CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (21,101)	$ (21,202)
Income before taxes	86,968	86,925
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications	3,119	3,620
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net unrealized holding losses on securities transferred between available-for-sale and held-to-maturity:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized losses to income during the period	4,195	4,827
Income taxes	(1,007)	(1,158)
Total reclassifications	3,188	3,669
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Prior service credits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior service credits	(19)	(19)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Amortization of defined benefit pension plan-related items:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	22	15
Actuarial gains	(72)	(45)
Income before taxes	(91)	(64)
Total reclassifications	$ (69)	$ (49)