ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Change in unrealized gain (loss) on securities:
Change in net unrealized gain (loss) during the period	$ 3,775		$ (11,291)		$ 7,119	$ (13,593)
Reclassification adjustment for net losses included in net loss on sale of securities and other assets						1,447
Accretion of net unrealized loss on securities transferred to held-to-maturity	818		796		1,536	1,553
Net change	4,593		(10,495)		8,655	(10,593)
Tax expense (benefit)	1,634		(3,109)		2,846	(445)
Net change in unrealized gain (loss) on securities, net of reclassification adjustments and tax	2,959		(7,386)		5,809	(10,148)
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	(318)		(370)		(635)	(740)
Change in the net actuarial gain	520		814		1,040	1,035
Net change	202		444		405	295
Tax expense (benefit)	77		131		135	87
Net change in pension and other postretirement obligations	125		313		270	208
Change in unrealized gain (loss) on derivatives:
Change in net unrealized (loss) gain during the period	(3,128)		1,586		(983)	(525)
Reclassification adjustment for expense included in interest expense	2,520		299		4,955	(14)
Net change	(608)		1,885		3,972	(539)
Tax expense (benefit)	(210)		559		1,252	(473)
Net change in unrealized gain (loss) on derivatives, net of reclassification adjustments and tax	(398)		1,326		2,720	(66)
Total other comprehensive income (loss), net of tax	$ 2,686	$ 6,113	$ (5,747)	$ (4,259)	$ 8,799	$ (10,006)