SECURITIES AVAILABLE FOR SALE - Summary of Securities Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	$ 719,983	$ 532,125
Gross Unrealized Gains	5,036	5,627
Gross Unrealized Losses	7,777	8,896
Fair Value	717,242	528,856
Obligations of US Government sponsored enterprises
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	6,967
Gross Unrealized Gains	5
Gross Unrealized Losses	0
Fair Value	6,972
US Government-sponsored enterprises
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	447,081	330,635
Gross Unrealized Gains	1,738	2,682
Gross Unrealized Losses	5,816	4,865
Fair Value	443,003	328,452
US Government agency
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	96,357	76,722
Gross Unrealized Gains	413	797
Gross Unrealized Losses	1,174	613
Fair Value	95,596	76,906
Private label
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	529	936
Gross Unrealized Gains	150	207
Gross Unrealized Losses	5	11
Fair Value	674	1,132
Obligations of states and political subdivisions thereof
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	138,522	123,832
Gross Unrealized Gains	2,407	1,941
Gross Unrealized Losses	729	3,407
Fair Value	140,200	122,366
Corporate bonds
Available-for-sale Securities, Fair Value to Amortized Cost Basis
Amortized Cost	30,527	0
Gross Unrealized Gains	323	0
Gross Unrealized Losses	53	0
Fair Value	$ 30,797	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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