CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (21,108)	$ (22,904)	$ (63,567)	$ (66,880)
Total before tax	85,517	97,167	262,907	272,400
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications	3,916	4,290	11,294	12,675
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	5,217	5,745	15,055	17,005
Income taxes	(1,252)	(1,379)	(3,613)	(4,081)
Total reclassifications	3,965	4,366	11,442	12,924
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)	(57)	(57)
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	47	45
Actuarial gains	(46)	(44)	(138)	(130)
Total before tax	(65)	(63)	(195)	(187)
Total reclassifications	(49)	(48)	(148)	(142)
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	(37)	0	(141)
Income taxes	0	9	0	34
Total reclassifications	$ 0	$ (28)	$ 0	$ (107)