ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in unrealized gain (loss) on securities:
Change in net unrealized gain (loss) during the period	$ 23,218	$ 10,355	$ (138,630)
Reclassification adjustment for net losses included in net loss on sale of securities and other assets	42,810	1,447
Accretion of net unrealized loss on securities transferred to held-to-maturity	3,028	3,142	2,953
Net change	69,056	14,944	(135,677)
Tax expense (benefit)	22,581	4,316	(42,671)
Net change in unrealized gain (loss) on securities, net of reclassification adjustments and tax	46,475	10,628	(93,006)
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	26	(1,547)	(3,715)
Change in the net actuarial gain	(1,426)	(190)	(2,062)
Net change	(1,400)	(1,737)	(5,777)
Tax benefit	(331)	(573)	(1,817)
Net change in pension and other postretirement obligations	(1,069)	(1,164)	(3,960)
Change in unrealized gain (loss) on derivatives:
Change in net unrealized (loss) gain during the period	(8,453)	(11,782)	14,412
Reclassification adjustment for expense included in interest expense	10,008	2,092	(1,621)
Net change	1,555	(9,690)	12,791
Tax expense (benefit)	400	(3,026)	4,023
Net change in unrealized gain (loss) on derivatives, net of reclassification adjustments and tax	1,155	(6,664)	8,768
Total other comprehensive income (loss), net of tax	$ 46,561	$ 2,800	$ (88,198)