OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 541,294	$ 529,314
Other comprehensive (loss) income before reclassifications	(69,771)	(12,316)
Less: Amounts reclassified from AOCI	(87)	(141)
Other comprehensive loss	(69,684)	(12,175)
Ending Balance	482,446	532,120
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,229)	20,740
Ending Balance	(75,913)	8,565
Net Unrealized Gains (Losses) on AFS Debt Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,173)	29,310
Other comprehensive (loss) income before reclassifications	(72,811)	(17,509)
Less: Amounts reclassified from AOCI	0	0
Other comprehensive loss	(72,811)	(17,509)
Ending Balance	(73,984)	11,801
Net Unrealized Losses (Gains) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,779)	(4,626)
Other comprehensive (loss) income before reclassifications	2,853	5,018
Less: Amounts reclassified from AOCI	(92)	(146)
Other comprehensive loss	2,945	5,164
Ending Balance	1,166	538
Defined Benefit Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,277)	(3,944)
Other comprehensive (loss) income before reclassifications	187	175
Less: Amounts reclassified from AOCI	5	5
Other comprehensive loss	182	170
Ending Balance	$ (3,095)	$ (3,774)