CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	$ (20,941)	$ (1,737)
Net current-period other comprehensive (loss) income	57,429	(276,012)
Net change in investment securities available-for-sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net current-period other comprehensive (loss) income	53,010	(275,918)
Amortization of defined benefit pension plan-related items:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net current-period other comprehensive (loss) income	(35)	(27)
Net unrealized gains on terminated cash flow hedges:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net current-period other comprehensive (loss) income	292	(39)
Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net current-period other comprehensive (loss) income	4,079	(151)
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	15	9
Prior service costs (credits)	(19)	(19)
Actuarial (gains) losses	(43)	(17)
Income before taxes	(62)	(36)
Net current-period other comprehensive (loss) income	(47)	(27)
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 gains to income during the period	(52)	(52)
Income taxes	12	12
Net current-period other comprehensive (loss) income	(40)	(40)
Reclassification out of Accumulated Other Comprehensive Income (Loss) \| Amortization of Net Unrealized Gains to Income During Period \| Net change in investment securities available-for-sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net unrealized gains to income during the period	5,481	(111)
Income taxes	(1,315)	27
Net current-period other comprehensive (loss) income	$ 4,166	$ (84)

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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