273	919,485
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	3,331
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	49,608
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	83,662
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	83,124
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	38,974
Held-to-maturity Securities, Amortized Cost	258,699	260,271
Held-to-maturity Securities, Fair Value, Maturing in one year or less	3,322
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	48,484
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	82,497
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	83,163
Held-to-maturity Securities, Fair Value, Maturing after twenty years	36,628
Debt Securities, Held-to-maturity, Fair Value	$ 254,094	$ 262,188