ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Change in unrealized holding loss on securities held-to-maturity and transferred securities [Abstract]
Accretion of previously recognized non-credit component of OTTI	$ 0	$ 8	$ 0	$ 17
Change in unrealized loss on securities transferred to held-to-maturity	0	22	0	47
Net change	0	30	0	64
Tax expense	0	12	0	28
Net change in unrealized holding loss on securities held-to-maturity and transferred securities	0	18	0	36
Change in unrealized holding gain on securities available-for-sale [Abstract]
Change in net unrealized gain during the period	(1,679)	104	(2,867)	224
Reclassification adjustment for net gains included in net gain on securities and other assets	0	0	(1,370)	0
Net change	(1,679)	104	(4,237)	224
Tax expense (benefit)	(534)	44	(1,384)	99
Net change in unrealized holding gain on securities available-for-sale	(1,145)	60	(2,853)	125
Change in pension and other postretirement obligations [Abstract]
Reclassification adjustment for expense included in other expense	37	355	323	657
Change in the net actuarial gain or loss	249	0	118	0
Net change	286	355	441	657
Tax expense	93	161	144	292
Net change in pension and other postretirement obligations	193	194	297	365
Change in unrealized loss on derivatives [Abstract]
Change in net unrealized loss during the period	745	(825)	2,826	(597)
Reclassification adjustment for expense included in interest expense	(185)	92	(250)	179
Net change	560	(733)	2,576	(418)
Tax expense (benefit)	149	(328)	836	(184)
Net change in unrealized loss on derivatives	411	(405)	1,740	(234)
Other comprehensive income (loss), net of tax	$ (541)	$ (133)	$ (816)	$ 292