SECURITIES - Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	$ 270,225	$ 587,315
Gross Unrealized Losses, Less than 12 Months	(8,821)	(9,756)
Fair Value, Less than 12 Months	261,404	577,559
Amortized Cost, More than 12 Months	343,998	29,526
Gross Unrealized Losses, More than 12 Months	(14,830)	(643)
Fair Value, More than 12 Months	329,168	28,883
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	35,649	3,520
Gross Unrealized Losses, Less than 12 Months	(559)	(29)
Fair Value, Less than 12 Months	35,090	3,491
Amortized Cost, More than 12 Months	8,846	6,265
Gross Unrealized Losses, More than 12 Months	(465)	(161)
Fair Value, More than 12 Months	8,381	6,104
SBA guaranteed securities
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	32,936	76,603
Gross Unrealized Losses, Less than 12 Months	(351)	(948)
Fair Value, Less than 12 Months	32,585	75,655
Amortized Cost, More than 12 Months	58,385
Gross Unrealized Losses, More than 12 Months	(1,945)
Fair Value, More than 12 Months	56,440
Mortgage-backed securities issued by U.S. government agencies or sponsored enterprises: residential
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	131,434	192,105
Gross Unrealized Losses, Less than 12 Months	(4,956)	(1,608)
Fair Value, Less than 12 Months	126,478	190,497
Amortized Cost, More than 12 Months	87,788	9,152
Gross Unrealized Losses, More than 12 Months	(3,896)	(93)
Fair Value, More than 12 Months	83,892	9,059
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	2,657	1,086
Gross Unrealized Losses, Less than 12 Months	(74)	(9)
Fair Value, Less than 12 Months	2,583	1,077
Amortized Cost, More than 12 Months	6,869	6,265
Gross Unrealized Losses, More than 12 Months	(409)	(161)
Fair Value, More than 12 Months	6,460	6,104
Mortgage-backed securities issued by U.S. government agencies or sponsored enterprises: commercial
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	32,888	65,986
Gross Unrealized Losses, Less than 12 Months	(1,848)	(500)
Fair Value, Less than 12 Months	31,040	65,486
Amortized Cost, More than 12 Months	21,904
Gross Unrealized Losses, More than 12 Months	(1,107)
Fair Value, More than 12 Months	20,797
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	2,488
Gross Unrealized Losses, Less than 12 Months	(142)
Fair Value, Less than 12 Months	2,346
Collateralized mortgage obligations issued by U.S. government agencies or sponsored enterprises: residential
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	59,079	210,034
Gross Unrealized Losses, Less than 12 Months	(1,366)	(6,183)
Fair Value, Less than 12 Months	57,713	203,851
Amortized Cost, More than 12 Months	144,981	9,037
Gross Unrealized Losses, More than 12 Months	(6,639)	(251)
Fair Value, More than 12 Months	138,342	8,786
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	24,321	2,434
Gross Unrealized Losses, Less than 12 Months	(233)	(20)
Fair Value, Less than 12 Months	24,088	2,414
Amortized Cost, More than 12 Months	1,977
Gross Unrealized Losses, More than 12 Months	(56)
Fair Value, More than 12 Months	1,921
Collateralized mortgage obligations issued by U.S. government agencies or sponsored enterprises: commercial
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	4,971	36,151
Gross Unrealized Losses, Less than 12 Months	(223)	(472)
Fair Value, Less than 12 Months	4,748	35,679
Amortized Cost, More than 12 Months	30,940
Gross Unrealized Losses, More than 12 Months	(1,243)
Fair Value, More than 12 Months	29,697
Corporate debt securities
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	8,917
Gross Unrealized Losses, Less than 12 Months	(77)
Fair Value, Less than 12 Months	8,840
Municipal bonds
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months		6,436
Gross Unrealized Losses, Less than 12 Months		(45)
Fair Value, Less than 12 Months		6,391
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	6,183
Gross Unrealized Losses, Less than 12 Months	(110)
Fair Value, Less than 12 Months	$ 6,073
CRA qualified investment fund
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, More than 12 Months		11,337
Gross Unrealized Losses, More than 12 Months		(299)
Fair Value, More than 12 Months		$ 11,038