CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (23,319)	$ (21,257)	$ (44,420)	$ (42,459)
Income before taxes	95,540	90,465	182,508	177,390
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications	3,197	3,758	6,316	7,378
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	4,299	5,011	8,494	9,838
Income taxes	(1,032)	(1,203)	(2,039)	(2,361)
Total reclassifications	3,267	3,808	6,455	7,477
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)	(38)	(38)
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	16	44	31
Actuarial gains	(73)	(47)	(145)	(92)
Income before taxes	(92)	(66)	(183)	(130)
Total reclassifications	$ (70)	$ (50)	$ (139)	$ (99)