OTHER COMPREHENSIVE INCOME (LOSS), Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Change in unrealized holding loss on securities held-to-maturity and transferred securities [Abstract]
Accretion of previously recognized non-credit component of OTTI	$ 3	$ 9	$ 20	$ 25
Change in unrealized loss on securities transferred to held-to-maturity	3	12	50	37
Reclassification adjustment for net gains included in net gain on securities and other assets	1,229	0	1,229	0
Net change	1,235	21	1,299	62
Tax expense	558	7	586	26
Net change in unrealized holding loss on securities held-to-maturity and transferred securities	677	14	713	36
Change in unrealized holding gain on securities available-for-sale [Abstract]
Change in net unrealized gain during the period	27	107	251	169
Tax expense	19	43	118	71
Net change in unrealized holding gain on securities available-for-sale	8	64	133	98
Change in pension and other postretirement obligations [Abstract]
Reclassification adjustment for expense included in salaries and employee benefits expense	355	425	1,012	1,275
Tax expense	160	191	452	573
Net change in pension and other postretirement obligations	195	234	560	702
Change in unrealized loss on derivatives:
Change in net unrealized loss during the period	24	717	(573)	(281)
Reclassification adjustment for expense included in interest expense	68	(9)	247	32
Net change	92	708	(326)	(249)
Tax expense (benefit)	36	327	(148)	(104)
Net change in unrealized loss on derivatives	56	381	(178)	(145)
Other comprehensive income, net of tax	$ 936	$ 693	$ 1,228	$ 691