SECURITIES - Contractual Maturities of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale, Amortized Cost
Due in one year or less	$ 0
Due after one year through five years	4,917
Due after five years through ten years	11,236
Due after ten years	0
Total	16,153
Available-for-sale, Amortized Cost	634,115	$ 715,507
Available-for-sale, Fair Value
Due in one year or less	0
Due after one year through five years	4,867
Due after five years through ten years	11,226
Due after ten years	0
Total	16,093
Available-for-sale Securities, Total	610,494	705,539
Held-to-maturity, Amortized Cost
Due after ten years	6,183
Total	6,183
Held-to-maturity, Amortized Cost	62,595	13,275
Held-to-maturity, Fair Value
Due after ten years	6,073
Total	6,073
Held-to-maturity, fair value	61,667	13,146
Mortgage-backed securities and collateralized mortgage obligations
Available-for-sale, Amortized Cost
Amortized cost	522,324
Available-for-sale, Fair Value
Fair value	501,046
Held-to-maturity, Amortized Cost
Amortized cost	56,412
Held-to-maturity, Fair Value
Fair value	55,594
SBA guaranteed securities
Available-for-sale, Amortized Cost
Amortized cost	95,638
Available-for-sale, Amortized Cost	95,638	104,111
Available-for-sale, Fair Value
Fair value	93,355
Available-for-sale Securities, Total	$ 93,355	$ 103,292