ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Components and Related Income Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME
Unrealized holding (losses) gains on available for sale securities	$ (4,319)	$ 517	$ (17,137)	$ 4,728
Reclassification adjustment for (gains) losses realized in income	0	(260)	7,921	(260)
Income tax effect	1,256	(105)	2,681	(1,773)
Net change in unrealized (losses) gains on available for sale securities	(3,063)	152	(6,535)	2,695
Reclassification adjustment for amortization realized in income	94	112	284	339
Income tax effect	(27)	(45)	(82)	(109)
Net change in post-retirement obligation	67	67	202	230
Change in fair value of derivatives used for cash flow hedges	584	144	4,431	(1,216)
Reclassification adjustment for (gains) losses realized in income	(374)	369	(653)	1,103
Income tax effect	(61)	(210)	(1,099)	43
Net change in unrealized gains (losses) on cash flow hedges	149	303	2,679	(70)
Other comprehensive (loss) income	$ (2,847)	$ 522	$ (3,654)	$ 2,855

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