INVESTMENT SECURITIES - INVESTMENT CATEGORY (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale debt securities
Less than 12 months Fair Value	$ 197,306	$ 301,476
Less than 12 months Unrealized Losses	(3,134)	(1,758)
12 months or more Fair Value	120,761	117,210
12 months or more Unrealized Losses	(2,222)	(1,641)
Total Fair Value	318,067	418,686
Total Unrealized Losses	$ (5,356)	$ (3,399)
Number of securities held	182	185
Number of securities held in an unrealized loss position	58	58
Held-to-maturity debt securities
Less than 12 months Fair Value	$ 451	$ 5,455
Less than 12 months Unrealized Losses	(13)	(9)
12 months or more Fair Value	6,128	6,390
12 months or more Unrealized Losses	(16)	(17)
Total Fair Value	6,579	11,845
Total Unrealized Losses	(29)	(26)
U.S. Treasury securities and U.S. Government agencies
Available-for-sale debt securities
Less than 12 months Fair Value	98,699	209,165
Less than 12 months Unrealized Losses	(1,011)	(499)
12 months or more Fair Value	88,303	88,415
12 months or more Unrealized Losses	(1,145)	(952)
Total Fair Value	187,002	297,580
Total Unrealized Losses	(2,156)	(1,451)
Mortgage backed securities - residential
Available-for-sale debt securities
Less than 12 months Fair Value	58,202	61,348
Less than 12 months Unrealized Losses	(1,238)	(617)
12 months or more Fair Value	9,377	10,192
12 months or more Unrealized Losses	(333)	(256)
Total Fair Value	67,579	71,540
Total Unrealized Losses	(1,571)	(873)
Collateralized mortgage obligations
Available-for-sale debt securities
Less than 12 months Fair Value	30,426	30,963
Less than 12 months Unrealized Losses	(864)	(642)
12 months or more Fair Value	23,081	18,603
12 months or more Unrealized Losses	(744)	(433)
Total Fair Value	53,507	49,566
Total Unrealized Losses	(1,608)	(1,075)
Held-to-maturity debt securities
12 months or more Fair Value	6,128	6,390
12 months or more Unrealized Losses	(16)	(17)
Total Fair Value	6,128	6,390
Total Unrealized Losses	(16)	(17)
Corporate bonds
Available-for-sale debt securities
Less than 12 months Fair Value	9,979
Less than 12 months Unrealized Losses	(21)
Total Fair Value	9,979
Total Unrealized Losses	(21)
Held-to-maturity debt securities
Less than 12 months Fair Value		4,997
Less than 12 months Unrealized Losses		(3)
Total Fair Value		4,997
Total Unrealized Losses		(3)
Obligations of state and political subdivisions
Held-to-maturity debt securities
Less than 12 months Fair Value	451	458
Less than 12 months Unrealized Losses	(13)	(6)
Total Fair Value	451	458
Total Unrealized Losses	$ (13)	$ (6)