OTHER COMPREHENSIVE INCOME (LOSS) Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AFS Securities:
Unrealized holding gains, pre-tax amount	$ 9,082	$ 13,835	$ 33,197	$ 27,719
Unrealized holdings gains, tax (expense) benefit	(1,952)	(2,975)	(7,137)	(5,960)
Unrealized holdings gains, after-tax amount	7,130	10,860	26,060	21,759
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	0	27	0	27
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	0	(6)	0	(6)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	21	0	21
Net unrealized gains, pre-tax amount	9,082	13,808	33,197	27,692
Net unrealized gains, tax (expense) benefit	(1,952)	(2,969)	(7,137)	(5,954)
Net unrealized gains, after-tax amount	7,130	10,839	26,060	21,738
Cash Flow Hedges:
Net decrease in fair value, pre-tax amount	(14)	(1,533)	(1,162)	(2,711)
Net decrease in fair value, tax (expense) benefit	3	330	250	583
Net decrease in fair value, after-tax amount	(11)	(1,203)	(912)	(2,128)
Less: effective portion reclassified into interest expense, after-tax amount			(210)	(251)
Net decrease in fair value, pre-tax amount	66	(1,332)	(894)	(2,391)
Net decrease in fair value, tax (expense) benefit	(14)	286	192	514
Net decrease in fair value, after-tax amount	52	(1,046)	(702)	(1,877)
Postretirement Plans:
Net actuarial gain, pre-tax amount	175	67	351	134
Net actuarial gain, tax (expense) benefit	(37)	(15)	(76)	(29)
Net actuarial gain, after-tax amount	138	52	275	105
Less: Amortiaztion of net prior service credits, pre-tax amount	6	6	12	12
Less: Amortiaztion of net prior service credits, tax (expense) benefit	(1)	(2)	(3)	(3)
Less: Amortiaztion of net prior service credits, after-tax amount	5	4	9	9
Net gain on postretirement plans, pre-tax amount	169	61	339	122
Net gain on postretirement plans, tax (expense) benefit	(36)	(13)	(73)	(26)
Net gain on postretirement plans, net of tax	133	48	266	96
Other comprehensive income, pre-tax amount	9,317	12,537	32,642	25,423
Other comprehensive income, tax (expense) benefit	(2,002)	(2,696)	(7,018)	(5,466)
Other comprehensive income	7,315	9,841	25,624	19,957
Interest Expense, Borrowings
Cash Flow Hedges:
Less: effective portion reclassified into interest expense, pre-tax amount	(327)	(201)	(567)	(320)
Less: effective portion reclassified into interest expense, tax (expense) benefit	70	44	122	69
Less: effective portion reclassified into interest expense, after-tax amount	(257)	(157)	(445)	(251)
Interest Income, Interest and Fees on Loans
Cash Flow Hedges:
Less: effective portion reclassified into interest expense, pre-tax amount	247	0	299	0
Less: effective portion reclassified into interest expense, tax (expense) benefit	(53)	0	(64)	0
Less: effective portion reclassified into interest expense, after-tax amount	$ 194	$ 0	$ 235	$ 0