SECURITIES AVAILABLE FOR SALE - Summary of Securities with Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Gross Unrealized Losses
Less Than Twelve Months	$ 9,264	$ 2,565
Over Twelve Months	9,341	5,212
Total	18,605	7,777
Fair Value
Less Than Twelve Months	400,374	251,956
Over Twelve Months	173,420	175,168
Total	573,794	427,124
Obligations of US Government-sponsored enterprises
Gross Unrealized Losses
Less Than Twelve Months	3
Over Twelve Months	0
Total	3
Fair Value
Less Than Twelve Months	3,988
Over Twelve Months	0
Total	3,988
US Government-sponsored enterprises
Gross Unrealized Losses
Less Than Twelve Months	7,001	1,895
Over Twelve Months	6,627	3,921
Total	13,628	5,816
Fair Value
Less Than Twelve Months	294,523	189,486
Over Twelve Months	115,694	117,156
Total	410,217	306,642
US Government agency
Gross Unrealized Losses
Less Than Twelve Months	1,342	559
Over Twelve Months	1,144	615
Total	2,486	1,174
Fair Value
Less Than Twelve Months	46,242	45,221
Over Twelve Months	29,828	30,155
Total	76,070	75,376
Private label
Gross Unrealized Losses
Less Than Twelve Months	1	0
Over Twelve Months	5	5
Total	6	5
Fair Value
Less Than Twelve Months	115	8
Over Twelve Months	51	130
Total	166	138
Obligations of states and political subdivisions thereof
Gross Unrealized Losses
Less Than Twelve Months	476	58
Over Twelve Months	1,565	671
Total	2,041	729
Fair Value
Less Than Twelve Months	31,838	8,298
Over Twelve Months	27,847	27,727
Total	59,685	36,025
Corporate bonds
Gross Unrealized Losses
Less Than Twelve Months	441	53
Over Twelve Months	0	0
Total	441	53
Fair Value
Less Than Twelve Months	23,668	8,943
Over Twelve Months	0	0
Total	$ 23,668	$ 8,943