ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Change in unrealized holding gain or loss on securities available-for-sale [Abstract]
Change in net unrealized gain or loss during the period	$ 4,204	$ (1,679)	$ 8,815	$ (2,867)
Reclassification adjustment for net (gains) losses included in net gain on securities and other assets	57	0	133	(1,370)
Net change	4,261	(1,679)	8,948	(4,237)
Tax expense (benefit)	1,371	(534)	2,878	(1,384)
Net change in unrealized holding gain or loss on securities available-for-sale	2,890	(1,145)	6,070	(2,853)
Change in pension and other postretirement obligations [Abstract]
Reclassification adjustment for expense included in other expense	181	37	364	323
Change in the net actuarial gain or loss	56	249	365	118
Net change	237	286	729	441
Tax expense	76	93	234	144
Net change in pension and other postretirement obligations	161	193	495	297
Change in unrealized gain or loss on derivatives:
Change in net unrealized gain or loss during the period	(5,745)	745	(8,673)	2,826
Reclassification adjustment for expense included in interest expense	(332)	(185)	(688)	(250)
Net change	(6,077)	560	(9,361)	2,576
Tax expense (benefit)	(1,970)	149	(3,008)	836
Net change in unrealized gain or loss on derivatives	(4,107)	411	(6,353)	1,740
Other comprehensive income (loss), net of tax	$ (1,056)	$ (541)	$ 212	$ (816)