SECURITIES - Contractual Maturities of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale, Amortized Cost
Due in one year or less	$ 1,790
Due after one year through five years	0
Due after five years through ten years	4,236
Due after ten years	7,000
Total	13,026
Available-for-sale, Amortized Cost	679,352	$ 715,507
Available-for-sale, Fair Value
Due in one year or less	1,790
Due after one year through five years	0
Due after five years through ten years	4,237
Due after ten years	7,035
Total	13,062
Available-for-sale Securities, Total	664,045	705,539
Held-to-maturity, Amortized Cost
Due after ten years	6,199
Total	6,199
Held-to-maturity, Amortized Cost	65,101	13,275
Held-to-maturity, Fair Value
Due after ten years	6,245
Total	6,245
Held-to-maturity, fair value	65,037	13,146
Mortgage-backed securities and collateralized mortgage obligations
Available-for-sale, Amortized Cost
Amortized cost	564,911
Available-for-sale, Fair Value
Fair value	551,040
Held-to-maturity, Amortized Cost
Amortized cost	58,902
Held-to-maturity, Fair Value
Fair value	58,792
SBA guaranteed securities
Available-for-sale, Amortized Cost
Amortized cost	101,415
Available-for-sale, Amortized Cost	101,415	104,111
Available-for-sale, Fair Value
Fair value	99,943
Available-for-sale Securities, Total	$ 99,943	$ 103,292