ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in unrealized holding loss on securities held-to-maturity and transferred securities [Abstract]
Accretion of previously recognized non-credit component of OTTI	$ 0	$ 20	$ 34
Change in unrealized loss on securities transferred to held-to-maturity	0	50	51
Reclassification adjustment for net gains included in net gain on securities and other assets	0	1,229	0
Net change	0	1,299	85
Tax expense	0	586	38
Net change in unrealized holding loss on securities held-to-maturity and transferred securities	0	713	47
Change in unrealized holding gain on securities available-for-sale [Abstract]
Change in net unrealized (loss) gain during the period	(1,726)	551	56
Reclassification adjustment for net (losses) gains included in net gain on securities and other assets	(1,370)	36	0
Net change	(3,096)	587	56
Tax expense (benefit)	(1,007)	260	26
Net change in unrealized holding gain on securities available-for-sale	(2,089)	327	30
Change in pension and other postretirement obligations [Abstract]
Reclassification adjustment for expense included in other expense	514	1,421	1,841
Change in the net actuarial gain	34	1,337	0
Net change	548	2,758	1,841
Tax expense	237	1,239	832
Net change in pension and other postretirement obligations	311	1,519	1,009
Change in unrealized loss on derivatives [Abstract]
Change in net unrealized loss during the period	(758)	511	3,205
Reclassification adjustment for expense included in interest expense	(692)	283	23
Net change	(1,450)	794	3,228
Tax expense (benefit)	(490)	342	1,452
Net change in unrealized loss on derivatives	(960)	452	1,776
Other comprehensive income (loss), net of tax	$ (2,738)	$ 3,011	$ 2,862