CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (21,257)	$ (23,035)	$ (42,459)	$ (43,976)
Income before taxes	90,465	91,630	177,390	175,233
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications	3,758	4,306	7,378	8,384
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net change in investment securities available-for-sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized losses to income during the period	5,011	5,779	9,838	11,260
Income taxes	(1,203)	(1,386)	(2,361)	(2,702)
Total reclassifications	3,808	4,393	7,477	8,558
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	16	15	31	30
Actuarial gains	(47)	(43)	(92)	(86)
Income before taxes	(66)	(62)	(130)	(124)
Total reclassifications	(50)	(47)	(99)	(94)
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Net unrealized gains on terminated cash flow hedges:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized losses to income during the period	0	(53)	0	(105)
Income taxes	0	13	0	25
Total reclassifications	$ 0	$ (40)	$ 0	$ (80)