SECURITIES (Securities Debt Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
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	25,672
Trading Securities, Fair Value, Maturing after twenty years	0
Trading Securities, Fair Value	25,672	25,896
Available-for-sale Securities, Amortized Cost, Maturing in one year or less	2,421
Available-for-sale Securities, Amortized Cost, Maturing after one year through five years	54,704
Available-for-sale Securities, Amortized Cost, Maturing after five years through ten years	373,474
Available-for-sale Securities, Amortized Cost, Maturing after ten years through twenty years	228,067
Available-for-sale Securities, Amortized Cost, Maturing after twenty years	850,144
Available-for-sale Securities, Amortized Cost	1,508,810	1,648,421
Available-for-sale Securities, Fair Value, Maturing in one year or less	2,423
Available-for-sale Securities, Fair Value, Maturing after one year through five years	55,751
Available-for-sale Securities, Fair Value, Maturing after five years through ten years	388,323
Available-for-sale Securities, Fair Value, Maturing after ten years through twenty years	234,354
Available-for-sale Securities, Fair Value, Maturing after twenty years	859,057
Available-for-sale Securities, Fair Value	1,539,908	1,636,223
Held-to-maturity Securities, Amortized Cost, Maturing in one year or less	3,339
Held-to-maturity Securities, Amortized Cost, Maturing after one year through five years	62,060
Held-to-maturity Securities, Amortized Cost, Maturing after five years through ten years	43,592
Held-to-maturity Securities, Amortized Cost, Maturing after ten years through twenty years	91,041
Held-to-maturity Securities, Amortized Cost, Maturing after twenty years	30,024
Held-to-maturity Securities, Amortized Cost	230,056	234,220
Held-to-maturity Securities, Fair Value, Maturing in one year or less	3,341
Held-to-maturity Securities, Fair Value, Maturing after one year through five years	63,122
Held-to-maturity Securities, Fair Value, Maturing after five years through ten years	45,338
Held-to-maturity Securities, Fair Value, Maturing after ten years through twenty years	92,108
Held-to-maturity Securities, Fair Value, Maturing after twenty years	29,812
Debt Securities, Held-to-maturity, Fair Value	$ 233,721	$ 232,537