ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Other Comprehensive Income (Loss), before Reclassification Adjustments and Tax [Abstract]
Unrealized gain (loss) on investment securities	$ (16,734)	$ 39,079
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax	(5,521)	0
Retirement obligation	0	0
Foreign currency translation	(301)	4
Total	(22,556)	39,083
Other Comprehensive Income (Loss) Reclassifications before Tax [Abstract]
Realized gain (loss) on securities available-for-sale	(7,518)	(19)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax	(199)	0
Retirement obligation	(375)	(150)
Foreign currency translation	0	0
Total	(8,092)	(169)
Transactions Pre-tax
Unrealized gain (loss) on investment securities	(9,216)	39,098
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax	(5,322)	0
Unfunded pension obligation	375	150
Foreign currency translation	(301)	4
Total	(14,464)	39,252
Transactions Tax-effect
Unrealized gain (loss) on investment securities	2,030	(8,613)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	(1,231)	0
Retirement obligation	(87)	(35)
Foreign currency translation	0	0
Total	3,174	(8,648)
Transactions Net of tax
Unrealized gain (loss) on investment securities	(7,186)	30,485
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(4,091)	0
Retirement obligation	288	115
Foreign currency translation	(301)	4
Total	(11,290)	30,604
Balances Net of tax
Unrealized gain (loss) on investment securities	(289,144)	(295,440)	$ (281,958)	$ (325,925)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(336)	0	3,755	0
Retirement obligation	(30,829)	(31,908)	(31,117)	(32,023)
Foreign currency translation	(800)	(711)	(499)	(715)
Accumulated other comprehensive loss	(321,109)	(328,059)	$ (309,819)	$ (358,663)
Accumulated other comprehensive income (loss)
Transactions Net of tax
Total	$ (11,290)	$ 30,604