SECURITIES - Investment Securities Available for Sale in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	$ 132,542	$ 123,007
12 months or longer	134,138	131,436
Total	266,680	254,443
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	2,746	1,199
12 months or longer	6,696	4,171
Total	9,442	5,370
Obligations of U.S. Government and U.S. Government sponsored enterprises
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months		14,982	$ 14,947
12 months or longer		0	0
Total		14,982	14,947
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months		21	54
12 months or longer		0	0
Total		21	$ 54
Mortgage-backed securities, residential
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	73,034	83,562
12 months or longer	132,122	131,165
Total	205,156	214,727
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	2,093	1,013
12 months or longer	6,664	4,153
Total	8,757	5,166
Obligations of states and political subdivisions
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	42,728	20,526
12 months or longer	260	271
Total	42,988	20,797
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	574	133
12 months or longer	30	18
Total	604	151
SBA loan pools
Available-for-sale securities in a continuous unrealized loss position, fair value [Abstract]
Less than 12 months	1,833	3,937
12 months or longer	1,756	0
Total	3,589	3,937
Available-for-sale securities in a continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	25	32
12 months or longer	2	0
Total	$ 27	$ 32