OTHER COMPREHENSIVE INCOME (LOSS) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 482,446	$ 532,120	$ 541,294	$ 529,314
Other comprehensive (loss) income before reclassifications	(39,058)	(43)	(108,829)	(12,359)
Less: Amounts reclassified from AOCI	(5)	(146)	(92)	(287)
Other comprehensive (loss) income	(39,053)	103	(108,737)	(12,072)
Ending Balance	446,381	545,548	446,381	545,548
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(75,913)	8,565	(6,229)	20,740
Ending Balance	(114,966)	8,668	(114,966)	8,668
Net Unrealized Gains (Losses) on Debt Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(73,984)	11,801	(1,173)	29,310
Other comprehensive (loss) income before reclassifications	(42,060)	2,296	(114,871)	(15,213)
Less: Amounts reclassified from AOCI	(7)	0	(7)	0
Other comprehensive (loss) income	(42,053)	2,296	(114,864)	(15,213)
Ending Balance	(116,037)	14,097	(116,037)	14,097
Net Unrealized Losses (Gains) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	1,166	538	(1,779)	(4,626)
Other comprehensive (loss) income before reclassifications	2,817	(2,514)	5,670	2,504
Less: Amounts reclassified from AOCI	(2)	(150)	(94)	(296)
Other comprehensive (loss) income	2,819	(2,364)	5,764	2,800
Ending Balance	3,985	(1,826)	3,985	(1,826)
Defined Benefit Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,095)	(3,774)	(3,277)	(3,944)
Other comprehensive (loss) income before reclassifications	185	175	372	350
Less: Amounts reclassified from AOCI	4	4	9	9
Other comprehensive (loss) income	181	171	363	341
Ending Balance	$ (2,914)	$ (3,603)	$ (2,914)	$ (3,603)