GOODWILL AND INTANGIBLE ASSETS - Changes in carrying values of goodwill and intangible assets (Details) - Changes in carrying values of goodwill and intangible assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Balance, beginning of period	$ 12,552	$ 12,552	$ 12,552
Additions	1,263
Impairment
Balance, end of period	13,815	12,552	12,552
Core Deposit Intangibles
Cost, beginning of period	5,248	5,248	5,248
New York branch purchase	633
Impairment
Cost, end of period	5,881	5,248	5,248
Amortization, beginning of period	(3,511)	(2,910)	(2,258)
Amortization	(533)	(601)	(652)
Amortization, end of period	(4,044)	(3,511)	(2,910)
Core deposit intangibles, net	$ 1,837	$ 1,737	$ 2,338