SECURITIES - Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale:
Amortized Cost, Less than 12 Months	$ 587,315	$ 203,870
Gross Unrealized Losses, Less than 12 Months	(9,756)	(1,585)
Fair Value, Less than 12 Months	577,559	202,285
Amortized Cost, More than 12 Months	29,526	6,995
Gross Unrealized Losses, More than 12 Months	(643)	(96)
Fair Value, More than 12 Months	28,883	6,899
Held-to-maturity:
Amortized Cost, Less than 12 Months	3,520	20,692
Gross Unrealized Losses, Less than 12 Months	(29)	(425)
Fair Value, Less than 12 Months	3,491	20,267
Amortized Cost, More than 12 Months	6,265	8,504
Gross Unrealized Losses, More than 12 Months	(161)	(378)
Fair Value, More than 12 Months	6,104	8,126
SBA guaranteed securities
Available-for-sale:
Amortized Cost, Less than 12 Months	76,603
Gross Unrealized Losses, Less than 12 Months	(948)
Fair Value, Less than 12 Months	75,655
Obligations of the U.S. Treasury and other U.S. government agencies or sponsored enterprises
Available-for-sale:
Amortized Cost, Less than 12 Months		100,517
Gross Unrealized Losses, Less than 12 Months		(403)
Fair Value, Less than 12 Months		100,114
Mortgage-backed securities issued by U.S. government agencies or sponsored enterprises: residential
Available-for-sale:
Amortized Cost, Less than 12 Months	192,105	60,233
Gross Unrealized Losses, Less than 12 Months	(1,608)	(405)
Fair Value, Less than 12 Months	190,497	59,828
Amortized Cost, More than 12 Months	9,152	4,121
Gross Unrealized Losses, More than 12 Months	(93)	(25)
Fair Value, More than 12 Months	9,059	4,096
Held-to-maturity:
Amortized Cost, Less than 12 Months	1,086	8,551
Gross Unrealized Losses, Less than 12 Months	(9)	(234)
Fair Value, Less than 12 Months	1,077	8,317
Amortized Cost, More than 12 Months	6,265	860
Gross Unrealized Losses, More than 12 Months	(161)	(33)
Fair Value, More than 12 Months	6,104	827
Mortgage-backed securities issued by U.S. government agencies or sponsored enterprises: commercial
Available-for-sale:
Amortized Cost, Less than 12 Months	65,986
Gross Unrealized Losses, Less than 12 Months	(500)
Fair Value, Less than 12 Months	65,486
Collateralized mortgage obligations issued by U.S. government agencies or sponsored enterprises: residential
Available-for-sale:
Amortized Cost, Less than 12 Months	210,034	29,916
Gross Unrealized Losses, Less than 12 Months	(6,183)	(492)
Fair Value, Less than 12 Months	203,851	29,424
Amortized Cost, More than 12 Months	9,037	2,874
Gross Unrealized Losses, More than 12 Months	(251)	(71)
Fair Value, More than 12 Months	8,786	2,803
Held-to-maturity:
Amortized Cost, Less than 12 Months	2,434	12,141
Gross Unrealized Losses, Less than 12 Months	(20)	(191)
Fair Value, Less than 12 Months	2,414	11,950
Amortized Cost, More than 12 Months		7,644
Gross Unrealized Losses, More than 12 Months		(345)
Fair Value, More than 12 Months		7,299
Collateralized mortgage obligations issued by U.S. government agencies or sponsored enterprises: commercial
Available-for-sale:
Amortized Cost, Less than 12 Months	36,151
Gross Unrealized Losses, Less than 12 Months	(472)
Fair Value, Less than 12 Months	35,679
Corporate debt securities
Available-for-sale:
Amortized Cost, Less than 12 Months		1,785
Gross Unrealized Losses, Less than 12 Months		(14)
Fair Value, Less than 12 Months		1,771
Obligations of municipal subdivisions
Available-for-sale:
Amortized Cost, Less than 12 Months	6,436	236
Gross Unrealized Losses, Less than 12 Months	(45)	(1)
Fair Value, Less than 12 Months	6,391	235
CRA qualified investment fund
Available-for-sale:
Amortized Cost, Less than 12 Months		11,183
Gross Unrealized Losses, Less than 12 Months		(270)
Fair Value, Less than 12 Months		$ 10,913
Amortized Cost, More than 12 Months	11,337
Gross Unrealized Losses, More than 12 Months	(299)
Fair Value, More than 12 Months	$ 11,038