ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Components and Related Income Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME
Unrealized holding gains on available for sale securities	$ 4,308	$ 8,489	$ 10,121	$ 14,020
Reclassification adjustments for (gains) losses realized in income		(201)	15	(201)
Income tax effect	(1,260)	(2,417)	(2,964)	(4,030)
Net change in unrealized gains on available for sale securities	3,048	5,871	7,172	9,789
Reclassification adjustments for amortization realized in income	138	129	276	257
Income tax effect	(41)	(38)	(81)	(76)
Net change in post-retirement obligation	97	91	195	181
Change in fair value of derivatives used for cash flow hedges	(1,563)	(3,106)	(11,073)	(4,703)
Reclassification adjustments for losses (gains) realized in income	176	(466)	66	(1,022)
Income tax effect	406	1,042	3,219	1,670
Net change in unrealized losses on cash flow hedges	(981)	(2,530)	(7,788)	(4,055)
Other comprehensive income (loss)	$ 2,164	$ 3,432	$ (421)	$ 5,915

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